Abstract

Basaltic lavas from Hainan Island near the northern edge of the South China Sea have an age range of between late Miocene (about 13 Ma) and Holocene, with a peak age of late Pliocene to middle Pleistocene. The basaltic province is dominated by tholeiites with subordinate alkali basalts. Most analysed samples display light rare earth element (LREE) enriched REE patterns and ocean island basalt (OIB)-like incompatible element distributions. The basalts contain abundant undeformed high-Mg olivine phenocrysts (up to Fo90·7) that are high in CaO and MnO, indicating high-magnesian parental magmas. Independent barometers indicate that clinopyroxenes in the basalts crystallized over a wide range of pressures of 2–25 kbar (dominantly at 10–15 kbar) and that the melt cooled from about 1350°C to 1100°C during their crystallization. The compositional characteristics of the basalts indicate that their generation most probably involved both low-silica and high-silica melts, as represented by the alkali basalts and tholeiites, respectively. Our results show that the source region for the Hainan basalts is highly heterogeneous. The source for the tholeiites is mainly composed of peridotite and recycled oceanic crust, whereas the source for the bulk of the low-Th alkali basalts consists predominantly of peridotite and low-silica eclogite (garnet pyroxenite). Some high-Th (≥  4 ppm) alkali basalts may have been produced by partial melting of low-silica garnet pyroxenite (eclogite). We estimated the primary melt compositions for the Hainan basalts using the most forsteritic olivine (Fo90·7) composition and the most primitive bulk-rock samples (MgO > 9·0 wt % and CaO >8·0 wt %), assuming a constant Fe–Mg exchange partition coefficient of KD = 0·31 and Fe3+/FeT = 0·1. The effective melting pressure (Pf) and melting temperature (T) of the primary melts are Pf = 18–32 kbar (weighted average = 23·8 ± 1·8 kbar) and T = 1420–1520°C for the tholeiites, and Pf = 25–32 (weighted average = 28·3 ± 1·4 kbar) and T = 1480–1530°C for the alkali basalts. The Pf  –T data form an array that plots systematically above the dry lherzolite solidus but below the base of the lithosphere (∼55 km) and intersects the dry peridotite solidus at a pressure of about 50 kbar. The mantle potential temperature beneath Hainan Island, based on the estimate primary melt compositions, varies from about 1500 to 1580°C with a weighted average of 1541 ± 10°C. The high-magnesian olivine phenocrysts, high mantle potential temperature, and the presence of recycled oceanic crust in the source region provide independent support for the Hainan plume model that has previously been proposed largely based on geophysical observations. The Hainan plume thus provides a rare example of a young mantle plume associated with deep slab subduction.

INTRODUCTION

Southeast Asia (including southeastern China, the South China Sea, and the Indochina Block) has one of the most cryptic tectonic settings (Taylor & Hayes, 1980; Chung et al., 1997; Yin & Harrison, 2000; Sun et al., 2009; Fig. 1a). Extensive and voluminous late Cenozoic basalts are a prominent feature in this region (e.g. Zhu & Wang, 1989; Flower et al., 1992; Zhou & Mukasa, 1997; Hoang & Flower, 1998; Ho et al., 2000; Fedorov & Koloskov, 2005; Zou & Fan, 2010). These basalts are widespread inside the South China Sea Basin (e.g. Yan et al., 2008), in Hainan Island–Leizhou Peninsula (e.g. Tu et al., 1991; Flower et al., 1992; Ho et al., 2000; Zou & Fan, 2010), and in the Indochina Peninsula (e.g. Zhou & Mukasa, 1997; Hoang & Flower, 1998). These basalts comprise an oceanic island basalt (OIB)-like suite dominated by quartz and olivine tholeiites with subsidiary alkali basalts (e.g. Flower et al., 1992; Hoang & Flower, 1998; Ho et al., 2000). The basalts are younger than the South China Sea sea-floor extension (between c. 30 and 16 Ma; Sun et al., 2009, and references therein) and have a peak age <9 Ma (e.g. Hoang & Flower, 1998; Ho et al., 2000, 2003; Fan et al., 2004; Yan et al., 2008). They are characterized by OIB-type incompatible element distributions, an intriguing Dupal-like Pb isotopic signature, and depleted Sr–Nd isotopic compositions (e.g. Tu et al., 1991; Flower et al., 1992; Hoang & Flower, 1998; Yan et al., 2008). Such a widespread intraplate basaltic magmatism has variously been attributed to lithosphere extension (e.g. Zhu & Wang, 1989; Tu et al., 1991; Flower et al., 1992), mantle escape from under Asia in response to lithospheric thickening in the Indo-Eurasian collision zone (e.g. Hoang & Flower, 1998), and mantle plumes or hotspots (e.g. Yan et al., 2008; Lei et al., 2009; Zou & Fan, 2010).

Fig. 1.

(a) Simplified geological map of the Indochina Block, Leizhou Peninsula–Hainan Island, South China Sea and surrounding areas showing the distribution of late Cenozoic basaltic volcanism and major continental rift basins (Hoang & Flower, 1998; Ho et al., 2000; Fan et al., 2004; Sun et al., 2009). ASRRF, Ailaoshan–Red River Fault; EVF, Eastern Vietnam Fault; COT, continental–oceanic transition. (b) Index map showing the sampling locations and 40Ar/39Ar and K–Ar ages of late Cenozoic basalts from Hainan Island. Distribution and eruptive episodes of basaltic rocks are from Ho et al. (2000), Fan et al. (2004), Long et al. (2006a, 2006b) and Han (2009).

Fig. 1.

(a) Simplified geological map of the Indochina Block, Leizhou Peninsula–Hainan Island, South China Sea and surrounding areas showing the distribution of late Cenozoic basaltic volcanism and major continental rift basins (Hoang & Flower, 1998; Ho et al., 2000; Fan et al., 2004; Sun et al., 2009). ASRRF, Ailaoshan–Red River Fault; EVF, Eastern Vietnam Fault; COT, continental–oceanic transition. (b) Index map showing the sampling locations and 40Ar/39Ar and K–Ar ages of late Cenozoic basalts from Hainan Island. Distribution and eruptive episodes of basaltic rocks are from Ho et al. (2000), Fan et al. (2004), Long et al. (2006a, 2006b) and Han (2009).

Up to now, the most compelling evidence for the plume or hotspot model comes from seismic tomography that defines a plume-like mantle low-velocity structure beneath the north Hainan Island–Leizhou Peninsula basalt province (e.g. Lebedev & Nolet, 2003; Montelli et al., 2004, 2006; Zhao, 2004, 2007; Huang & Zhao, 2006; Lei et al., 2009). High-resolution tomographic images of the upper mantle show a clear geometry of a SE-plunging, low-velocity column with a diameter of about 80 km continuous from the surface down to about 250 km (Lei et al., 2009). On a global scale, the hypothesized Hainan plume extends down to about 1900 km depth (e.g. Ritsema et al., 1999; Montelli et al., 2006) or to the lowermost mantle (e.g. Zhao, 2004, 2007; Lei & Zhao, 2006).

The hypothesized Hainan plume is provocative because so far plumes, with the exception of the Yellowstone plume in western North America, that appear to have existed in the past 150 Myr are located above either the Pacific superplume or the African superplume, where broad low-velocity zones of >6000 km in dimension exist in the lower mantle (e.g. Ritsema et al., 1999; Friederich, 2003; Thorne et al., 2004; Zhao, 2004; Montelli et al., 2006; Schmerr et al., 2010). However, like the Yellowstone plume, the proposed Hainan plume is located at the fringe of the Asian downwelling zone away from both Pacific and African superplumes, making it more intriguing as to whether it is a mantle plume and, if it is, why it is there. The current Hainan plume model was developed largely from geophysical observations that are still subject to debate. Questions remain regarding the geological manifestations of such a mantle plume. For instance, what are the petrological–geochemical manifestations of the Hainan plume? What is the thermochemical structure of the plume? Is it indeed hotter than the ambient asthenospheric mantle? Were the Hainan basalts derived from high-temperature primary melts involving recycled components, similar to typical plume-originated oceanic hotspot basalts such as Hawaiian OIB?

In this study, we present a comprehensive set of whole-rock and mineral chemical and 40Ar/39Ar geochronological data, with the aim of evaluating the mantle sources, residual phases and mantle thermal state of the Hainan basalts. We estimate the primary melt compositions by combining the most forsteritic olivine phenocryst compositions (Fo90·7) with whole-rock geochemical data. Mantle potential temperature, melting conditions and T–P for the crystallization of clinopyroxene phenocrysts are estimated, and the geodynamic significance of these findings will be discussed.

GEOLOGICAL BACKGROUND

Hainan Island is located near the southeastern margin of the Eurasian plate, and has been affected by the motions of, and interactions between, the Indian and Philippine Sea plates and by the extension of the South China Sea Basin (Fig. 1a). This region records a diverse array of tectonic processes with rifting, subduction, terrane collision and large-scale continental strike-slip faulting occurring in spatially and temporally complex relations (e.g. Cullen et al., 2010).

Late Cenozoic basaltic flows occur in northern Hainan Island and the adjacent Leizhou Peninsula, located at the northern edge of the South China Sea Basin (Fig. 1a). The basaltic plateau in Hainan Island has elevations up to >100 m, with a maximum thickness of ∼1000 m and covering a total of ∼4160 km2 (e.g. Flower et al., 1992; Ho et al., 2000; Fan et al., 2004; Long et al., 2006a, 2006b). Two eruptive styles have been recognized: massive eruptions from extensional fissures, and thinner, more sporadic eruptions from central volcanoes (e.g. Flower et al., 1992; Ho et al., 2000). Fissure eruptive rocks account for the bulk of the sequence and consist almost entirely of quartz- or olivine-normative tholeiite (e.g. Flower et al., 1992). The central volcanoes have produced alkali olivine basalts and basanites, some of which contain spinel-lherzolite and harzburgite mantle xenoliths and megacrysts of clinopyroxene, sapphire (corundum), zircon and anorthoclase. Ho et al. (2000) reviewed all published K–Ar and 40Ar/39Ar data for the Cenozoic basalts in Hainan Island and the Leizhou Peninsula, and concluded that incipient volcanism took place in late Oligocene times; the intensity of volcanism gradually increased during the Miocene and Pliocene Epochs; volcanism peaked in the Pleistocene and terminated in the Holocene.

Volcanic rocks exposed in northern Hainan Island have been subdivided into five eruptive episodes; these are, from old to young in the order of their eruptive ages (Ho et al., 2000, 2003; Fan et al., 2004; Long et al., 2006a, 2006b; Fig. 1b): (1) the Pliocene–Miocene episode as represented by the Shimengou and Shimacun volcanism; (2) the early to middle Pleistocene as represented by the Duowen volcanism; (3) the middle Pleistocene episode as represented by the Dongying volcanism; (4) the late Pleistocene episode as represented by the Daotang volcanism; (5) the Holocene episode as represented by the Shishan volcanism. The Duowen volcanism is the largest basaltic outcrop in this region and can be divided into lower and upper sections (e.g. Long et al., 2006a, 2006b). The lower section lasted from early to middle Pleistocene, and the upper section was formed during the middle Pleistocene (e.g. Long et al., 2006a, 2006b). It is dominated by quartz and olivine tholeiites with minor volcaniclastic rocks. The late facies of the Duowen volcanism comprise minor alkali olivine basalts. The total thicknesses of the lava sheets vary from 5 to 250 m (Long et al., 2006b). The Dongying volcanism is dominated by dispersed quartz and olivine tholeiites, and its thickness varies between 4 and 200 m (Fan et al., 2004). The Daotang volcanism can be divided into lower, middle, and upper sections (Long et al., 2006a). The upper and lower sections are dominated by basaltic pyroclastic rocks. The middle section comprises mainly vesicular olivine tholeiites. The Daotang volcanism covers about 600 km2 with a thickness of up to 330 m (Long et al., 2006a). The Shishan volcanism is the youngest volcanic unit in the region (e.g. Huang & Cai, 1994; Ho et al., 2000; Fan et al., 2004). This volcanism is dominated by olivine basalts and olivine tholeiites, and has a total thickness of >95 m. Sandstone xenoliths have been identified in the lavas (e.g. Fan et al., 2004).

PETROGRAPHY

Olivine tholeiites are generally moderately phyric (<15% phenocrysts). The phenocrysts are typically euhedral to subhedral and in the size range of 0·1–2·5 mm, although occasionally they reach 4 mm. Most olivine tholeiites contain olivine as the only phenocryst phase, but some also contain small amounts of plagioclase (0·5–2 mm in length), sometimes accompanied by clinopyroxene in the size range of 0·3–0·8 mm. The groundmass comprises plagioclase (40–75%), pyroxene (15–30%), microphenocryst olivine (0–5%), Fe–Ti oxides (2–5%) and glass (0–10%). Olivine tholeiites are the dominant lithology within the Hainan basalts. Quartz tholeiites are generally aphyric (<3% phenocrysts) to moderately phyric (<10% phenocrysts) with plagioclase, olivine and augite phenocrysts. Alkalic basalts are phyric (5–15% phenocrysts). Olivine occurs dominantly as phenocrysts in alkali basalts, and is euhedral to subhedral. It occasionally occurs in glomeroporphyritic aggregates. The assemblage of olivine + augite (i.e. without plagioclase) has also been noted. Alkali olivine basalts occur in the Leihuling, Qiongshan, and Penglai areas. The alkali and transitional basalts usually occur in the late phase of each volcanic episode and are abundant in the Holocene volcanism.

SAMPLE PREPARATION AND ANALYTICAL TECHNIQUES

Samples were sawn into slabs and the central parts (>200 g) were used for bulk-rock analysis. The rocks were crushed into small fragments (<0·5 cm in diameter) before being further cleaned and powdered in a corundum mill. Bulk-rock geochemical analyses were carried out at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. Bulk-rock major element oxides were analyzed by X-ray fluorescence (XRF) with analytical uncertainties better than 3% for SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O and K2O, and better than 5% for TiO2, MnO and P2O5. Trace elements were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). Repeated runs give <3% RSD (relative standard deviation) for most trace elements analyzed. Fe/Mn ratios were also measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). Precision for Fe/Mn ratios is generally better than 2%. Detailed analytical methods have been described by Liu et al. (1996) and Li et al. (2002, 2005).

Twelve groundmass samples were dated using the step-heating 40Ar/39Ar method. 40Ar/39Ar measurements were performed at the Institute of Geology and Geophysics of the Chinese Science Academy (IGGCAS), Beijing. To constrain the eruption age and avoid excess argon, groundmass grains in the size range of 0·2–0·3 mm were picked carefully under a binocular microscope to remove the visible phenocrysts and xenocrysts. The samples were cleaned with acetone followed by further cleaning with deionized water in an ultrasonic bath for three times, each for 40 min. The cleaned samples were then dried at ∼100°C for 20 min. Groundmass wafers weighing 3–16 mg, and multiple samples of the 18·6 ± 0·4 Ma neutron fluence monitor mineral Brione muscovite, were irradiated in vacuo within a cadmium-coated quartz vial for 5 h in position H8 of the Beijing Atomic Energy Research Institute reactor (49-2). The argon isotopes were analysed using a MM5400 mass spectrometer. Further details about the step-heating 40Ar/39Ar method have been given by Wang et al. (2006).

Major element analyses of minerals were carried out using a JEOL JXA-8100 Superprobe at the IGGCAS. The operating conditions are: 15 kV accelerating voltage, 20 nA beam current, 3 μm beam diameter, and 10 s peak counting time for most elements (30 s for Ca and Ni in olivine, 7 s for Na and 8 s for K). The data reduction was carried out using ZAF correction.

RESULTS

40Ar/39Ar age data

The age results from the step-heating experiments are presented in Table 1 and Figs 1b and 2. The 40Ar/36Ar initial ratios (Table 1) of all samples show no significant deviation from atmospheric values (295·5), suggesting that there is no excess argon component in the trapped argon from the samples and that the plateau ages are reliable. The plateau ages of all samples were obtained from at least three contiguous steps, comprising more than 70% cumulative 39Ar released (Fig. 2). Samples 08HN-13A, 08HN-16C, and 08HN-24B from the lower section of the Duowen volcanism gave plateau ages of 1·08 ± 0·19 Ma, 1·14 ± 0·11 Ma, and 1·33 ± 0·15 Ma, respectively (Table 1, Fig. 2). Samples 08HN-6D and 08HN-19A are from the upper section of the Duowen volcanism and yielded plateau ages of 0·68 ± 0·44 Ma and 0·71 ± 0·12 Ma, respectively. These plateau ages define an age range of c. 1·3–0·6 Ma for the Duowen volcanism. Sample 08HN-7A is from the Shimengou volcanism and gave a plateau age of 2·49 ± 1· 09 Ma, but this age is not regarded as reliable because of its poor plateau shape. Sample 08HN-10A from the upper section of the Shimengou volcanism gave a plateau age of 3·26 ± 0·60 Ma. Four samples (three drilling core samples ZK04-10·5, ZK04-26·8 and ZK05-20.1, and one surface sample 08HN-5D) were collected from the Penglai area (Fig. 2). Sample 08HN-5D is from the Shimengou volcanism and gave a plateau age of 4·80 ± 0·30 Ma. Drilling core samples ZK04-10.5 and ZK04-26.8 were collected at depths of 10·5 m and 26·8 m, respectively, from drilling core ZK04, which penetrated two layers of basalts. The lower layer occurs at depths between 32 and 21·9 m and is separated from the upper layer by about 9 m of sediments. The upper layer occurs at depths of between 13 and 8·2 m. Samples ZK04-10.5 and ZK04-26.8 gave plateau ages of 5·86 ± 0·35 Ma and 12·89 ± 1·15 Ma, respectively. Sample ZK05-20.1 gave a plateau age of 4·63 ± 0·18 Ma. These data indicate that eruption of the outcropping basalts in the Penglai area (the Shimengou–Shimacun volcanism) may have lasted from c. 6·0 to 3·0 Ma and incipient volcanism may have taken place in the late Miocene (about 13 Ma). Four samples (08HN-4D, 08HN-7A, 08HN-10A and ZK04-26.8) produced large errors in their plateau ages. This may be attributed to the depletion of radiogenic 40Ar because of the low K contents in the matrix of the rocks (K2O ranging from 0·5 to 0·8 wt %; Table 2), and the effect of alteration on drilling core sample ZK04-26.8 [loss on ignition (LOI) = 4·2 wt %; Table 2]. All available 40Ar/39Ar data (including those obtained in this study), and some high-quality K–Ar data for the basalts are given in parentheses in Fig. 1b.

Fig. 2.

Age spectra, integrated and plateau ages for the 11 samples studied.

Fig. 2.

Age spectra, integrated and plateau ages for the 11 samples studied.

Table 1:

40Ar/  39Ar dating of the Hainan basalts

Sample Eruptive episode Position Plateau age (Ma) 40Ar/39Ar (initial) 
08HN-5D Shimacun 19°34'44"E 4·80 ± 0·30 295·8 ± 1·7 
  110°38'38·7"N   
08HN-6D Duowen (upper) 19°24'6"E 0·68 ± 0·44 296·1 ± 2·9 
  110°34'49·5"N   
08HN-7A Shimengou 19°59'48"E 2·45 ± 1·09 295·6 ± 3·8 
  109°38'53·7"N   
08HN-10A Shimengou 19°57'10·6"E 3·26 ± 0·60 295·4 ± 1·5 
  110°01'02·0"N   
08HN-13A Duowen (lower) 19°48'28·7"E 1·08 ± 0·19 297·1 ± 5·5 
  109°13'48·7"N   
08HN-16C Duowen (lower) 19°51'25·3"E 1·14 ± 0·11 297·0 ± 1·8 
  109°17'12"N   
08HN-19A Duowen (upper) 19°47'30"E 0·71 ± 0·12 295·4 ± 2·6 
  109°45'43·7"N   
08HN-24B Duowen (lower) 19°48'33·2"E 1·33 ± 0·15 296·2 ± 1·5 
  110°26'45·6"N   
ZK05-20.1 Drill core at 20·1 m 19°33'30·8"E 4·63 ± 0·18 296·1 ± 5·3 
  110°39'10·1"N   
ZK04-10.5 Drill core at 10·5 m 19°32'0·9"E 5·86 ± 0·35 296·9 ± 1·9 
  110°38'57·8"N   
ZK04-26.8 Drill core at 26·8 m 110°38'57·8"N 12·89 ± 1·15 295·9 ± 1·5 
  110°38'57·8"N   
Sample Eruptive episode Position Plateau age (Ma) 40Ar/39Ar (initial) 
08HN-5D Shimacun 19°34'44"E 4·80 ± 0·30 295·8 ± 1·7 
  110°38'38·7"N   
08HN-6D Duowen (upper) 19°24'6"E 0·68 ± 0·44 296·1 ± 2·9 
  110°34'49·5"N   
08HN-7A Shimengou 19°59'48"E 2·45 ± 1·09 295·6 ± 3·8 
  109°38'53·7"N   
08HN-10A Shimengou 19°57'10·6"E 3·26 ± 0·60 295·4 ± 1·5 
  110°01'02·0"N   
08HN-13A Duowen (lower) 19°48'28·7"E 1·08 ± 0·19 297·1 ± 5·5 
  109°13'48·7"N   
08HN-16C Duowen (lower) 19°51'25·3"E 1·14 ± 0·11 297·0 ± 1·8 
  109°17'12"N   
08HN-19A Duowen (upper) 19°47'30"E 0·71 ± 0·12 295·4 ± 2·6 
  109°45'43·7"N   
08HN-24B Duowen (lower) 19°48'33·2"E 1·33 ± 0·15 296·2 ± 1·5 
  110°26'45·6"N   
ZK05-20.1 Drill core at 20·1 m 19°33'30·8"E 4·63 ± 0·18 296·1 ± 5·3 
  110°39'10·1"N   
ZK04-10.5 Drill core at 10·5 m 19°32'0·9"E 5·86 ± 0·35 296·9 ± 1·9 
  110°38'57·8"N   
ZK04-26.8 Drill core at 26·8 m 110°38'57·8"N 12·89 ± 1·15 295·9 ± 1·5 
  110°38'57·8"N   
Table 2:

Major element concentrations (in wt %) and normative mineral compositions (%) of the Hainan basalts

Sample: 08HN-1A 08HN-2A 08HN-2B 08HN-3 08HN-4A 08HN-4B 08HN-4C 08HN-4D 08HN-4G 08HN-5A 08HN-5B 08HN-5C 08HN-5D 08HN-5E 08HN-5F 08HN-5G 08HN-5H 
Rock: Olivine tholeiite Alkali basalt Alkali basalt Olivine tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Olivine tholeiite Olivine tholeiite 
Episode: 
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Slight Fresh Fresh Fresh Fresh Fresh Fresh Slight 
SiO2 48·1 47·5 47·8 47·3 52·1 52 52 50·5 52 51·2 51·1 51 50·9 51·1 52·1 51·2 51 
TiO2 2·42 2·98 2·85 2·7 1·98 1·91 2·12 1·83 2·02 1·91 1·99 1·96 1·99 1·98 1·93 1·97 
Al2O3 12·6 13 13·2 12·7 13·8 13·6 14 12·9 13·9 13·7 13·9 14 13·9 13·9 13·9 13·9 14 
CaO 8·17 7·89 8·22 8·6 8·47 8·79 8·58 8·49 8·92 8·56 8·63 8·6 8·76 8·63 8·63 8·55 
Fe2O3T 12·5 13·2 13 13·5 11·6 11·8 11·6 12 11·6 12·3 11·9 11·9 12 11·8 11·8 11·8 11·9 
K21·91 1·52 1·64 1·59 0·808 0·816 0·845 0·643 0·948 0·727 1·11 1·01 1·11 1·07 0·796 1·11 1·1 
MgO 10·6 9·68 9·29 10·6 7·79 8·13 7·25 10·4 7·47 7·85 7·75 7·99 7·83 7·76 7·36 7·61 7·81 
MnO 0·135 0·139 0·14 0·143 0·122 0·125 0·125 0·149 0·129 0·131 0·137 0·135 0·137 0·135 0·135 0·136 0·132 
Na22·96 3·4 3·32 2·69 2·94 2·89 2·96 2·7 3·09 2·91 3·15 3·08 3·16 3·16 3·03 3·2 3·15 
P2O5 0·635 0·671 0·688 0·489 0·238 0·225 0·32 0·278 0·281 0·298 0·356 0·346 0·363 0·364 0·275 0·367 0·357 
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 
LOI 0·982 0·733 0·718 0·849 0·598 0·761 0·891 0·682 0·204 1·29 0·705 0·921 0·68 0·67 0·984 0·708 1·02 
Mg# 65·1 61·7 61·1 63·3 59·7 60·2 57·8 65·6 58·5 58·4 58·9 59·6 59 59·1 57·8 58·7 59 
Quartz 0·703 0·354 1·08 0·789 
Orthoclase 11·6 9·13 9·79 9·51 4·83 4·88 5·05 3·85 5·67 4·35 6·64 6·05 6·63 6·39 4·76 6·64 6·6 
Plagioclase 41·5 41·9 43 41·3 47·5 46·8 47·9 44·6 48·1 47·4 47·8 47·9 47·8 47·9 48·1 48 47·9 
Nepheline 1·75 1·11 
Diopside 12·4 15·6 15·5 16·1 15·7 15·5 15·9 16 15·6 16·6 16·2 15·9 16·4 16·9 15·8 16·6 16 
Hypersthene 3·9 0·866 25·2 26·6 23·5 21·8 24·3 24 16·6 17·5 15·4 15·8 24·5 16·2 16·3 
Olivine 22·5 22·3 21·6 23·9 7·78 0·066 1·49 6·35 6·22 7·4 6·56 6·14 6·8 
Magnetite 1·86 1·94 1·91 1·99 1·7 1·73 1·71 1·76 1·71 1·8 1·75 1·75 1·76 1·73 1·74 1·73 1·75 
Ilmenite 4·71 5·74 5·48 5·2 3·8 3·67 4·08 3·51 3·88 3·68 3·82 3·77 3·82 3·8 3·72 3·84 3·8 
Apatite 1·51 1·58 1·62 1·15 0·558 0·528 0·751 0·651 0·658 0·7 0·834 0·811 0·85 0·853 0·644 0·86 0·836 
Sample: 08HN-1A 08HN-2A 08HN-2B 08HN-3 08HN-4A 08HN-4B 08HN-4C 08HN-4D 08HN-4G 08HN-5A 08HN-5B 08HN-5C 08HN-5D 08HN-5E 08HN-5F 08HN-5G 08HN-5H 
Rock: Olivine tholeiite Alkali basalt Alkali basalt Olivine tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Olivine tholeiite Olivine tholeiite 
Episode: 
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Slight Fresh Fresh Fresh Fresh Fresh Fresh Slight 
SiO2 48·1 47·5 47·8 47·3 52·1 52 52 50·5 52 51·2 51·1 51 50·9 51·1 52·1 51·2 51 
TiO2 2·42 2·98 2·85 2·7 1·98 1·91 2·12 1·83 2·02 1·91 1·99 1·96 1·99 1·98 1·93 1·97 
Al2O3 12·6 13 13·2 12·7 13·8 13·6 14 12·9 13·9 13·7 13·9 14 13·9 13·9 13·9 13·9 14 
CaO 8·17 7·89 8·22 8·6 8·47 8·79 8·58 8·49 8·92 8·56 8·63 8·6 8·76 8·63 8·63 8·55 
Fe2O3T 12·5 13·2 13 13·5 11·6 11·8 11·6 12 11·6 12·3 11·9 11·9 12 11·8 11·8 11·8 11·9 
K21·91 1·52 1·64 1·59 0·808 0·816 0·845 0·643 0·948 0·727 1·11 1·01 1·11 1·07 0·796 1·11 1·1 
MgO 10·6 9·68 9·29 10·6 7·79 8·13 7·25 10·4 7·47 7·85 7·75 7·99 7·83 7·76 7·36 7·61 7·81 
MnO 0·135 0·139 0·14 0·143 0·122 0·125 0·125 0·149 0·129 0·131 0·137 0·135 0·137 0·135 0·135 0·136 0·132 
Na22·96 3·4 3·32 2·69 2·94 2·89 2·96 2·7 3·09 2·91 3·15 3·08 3·16 3·16 3·03 3·2 3·15 
P2O5 0·635 0·671 0·688 0·489 0·238 0·225 0·32 0·278 0·281 0·298 0·356 0·346 0·363 0·364 0·275 0·367 0·357 
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 
LOI 0·982 0·733 0·718 0·849 0·598 0·761 0·891 0·682 0·204 1·29 0·705 0·921 0·68 0·67 0·984 0·708 1·02 
Mg# 65·1 61·7 61·1 63·3 59·7 60·2 57·8 65·6 58·5 58·4 58·9 59·6 59 59·1 57·8 58·7 59 
Quartz 0·703 0·354 1·08 0·789 
Orthoclase 11·6 9·13 9·79 9·51 4·83 4·88 5·05 3·85 5·67 4·35 6·64 6·05 6·63 6·39 4·76 6·64 6·6 
Plagioclase 41·5 41·9 43 41·3 47·5 46·8 47·9 44·6 48·1 47·4 47·8 47·9 47·8 47·9 48·1 48 47·9 
Nepheline 1·75 1·11 
Diopside 12·4 15·6 15·5 16·1 15·7 15·5 15·9 16 15·6 16·6 16·2 15·9 16·4 16·9 15·8 16·6 16 
Hypersthene 3·9 0·866 25·2 26·6 23·5 21·8 24·3 24 16·6 17·5 15·4 15·8 24·5 16·2 16·3 
Olivine 22·5 22·3 21·6 23·9 7·78 0·066 1·49 6·35 6·22 7·4 6·56 6·14 6·8 
Magnetite 1·86 1·94 1·91 1·99 1·7 1·73 1·71 1·76 1·71 1·8 1·75 1·75 1·76 1·73 1·74 1·73 1·75 
Ilmenite 4·71 5·74 5·48 5·2 3·8 3·67 4·08 3·51 3·88 3·68 3·82 3·77 3·82 3·8 3·72 3·84 3·8 
Apatite 1·51 1·58 1·62 1·15 0·558 0·528 0·751 0·651 0·658 0·7 0·834 0·811 0·85 0·853 0·644 0·86 0·836 
Sample: 08HN-5I 08HN-5J 08HN-5K 08HN-6A 08HN-6B 08HN-6C 08HN-6D 08HN-6F 08HN-7A 08HN-7B 08HN-7D 08HN-7E 08HN-8A 08HN-8B 08HN-9A 08HN-9B  
Rock: Quartz tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Alkali basalt Quartz tholeiite Quartz tholeiite  
Episode:  
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh  
SiO2 51·5 51 51·1 53·2 52·9 52·9 53·3 52·9 52·8 53·1 53·3 53·2 49·6 49·9 52·5 52·9  
TiO2 1·96 1·89 2·22 1·81 1·78 1·8 1·84 1·78 1·77 1·66 1·64 1·66 2·25 2·36 1·71 1·74  
Al2O3 13·9 13·9 13·9 14·4 14·3 14·4 14·5 14·2 14·5 14·5 14·5 14·5 12·8 13·4 14·3 14·5  
CaO 8·77 8·44 8·4 8·36 8·63 8·62 8·24 8·43 8·53 8·71 8·69 8·36 8·31 8·61 8·66 8·38  
Fe2O3T 12·1 12 12·7 12·3 12·4 12·3 12 12·7 12·6 12 11·9 12·1 12·7 12·3 13·2 12·7  
K20·751 0·856 1·09 0·685 0·832 0·814 0·715 0·67 0·507 0·457 0·528 0·52 1·5 1·71 0·453 0·5  
MgO 7·56 8·63 6·86 5·91 5·84 5·94 5·93 5·94 5·86 6·26 6·18 6·43 8·96 7·61 5·97 6·05  
MnO 0·138 0·145 0·133 0·119 0·139 0·135 0·117 0·126 0·132 0·127 0·13 0·127 0·172 0·13 0·131 0·133  
Na22·96 2·88 3·19 3·06 2·88 2·87 3·04 3·17 2·96 2·94 2·9 3·24 3·47 2·91 2·89  
P2O5 0·305 0·333 0·353 0·231 0·224 0·223 0·234 0·227 0·188 0·158 0·158 0·168 0·442 0·48 0·174 0·176  
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100  
LOI 0·736 2·03 0·0101 0·53 0·789 0·672 0·801 0·71 0·49 0·168 0·0128 0·208 −0·181 0·176 0·273 0·233  
Mg# 57·9 61·4 54·3 51·4 50·8 51·5 52·1 50·7 50·6 53·4 53·3 53·8 60·8 57·6 49·8 51·1  
Quartz 0·023 3·76 3·65 3·54 4·14 3·5 2·92 3·83 4·1 4·09 3·44 4·14  
Orthoclase 4·49 5·12 6·54 4·1 4·98 4·87 4·28 4·01 3·03 2·74 3·16 3·11 8·98 10·2 2·71 2·99  
Plagioclase 48·1 47·4 48 50 48·7 49 50·2 49·4 51·3 50·7 50·4 50·3 43·9 45·6 49·8 50·3  
Nepheline 0·186  
Diopside 15·8 14·2 15·7 13·7 14·7 14·5 12·9 14·2 14·5 14·3 14·4 12·7 18·5 19·5 14·6 12·7  
Hypersthene 25·3 22·7 19·3 22·6 22·2 22·4 22·6 23·1 22·6 23·1 22·7 24·4 3·56 23·9 24·2  
Olivine 4·36 3·48 17·8 17  
Magnetite 1·78 1·75 1·87 1·8 1·82 1·81 1·76 1·87 1·85 1·77 1·75 1·78 1·86 1·81 1·95 1·87  
Ilmenite 3·76 3·63 4·28 3·48 3·42 3·45 3·53 3·42 3·41 3·18 3·16 3·2 4·33 4·53 3·28 3·34  
Apatite 0·716 0·781 0·829 0·542 0·526 0·524 0·549 0·533 0·44 0·371 0·371 0·394 1·04 1·13 0·408 0·412  
Sample: 08HN-5I 08HN-5J 08HN-5K 08HN-6A 08HN-6B 08HN-6C 08HN-6D 08HN-6F 08HN-7A 08HN-7B 08HN-7D 08HN-7E 08HN-8A 08HN-8B 08HN-9A 08HN-9B  
Rock: Quartz tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Alkali basalt Quartz tholeiite Quartz tholeiite  
Episode:  
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh  
SiO2 51·5 51 51·1 53·2 52·9 52·9 53·3 52·9 52·8 53·1 53·3 53·2 49·6 49·9 52·5 52·9  
TiO2 1·96 1·89 2·22 1·81 1·78 1·8 1·84 1·78 1·77 1·66 1·64 1·66 2·25 2·36 1·71 1·74  
Al2O3 13·9 13·9 13·9 14·4 14·3 14·4 14·5 14·2 14·5 14·5 14·5 14·5 12·8 13·4 14·3 14·5  
CaO 8·77 8·44 8·4 8·36 8·63 8·62 8·24 8·43 8·53 8·71 8·69 8·36 8·31 8·61 8·66 8·38  
Fe2O3T 12·1 12 12·7 12·3 12·4 12·3 12 12·7 12·6 12 11·9 12·1 12·7 12·3 13·2 12·7  
K20·751 0·856 1·09 0·685 0·832 0·814 0·715 0·67 0·507 0·457 0·528 0·52 1·5 1·71 0·453 0·5  
MgO 7·56 8·63 6·86 5·91 5·84 5·94 5·93 5·94 5·86 6·26 6·18 6·43 8·96 7·61 5·97 6·05  
MnO 0·138 0·145 0·133 0·119 0·139 0·135 0·117 0·126 0·132 0·127 0·13 0·127 0·172 0·13 0·131 0·133  
Na22·96 2·88 3·19 3·06 2·88 2·87 3·04 3·17 2·96 2·94 2·9 3·24 3·47 2·91 2·89  
P2O5 0·305 0·333 0·353 0·231 0·224 0·223 0·234 0·227 0·188 0·158 0·158 0·168 0·442 0·48 0·174 0·176  
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100  
LOI 0·736 2·03 0·0101 0·53 0·789 0·672 0·801 0·71 0·49 0·168 0·0128 0·208 −0·181 0·176 0·273 0·233  
Mg# 57·9 61·4 54·3 51·4 50·8 51·5 52·1 50·7 50·6 53·4 53·3 53·8 60·8 57·6 49·8 51·1  
Quartz 0·023 3·76 3·65 3·54 4·14 3·5 2·92 3·83 4·1 4·09 3·44 4·14  
Orthoclase 4·49 5·12 6·54 4·1 4·98 4·87 4·28 4·01 3·03 2·74 3·16 3·11 8·98 10·2 2·71 2·99  
Plagioclase 48·1 47·4 48 50 48·7 49 50·2 49·4 51·3 50·7 50·4 50·3 43·9 45·6 49·8 50·3  
Nepheline 0·186  
Diopside 15·8 14·2 15·7 13·7 14·7 14·5 12·9 14·2 14·5 14·3 14·4 12·7 18·5 19·5 14·6 12·7  
Hypersthene 25·3 22·7 19·3 22·6 22·2 22·4 22·6 23·1 22·6 23·1 22·7 24·4 3·56 23·9 24·2  
Olivine 4·36 3·48 17·8 17  
Magnetite 1·78 1·75 1·87 1·8 1·82 1·81 1·76 1·87 1·85 1·77 1·75 1·78 1·86 1·81 1·95 1·87  
Ilmenite 3·76 3·63 4·28 3·48 3·42 3·45 3·53 3·42 3·41 3·18 3·16 3·2 4·33 4·53 3·28 3·34  
Apatite 0·716 0·781 0·829 0·542 0·526 0·524 0·549 0·533 0·44 0·371 0·371 0·394 1·04 1·13 0·408 0·412  
Sample: 08HN-9C 08HN-10A 08HN-10B 08HN-10C 08HN-11A 08HN-11B 08HN-12A 08HN-12B 08HN-13A 08HN-13B 08HN-14A 08HN-14B 08HN-15A 08HN-15B 08HN-16A   
Rock: Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Quartz tholeiite Alkali basalt   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Slight Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh   
SiO2 52·9 52·2 52·8 52·8 52·7 52·8 51·1 51·1 51·6 51·7 53·9 53·8 52·8 52·9 51·4   
TiO2 1·75 1·92 1·91 1·96 1·98 1·99 1·9 1·96 1·67 1·67 1·71 1·71 1·65 1·59 2·06   
Al2O3 14·5 13·5 13·7 13·9 13·8 13·9 14 13·9 14·4 14·4 14·8 14·6 14·3 14·3 14·2   
CaO 8·73 9·27 8·26 8·4 9·04 8·97 8·88 7·79 8·19 8·1 6·01 6·2 8·43 8·5 6·86   
Fe2O3T 11·8 11·7 11·8 11·4 11·4 11·2 11·3 11·9 11·7 11·8 10·4 10·4 12·3 12·3 11·3   
K20·58 0·708 0·912 0·969 1·1 1·11 1·63 1·68 1·36 1·35 2·65 2·59 0·584 0·582 2·62   
MgO 7·05 7·19 7·15 6·77 6·78 7·09 7·32 7·09 6·98 5·54 5·83 6·66 6·64 6·69   
MnO 0·126 0·123 0·128 0·13 0·13 0·124 0·1 0·121 0·121 0·13 0·101 0·0992 0·134 0·134 0·11   
Na23·41 2·97 3·08 2·88 2·9 3·56 3·73 3·56 3·56 4·52 4·45 3·01 2·99 4·3   
P2O5 0·176 0·26 0·258 0·264 0·272 0·269 0·391 0·391 0·294 0·293 0·439 0·427 0·172 0·163 0·479   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI 0·195 0·871 0·0156 −0·163 0·533 0·343 1·61 −0·622 −0·17 −0·0149 −0·284 −0·472 −0·324 −0·412 −0·462   
Mg# 52·7 57 57·3 58 56·7 57·2 58 57·4 57·2 56·5 54 55·3 54·4 54·4 56·7   
Quartz 1·61 0·819 1·89 1·46 1·89 2·1 2·59 2·67   
Orthoclase 3·47 5·43 5·46 5·79 6·55 6·6 9·73 10·1 8·13 8·08 15·8 15·5 3·49 3·48 15·6   
Plagioclase 52·1 46·6 47·2 47·8 46·4 46·6 48·2 48·4 50 50·1 51 50·3 49·8 49·7 42·7   
Nepheline 3·3   
Diopside 16·3 19·4 15 15·5 17·9 17·6 19·8 16·4 16·1 15·7 12·2 13·2 14·2 14·5 15·8   
Hypersthene 21 21·7 24·4 23·4 21·2 21 2·39 3·78 10 11·2 2·25 2·12 24·5 24·5   
Olivine 13·6 14·9 10·1 9·32 12·9 13·2 15·8   
Magnetite 1·74 1·72 1·73 1·67 1·67 1·64 1·66 1·75 1·72 1·73 1·52 1·52 1·8 1·8 1·65   
Ilmenite 3·36 3·69 3·68 3·76 3·81 3·82 3·66 3·77 3·21 3·21 3·28 3·27 3·17 3·05 3·96   
Apatite 0·412 0·609 0·605 0·619 0·637 0·63 0·915 0·917 0·688 0·686 1·03 0·999 0·403 0·382 1·12   
Sample: 08HN-9C 08HN-10A 08HN-10B 08HN-10C 08HN-11A 08HN-11B 08HN-12A 08HN-12B 08HN-13A 08HN-13B 08HN-14A 08HN-14B 08HN-15A 08HN-15B 08HN-16A   
Rock: Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Quartz tholeiite Alkali basalt   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Slight Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh   
SiO2 52·9 52·2 52·8 52·8 52·7 52·8 51·1 51·1 51·6 51·7 53·9 53·8 52·8 52·9 51·4   
TiO2 1·75 1·92 1·91 1·96 1·98 1·99 1·9 1·96 1·67 1·67 1·71 1·71 1·65 1·59 2·06   
Al2O3 14·5 13·5 13·7 13·9 13·8 13·9 14 13·9 14·4 14·4 14·8 14·6 14·3 14·3 14·2   
CaO 8·73 9·27 8·26 8·4 9·04 8·97 8·88 7·79 8·19 8·1 6·01 6·2 8·43 8·5 6·86   
Fe2O3T 11·8 11·7 11·8 11·4 11·4 11·2 11·3 11·9 11·7 11·8 10·4 10·4 12·3 12·3 11·3   
K20·58 0·708 0·912 0·969 1·1 1·11 1·63 1·68 1·36 1·35 2·65 2·59 0·584 0·582 2·62   
MgO 7·05 7·19 7·15 6·77 6·78 7·09 7·32 7·09 6·98 5·54 5·83 6·66 6·64 6·69   
MnO 0·126 0·123 0·128 0·13 0·13 0·124 0·1 0·121 0·121 0·13 0·101 0·0992 0·134 0·134 0·11   
Na23·41 2·97 3·08 2·88 2·9 3·56 3·73 3·56 3·56 4·52 4·45 3·01 2·99 4·3   
P2O5 0·176 0·26 0·258 0·264 0·272 0·269 0·391 0·391 0·294 0·293 0·439 0·427 0·172 0·163 0·479   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI 0·195 0·871 0·0156 −0·163 0·533 0·343 1·61 −0·622 −0·17 −0·0149 −0·284 −0·472 −0·324 −0·412 −0·462   
Mg# 52·7 57 57·3 58 56·7 57·2 58 57·4 57·2 56·5 54 55·3 54·4 54·4 56·7   
Quartz 1·61 0·819 1·89 1·46 1·89 2·1 2·59 2·67   
Orthoclase 3·47 5·43 5·46 5·79 6·55 6·6 9·73 10·1 8·13 8·08 15·8 15·5 3·49 3·48 15·6   
Plagioclase 52·1 46·6 47·2 47·8 46·4 46·6 48·2 48·4 50 50·1 51 50·3 49·8 49·7 42·7   
Nepheline 3·3   
Diopside 16·3 19·4 15 15·5 17·9 17·6 19·8 16·4 16·1 15·7 12·2 13·2 14·2 14·5 15·8   
Hypersthene 21 21·7 24·4 23·4 21·2 21 2·39 3·78 10 11·2 2·25 2·12 24·5 24·5   
Olivine 13·6 14·9 10·1 9·32 12·9 13·2 15·8   
Magnetite 1·74 1·72 1·73 1·67 1·67 1·64 1·66 1·75 1·72 1·73 1·52 1·52 1·8 1·8 1·65   
Ilmenite 3·36 3·69 3·68 3·76 3·81 3·82 3·66 3·77 3·21 3·21 3·28 3·27 3·17 3·05 3·96   
Apatite 0·412 0·609 0·605 0·619 0·637 0·63 0·915 0·917 0·688 0·686 1·03 0·999 0·403 0·382 1·12   
Sample: 08HN-16B 08HN-16C 08HN-17A 08HN-17B 08HN-18A 08HN-18B 08HN-18C 08HN-18D 08HN-19A 08HN-19B 08HN-19C 08HN-19D 08HN-20A 08HN-20B 08HN-21A   
Rock: Alkali basalt Alkali basalt Olivine tholeiite Alkali basalt Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Alkali basalt Alkali basalt Alkali basalt Alkali basalt Olivine tholeiite Olivine tholeiite Olivine tholeiite   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh   
SiO2 51·3 51·4 55·7 55·5 52·8 52·8 52·9 52·8 48·1 48·1 48·4 48·4 51 51·1 52·1   
TiO2 2·09 2·04 1·54 1·53 1·63 1·59 1·61 1·62 3·19 3·15 3·16 3·19 2·41 2·43 1·92   
Al2O3 14·2 14·1 15 14·9 14·2 14·3 14·2 14·3 13·1 13 13 13·3 13·6 13·6 14·3   
CaO 7·03 6·94 4·9 4·86 8·48 8·47 8·4 8·46 8·6 8·63 8·68 8·52 8·13 8·06 8·11   
Fe2O3T 11·4 11·3 9·1 9·04 12·5 12·4 12·5 12·4 12·9 12·8 12·8 12·8 12·2 12·2 11·8   
K22·55 2·59 3·46 3·46 0·563 0·524 0·563 0·513 1·91 1·89 1·89 1·95 1·35 1·36 1·22   
MgO 6·8 6·79 4·89 4·96 6·56 6·71 6·62 6·66 8·22 8·22 8·04 7·82 7·46 7·37 6·9   
MnO 0·114 0·113 0·0856 0·0904 0·134 0·126 0·127 0·131 0·159 0·137 0·14 0·155 0·134 0·123 0·127   
Na24·1 4·28 4·89 5·11 2·96 2·95 2·95 2·96 3·19 3·34 3·27 3·3 3·37 3·31 3·27   
P2O5 0·481 0·474 0·494 0·474 0·176 0·166 0·174 0·171 0·661 0·651 0·646 0·677 0·405 0·409 0·315   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI −0·261 −0·541 0·197 −0·00763 0·524 0·361 0·327 0·405 −0·389 −0·513 −0·407 −0·413 −0·401 −0·219 −0·298   
Mg# 56·8 57·1 54·2 54·7 53·6 54·4 53·9 54·2 58·4 58·5 58·1 57·4 57·4 57·1 56·3   
Quartz 2·9 2·9 3·1 2·99   
Orthoclase 15·2 15·5 20·6 20·6 3·37 3·13 3·37 3·07 11·4 11·3 11·3 11·7 8·06 8·14 7·29   
Plagioclase 43·8 42·4 50·4 48·9 49·5 49·7 49·4 49·8 41·2 40 41·2 41·9 47 46·8 48·9   
Nepheline 2·28 3·28 1·29 1·14 2·08 1·17 1·17   
Diopside 15·7 16·3 10·3 11·1 14·3 14 14 13·9 18·7 19·4 19·6 18·4 16·4 15·8 14·5   
Hypersthene 1·07 24·6 25 24·9 24·9 13·2 15·4 21·1   
Olivine 16·2 15·9 12·1 12·7 18 17·7 17·2 17·2 7·99 6·4 2·06   
Magnetite 1·67 1·65 1·33 1·32 1·83 1·82 1·83 1·82 1·89 1·89 1·88 1·88 1·79 1·79 1·73   
Ilmenite 4·01 3·92 2·94 2·94 3·14 3·06 3·09 3·12 6·14 6·05 6·09 6·14 4·64 4·68 3·69   
Apatite 1·13 1·11 1·15 1·11 0·412 0·389 0·408 0·401 1·55 1·53 1·52 1·59 0·95 0·959 0·739   
Sample: 08HN-16B 08HN-16C 08HN-17A 08HN-17B 08HN-18A 08HN-18B 08HN-18C 08HN-18D 08HN-19A 08HN-19B 08HN-19C 08HN-19D 08HN-20A 08HN-20B 08HN-21A   
Rock: Alkali basalt Alkali basalt Olivine tholeiite Alkali basalt Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Alkali basalt Alkali basalt Alkali basalt Alkali basalt Olivine tholeiite Olivine tholeiite Olivine tholeiite   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh   
SiO2 51·3 51·4 55·7 55·5 52·8 52·8 52·9 52·8 48·1 48·1 48·4 48·4 51 51·1 52·1   
TiO2 2·09 2·04 1·54 1·53 1·63 1·59 1·61 1·62 3·19 3·15 3·16 3·19 2·41 2·43 1·92   
Al2O3 14·2 14·1 15 14·9 14·2 14·3 14·2 14·3 13·1 13 13 13·3 13·6 13·6 14·3   
CaO 7·03 6·94 4·9 4·86 8·48 8·47 8·4 8·46 8·6 8·63 8·68 8·52 8·13 8·06 8·11   
Fe2O3T 11·4 11·3 9·1 9·04 12·5 12·4 12·5 12·4 12·9 12·8 12·8 12·8 12·2 12·2 11·8   
K22·55 2·59 3·46 3·46 0·563 0·524 0·563 0·513 1·91 1·89 1·89 1·95 1·35 1·36 1·22   
MgO 6·8 6·79 4·89 4·96 6·56 6·71 6·62 6·66 8·22 8·22 8·04 7·82 7·46 7·37 6·9   
MnO 0·114 0·113 0·0856 0·0904 0·134 0·126 0·127 0·131 0·159 0·137 0·14 0·155 0·134 0·123 0·127   
Na24·1 4·28 4·89 5·11 2·96 2·95 2·95 2·96 3·19 3·34 3·27 3·3 3·37 3·31 3·27   
P2O5 0·481 0·474 0·494 0·474 0·176 0·166 0·174 0·171 0·661 0·651 0·646 0·677 0·405 0·409 0·315   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI −0·261 −0·541 0·197 −0·00763 0·524 0·361 0·327 0·405 −0·389 −0·513 −0·407 −0·413 −0·401 −0·219 −0·298   
Mg# 56·8 57·1 54·2 54·7 53·6 54·4 53·9 54·2 58·4 58·5 58·1 57·4 57·4 57·1 56·3   
Quartz 2·9 2·9 3·1 2·99   
Orthoclase 15·2 15·5 20·6 20·6 3·37 3·13 3·37 3·07 11·4 11·3 11·3 11·7 8·06 8·14 7·29   
Plagioclase 43·8 42·4 50·4 48·9 49·5 49·7 49·4 49·8 41·2 40 41·2 41·9 47 46·8 48·9   
Nepheline 2·28 3·28 1·29 1·14 2·08 1·17 1·17   
Diopside 15·7 16·3 10·3 11·1 14·3 14 14 13·9 18·7 19·4 19·6 18·4 16·4 15·8 14·5   
Hypersthene 1·07 24·6 25 24·9 24·9 13·2 15·4 21·1   
Olivine 16·2 15·9 12·1 12·7 18 17·7 17·2 17·2 7·99 6·4 2·06   
Magnetite 1·67 1·65 1·33 1·32 1·83 1·82 1·83 1·82 1·89 1·89 1·88 1·88 1·79 1·79 1·73   
Ilmenite 4·01 3·92 2·94 2·94 3·14 3·06 3·09 3·12 6·14 6·05 6·09 6·14 4·64 4·68 3·69   
Apatite 1·13 1·11 1·15 1·11 0·412 0·389 0·408 0·401 1·55 1·53 1·52 1·59 0·95 0·959 0·739   
Sample: 08HN-21B 08HN-21C 08HN-21D 08HN-21E 08HN-22A 08HN-22B 08HN-22C 08HN-22D 08HN-23A 08HN-23B 08HN-24A 08HN-24B 08HN-24C 08HN-24D 08HN-25A   
Rock: Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Olivine tholeiite Alkali basalt Alkali basalt Alkali basalt Alkali basalt Olivine tholeiite Alkali basalt Alkali basalt Olivine tholeiite Alkali basalt Olivine tholeiite   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh   
SiO2 51·9 52·2 52·2 53·1 49·3 49·3 49·5 46·6 49·4 49·2 48 47·8 50·6 48 49·8   
TiO2 1·85 1·95 1·96 2·1 2·51 2·5 2·58 2·64 2·6 2·55 2·43 2·41 2·05 2·33 2·1   
Al2O3 14·2 14·2 14·2 14·1 13·4 13·3 13·5 12·9 13·5 13·3 13 13·1 14·2 13·2 13·7   
CaO 8·08 8·02 8·02 8·13 9·03 9·05 9·15 9·85 8·99 9·05 9·5 9·37 8·57 9·47 8·92   
Fe2O3T 12 12 12 11·5 12 11·9 11·8 13·2 12 12 12·3 12·6 12 12·3 12·4   
K21·18 1·22 1·17 1·23 1·92 1·91 1·99 1·67 1·92 1·96 1·59 1·55 1·26 1·51 1·43   
MgO 7·05 6·61 6·67 5·92 8·28 8·25 7·52 9·25 7·8 8·31 9·55 9·78 7·85 9·8 8·18   
MnO 0·126 0·127 0·132 0·119 0·137 0·136 0·133 0·161 0·142 0·138 0·144 0·147 0·129 0·145 0·149   
Na23·3 3·34 3·32 3·42 3·01 3·15 3·27 3·05 3·18 2·94 2·98 2·85 2·86 2·73   
P2O5 0·312 0·333 0·333 0·358 0·493 0·493 0·506 0·625 0·519 0·511 0·473 0·443 0·356 0·441 0·354   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI −0·537 −0·262 −0·264 0·65 −0·389 −0·559 −0·607 −0·617 −0·52 −0·183 −0·623 −0·393 0·122 −0·155 −0·21   
Mg# 56·5 54·8 55·1 53·1 60·4 60·5 58·3 60·6 59 60·4 63 63·1 59 63·7 59·2   
Quartz 1·43   
Orthoclase 7·03 7·29 6·99 7·36 11·5 11·4 11·9 10 11·5 11·7 9·53 9·26 7·56 9·04 8·56   
Plagioclase 49·1 48·9 49 49·1 43·3 42·4 42·3 34·2 43·6 42·7 39·3 40·2 47 42·1 45·6   
Nepheline 0·745 1·23 4·8 0·308 2·12 1·48 0·467   
Diopside 14·5 14·6 14·4 15·4 20 20·6 21·3 23·2 20·2 20 21·8 20·8 14·8 20·4 18·4   
Hypersthene 20 21·9 22·8 20·2 0·094 0·748 18·1 7·02   
Olivine 3·4 1·06 0·587 17·4 17·1 15·4 19·3 16·4 17 19·6 20·7 5·98 20·7 13·7   
Magnetite 1·75 1·76 1·76 1·69 1·76 1·74 1·74 1·94 1·75 1·76 1·81 1·85 1·77 1·81 1·82   
Ilmenite 3·56 3·74 3·76 4·03 4·83 4·81 4·96 5·08 4·91 4·67 4·64 3·93 4·49 4·04   
Apatite 0·732 0·781 0·781 0·839 1·16 1·16 1·19 1·47 1·22 1·2 1·11 1·04 0·834 1·03 0·829   
Sample: 08HN-21B 08HN-21C 08HN-21D 08HN-21E 08HN-22A 08HN-22B 08HN-22C 08HN-22D 08HN-23A 08HN-23B 08HN-24A 08HN-24B 08HN-24C 08HN-24D 08HN-25A   
Rock: Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Olivine tholeiite Alkali basalt Alkali basalt Alkali basalt Alkali basalt Olivine tholeiite Alkali basalt Alkali basalt Olivine tholeiite Alkali basalt Olivine tholeiite   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh Fresh   
SiO2 51·9 52·2 52·2 53·1 49·3 49·3 49·5 46·6 49·4 49·2 48 47·8 50·6 48 49·8   
TiO2 1·85 1·95 1·96 2·1 2·51 2·5 2·58 2·64 2·6 2·55 2·43 2·41 2·05 2·33 2·1   
Al2O3 14·2 14·2 14·2 14·1 13·4 13·3 13·5 12·9 13·5 13·3 13 13·1 14·2 13·2 13·7   
CaO 8·08 8·02 8·02 8·13 9·03 9·05 9·15 9·85 8·99 9·05 9·5 9·37 8·57 9·47 8·92   
Fe2O3T 12 12 12 11·5 12 11·9 11·8 13·2 12 12 12·3 12·6 12 12·3 12·4   
K21·18 1·22 1·17 1·23 1·92 1·91 1·99 1·67 1·92 1·96 1·59 1·55 1·26 1·51 1·43   
MgO 7·05 6·61 6·67 5·92 8·28 8·25 7·52 9·25 7·8 8·31 9·55 9·78 7·85 9·8 8·18   
MnO 0·126 0·127 0·132 0·119 0·137 0·136 0·133 0·161 0·142 0·138 0·144 0·147 0·129 0·145 0·149   
Na23·3 3·34 3·32 3·42 3·01 3·15 3·27 3·05 3·18 2·94 2·98 2·85 2·86 2·73   
P2O5 0·312 0·333 0·333 0·358 0·493 0·493 0·506 0·625 0·519 0·511 0·473 0·443 0·356 0·441 0·354   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI −0·537 −0·262 −0·264 0·65 −0·389 −0·559 −0·607 −0·617 −0·52 −0·183 −0·623 −0·393 0·122 −0·155 −0·21   
Mg# 56·5 54·8 55·1 53·1 60·4 60·5 58·3 60·6 59 60·4 63 63·1 59 63·7 59·2   
Quartz 1·43   
Orthoclase 7·03 7·29 6·99 7·36 11·5 11·4 11·9 10 11·5 11·7 9·53 9·26 7·56 9·04 8·56   
Plagioclase 49·1 48·9 49 49·1 43·3 42·4 42·3 34·2 43·6 42·7 39·3 40·2 47 42·1 45·6   
Nepheline 0·745 1·23 4·8 0·308 2·12 1·48 0·467   
Diopside 14·5 14·6 14·4 15·4 20 20·6 21·3 23·2 20·2 20 21·8 20·8 14·8 20·4 18·4   
Hypersthene 20 21·9 22·8 20·2 0·094 0·748 18·1 7·02   
Olivine 3·4 1·06 0·587 17·4 17·1 15·4 19·3 16·4 17 19·6 20·7 5·98 20·7 13·7   
Magnetite 1·75 1·76 1·76 1·69 1·76 1·74 1·74 1·94 1·75 1·76 1·81 1·85 1·77 1·81 1·82   
Ilmenite 3·56 3·74 3·76 4·03 4·83 4·81 4·96 5·08 4·91 4·67 4·64 3·93 4·49 4·04   
Apatite 0·732 0·781 0·781 0·839 1·16 1·16 1·19 1·47 1·22 1·2 1·11 1·04 0·834 1·03 0·829   
Sample: 08HN-25B 08HN-25C 08HN-26A 08HN-26B 08HN-26C 08HN-26D ZK03-18.1 ZK03-20.1 ZK03-24.4 ZK03-25 ZK03-27 ZK03-27·5 ZK03-29.1 ZK03-30 ZK03-31   
Rock: Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Quartz tholeiite Basanite Basanite Basanite Alkali basalt Alkali basalt Olivine tholeiite Basanite   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Slight Slight Slight Slight Slight Slight Slight Slight Moderate   
SiO2 50 50·3 51·2 51·2 51·4 51·4 52·4 52·4 46·1 46·1 46·8 46·7 46·2 46·7 45·9   
TiO2 2·11 2·06 2·13 2·28 2·15 2·18 1·86 1·95 2·51 2·56 2·72 2·62 2·68 2·75 2·66   
Al2O3 13·8 13·9 14·1 14 14·2 14·1 14·1 13·9 13·2 13·1 13·9 13·4 13·4 13·7 13·1   
CaO 8·61 8·52 8·95 8·8 8·93 8·91 8·88 8·7 9·88 10·1 10·3 10·3 10·4 10·5 10·1   
Fe2O3T 12·6 12·5 11·6 11·8 11·5 11·6 12·4 11·7 13·7 13·6 14·7 13·7 13·6 14·8 14·1   
K21·28 1·2 1·34 1·37 1·35 1·37 0·511 0·877 2·01 1·93 1·46 1·48 1·83 2·14 2·16   
MgO 8·12 8·11 7·08 6·81 6·88 6·85 6·68 7·03 7·57 7·91 6·62 7·32 7·38 5·54   
MnO 0·135 0·138 0·129 0·132 0·129 0·13 0·101 0·147 0·192 0·194 0·18 0·217 0·18 0·176 0·271   
Na23·05 3·2 3·25 3·2 3·22 2·81 3·06 3·74 3·27 2·02 2·93 3·02 2·2 3·46   
P2O5 0·356 0·345 0·349 0·362 0·351 0·359 0·259 0·285 1·21 1·22 1·3 1·23 1·34 1·39 1·32   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI −0·155 −0·256 −0·421 −0·613 −0·4 −0·513 2·17 1·22 1·29 2·34 2·15 2·88 2·64 2·93 4·68   
Mg# 58·7 58·8 57·4 56·1 56·9 56·6 54·3 57 55 56·2 49·8 54 54·5 45·1 52·3   
Quartz 3·21 1·14   
Orthoclase 7·65 7·17 7·99 8·22 8·05 8·17 3·06 5·24 12 11·6 8·76 8·84 11 12·9 12·9   
Plagioclase 46·5 46·8 47·7 47·7 47·9 47·7 48·8 48 29·5 32·8 42·2 42·5 36·9 40·4 30·1   
Nepheline 8·63 5·9 1·07 3·66 7·44   
Diopside 16·8 15·8 18·3 17·9 18 18·2 15 16·3 23·2 22·2 15·1 20·1 21·1 18·5 22·8   
Hypersthene 10·4 14 12·9 13·4 14·3 13·9 23·9 23·1 17·1 6·28   
Olivine 11·9 9·56 6·5 5·78 5·12 5·34 16·9 17·7 6·36 17·5 17·1 11·2 16·4   
Magnetite 1·85 1·83 1·7 1·72 1·68 1·7 1·82 1·71 2·01 1·99 2·16 2·02 2·18 2·07   
Ilmenite 4·06 3·96 4·1 4·38 4·14 4·2 3·58 3·75 4·83 4·92 5·25 5·05 5·17 5·31 5·12   
Apatite 0·834 0·809 0·818 0·848 0·822 0·841 0·607 0·667 2·85 2·87 3·06 2·88 3·14 3·27 3·11   
Sample: 08HN-25B 08HN-25C 08HN-26A 08HN-26B 08HN-26C 08HN-26D ZK03-18.1 ZK03-20.1 ZK03-24.4 ZK03-25 ZK03-27 ZK03-27·5 ZK03-29.1 ZK03-30 ZK03-31   
Rock: Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Olivine tholeiite Quartz tholeiite Quartz tholeiite Basanite Basanite Basanite Alkali basalt Alkali basalt Olivine tholeiite Basanite   
Episode:   
Alteration: Fresh Fresh Fresh Fresh Fresh Fresh Slight Slight Slight Slight Slight Slight Slight Slight Moderate   
SiO2 50 50·3 51·2 51·2 51·4 51·4 52·4 52·4 46·1 46·1 46·8 46·7 46·2 46·7 45·9   
TiO2 2·11 2·06 2·13 2·28 2·15 2·18 1·86 1·95 2·51 2·56 2·72 2·62 2·68 2·75 2·66   
Al2O3 13·8 13·9 14·1 14 14·2 14·1 14·1 13·9 13·2 13·1 13·9 13·4 13·4 13·7 13·1   
CaO 8·61 8·52 8·95 8·8 8·93 8·91 8·88 8·7 9·88 10·1 10·3 10·3 10·4 10·5 10·1   
Fe2O3T 12·6 12·5 11·6 11·8 11·5 11·6 12·4 11·7 13·7 13·6 14·7 13·7 13·6 14·8 14·1   
K21·28 1·2 1·34 1·37 1·35 1·37 0·511 0·877 2·01 1·93 1·46 1·48 1·83 2·14 2·16   
MgO 8·12 8·11 7·08 6·81 6·88 6·85 6·68 7·03 7·57 7·91 6·62 7·32 7·38 5·54   
MnO 0·135 0·138 0·129 0·132 0·129 0·13 0·101 0·147 0·192 0·194 0·18 0·217 0·18 0·176 0·271   
Na23·05 3·2 3·25 3·2 3·22 2·81 3·06 3·74 3·27 2·02 2·93 3·02 2·2 3·46   
P2O5 0·356 0·345 0·349 0·362 0·351 0·359 0·259 0·285 1·21 1·22 1·3 1·23 1·34 1·39 1·32   
Total 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100   
LOI −0·155 −0·256 −0·421 −0·613 −0·4 −0·513 2·17 1·22 1·29 2·34 2·15 2·88 2·64 2·93 4·68   
Mg# 58·7 58·8 57·4 56·1 56·9 56·6 54·3 57 55 56·2 49·8 54 54·5 45·1 52·3   
Quartz 3·21 1·14   
Orthoclase 7·65 7·17 7·99 8·22 8·05 8·17 3·06 5·24 12 11·6 8·76 8·84 11 12·9 12·9   
Plagioclase 46·5 46·8 47·7 47·7 47·9 47·7 48·8 48 29·5 32·8 42·2 42·5 36·9 40·4 30·1   
Nepheline 8·63 5·9 1·07 3·66 7·44   
Diopside 16·8 15·8 18·3 17·9 18 18·2 15 16·3 23·2 22·2 15·1 20·1 21·1 18·5 22·8   
Hypersthene 10·4 14 12·9 13·4 14·3 13·9 23·9 23·1 17·1 6·28   
Olivine 11·9 9·56 6·5 5·78 5·12 5·34 16·9 17·7 6·36 17·5 17·1 11·2 16·4   
Magnetite 1·85 1·83 1·7 1·72 1·68 1·7 1·82 1·71 2·01 1·99 2·16 2·02 2·18 2·07   
Ilmenite 4·06 3·96 4·1 4·38 4·14 4·2 3·58 3·75 4·83 4·92 5·25 5·05 5·17 5·31 5·12   
Apatite 0·834 0·809 0·818 0·848 0·822 0·841 0·607 0·667 2·85 2·87 3·06 2·88 3·14 3·27 3·11   
Sample: ZK04-10.5 ZK04-26.8 ZK04-30.7 ZK04-9.2 ZK05-20.1 ZK05-22.3 ZK05-25.4 ZK05-28.1 ZK05-32.1 ZK05-33.6 ZK05-36.5       
Rock: Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Quartz tholeiite       
Episode:       
Alteration: Slight Moderate Moderate Slight Slight Slight Slight Slight Slight Slight Severe       
SiO2 52·8 52·9 54·2 52·7 51·8 52 51·6 51·6 50·9 49·4 47·5       
TiO2 1·93 1·91 2·73 1·88 1·81 1·97 1·92 1·89 1·96 1·99 2·14       
Al2O3 13·9 14·3 19·8 13·9 14·1 14 13·8 14·1 14·4 14·6 15·4       
CaO 9·05 11·5 8·29 8·97 9·06 9·01 8·95 9·18 8·75 8·41 10·344       
Fe2O3T 12·1 11·4 8·63 11·8 11·8 11·8 12·1 11·6 12·3 13·7 14·1       
K20·767 0·833 0·388 0·731 0·434 0·618 0·397 0·314 0·451 0·416 0·302       
MgO 5·97 4·83 1·86 6·53 7·77 7·13 8·09 8·07 8·07 8·56 7·4       
MnO 0·156 0·187 0·134 0·135 0·12 0·124 0·125 0·134 0·129 0·133 0·360       
Na23·14 2·96 3·5 3·09 2·81 2·98 2·73 2·76 2·74 2·54 2·24       
P2O5 0·25 0·262 0·465 0·237 0·276 0·3 0·311 0·307 0·311 0·292 0·36       
Total 100 100 100 100 100 100 100 100 100 100 100       
LOI 2·43 4·21 3·66 1·63 1·52 1·57 1·05 1·95 2·59 2·79 8·64       
Mg# 52·1 50·6 32·2 54·8 59·2 57 59·6 60·4 59 57·8 53·7       
Quartz 2·36 3·06 9·87 1·99 1·36 1·4 1·43 1·43 0·254       
Orthoclase 4·59 4·98 2·31 4·37 2·59 3·69 2·38 1·88 2·7 2·49 1·97       
Plagioclase 48·6 48·8 67·4 48·6 49 48·9 47·9 49·1 49·4 49·2 50·5       
Nepheline       
Diopside 18·2 26·7 0·755 17·5 15·3 16·3 15 15·2 13·1 10·6 15·1       
Hypersthene 20·1 10·6 12·1 21·6 25·9 23·5 27·1 26·4 28·2 27·1 17·9       
Olivine 4·05 7·38       
Magnetite 1·78 1·52 1·26 1·74 1·73 1·73 1·77 1·71 1·81 2·02 2·07       
Ilmenite 3·71 3·67 5·23 3·61 3·48 3·8 3·7 3·63 3·77 3·82 4·13       
Apatite 0·586 0·614 1·09 0·556 0·646 0·704 0·73 0·721 0·73 0·686 0·843       
Sample: ZK04-10.5 ZK04-26.8 ZK04-30.7 ZK04-9.2 ZK05-20.1 ZK05-22.3 ZK05-25.4 ZK05-28.1 ZK05-32.1 ZK05-33.6 ZK05-36.5       
Rock: Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Quartz tholeiite Olivine tholeiite Quartz tholeiite       
Episode:       
Alteration: Slight Moderate Moderate Slight Slight Slight Slight Slight Slight Slight Severe       
SiO2 52·8 52·9 54·2 52·7 51·8 52 51·6 51·6 50·9 49·4 47·5       
TiO2 1·93 1·91 2·73 1·88 1·81 1·97 1·92 1·89 1·96 1·99 2·14       
Al2O3 13·9 14·3 19·8 13·9 14·1 14 13·8 14·1 14·4 14·6 15·4       
CaO 9·05 11·5 8·29 8·97 9·06 9·01 8·95 9·18 8·75 8·41 10·344       
Fe2O3T 12·1 11·4 8·63 11·8 11·8 11·8 12·1 11·6 12·3 13·7 14·1       
K20·767 0·833 0·388 0·731 0·434 0·618 0·397 0·314 0·451 0·416 0·302       
MgO 5·97 4·83 1·86 6·53 7·77 7·13 8·09 8·07 8·07 8·56 7·4       
MnO 0·156 0·187 0·134 0·135 0·12 0·124 0·125 0·134 0·129 0·133 0·360       
Na23·14 2·96 3·5 3·09 2·81 2·98 2·73 2·76 2·74 2·54 2·24       
P2O5 0·25 0·262 0·465 0·237 0·276 0·3 0·311 0·307 0·311 0·292 0·36       
Total 100 100 100 100 100 100 100 100 100 100 100       
LOI 2·43 4·21 3·66 1·63 1·52 1·57 1·05 1·95 2·59 2·79 8·64       
Mg# 52·1 50·6 32·2 54·8 59·2 57 59·6 60·4 59 57·8 53·7       
Quartz 2·36 3·06 9·87 1·99 1·36 1·4 1·43 1·43 0·254       
Orthoclase 4·59 4·98 2·31 4·37 2·59 3·69 2·38 1·88 2·7 2·49 1·97       
Plagioclase 48·6 48·8 67·4 48·6 49 48·9 47·9 49·1 49·4 49·2 50·5       
Nepheline       
Diopside 18·2 26·7 0·755 17·5 15·3 16·3 15 15·2 13·1 10·6 15·1       
Hypersthene 20·1 10·6 12·1 21·6 25·9 23·5 27·1 26·4 28·2 27·1 17·9       
Olivine 4·05 7·38       
Magnetite 1·78 1·52 1·26 1·74 1·73 1·73 1·77 1·71 1·81 2·02 2·07       
Ilmenite 3·71 3·67 5·23 3·61 3·48 3·8 3·7 3·63 3·77 3·82 4·13       
Apatite 0·586 0·614 1·09 0·556 0·646 0·704 0·73 0·721 0·73 0·686 0·843       

Mg# = Mg/(Mg + Fe2+), assuming Fe3+/Fetotal = 0·10, cation ratio. Fe2O3T, total iron as Fe2O3. Episodes: 1, Pliocene–Miocene (Shimengou and Shimacun volcanism); 2, early to middle Pleistocene (Duowen volcanism); 3, middle Pleistocene (Dongying volcanism); 4, late Pleistocene (Daotang volcanism); 5, Holocene (Shishan volcanism). The distribution of the episodic volcanism is shown in Fig. 1b.

Bulk-rock major and trace element compositions

Most studied samples have low LOI values (<1· 0 wt %) and insignificant secondary minerals, indicating that these samples are fresh. Only four drilling core samples (ZK03-31, ZK04-30.7, ZK04-10.5, and ZK05-36.5) have LOI values >3 wt %. Bulk-rock chemical compositions of the Hainan basalts are listed in Tables 2 and 3. All the samples have <56 wt % SiO2. A distinctive compositional feature of the Hainan basalts is the broad scatter in SiO2, FeOT, CaO, TiO2, and K2O. The total alkali contents (Na2O + K2O) of the basalts are higher than 2·6 wt % and the Na2O/K2O ratios of all basalts studied are more than unity (mostly >2), indicating their alkali-enriched and high-sodium nature. Most of the studied samples are silica-saturated with SiO2 >50 wt %. Forty-one samples contain normative quartz (Table 2). CIPW-normative compositions of the studied samples span the range from quartz tholeiite (QT) (quartz-normative), olivine tholeiite (OT) (olivine + hypersthene) to alkali basalt (AB) (nepheline <5%), with tholeiite being the dominant rock type and alkali basalts subordinate (Fig. 3a; Table 2). Only three samples (ZK03-25, ZK03-31 and ZK03-24-4) contain >5% nepheline and were classified as basanite (e.g. Flower et al., 1992). On a total alkalis–silica (TAS) diagram (Fig. 3b), the samples plot predominantly within the sub-alkaline field, with the alkaline series field being subordinate. For the alkaline series, the total alkalis increase with increasing SiO2, and two samples with high SiO2 (55·6–55·7%) and Na2O + K2O (8·3–8·6%) plot into the trachyandesite field (Fig. 3b).

Fig. 3.

(a) CIPW normative compositions of the Hainan basalts. Norms were calculated assuming Fe2+/Fetotal = 0·9. The 1 atm and 9 (±1·5) kbar cotectics are from Thompson (1983) and Thompson et al. (2001). Arrows point in the direction of decreasing temperature. (b) Total alkalis vs SiO2 diagram (Middlemost, 1994) for the classification of the Hainan basalts.

Fig. 3.

(a) CIPW normative compositions of the Hainan basalts. Norms were calculated assuming Fe2+/Fetotal = 0·9. The 1 atm and 9 (±1·5) kbar cotectics are from Thompson (1983) and Thompson et al. (2001). Arrows point in the direction of decreasing temperature. (b) Total alkalis vs SiO2 diagram (Middlemost, 1994) for the classification of the Hainan basalts.

Table 3:

Trace element concentrations (in ppm) of the Hainan basalts

Sample: 08HN-1A 08HN-2A 08HN-2B 08HN-3 08HN-4B 08HN-4C 08HN-4D 08HN-5C 08HN-5D  
Sc 16·7 17·9 16·8 20 20·4 21·4 21 20·8 20·1  
Ti 13542 16400 14780 14480 10824 12572 10830 11080 10824  
135 156 144 159 142 154 142 150 154  
Cr 373 284 248 314 273 207 386 214 196  
Mn 1107 1197 1118 1161 1028 1048 1190 1094 1120  
Co 48·7 50·5 47 55·9 43·7 40·5 49·5 41·6 43·3  
Ni 315 268 248 307 191 168 310 156 162  
Cu 37·7 47·8 41·2 51·4 60·6 66·4 53·3 56·6 57·7  
Zn 130 140 125 120 113 114 104 105 109  
Ga 20·6 21·6 20·3 19·5 18·5 19·8 17·2 18·5 18·8  
Ge 1·57 1·46 1·48 1·58 1·66 1·52 1·48 1·52 1·46  
Rb 33·8 50 50·1 26·4 15·8 13·4 6·44 15·9 21·9  
Sr 602 764 906 587 318 382 388 391 429  
22·8 23 23·2 20·3 17·1 19·9 16·6 19 20·5  
Zr 255 264 260 189 106 138 115 126 138  
Nb 55·6 61·2 58·8 41·7 18·1 27 23·9 29·6 31·2  
Ba 497 626 870 424 185 221 231 284 339  
La 38·1 39·7 40·3 26·7 12·4 18 17·4 21 22·7  
Ce 78·4 81·8 82 55·1 25·6 36·3 34·6 41·6 45·2  
Pr 9·64 10·2 10·2 7·11 3·27 4·5 4·22 5·43  
Nd 37·6 41 41·2 29·7 14·2 19·1 17·2 20·2 22·1  
Sm 7·87 8·76 8·62 6·72 3·86 4·71 4·08 4·8 5·12  
Eu 2·52 2·87 2·85 2·26 1·44 1·75 1·52 1·7 1·78  
Gd 7·01 7·94 7·57 6·35 4·25 5·13 4·33 5·15 5·29  
Tb 1·06 1·1 1·05 0·895 0·687 0·767 0·678 0·826 0·823  
Dy 5·07 5·52 5·4 4·49 3·83 4·11 3·68 4·38 4·44  
Ho 0·885 0·933 0·898 0·779 0·693 0·735 0·653 0·76 0·816  
Er 2·07 2·22 2·12 1·86 1·78 1·86 1·58 1·96 2·01  
Tm 0·267 0·269 0·266 0·244 0·224 0·237 0·207 0·255 0·257  
Yb 1·46 1·53 1·56 1·42 1·31 1·39 1·23 1·49 1·51  
Lu 0·2 0·207 0·218 0·209 0·192 0·199 0·181 0·214 0·222  
Hf 5·85 6·23 6·25 4·55 2·76 3·41 2·96 3·25 3·34  
Ta 3·6 4·18 3·98 2·81 1·13 1·57 1·5 1·74 1·84  
Pb 5·14 2·69 2·4 1·88 5·45 1·34 1·57 4·43 1·61  
Th 5·03 5·2 5·2 3·65 1·85 2·8 2·61 3·04 3·51  
1·2 1·26 1·28 0·895 0·426 0·594 0·572 0·647 0·74  
Sr* 0·815 0·97 1·15 1·07 1·22 1·07 1·17 0·99 0·998  
Fe/Mn1 79 76·5 80·7 80·7 79·6 76·8 69·9 75·4 74·3  
Fe/Mn2 79 77·3 81·5 81·6 80·4 77·7 70·6 76·3 74·9  
Fe/Mn3 83·6 85·7 83·8 85·2 85·2 83·8 72·6 79·5 79  
Zr/Hf 43·6 42·3 41·6 41·6 38·3 40·4 39 38·6 41·3  
Nb/Ta 15·4 14·6 14·8 14·9 16 17·3 15·9 17·1 17  
Lu/Hf 0·034 0·033 0·035 0·046 0·07 0·058 0·061 0·066 0·067  
Sm/Nd 0·209 0·214 0·209 0·226 0·272 0·246 0·237 0·237 0·232  
Sample: 08HN-1A 08HN-2A 08HN-2B 08HN-3 08HN-4B 08HN-4C 08HN-4D 08HN-5C 08HN-5D  
Sc 16·7 17·9 16·8 20 20·4 21·4 21 20·8 20·1  
Ti 13542 16400 14780 14480 10824 12572 10830 11080 10824  
135 156 144 159 142 154 142 150 154  
Cr 373 284 248 314 273 207 386 214 196  
Mn 1107 1197 1118 1161 1028 1048 1190 1094 1120  
Co 48·7 50·5 47 55·9 43·7 40·5 49·5 41·6 43·3  
Ni 315 268 248 307 191 168 310 156 162  
Cu 37·7 47·8 41·2 51·4 60·6 66·4 53·3 56·6 57·7  
Zn 130 140 125 120 113 114 104 105 109  
Ga 20·6 21·6 20·3 19·5 18·5 19·8 17·2 18·5 18·8  
Ge 1·57 1·46 1·48 1·58 1·66 1·52 1·48 1·52 1·46  
Rb 33·8 50 50·1 26·4 15·8 13·4 6·44 15·9 21·9  
Sr 602 764 906 587 318 382 388 391 429  
22·8 23 23·2 20·3 17·1 19·9 16·6 19 20·5  
Zr 255 264 260 189 106 138 115 126 138  
Nb 55·6 61·2 58·8 41·7 18·1 27 23·9 29·6 31·2  
Ba 497 626 870 424 185 221 231 284 339  
La 38·1 39·7 40·3 26·7 12·4 18 17·4 21 22·7  
Ce 78·4 81·8 82 55·1 25·6 36·3 34·6 41·6 45·2  
Pr 9·64 10·2 10·2 7·11 3·27 4·5 4·22 5·43  
Nd 37·6 41 41·2 29·7 14·2 19·1 17·2 20·2 22·1  
Sm 7·87 8·76 8·62 6·72 3·86 4·71 4·08 4·8 5·12  
Eu 2·52 2·87 2·85 2·26 1·44 1·75 1·52 1·7 1·78  
Gd 7·01 7·94 7·57 6·35 4·25 5·13 4·33 5·15 5·29  
Tb 1·06 1·1 1·05 0·895 0·687 0·767 0·678 0·826 0·823  
Dy 5·07 5·52 5·4 4·49 3·83 4·11 3·68 4·38 4·44  
Ho 0·885 0·933 0·898 0·779 0·693 0·735 0·653 0·76 0·816  
Er 2·07 2·22 2·12 1·86 1·78 1·86 1·58 1·96 2·01  
Tm 0·267 0·269 0·266 0·244 0·224 0·237 0·207 0·255 0·257  
Yb 1·46 1·53 1·56 1·42 1·31 1·39 1·23 1·49 1·51  
Lu 0·2 0·207 0·218 0·209 0·192 0·199 0·181 0·214 0·222  
Hf 5·85 6·23 6·25 4·55 2·76 3·41 2·96 3·25 3·34  
Ta 3·6 4·18 3·98 2·81 1·13 1·57 1·5 1·74 1·84  
Pb 5·14 2·69 2·4 1·88 5·45 1·34 1·57 4·43 1·61  
Th 5·03 5·2 5·2 3·65 1·85 2·8 2·61 3·04 3·51  
1·2 1·26 1·28 0·895 0·426 0·594 0·572 0·647 0·74  
Sr* 0·815 0·97 1·15 1·07 1·22 1·07 1·17 0·99 0·998  
Fe/Mn1 79 76·5 80·7 80·7 79·6 76·8 69·9 75·4 74·3  
Fe/Mn2 79 77·3 81·5 81·6 80·4 77·7 70·6 76·3 74·9  
Fe/Mn3 83·6 85·7 83·8 85·2 85·2 83·8 72·6 79·5 79  
Zr/Hf 43·6 42·3 41·6 41·6 38·3 40·4 39 38·6 41·3  
Nb/Ta 15·4 14·6 14·8 14·9 16 17·3 15·9 17·1 17  
Lu/Hf 0·034 0·033 0·035 0·046 0·07 0·058 0·061 0·066 0·067  
Sm/Nd 0·209 0·214 0·209 0·226 0·272 0·246 0·237 0·237 0·232  
Sample: 08HN-5E 08HN-5F 08HN-5I 08HN-5J 08HN-5K 08HN-6A 08HN-6C 08HN-6D 08HN-7B 08HN-7E 
Sc 20·9 20·9 22·3 20·5 22 20·3 21·4 20·2 22·2 21·3 
Ti 11010 11072 11648 10355 12152 10547 10554 10180 9699 9375 
175 146 152 140 161 141 144 136 142 133 
Cr 209 200 196 214 171 138 150 154 167 170 
Mn 1102 1078 1152 1235 1082 960 1153 940 1028 1079 
Co 43·2 41·9 40·2 45 41·5 38·9 41 39·4 41·6 43·2 
Ni 162 152 145 176 134 95·2 98·9 96·5 99·5 102 
Cu 58·4 64·3 60·6 59·6 65 53·4 55·6 40·4 51·9 51 
Zn 108 109 109 108 123 111 112 116 109 107 
Ga 18·7 19·2 19·2 18·7 19·8 19·6 19·9 20·5 19·8 19·3 
Ge 1·47 1·52 1·49 1·58 1·57 1·47 1·46 1·62 1·65 1·42 
Rb 17·7 12·1 14·3 11·6 23·5 8·98 12·4 9·92 6·44 7·07 
Sr 431 350 387 380 367 310 327 325 268 209 
20·2 19·7 20·3 19·4 22·1 17 16·6 17·3 17·4 16·4 
Zr 135 116 124 125 146 111 110 117 90·6 90·4 
Nb 31 20·7 25 28·5 28·6 14·6 14·6 15·7 9·69 10·1 
Ba 335 205 228 292 239 145 136 151 81·8 93·9 
La 22·6 15·7 18 20·4 20·1 11·3 11·3 11·7 8·19 8·44 
Ce 45 31·8 36·4 40·8 40·8 24·2 24·7 25·7 17·6 18·5 
Pr 5·49 3·98 4·59 4·98 5·12 3·23 3·3 3·36 2·56 2·71 
Nd 21·7 16·9 18·4 20·3 21·3 14·4 14·5 14·6 12·2 12·7 
Sm 4·96 4·46 4·57 4·77 5·07 3·97 3·97 4·04 3·56 3·71 
Eu 1·7 1·57 1·68 1·64 1·7 1·46 1·48 1·53 1·36 1·44 
Gd 5·25 4·81 5·05 4·87 5·49 4·32 4·27 4·43 4·1 4·15 
Tb 0·83 0·782 0·8 0·773 0·887 0·716 0·708 0·702 0·678 0·678 
Dy 4·46 4·27 4·3 4·16 4·74 3·91 3·79 3·75 3·81 3·72 
Ho 0·801 0·779 0·77 0·772 0·874 0·715 0·687 0·672 0·708 0·699 
Er 1·97 1·92 1·96 1·9 2·14 1·79 1·73 1·62 1·77 1·72 
Tm 0·274 0·263 0·269 0·253 0·283 0·238 0·228 0·228 0·233 0·229 
Yb 1·53 1·5 1·54 1·52 1·7 1·39 1·33 1·29 1·38 1·34 
Lu 0·22 0·222 0·218 0·225 0·24 0·205 0·188 0·2 0·197 0·2 
Hf 3·33 3·21 3·17 3·27 3·82 3·08 2·93 3·04 2·56 2·54 
Ta 1·8 1·28 1·5 1·7 1·8 0·957 0·912 0·934 0·609 0·63 
Pb 2·43 1·56 1·57 1·54 2·22 1·26 1·51 1·69 1·24 0·891 
Th 3·39 2·38 2·78 3·15 3·13 1·55 1·54 1·6 0·983 1·04 
0·694 0·505 0·57 0·633 0·657 0·351 0·376 0·37 0·225 0·26 
Sr* 1·01 1·11 1·1 0·97 0·916 1·22 1·27 1·23 1·35 
Fe/Mn1 74·3 75·9 72·8 66·3 82·1 88·9 74 88·5 81·6 78·4 
Fe/Mn2 74·9 76·9 73·5 67·7 82·3 89·5 74·6 89·4 81·9 78·7 
Fe/Mn3 78·9 79·5 79·1 74·4 86·2 93·4 82·2 92·7 85·3 86·1 
Zr/Hf 40·6 36 39·2 38·2 38·3 36 37·7 38·6 35·3 35·5 
Nb/Ta 17·2 16·1 16·7 16·7 16 15·3 16 16·8 15·9 16·1 
Lu/Hf 0·066 0·069 0·069 0·069 0·063 0·067 0·064 0·066 0·077 0·079 
Sm/Nd 0·229 0·264 0·248 0·235 0·238 0·276 0·273 0·278 0·293 0·293 
Sample: 08HN-5E 08HN-5F 08HN-5I 08HN-5J 08HN-5K 08HN-6A 08HN-6C 08HN-6D 08HN-7B 08HN-7E 
Sc 20·9 20·9 22·3 20·5 22 20·3 21·4 20·2 22·2 21·3 
Ti 11010 11072 11648 10355 12152 10547 10554 10180 9699 9375 
175 146 152 140 161 141 144 136 142 133 
Cr 209 200 196 214 171 138 150 154 167 170 
Mn 1102 1078 1152 1235 1082 960 1153 940 1028 1079 
Co 43·2 41·9 40·2 45 41·5 38·9 41 39·4 41·6 43·2 
Ni 162 152 145 176 134 95·2 98·9 96·5 99·5 102 
Cu 58·4 64·3 60·6 59·6 65 53·4 55·6 40·4 51·9 51 
Zn 108 109 109 108 123 111 112 116 109 107 
Ga 18·7 19·2 19·2 18·7 19·8 19·6 19·9 20·5 19·8 19·3 
Ge 1·47 1·52 1·49 1·58 1·57 1·47 1·46 1·62 1·65 1·42 
Rb 17·7 12·1 14·3 11·6 23·5 8·98 12·4 9·92 6·44 7·07 
Sr 431 350 387 380 367 310 327 325 268 209 
20·2 19·7 20·3 19·4 22·1 17 16·6 17·3 17·4 16·4 
Zr 135 116 124 125 146 111 110 117 90·6 90·4 
Nb 31 20·7 25 28·5 28·6 14·6 14·6 15·7 9·69 10·1 
Ba 335 205 228 292 239 145 136 151 81·8 93·9 
La 22·6 15·7 18 20·4 20·1 11·3 11·3 11·7 8·19 8·44 
Ce 45 31·8 36·4 40·8 40·8 24·2 24·7 25·7 17·6 18·5 
Pr 5·49 3·98 4·59 4·98 5·12 3·23 3·3 3·36 2·56 2·71 
Nd 21·7 16·9 18·4 20·3 21·3 14·4 14·5 14·6 12·2 12·7 
Sm 4·96 4·46 4·57 4·77 5·07 3·97 3·97 4·04 3·56 3·71 
Eu 1·7 1·57 1·68 1·64 1·7 1·46 1·48 1·53 1·36 1·44 
Gd 5·25 4·81 5·05 4·87 5·49 4·32 4·27 4·43 4·1 4·15 
Tb 0·83 0·782 0·8 0·773 0·887 0·716 0·708 0·702 0·678 0·678 
Dy 4·46 4·27 4·3 4·16 4·74 3·91 3·79 3·75 3·81 3·72 
Ho 0·801 0·779 0·77 0·772 0·874 0·715 0·687 0·672 0·708 0·699 
Er 1·97 1·92 1·96 1·9 2·14 1·79 1·73 1·62 1·77 1·72 
Tm 0·274 0·263 0·269 0·253 0·283 0·238 0·228 0·228 0·233 0·229 
Yb 1·53 1·5 1·54 1·52 1·7 1·39 1·33 1·29 1·38 1·34 
Lu 0·22 0·222 0·218 0·225 0·24 0·205 0·188 0·2 0·197 0·2 
Hf 3·33 3·21 3·17 3·27 3·82 3·08 2·93 3·04 2·56 2·54 
Ta 1·8 1·28 1·5 1·7 1·8 0·957 0·912 0·934 0·609 0·63 
Pb 2·43 1·56 1·57 1·54 2·22 1·26 1·51 1·69 1·24 0·891 
Th 3·39 2·38 2·78 3·15 3·13 1·55 1·54 1·6 0·983 1·04 
0·694 0·505 0·57 0·633 0·657 0·351 0·376 0·37 0·225 0·26 
Sr* 1·01 1·11 1·1 0·97 0·916 1·22 1·27 1·23 1·35 
Fe/Mn1 74·3 75·9 72·8 66·3 82·1 88·9 74 88·5 81·6 78·4 
Fe/Mn2 74·9 76·9 73·5 67·7 82·3 89·5 74·6 89·4 81·9 78·7 
Fe/Mn3 78·9 79·5 79·1 74·4 86·2 93·4 82·2 92·7 85·3 86·1 
Zr/Hf 40·6 36 39·2 38·2 38·3 36 37·7 38·6 35·3 35·5 
Nb/Ta 17·2 16·1 16·7 16·7 16 15·3 16 16·8 15·9 16·1 
Lu/Hf 0·066 0·069 0·069 0·069 0·063 0·067 0·064 0·066 0·077 0·079 
Sm/Nd 0·229 0·264 0·248 0·235 0·238 0·276 0·273 0·278 0·293 0·293 
Sample: 08HN-8A 08HN-9B 08HN-10A 08HN-10B 08HN-11A 08HN-12A 08HN-13A 08HN-14A 08HN-15A 08HN-16A 
Sc 22·1 21 20 19·4 19·6 16·6 18·8 12·9 21·7 18·4 
Ti 14138 9676 10869 11212 11086 11331 10084 10181 9799 11716 
170 140 144 151 145 131 128 99·6 143 133 
Cr 248 159 206 217 204 202 267 178 190 173 
Mn 1487 1074 990 1033 1047 836 1035 881 1145 922 
Co 58·7 42·9 42 41·7 41 44·1 46 35·8 45·5 41·5 
Ni 165 111 156 156 138 144 166 116 130 144 
Cu 47·9 45 55·8 57·2 53·3 54·9 52·6 33·1 62 55·5 
Zn 128 111 111 111 106 118 118 140 114 128 
Ga 20·6 19·4 19·3 19·1 19·2 20·6 21·5 27·4 20·3 20·7 
Ge 1·59 1·6 1·58 1·56 1·53 1·3 1·41 1·32 1·61 1·38 
Rb 22 7·23 13·9 13·9 17·2 20·2 20 35·3 8·38 17·4 
Sr 558 198 433 348 373 525 532 672 293 416 
21·3 44·6 19·5 18·8 19·4 16·3 15·1 14·6 16·1 18·8 
Zr 199 94 122 122 128 170 135 291 93·8 148 
Nb 37·3 11·3 15·6 15·9 16·6 39·6 31·1 57·8 11·2 26·7 
Ba 524 114 146 143 159 443 365 644 106 218 
La 25·4 37·3 12·4 12·3 12·6 25·2 19·2 39·6 8·21 17·9 
Ce 50·7 82·2 27·5 27 27·6 48·7 38·5 73·8 18·3 37·4 
Pr 6·4 10·9 3·66 3·59 3·7 5·9 4·8 9·24 2·5 4·8 
Nd 27·1 45·5 16·3 16 16·4 23·7 19·3 36 11·8 20·9 
Sm 6·4 11·7 4·55 4·4 4·36 5·48 4·65 7·67 3·54 5·14 
Eu 2·26 4·18 1·63 1·59 1·6 1·62 2·62 1·34 1·77 
Gd 6·35 11·6 4·79 4·74 4·71 5·56 4·45 6·89 3·9 5·14 
Tb 0·899 1·93 0·762 0·752 0·775 0·81 0·681 0·923 0·64 0·817 
Dy 4·61 9·99 4·23 4·11 4·22 3·89 3·43 4·08 3·45 4·18 
Ho 0·8 1·75 0·767 0·765 0·746 0·628 0·565 0·598 0·654 0·756 
Er 1·86 4·12 1·88 1·93 1·88 1·46 1·38 1·3 1·66 1·78 
Tm 0·234 0·557 0·257 0·255 0·247 0·177 0·173 0·155 0·222 0·234 
Yb 1·36 3·12 1·45 1·47 1·48 1·02 0·989 0·794 1·24 1·34 
Lu 0·191 0·425 0·212 0·211 0·207 0·141 0·135 0·112 0·186 0·195 
Hf 4·98 2·64 3·17 3·32 3·46 4·08 3·51 6·97 2·57 3·7 
Ta 2·24 0·714 0·955 1·01 1·04 2·44 1·85 3·77 0·709 1·68 
Pb 0·316 1·17 2·08 2·2 2·05 2·09 1·27 3·37 1·26 2·37 
Th 3·32 1·06 1·98 2·02 2·21 4·13 2·95 5·88 1·18 2·77 
0·863 0·324 0·481 0·48 0·53 0·291 0·441 0·661 0·267 0·679 
Sr* 1·11 0·238 1·5 1·23 1·29 1·14 1·43 0·959 1·47 1·09 
Fe/Mn1 59·7  82 79·9 75·5 92·9 79·1 82·6  85·7 
Fe/Mn2 59·8 83 82·8 80 76 94·6 79·1 82·5 75 85·4 
Fe/Mn3 66·7 86·2 85·9 83·3 79·1 102 87·3 93 82·9 92·8 
Zr/Hf 40·1 35·6 38·4 36·8 37 41·8 38·5 41·7 36·5 39·9 
Nb/Ta 16·7 15·8 16·3 15·7 16 16·3 16·8 15·3 15·8 16 
Lu/Hf 0·038 0·161 0·067 0·064 0·06 0·035 0·039 0·016 0·072 0·053 
Sm/Nd 0·236 0·256 0·279 0·275 0·266 0·232 0·241 0·213 0·302 0·246 
Sample: 08HN-8A 08HN-9B 08HN-10A 08HN-10B 08HN-11A 08HN-12A 08HN-13A 08HN-14A 08HN-15A 08HN-16A 
Sc 22·1 21 20 19·4 19·6 16·6 18·8 12·9 21·7 18·4 
Ti 14138 9676 10869 11212 11086 11331 10084 10181 9799 11716 
170 140 144 151 145 131 128 99·6 143 133 
Cr 248 159 206 217 204 202 267 178 190 173 
Mn 1487 1074 990 1033 1047 836 1035 881 1145 922 
Co 58·7 42·9 42 41·7 41 44·1 46 35·8 45·5 41·5 
Ni 165 111 156 156 138 144 166 116 130 144 
Cu 47·9 45 55·8 57·2 53·3 54·9 52·6 33·1 62 55·5 
Zn 128 111 111 111 106 118 118 140 114 128 
Ga 20·6 19·4 19·3 19·1 19·2 20·6 21·5 27·4 20·3 20·7 
Ge 1·59 1·6 1·58 1·56 1·53 1·3 1·41 1·32 1·61 1·38 
Rb 22 7·23 13·9 13·9 17·2 20·2 20 35·3 8·38 17·4 
Sr 558 198 433 348 373 525 532 672 293 416 
21·3 44·6 19·5 18·8 19·4 16·3 15·1 14·6 16·1 18·8 
Zr 199 94 122 122 128 170 135 291 93·8 148 
Nb 37·3 11·3 15·6 15·9 16·6 39·6 31·1 57·8 11·2 26·7 
Ba 524 114 146 143 159 443 365 644 106 218 
La 25·4 37·3 12·4 12·3 12·6 25·2 19·2 39·6 8·21 17·9 
Ce 50·7 82·2 27·5 27 27·6 48·7 38·5 73·8 18·3 37·4 
Pr 6·4 10·9 3·66 3·59 3·7 5·9 4·8 9·24 2·5 4·8 
Nd 27·1 45·5 16·3 16 16·4 23·7 19·3 36 11·8 20·9 
Sm 6·4 11·7 4·55 4·4 4·36 5·48 4·65 7·67 3·54 5·14 
Eu 2·26 4·18 1·63 1·59 1·6 1·62 2·62 1·34 1·77 
Gd 6·35 11·6 4·79 4·74 4·71 5·56 4·45 6·89 3·9 5·14 
Tb 0·899 1·93 0·762 0·752 0·775 0·81 0·681 0·923 0·64 0·817 
Dy 4·61 9·99 4·23 4·11 4·22 3·89 3·43 4·08 3·45 4·18 
Ho 0·8 1·75 0·767 0·765 0·746 0·628 0·565 0·598 0·654 0·756 
Er 1·86 4·12 1·88 1·93 1·88 1·46 1·38 1·3 1·66 1·78 
Tm 0·234 0·557 0·257 0·255 0·247 0·177 0·173 0·155 0·222 0·234 
Yb 1·36 3·12 1·45 1·47 1·48 1·02 0·989 0·794 1·24 1·34 
Lu 0·191 0·425 0·212 0·211 0·207 0·141 0·135 0·112 0·186 0·195 
Hf 4·98 2·64 3·17 3·32 3·46 4·08 3·51 6·97 2·57 3·7 
Ta 2·24 0·714 0·955 1·01 1·04 2·44 1·85 3·77 0·709 1·68 
Pb 0·316 1·17 2·08 2·2 2·05 2·09 1·27 3·37 1·26 2·37 
Th 3·32 1·06 1·98 2·02 2·21 4·13 2·95 5·88 1·18 2·77 
0·863 0·324 0·481 0·48 0·53 0·291 0·441 0·661 0·267 0·679 
Sr* 1·11 0·238 1·5 1·23 1·29 1·14 1·43 0·959 1·47 1·09 
Fe/Mn1 59·7  82 79·9 75·5 92·9 79·1 82·6  85·7 
Fe/Mn2 59·8 83 82·8 80 76 94·6 79·1 82·5 75 85·4 
Fe/Mn3 66·7 86·2 85·9 83·3 79·1 102 87·3 93 82·9 92·8 
Zr/Hf 40·1 35·6 38·4 36·8 37 41·8 38·5 41·7 36·5 39·9 
Nb/Ta 16·7 15·8 16·3 15·7 16 16·3 16·8 15·3 15·8 16 
Lu/Hf 0·038 0·161 0·067 0·064 0·06 0·035 0·039 0·016 0·072 0·053 
Sm/Nd 0·236 0·256 0·279 0·275 0·266 0·232 0·241 0·213 0·302 0·246 
Sample: 08HN-16C 08HN-17B 08HN-18B 08HN-19A 08HN-19C 08HN-20A 08HN-21A 08HN-21B 08HN-21E 08HN-22A 
Sc 14·6 9·48 21·5 19·5 19·1 18·7 18·6 18·5 15·6 19·7 
Ti 12230 8998 9581 18937 17854 13910 11441 10999 12925 15235 
135 86·1 134 194 177 159 152 140 147 200 
Cr 171 116 181 229 220 217 197 197 304 277 
Mn 941 728 1098 1325 1176 1118 1118 1086 1032 1170 
Co 39·5 29·1 44·7 49·3 47·6 44·5 46 43·9 43·4 46·2 
Ni 103 84 134 144 138 141 162 156 177 151 
Cu 48·6 42·3 76·4 62·9 57 62 53 50·7 64·3 47 
Zn 144 152 116 147 139 124 127 117 141 122 
Ga 25·8 31·2 19·7 22·3 21·2 21·1 21·8 19·7 26·4 21·6 
Ge 1·36 1·31 1·52 1·44 1·37 1·39 1·56 1·42 1·43 1·59 
Rb 39·2 56·5 7·37 31·9 30·8 16·9 20·2 19·2 40·6 34·2 
Sr 680 742 286 665 626 486 458 434 720 617 
16·1 14·1 14·8 26·8 28·5 26·2 18·1 17·8 17 22·3 
Zr 275 440 91·5 257 243 172 141 138 293 213 
Nb 55·6 79·8 12·1 48 46·2 28·7 25·7 24·6 58 41·9 
Ba 533 711 111 636 616 220 215 208 583 492 
La 33·5 49·6 8·54 33·3 33·7 18·3 16·5 16·3 36·3 30·8 
Ce 66·6 92·6 18·7 69 67·3 37·3 34·4 33·5 71·5 62·3 
Pr 7·99 10·6 2·49 8·96 8·84 4·97 4·44 4·27 8·62 7·76 
Nd 31·3 38·7 11·2 38·1 37·3 22·1 19 18·1 33·3 30·8 
Sm 6·75 7·88 3·26 8·82 8·57 5·76 4·84 4·58 7·26 6·76 
Eu 2·28 2·57 1·26 2·8 2·85 2·12 1·68 1·72 2·42 2·22 
Gd 5·99 6·78 3·69 8·36 8·56 6·09 4·9 4·76 6·45 6·53 
Tb 0·84 0·9 0·597 1·22 1·24 0·935 0·748 0·724 0·914 0·955 
Dy 3·98 3·84 3·3 6·01 6·1 4·83 3·98 3·78 4·28 4·8 
Ho 0·611 0·545 0·606 1·05 1·02 0·84 0·686 0·658 0·662 0·831 
Er 1·39 1·09 1·55 2·32 2·4 2·01 1·7 1·62 1·46 2·04 
Tm 0·168 0·12 0·206 0·284 0·286 0·254 0·23 0·215 0·176 0·263 
Yb 0·945 0·676 1·18 1·62 1·6 1·32 1·31 1·23 1·01 1·47 
Lu 0·129 0·088 0·168 0·219 0·225 0·191 0·185 0·173 0·132 0·203 
Hf 6·48 9·69 2·53 6·08 5·62 4·12 3·42 3·33 6·47 4·81 
Ta 3·6 5·47 0·78 3·14 2·98 1·76 1·56 1·49 3·74 2·51 
Pb 2·91 4·36 3·52 2·08 2·18 2·66 1·76 2·72 2·96 
Th 5·44 8·63 1·25 4·59 4·34 2·28 2·61 2·42 5·28 4·61 
1·31 1·53 0·259 1·04 0·974 0·617 0·687 0·635 1·27 0·965 
Sr* 1·09 0·911 1·45 0·953 0·918 1·24 1·31 1·29 1·08 1·03 
Fe/Mn1 84  78·3 68·1 76·1  73·8  77·3  
Fe/Mn2 83·7 86·8 78·8 68 76 76·2 73·7 77 78 71·6 
Fe/Mn3 90·3 90·3 88·9 73·3 82·6 82·2 83·9 86 87·3 79·1 
Zr/Hf 42·5 45·4 36·2 42·2 43·2 41·6 41·2 41·4 45·3 44·3 
Nb/Ta 15·4 14·6 15·6 15·3 15·5 16·3 16·5 16·4 15·5 16·7 
Lu/Hf 0·02 0·009 0·067 0·036 0·04 0·046 0·054 0·052 0·02 0·042 
Sm/Nd 0·215 0·204 0·29 0·231 0·23 0·261 0·254 0·254 0·218 0·219 
Sample: 08HN-16C 08HN-17B 08HN-18B 08HN-19A 08HN-19C 08HN-20A 08HN-21A 08HN-21B 08HN-21E 08HN-22A 
Sc 14·6 9·48 21·5 19·5 19·1 18·7 18·6 18·5 15·6 19·7 
Ti 12230 8998 9581 18937 17854 13910 11441 10999 12925 15235 
135 86·1 134 194 177 159 152 140 147 200 
Cr 171 116 181 229 220 217 197 197 304 277 
Mn 941 728 1098 1325 1176 1118 1118 1086 1032 1170 
Co 39·5 29·1 44·7 49·3 47·6 44·5 46 43·9 43·4 46·2 
Ni 103 84 134 144 138 141 162 156 177 151 
Cu 48·6 42·3 76·4 62·9 57 62 53 50·7 64·3 47 
Zn 144 152 116 147 139 124 127 117 141 122 
Ga 25·8 31·2 19·7 22·3 21·2 21·1 21·8 19·7 26·4 21·6 
Ge 1·36 1·31 1·52 1·44 1·37 1·39 1·56 1·42 1·43 1·59 
Rb 39·2 56·5 7·37 31·9 30·8 16·9 20·2 19·2 40·6 34·2 
Sr 680 742 286 665 626 486 458 434 720 617 
16·1 14·1 14·8 26·8 28·5 26·2 18·1 17·8 17 22·3 
Zr 275 440 91·5 257 243 172 141 138 293 213 
Nb 55·6 79·8 12·1 48 46·2 28·7 25·7 24·6 58 41·9 
Ba 533 711 111 636 616 220 215 208 583 492 
La 33·5 49·6 8·54 33·3 33·7 18·3 16·5 16·3 36·3 30·8 
Ce 66·6 92·6 18·7 69 67·3 37·3 34·4 33·5 71·5 62·3 
Pr 7·99 10·6 2·49 8·96 8·84 4·97 4·44 4·27 8·62 7·76 
Nd 31·3 38·7 11·2 38·1 37·3 22·1 19 18·1 33·3 30·8 
Sm 6·75 7·88 3·26 8·82 8·57 5·76 4·84 4·58 7·26 6·76 
Eu 2·28 2·57 1·26 2·8 2·85 2·12 1·68 1·72 2·42 2·22 
Gd 5·99 6·78 3·69 8·36 8·56 6·09 4·9 4·76 6·45 6·53 
Tb 0·84 0·9 0·597 1·22 1·24 0·935 0·748 0·724 0·914 0·955 
Dy 3·98 3·84 3·3 6·01 6·1 4·83 3·98 3·78 4·28 4·8 
Ho 0·611 0·545 0·606 1·05 1·02 0·84 0·686 0·658 0·662 0·831 
Er 1·39 1·09 1·55 2·32 2·4 2·01 1·7 1·62 1·46 2·04 
Tm 0·168 0·12 0·206 0·284 0·286 0·254 0·23 0·215 0·176 0·263 
Yb 0·945 0·676 1·18 1·62 1·6 1·32 1·31 1·23 1·01 1·47 
Lu 0·129 0·088 0·168 0·219 0·225 0·191 0·185 0·173 0·132 0·203 
Hf 6·48 9·69 2·53 6·08 5·62 4·12 3·42 3·33 6·47 4·81 
Ta 3·6 5·47 0·78 3·14 2·98 1·76 1·56 1·49 3·74 2·51 
Pb 2·91 4·36 3·52 2·08 2·18 2·66 1·76 2·72 2·96 
Th 5·44 8·63 1·25 4·59 4·34 2·28 2·61 2·42 5·28 4·61 
1·31 1·53 0·259 1·04 0·974 0·617 0·687 0·635 1·27 0·965 
Sr* 1·09 0·911 1·45 0·953 0·918 1·24 1·31 1·29 1·08 1·03 
Fe/Mn1 84  78·3 68·1 76·1  73·8  77·3  
Fe/Mn2 83·7 86·8 78·8 68 76 76·2 73·7 77 78 71·6 
Fe/Mn3 90·3 90·3 88·9 73·3 82·6 82·2 83·9 86 87·3 79·1 
Zr/Hf 42·5 45·4 36·2 42·2 43·2 41·6 41·2 41·4 45·3 44·3 
Nb/Ta 15·4 14·6 15·6 15·3 15·5 16·3 16·5 16·4 15·5 16·7 
Lu/Hf 0·02 0·009 0·067 0·036 0·04 0·046 0·054 0·052 0·02 0·042 
Sm/Nd 0·215 0·204 0·29 0·231 0·23 0·261 0·254 0·254 0·218 0·219 
Sample: 08HN-22D 08HN-23B 08HN-24A 08HN-24B 08HN-24D 08HN-25A 08HN-25C 08HN-26A 08HN-26C  
Sc 24·5 20 25·6 25·5 25·2 18 20·1 21·8 21·5  
Ti 16298 14422 15187 14818 14051 11846 12020 13034 13394  
238 188 218 208 207 156 154 193 190  
Cr 222 258 248 259 283 228 250 252 241  
Mn 1401 1112 1290 1250 1227 1277 1123 1162 1135  
Co 50·3 44·8 51·2 50·9 50·4 44·3 43·3 43·5 40·6  
Ni 172 150 205 205 208 164 168 107 93·4  
Cu 59·1 55 60·5 59·9 56·6 49·1 59·1 57·9 52·2  
Zn 132 115 117 119 112 108 113 126 112  
Ga 21·7 20·3 19·6 19·8 19·8 18·8 19·4 22·4 21  
Ge 1·58 1·53 1·57 1·68 1·68 1·26 1·47 1·72 1·49  
Rb 31·9 33·7 28·5 27·6 25·8 19·5 15·7 22·9 21·9  
Sr 699 624 573 577 585 453 461 504 479  
25·3 22·4 22·2 21·2 20·9 18·5 19·3 21·1 20·4  
Zr 256 212 205 186 179 143 146 170 165  
Nb 63·4 43·6 46·5 44·2 42·2 25·8 24·5 26·6 26·9  
Ba 505 502 426 407 404 217 223 236 245  
La 47·2 31·5 33·5 28·9 28·4 16·8 17 19·5 19·7  
Ce 96·5 64 69·2 60·7 58 35·9 36·3 42·1 41·3  
Pr 11·5 7·82 8·48 7·48 7·08 4·54 4·67 5·38 5·34  
Nd 43·3 31·7 32·8 29·4 28 19·4 19·6 21·9 22·3  
Sm 8·1 6·9 6·72 6·03 5·97 4·61 4·82 5·34 5·44  
Eu 2·54 2·19 2·04 1·95 1·93 1·58 1·66 1·82 1·91  
Gd 7·35 6·31 5·97 5·69 5·46 4·75 4·64 5·26 5·45  
Tb 1·03 0·944 0·854 0·844 0·821 0·737 0·709 0·798 0·828  
Dy 5·24 4·81 4·52 4·46 4·22 3·89 3·93 4·27 4·32  
Ho 0·939 0·829 0·81 0·775 0·769 0·708 0·696 0·764 0·742  
Er 2·23 1·94 1·98 1·91 1·9 1·66 1·73 1·94 1·83  
Tm 0·304 0·243 0·272 0·254 0·253 0·218 0·222 0·249 0·231  
Yb 1·8 1·44 1·57 1·53 1·52 1·25 1·29 1·46 1·37  
Lu 0·249 0·211 0·227 0·221 0·22 0·176 0·189 0·197 0·2  
Hf 5·76 4·88 4·67 4·29 4·1 3·27 3·38 3·89 3·87  
Ta 3·93 2·65 2·77 2·73 2·44 1·49 1·46 1·58 1·67  
Pb 4·15 3·55 2·84 2·54 2·21 1·54 1·67 2·14 2·6  
Th 5·81 4·65 4·31 3·96 3·67 2·31 2·32 2·82 2·89  
1·38 1·04 1·01 0·954 0·916 0·549 0·476 0·66 0·689  
Sr* 0·795 1·02 0·883 1·07 1·26 1·27 1·22 1·16  
Fe/Mn1 66·4  67·2 70·5  67·9 77·8 69·9 70·9  
Fe/Mn2 66·1 75·5 66·9 70·4 70·2 67·9 77·8 69·7 70·7  
Fe/Mn3 74·2 78·5 77·2 77·4 76·6 75·2 81·8 81·2 80·5  
Zr/Hf 44·5 43·4 43·9 43·3 43·6 43·7 43·1 43·8 42·7  
Nb/Ta 16·1 16·5 16·8 16·2 17·3 17·3 16·8 16·8 16·1  
Lu/Hf 0·043 0·043 0·049 0·052 0·054 0·054 0·056 0·051 0·052  
Sm/Nd 0·187 0·218 0·205 0·206 0·213 0·238 0·246 0·243 0·244  
Sample: 08HN-22D 08HN-23B 08HN-24A 08HN-24B 08HN-24D 08HN-25A 08HN-25C 08HN-26A 08HN-26C  
Sc 24·5 20 25·6 25·5 25·2 18 20·1 21·8 21·5  
Ti 16298 14422 15187 14818 14051 11846 12020 13034 13394  
238 188 218 208 207 156 154 193 190  
Cr 222 258 248 259 283 228 250 252 241  
Mn 1401 1112 1290 1250 1227 1277 1123 1162 1135  
Co 50·3 44·8 51·2 50·9 50·4 44·3 43·3 43·5 40·6  
Ni 172 150 205 205 208 164 168 107 93·4  
Cu 59·1 55 60·5 59·9 56·6 49·1 59·1 57·9 52·2  
Zn 132 115 117 119 112 108 113 126 112  
Ga 21·7 20·3 19·6 19·8 19·8 18·8 19·4 22·4 21  
Ge 1·58 1·53 1·57 1·68 1·68 1·26 1·47 1·72 1·49  
Rb 31·9 33·7 28·5 27·6 25·8 19·5 15·7 22·9 21·9  
Sr 699 624 573 577 585 453 461 504 479  
25·3 22·4 22·2 21·2 20·9 18·5 19·3 21·1 20·4  
Zr 256 212 205 186 179 143 146 170 165  
Nb 63·4 43·6 46·5 44·2 42·2 25·8 24·5 26·6 26·9  
Ba 505 502 426 407 404 217 223 236 245  
La 47·2 31·5 33·5 28·9 28·4 16·8 17 19·5 19·7  
Ce 96·5 64 69·2 60·7 58 35·9 36·3 42·1 41·3  
Pr 11·5 7·82 8·48 7·48 7·08 4·54 4·67 5·38 5·34  
Nd 43·3 31·7 32·8 29·4 28 19·4 19·6 21·9 22·3  
Sm 8·1 6·9 6·72 6·03 5·97 4·61 4·82 5·34 5·44  
Eu 2·54 2·19 2·04 1·95 1·93 1·58 1·66 1·82 1·91  
Gd 7·35 6·31 5·97 5·69 5·46 4·75 4·64 5·26 5·45  
Tb 1·03 0·944 0·854 0·844 0·821 0·737 0·709 0·798 0·828  
Dy 5·24 4·81 4·52 4·46 4·22 3·89 3·93 4·27 4·32  
Ho 0·939 0·829 0·81 0·775 0·769 0·708 0·696 0·764 0·742  
Er 2·23 1·94 1·98 1·91 1·9 1·66 1·73 1·94 1·83  
Tm 0·304 0·243 0·272 0·254 0·253 0·218 0·222 0·249 0·231  
Yb 1·8 1·44 1·57 1·53 1·52 1·25 1·29 1·46 1·37  
Lu 0·249 0·211 0·227 0·221 0·22 0·176 0·189 0·197 0·2  
Hf 5·76 4·88 4·67 4·29 4·1 3·27 3·38 3·89 3·87  
Ta 3·93 2·65 2·77 2·73 2·44 1·49 1·46 1·58 1·67  
Pb 4·15 3·55 2·84 2·54 2·21 1·54 1·67 2·14 2·6  
Th 5·81 4·65 4·31 3·96 3·67 2·31 2·32 2·82 2·89  
1·38 1·04 1·01 0·954 0·916 0·549 0·476 0·66 0·689  
Sr* 0·795 1·02 0·883 1·07 1·26 1·27 1·22 1·16  
Fe/Mn1 66·4  67·2 70·5  67·9 77·8 69·9 70·9  
Fe/Mn2 66·1 75·5 66·9 70·4 70·2 67·9 77·8 69·7 70·7  
Fe/Mn3 74·2 78·5 77·2 77·4 76·6 75·2 81·8 81·2 80·5  
Zr/Hf 44·5 43·4 43·9 43·3 43·6 43·7 43·1 43·8 42·7  
Nb/Ta 16·1 16·5 16·8 16·2 17·3 17·3 16·8 16·8 16·1  
Lu/Hf 0·043 0·043 0·049 0·052 0·054 0·054 0·056 0·051 0·052  
Sm/Nd 0·187 0·218 0·205 0·206 0·213 0·238 0·246 0·243 0·244  
Sample: ZK03-24.4 ZK03-29.1 ZK04-26.8 ZK05-20.1 ZK05-36.5 ZK05-25.4     
Sc 16·2 16·6 21·1 21·6 23·5 20·7     
Ti 14936 15734 10905 10579 11723 11276     
150 152 138 143 154 144     
Cr 131 114 214 226 282 199     
Mn 1564 1504 1512 974 2324 1032     
Co 42·9 44 37·7 44 47 41·4     
Ni 129 115 90·3 173 174 160     
Cu 51·8 49·7 67·7 61·7 69 65·4     
Zn 161 160 120 108 134 110     
Ga 22·5 22·4 18·4 18·2 19·5 18·3     
Ge 1·68 1·73 1·54 1·56 1·54 1·47     
Rb 55·4 35·6 16·5 3·2 4·8 5·32     
Sr 1327 1341 439 372 349 397     
33·2 34·7 19·5 18 20 19·1     
Zr 361 360 117 110 123 121     
Nb 122 118 20·2 21·5 25·5 25·4     
Ba 858 916 224 202 194 182     
La 97·2 100 16·6 16 19 18·5     
Ce 175 180 31·9 31·4 37 35·8     
Pr 19·7 20·5 3·98 3·83 4·61 4·39     
Nd 72·2 77·1 16·8 16·1 18·9 18·1     
Sm 13 14·1 4·52 4·05 4·53 4·48     
Eu 4·12 4·48 1·63 1·55 1·64 1·62     
Gd 11·9 12·3 4·92 4·58 4·98 4·81     
Tb 1·54 1·52 0·763 0·721 0·775 0·749     
Dy 7·66 7·63 4·2 3·94 4·32 4·34     
Ho 1·29 1·28 0·766 0·728 0·785 0·752     
Er 3·09 3·03 1·89 1·84 1·93 1·87     
Tm 0·389 0·377 0·242 0·234 0·261 0·238     
Yb 2·24 2·27 1·54 1·46 1·57 1·49     
Lu 0·309 0·311 0·221 0·21 0·225 0·207     
Hf 8·55 8·48 3·39 3·18 3·52 3·37     
Ta 12·3 12 1·21 1·25 1·54 1·45     
Pb 5·73 5·58 1·89 1·64 2·60 2·01     
Th 13·4 12·9 2·56 2·46 2·77 2·8     
2·53 3·01 0·541 0·529 0·461 0·581     
Sr* 0·868 0·836 1·39 1·22 0·94 1·15     
Fe/Mn1 59·9 61·4 45·8 83·3 38 80     
Fe/Mn2 61·1 63 47·9 84·8 38 81·8     
Fe/Mn3 64·4 66·8 50 88·8 41 87·4     
Zr/Hf 42·2 42·4 34·5 34·6 35·2 36·1     
Nb/Ta 9·95 9·84 16·7 17·2 16·5 17·6     
Lu/Hf 0·036 0·037 0·065 0·066 0·064 0·062     
Sm/Nd 0·18 0·183 0·269 0·251 0·240 0·248     
Sample: ZK03-24.4 ZK03-29.1 ZK04-26.8 ZK05-20.1 ZK05-36.5 ZK05-25.4     
Sc 16·2 16·6 21·1 21·6 23·5 20·7     
Ti 14936 15734 10905 10579 11723 11276     
150 152 138 143 154 144     
Cr 131 114 214 226 282 199     
Mn 1564 1504 1512 974 2324 1032     
Co 42·9 44 37·7 44 47 41·4     
Ni 129 115 90·3 173 174 160     
Cu 51·8 49·7 67·7 61·7 69 65·4     
Zn 161 160 120 108 134 110     
Ga 22·5 22·4 18·4 18·2 19·5 18·3     
Ge 1·68 1·73 1·54 1·56 1·54 1·47     
Rb 55·4 35·6 16·5 3·2 4·8 5·32     
Sr 1327 1341 439 372 349 397     
33·2 34·7 19·5 18 20 19·1     
Zr 361 360 117 110 123 121     
Nb 122 118 20·2 21·5 25·5 25·4     
Ba 858 916 224 202 194 182     
La 97·2 100 16·6 16 19 18·5     
Ce 175 180 31·9 31·4 37 35·8     
Pr 19·7 20·5 3·98 3·83 4·61 4·39     
Nd 72·2 77·1 16·8 16·1 18·9 18·1     
Sm 13 14·1 4·52 4·05 4·53 4·48     
Eu 4·12 4·48 1·63 1·55 1·64 1·62     
Gd 11·9 12·3 4·92 4·58 4·98 4·81     
Tb 1·54 1·52 0·763 0·721 0·775 0·749     
Dy 7·66 7·63 4·2 3·94 4·32 4·34     
Ho 1·29 1·28 0·766 0·728 0·785 0·752     
Er 3·09 3·03 1·89 1·84 1·93 1·87     
Tm 0·389 0·377 0·242 0·234 0·261 0·238     
Yb 2·24 2·27 1·54 1·46 1·57 1·49     
Lu 0·309 0·311 0·221 0·21 0·225 0·207     
Hf 8·55 8·48 3·39 3·18 3·52 3·37     
Ta 12·3 12 1·21 1·25 1·54 1·45     
Pb 5·73 5·58 1·89 1·64 2·60 2·01     
Th 13·4 12·9 2·56 2·46 2·77 2·8     
2·53 3·01 0·541 0·529 0·461 0·581     
Sr* 0·868 0·836 1·39 1·22 0·94 1·15     
Fe/Mn1 59·9 61·4 45·8 83·3 38 80     
Fe/Mn2 61·1 63 47·9 84·8 38 81·8     
Fe/Mn3 64·4 66·8 50 88·8 41 87·4     
Zr/Hf 42·2 42·4 34·5 34·6 35·2 36·1     
Nb/Ta 9·95 9·84 16·7 17·2 16·5 17·6     
Lu/Hf 0·036 0·037 0·065 0·066 0·064 0·062     
Sm/Nd 0·18 0·183 0·269 0·251 0·240 0·248     

Sr anomaly is given by Sr* = SrN/(CeN × NdN)0·5, where N denotes primitive mantle-normalized values. Fe/Mn1 was directly determined by ICP-AES. Fe/Mn2 was calculated using XRF-determined Fe and ICP-MS-determined Mn contents. Fe/Mn3 was calculated using XRF-determined Fe and Mn contents.

The MgO contents of the bulk-rocks range from 2 to 11 wt %, with 86 of 105 samples having >6 wt % MgO and 25 samples having MgO >8 wt % (Table 2). Figure 4 shows that the Ni and Cr contents in all analysed samples correlate positively with Mg#, whereas the other elements show complex behaviors. The SiO2 and Al2O3 contents in tholeiites increase with falling Mg# and reach their maximum values at Mg# ≈ 55–60, whereas at lower Mg# values (<55), SiO2 contents decrease slightly with falling Mg# (Fig. 4a and b). The tholeiites mostly fall within a narrow range of CaO contents (8–9 wt %; highlighted by the grey band in Fig. 4c), FeOT (11· 5–10 wt %; Fig. 4d), and CaO/Al2O3 values (0·55–0·65; Fig. 4i). The tholeiites have nearly constant Zn/Fe ratios (Zn/Fe × 104 = 10–13; Fig. 4h). The alkali basalts show scattered SiO2 and nearly constant Al2O3 contents (Fig. 4a and b) whereas the CaO and FeOT contents display more complex behavior. CaO contents increase with falling Mg# at Mg# > 64 and reach maximum values at Mg# = 64–65 (Fig. 4c). With further decrease in Mg#, CaO contents quickly decrease from >11 wt % to about 9 wt % at Mg# ∼60 and then flatten out (Fig. 4c). FeOT contents in the alkali basalts first increase from about 10 wt % to 12 wt % with falling Mg# at Mg# ≥ 63, then decrease quickly from >12 wt % to about 8 wt % with decreasing Mg# from 63 to 55, and finally increase again when Mg# falls to <55 (Fig. 4d). At high Mg# >61, the alkali basalts also have nearly constant Zn/Fe ratios, but the ratio correlates negatively with Mg# at Mg# <60–61 (Fig. 4h). Na2O contents in both the tholeiites and alkali basalts increase with falling Mg# and reach their maximum values at Mg# = 54 and 58, respectively. The Sc contents in the tholeiites and alkali basalts correlate negatively with Mg# at Mg# > 64, reach their maximum value at Mg# = 61–64 (Fig. 4j), and then decrease from about 25 to 15 ppm at Mg# < 61 (Fig. 4j).

Fig. 4.

Variations of selected oxides, trace element and element ratios in the Hainan basalts as functions of Mg#. Mg# = 100 × Mg/(Mg + Fe), Fe2+/Fetotal = 0.90, cation ratio. Large circles represent data from this study, and small circles are data from the literature (Flower et al., 1992; Fan et al., 2004; Zou & Fan, 2010). The grey bands indicate the range of y-axis values for most tholeiites.

Fig. 4.

Variations of selected oxides, trace element and element ratios in the Hainan basalts as functions of Mg#. Mg# = 100 × Mg/(Mg + Fe), Fe2+/Fetotal = 0.90, cation ratio. Large circles represent data from this study, and small circles are data from the literature (Flower et al., 1992; Fan et al., 2004; Zou & Fan, 2010). The grey bands indicate the range of y-axis values for most tholeiites.

The fundamental differences between the tholeiites and the alkali basalts are in their SiO2, Al2O3, FeOT, TiO2, and K2O contents. As shown in Fig. 4 and Table 2, the tholeiites are characterized by higher SiO2 (mostly ≥51 wt %) and Al2O3 (mostly >14·5 wt %) and lower FeOT (mostly ≤11 wt %), TiO2 (mostly <2·3 wt %), and K2O (mostly <1·5 wt %), whereas the alkali basalts have relatively low SiO2 (mostly ≤49 wt %) and Al2O3 (mostly <14·5 wt %), but higher FeOT (mostly >11 wt %), TiO2 (mostly >2·3 wt %), and K2O (mostly >1·5 wt %).

The Fe/Mn ratio an important indicator of the source of basaltic rocks (Liu et al., 2008, and references therein). In this study, Fe/Mn ratios can be directly measured by ICP-AES or be calculated according to Fe (by XRF) and Mn (by XRF or ICP-MS) contents. Fe/Mn ratios determined in the three different ways display no systematic differences (Fig. 5).

Fig. 5.

Comparison of Fe/Mn ratios determined by IPC-AES with (a) Fe/Mn1 (Fe determined by XRF and Mn by ICP-MS) and (b) Fe/Mn2 (both Fe and Mn measured by XRF). (c) Fe/Mn histograms showing that there is no systematic difference between datasets acquired using the XRF, ICP-MS and ICP-AES methods.

Fig. 5.

Comparison of Fe/Mn ratios determined by IPC-AES with (a) Fe/Mn1 (Fe determined by XRF and Mn by ICP-MS) and (b) Fe/Mn2 (both Fe and Mn measured by XRF). (c) Fe/Mn histograms showing that there is no systematic difference between datasets acquired using the XRF, ICP-MS and ICP-AES methods.

Both tholeiites and alkali basalts are characterized by high Fe/Mn ratios with an average of 74 (mostly >70, Figs 5 and 6), which is significantly higher than the average of mid-ocean ridge basalt (MORB; 57, n = 875, RidgePeDB), continental flood basalts (63·7, n = 4780, GEOROC), Hawaiian OIB (about 66–67; Humayun et al. 2004) and Mesozoic to Cenozoic basalts in eastern China (60–70; Liu et al. 2008). All but two samples plot within or above the field of primitive upper mantle (PUM; highlighted by the grey band in Fig. 6). Samples with LOI >1·5 wt % display negative and positive correlations of Fe/Mn–LOI and MnO–LOI, respectively (Fig. 6a and b). This indicates that the Fe/Mn ratios in the few relatively high LOI samples were affected by alteration processes, resulting in reductions in the Fe/Mn ratio (e.g. samples ZK04-26.8 and ZK05-36.5). Considering the effect of any undetected alteration on the Hainan basalts, their primary Fe/Mn ratios could be even higher.

Fig. 6.

(a, b) Variation of Fe/Mn ratios and MnO contents with LOI values. (c–f) Variation of Fe/Mn determined by ICP-AES with Yb, Mg#, CaO and FeOT. Calculated Cpx crystal fractionation trends for a MORB-like basalt (MORB) and the average of the estimated primary melts for the Hainan basalts (HN) are indicated. Because olivine fractionation would decrease the Fe/Mn ratio of the melt, only cpx was taken into account for evaluating the contribution of crystal fractionation to the high Fe/Mn ratios in the basalts. Parameters used in calculations are from Liu et al. (2008). A global suite of mantle peridotites (primitive upper mantle, PUM) yielded Fe/Mn = 60 ± 10 (1σ) (McDonough & Sun, 1995) and is highlighted by the horizontal grey bands. Each cross on the model curves represents a 10% increment of fractional crystallization.

Fig. 6.

(a, b) Variation of Fe/Mn ratios and MnO contents with LOI values. (c–f) Variation of Fe/Mn determined by ICP-AES with Yb, Mg#, CaO and FeOT. Calculated Cpx crystal fractionation trends for a MORB-like basalt (MORB) and the average of the estimated primary melts for the Hainan basalts (HN) are indicated. Because olivine fractionation would decrease the Fe/Mn ratio of the melt, only cpx was taken into account for evaluating the contribution of crystal fractionation to the high Fe/Mn ratios in the basalts. Parameters used in calculations are from Liu et al. (2008). A global suite of mantle peridotites (primitive upper mantle, PUM) yielded Fe/Mn = 60 ± 10 (1σ) (McDonough & Sun, 1995) and is highlighted by the horizontal grey bands. Each cross on the model curves represents a 10% increment of fractional crystallization.

The Fe/Mn ratios of the studied samples correlate negatively with heavy rare earth element (HREE) abundances (e.g. Yb; correlation coefficient r = −0·53; Fig. 6c), Lu (r = −0·52; not shown) and CaO (r = −0·51; Fig. 6e), but not with Mg# and FeOT (Fig. 6d and f). This suggests that magmatic differentiation had little effect on the Fe/Mn ratios. Therefore, the high Fe/Mn ratios may reflect the effects of melting processes and mantle source heterogeneity.

All the studied samples show typical OIB-like chondrite-normalized rare earth element (REE) patterns with enrichments in light rare earth elements (LREE) over HREE (Fig. 7a and b). The LREE enrichment increases systematically from subalkaline series to alkaline series basalts (Fig. 7a and b). A silica-oversaturated sample (08HN-17B) displays a strong depletion in HREE and Lu with Tb/Yb = 6·0 and Lu/Hf = 0·009. Compared with typical MORB and alkalic OIB (Fig. 7a), all studied samples are strongly depleted in HREE.

Fig. 7.

(a, b) Chondrite-normalized REE patterns for the Hainan basalts: (a) alkali basalts; (b) subalkaline (tholeiitic) basalts. (c, d) Primitive mantle-normalized incompatible trace element patterns: (c) alkali basalts; (d) tholeiites. Normalization values are from Sun & McDonough (1989).

Fig. 7.

(a, b) Chondrite-normalized REE patterns for the Hainan basalts: (a) alkali basalts; (b) subalkaline (tholeiitic) basalts. (c, d) Primitive mantle-normalized incompatible trace element patterns: (c) alkali basalts; (d) tholeiites. Normalization values are from Sun & McDonough (1989).

In the primitive mantle-normalized multi-element patterns, except for four drill samples (ZK05-25.4, ZK05-36.5, ZK03-24.4, and ZK03-29.1), all samples show appreciable enrichment in high field strength elements (HFSE), such as Nb and Ta. The most prominent feature of the trace element patterns of studied samples is the small but significant positive Sr anomalies (Fig. 7c and d). The four drill samples (ZK03-24.4, ZK03-29.1, ZK05-36.5, and ZK05-29.1) show strong depletion in K2O (Fig. 7c and d). The alkalic basalts display negative Ti and Th–U anomalies, whereas the tholeiites show no significant depletion in Ti and Th–U. Such patterns are comparable with those of intra-plate basalts, such as OIB (Sun & McDonough, 1989).

Mineral compositions

Olivine

We analyzed the compositions of 41 olivines with euhedral textures, 41 with subhedral–undeformed textures, and 19 with deformed textures (Table 4). In addition, we analyzed 125 unclassified olivine phenocrysts (data given in Supplementary Data Electronic Appendix Table R1, available for downloading at http://www.petrology.oxfordjournals.org). The olivines have a wide range of Fo contents [Fo = 100 × Mg/(Mg + Fe), cation ratio] varying from 55·2 to 91·9. Phenocrystic olivines have Fo contents of up to 90·7. Their CaO contents are all within the range of phenocrysts precipitated from basalt–picrite magmas, but are much higher than those of mantle xenoliths (CaO <0·1 wt %; Thompson & Gibson, 2000; Ren et al., 2004) (Fig. 8a). MnO contents are negatively correlated with Fo (Fig. 8b). NiO decreases with decreasing Fo content, which differs from the mantle olivine array (e.g. Sato, 1977) (Fig. 8c). The average contents of minor elements in olivines with Fo ≥85 are: CaO = 0·18 wt % (±0·07%, 2σ), NiO = 0·36 wt % (±0·05%, 2σ), MnO = 0·16 wt % (±0·03%, 2σ).

Fig. 8.

(a–c) Variations in the composition of olivine phenocrysts. The mantle olivine array and fractional crystallization trend in (c) are from Sato (1977). The dashed line that separates magmatic and xenocrystic olivines on the basis of CaO in (a) is from Thompson & Gibson (2000). The ‘common olivine’ field outlines the compositional range for olivines from peridotites, mantle xenoliths, orogenic massifs and ophiolites, oceanic abyssal basalts and MORB (Sobolev et al., 2005), whereas the Hawaiian olivine field denotes the range for olivine from Hawaiian basalts, which have been interpreted to have been derived from a hybridized pyroxenitic source formed by reaction of mantle peridotite with melts derived from recycled eclogitic oceanic crust (Sobolev et al., 2005).

Fig. 8.

(a–c) Variations in the composition of olivine phenocrysts. The mantle olivine array and fractional crystallization trend in (c) are from Sato (1977). The dashed line that separates magmatic and xenocrystic olivines on the basis of CaO in (a) is from Thompson & Gibson (2000). The ‘common olivine’ field outlines the compositional range for olivines from peridotites, mantle xenoliths, orogenic massifs and ophiolites, oceanic abyssal basalts and MORB (Sobolev et al., 2005), whereas the Hawaiian olivine field denotes the range for olivine from Hawaiian basalts, which have been interpreted to have been derived from a hybridized pyroxenitic source formed by reaction of mantle peridotite with melts derived from recycled eclogitic oceanic crust (Sobolev et al., 2005).

Table 4:

Microprobe analyses of euhedral, subhedral–undeformed, and deformed olivines from the Hainan basalts

Probe no. SiO2 MgO FeO MnO CaO NiO Fo Total 
Deformed olivine 
08HN-1A-1 41·57 49·19 8·92 0·14 0·07 0·44 90·8 100·32 
08HN-1A-2 40·48 49·04 8·93 0·11 0·07 0·42 90·7 99·05 
08HN-1A-3 39·50 46·68 9·98 0·12 0·08 0·40 89·3 96·75 
08HN-1A-4 39·61 48·27 9·07 0·16 0·08 0·39 90·5 97·58 
08HN-1A-5 41·78 48·77 8·89 0·11 0·05 0·44 90·7 100·05 
08HN-4D-1 40·20 50·52 7·92 0·08 0·02 0·24 91·9 98·98 
08HN-4D-2 40·52 50·78 8·98 0·08 0·05 0·25 91·0 100·66 
08HN-2B-19 40·48 46·97 10·87 0·18 0·09 0·37 88·5 98·95 
08HN-2B-20 41·65 48·18 9·42 0·16 0·10 0·42 90·1 99·93 
08HN-2B-21 40·71 44·73 14·03 0·24 0·06 0·29 85·0 100·07 
08HN-2B-22C 40·23 44·47 14·11 0·22 0·04 0·33 84·9 99·40 
08HN-2B-22M 38·74 43·67 15·88 0·26 0·11 0·28 83·1 98·93 
08HN-14B-22C 37·85 32·45 28·03 0·35 0·25 0·11 67·4 99·04 
08HN-14B-24R 37·10 32·11 29·67 0·37 0·25 0·14 65·9 99·64 
08HN-14B-12C 37·84 32·33 29·02 0·37 0·36 0·11 66·5 100·03 
08HN-14B-12R 38·24 31·54 29·91 0·33 0·28 0·13 65·3 100·44 
08HN-24B-29 39·64 45·20 14·10 0·20 0·22 0·28 85·1 99·65 
08HN-24B-30 38·09 41·75 19·10 0·30 0·28 0·23 79·6 99·75 
08HN-24B-31 38·46 44·13 16·91 0·22 0·32 0·16 82·3 100·20 
08HN-24B-32 36·66 39·76 21·98 0·32 0·28 0·22 76·3 99·21 
Subhedral–undeformed olivine 
08HN-1A-6 41·43 47·28 9·72 0·17 0·18 0·40 89·7 99·18 
08HN-1A-7 41·47 47·56 9·67 0·12 0·21 0·44 89·8 99·47 
08HN-1A-11 41·53 48·90 8·75 0·13 0·18 0·40 90·9 99·89 
08HN-1A-12 41·39 48·72 8·76 0·17 0·15 0·38 90·8 99·55 
08HN-2B-1 41·72 48·49 9·65 0·12 0·18 0·39 90·0 100·54 
08HN-2B-2 41·72 48·52 9·88 0·18 0·18 0·35 89·7 100·83 
08HN-2B-3 41·34 47·77 11·27 0·18 0·22 0·32 88·3 101·09 
08HN-2B-4 41·50 48·04 9·48 0·14 0·20 0·40 90·0 99·76 
08HN-2B-5 40·89 45·91 12·28 0·17 0·23 0·43 87·0 99·91 
08HN-2B-6 40·97 46·95 11·65 0·17 0·07 0·38 87·8 100·19 
08HN-2B-7 40·97 46·86 11·67 0·16 0·20 0·37 87·7 100·23 
08HN-2B-8 41·66 48·09 9·90 0·13 0·08 0·32 89·7 100·17 
08HN-2B-9 41·23 48·53 9·94 0·12 0·08 0·39 89·7 100·29 
08HN-2B-10 40·69 47·95 9·93 0·14 0·21 0·35 89·6 99·28 
08HN-2B-11 41·46 48·38 9·71 0·15 0·10 0·38 89·9 100·17 
08HN-2B-12 40·13 49·08 9·70 0·12 0·16 0·37 90·0 99·56 
08HN-2B-13 41·64 47·64 9·43 0·11 0·08 0·40 90·0 99·29 
Probe no. SiO2 MgO FeO MnO CaO NiO Fo Total 
Deformed olivine 
08HN-1A-1 41·57 49·19 8·92 0·14 0·07 0·44 90·8 100·32 
08HN-1A-2 40·48 49·04 8·93 0·11 0·07 0·42 90·7 99·05 
08HN-1A-3 39·50 46·68 9·98 0·12 0·08 0·40 89·3 96·75 
08HN-1A-4 39·61 48·27 9·07 0·16 0·08 0·39 90·5 97·58 
08HN-1A-5 41·78 48·77 8·89 0·11 0·05 0·44 90·7 100·05 
08HN-4D-1 40·20 50·52 7·92 0·08 0·02 0·24 91·9 98·98 
08HN-4D-2 40·52 50·78 8·98 0·08 0·05 0·25 91·0 100·66 
08HN-2B-19 40·48 46·97 10·87 0·18 0·09 0·37 88·5 98·95 
08HN-2B-20 41·65 48·18 9·42 0·16 0·10 0·42 90·1 99·93 
08HN-2B-21 40·71 44·73 14·03 0·24 0·06 0·29 85·0 100·07 
08HN-2B-22C 40·23 44·47 14·11 0·22 0·04 0·33 84·9 99·40 
08HN-2B-22M 38·74 43·67 15·88 0·26 0·11 0·28 83·1 98·93 
08HN-14B-22C 37·85 32·45 28·03 0·35 0·25 0·11 67·4 99·04 
08HN-14B-24R 37·10 32·11 29·67 0·37 0·25 0·14 65·9 99·64 
08HN-14B-12C 37·84 32·33 29·02 0·37 0·36 0·11 66·5 100·03 
08HN-14B-12R 38·24 31·54 29·91 0·33 0·28 0·13 65·3 100·44 
08HN-24B-29 39·64 45·20 14·10 0·20 0·22 0·28 85·1 99·65 
08HN-24B-30 38·09 41·75 19·10 0·30 0·28 0·23 79·6 99·75 
08HN-24B-31 38·46 44·13 16·91 0·22 0·32 0·16 82·3 100·20 
08HN-24B-32 36·66 39·76 21·98 0·32 0·28 0·22 76·3 99·21 
Subhedral–undeformed olivine 
08HN-1A-6 41·43 47·28 9·72 0·17 0·18 0·40 89·7 99·18 
08HN-1A-7 41·47 47·56 9·67 0·12 0·21 0·44 89·8 99·47 
08HN-1A-11 41·53 48·90 8·75 0·13 0·18 0·40 90·9 99·89 
08HN-1A-12 41·39 48·72 8·76 0·17 0·15 0·38 90·8 99·55 
08HN-2B-1 41·72 48·49 9·65 0·12 0·18 0·39 90·0 100·54 
08HN-2B-2 41·72 48·52 9·88 0·18 0·18 0·35 89·7 100·83 
08HN-2B-3 41·34 47·77 11·27 0·18 0·22 0·32 88·3 101·09 
08HN-2B-4 41·50 48·04 9·48 0·14 0·20 0·40 90·0 99·76 
08HN-2B-5 40·89 45·91 12·28 0·17 0·23 0·43 87·0 99·91 
08HN-2B-6 40·97 46·95 11·65 0·17 0·07 0·38 87·8 100·19 
08HN-2B-7 40·97 46·86 11·67 0·16 0·20 0·37 87·7 100·23 
08HN-2B-8 41·66 48·09 9·90 0·13 0·08 0·32 89·7 100·17 
08HN-2B-9 41·23 48·53 9·94 0·12 0·08 0·39 89·7 100·29 
08HN-2B-10 40·69 47·95 9·93 0·14 0·21 0·35 89·6 99·28 
08HN-2B-11 41·46 48·38 9·71 0·15 0·10 0·38 89·9 100·17 
08HN-2B-12 40·13 49·08 9·70 0·12 0·16 0·37 90·0 99·56 
08HN-2B-13 41·64 47·64 9·43 0·11 0·08 0·40 90·0 99·29 
Probe no. SiO2 MgO FeO MnO CaO NiO Fo Total 
08HN-2B-14 39·97 43·56 16·68 0·28 0·21 0·19 82·3 100·89 
08HN-2B-15 39·21 39·38 21·33 0·33 0·27 0·19 76·7 100·71 
08HN-2B-16 39·12 39·27 21·29 0·35 0·24 0·20 76·7 100·47 
08HN-2B-17 41·25 48·67 9·37 0·16 0·13 0·37 90·3 99·95 
08HN-2B-18C 41·68 48·27 9·99 0·13 0·19 0·38 89·6 100·64 
08HN-2B-18R 40·50 42·44 16·32 0·30 0·14 0·26 82·3 99·96 
08HN-14B-1 32·92 37·92 29·28 0·32 0·21 0·10 69·8 100·75 
08HN-14B-2 38·67 36·35 24·88 0·38 0·30 0·10 72·3 100·68 
08HN-14B-4 32·94 36·80 29·11 0·40 0·38 0·12 69·3 99·73 
08HN-14B-5 33·25 35·64 29·20 0·39 0·38 0·11 68·5 98·98 
08HN-14B-6 33·41 37·09 29·45 0·38 0·36 0·06 69·2 100·74 
08HN-2B-27 41·43 47·93 9·94 0·13 0·20 0·42 89·6 100·05 
08HN-2B-28 41·49 48·47 10·04 0·11 0·18 0·33 89·6 100·62 
08HN-2B-29 41·38 47·85 9·92 0·14 0·05 0·43 89·6 99·77 
08HN-2B-30 40·25 43·26 16·64 0·22 0·15 0·25 82·3 100·77 
08HN-2B-31 41·35 47·75 10·39 0·14 0·21 0·35 89·1 100·18 
08HN-4D-3 40·35 43·00 14·12 0·22 0·32 0·24 84·4 98·25 
08HN-4D-4 40·12 43·76 16·23 0·19 0·15 0·30 82·8 100·75 
08HN-24B-34-R 39·46 46·93 13·50 0·18 0·22 0·28 86·1 100·58 
08HN-24B-34-M 39·29 46·05 13·03 0·17 0·21 0·27 86·3 99·02 
08HN-24B-34-C 39·42 46·97 12·99 0·19 0·27 0·31 86·6 100·16 
Euhedral olivine 
08HN-1A-8 40·60 48·26 8·78 0·14 0·15 0·38 90·7 98·31 
08HN-1A-9 41·55 47·10 9·76 0·11 0·21 0·38 89·6 99·10 
08HN-1A-10 40·19 43·44 15·31 0·12 0·28 0·3 83·5 99·64 
08HN-1A-11 39·92 42·36 16·57 0·34 0·23 0·16 82·0 99·58 
08HN-1A-12 39·78 44·53 13·86 0·11 0·33 0·36 85·1 98·97 
08HN-1A-13 39·49 45·28 14·19 0·34 0·16 0·35 85·0 99·81 
08HN-1A-14 39·04 44·66 14·36 0·24 0·21 0·27 84·7 98·78 
08HN-1A-10 40·84 48·74 9·11 0·10 0·23 0·41 90·5 99·43 
08HN-2B-23 38·58 34·50 26·65 0·53 0·35 0·06 69·8 100·67 
08HN-2B-24C 40·26 48·74 10·21 0·17 0·06 0·41 89·5 99·85 
08HN-2B-24R 40·33 41·21 17·76 0·31 0·11 0·30 80·5 100·01 
08HN-2B-25 40·45 47·07 10·87 0·15 0·28 0·41 88·5 99·23 
08HN-2B-26C 40·62 49·30 9·18 0·14 0·05 0·37 90·5 99·64 
08HN-2B-26R 39·40 42·62 16·31 0·33 0·14 0·28 82·3 99·08 
08HN-16A-1 39·51 41·87 17·87 0·25 0·45 0·18 80·7 100·13 
08HN-16A-2 39·27 40·57 19·78 0·25 0·22 0·22 78·5 100·31 
08HN-24B-1 40·64 45·23 13·98 0·19 0·22 0·26 85·2 100·52 
08HN-24B-2 40·45 43·49 15·73 0·25 0·25 0·23 83·1 100·40 
08HN-24B-3 40·12 42·55 16·60 0·20 0·25 0·30 82·0 100·02 
08HN-24B-4 40·84 44·66 13·84 0·22 0·27 0·26 85·2 100·10 
Probe no. SiO2 MgO FeO MnO CaO NiO Fo Total 
08HN-2B-14 39·97 43·56 16·68 0·28 0·21 0·19 82·3 100·89 
08HN-2B-15 39·21 39·38 21·33 0·33 0·27 0·19 76·7 100·71 
08HN-2B-16 39·12 39·27 21·29 0·35 0·24 0·20 76·7 100·47 
08HN-2B-17 41·25 48·67 9·37 0·16 0·13 0·37 90·3 99·95 
08HN-2B-18C 41·68 48·27 9·99 0·13 0·19 0·38 89·6 100·64 
08HN-2B-18R 40·50 42·44 16·32 0·30 0·14 0·26 82·3 99·96 
08HN-14B-1 32·92 37·92 29·28 0·32 0·21 0·10 69·8 100·75 
08HN-14B-2 38·67 36·35 24·88 0·38 0·30 0·10 72·3 100·68 
08HN-14B-4 32·94 36·80 29·11 0·40 0·38 0·12 69·3 99·73 
08HN-14B-5 33·25 35·64 29·20 0·39 0·38 0·11 68·5 98·98 
08HN-14B-6 33·41 37·09 29·45 0·38 0·36 0·06 69·2 100·74 
08HN-2B-27 41·43 47·93 9·94 0·13 0·20 0·42 89·6 100·05 
08HN-2B-28 41·49 48·47 10·04 0·11 0·18 0·33 89·6 100·62 
08HN-2B-29 41·38 47·85 9·92 0·14 0·05 0·43 89·6 99·77 
08HN-2B-30 40·25 43·26 16·64 0·22 0·15 0·25 82·3 100·77 
08HN-2B-31 41·35 47·75 10·39 0·14 0·21 0·35 89·1 100·18 
08HN-4D-3 40·35 43·00 14·12 0·22 0·32 0·24 84·4 98·25 
08HN-4D-4 40·12 43·76 16·23 0·19 0·15 0·30 82·8 100·75 
08HN-24B-34-R 39·46 46·93 13·50 0·18 0·22 0·28 86·1 100·58 
08HN-24B-34-M 39·29 46·05 13·03 0·17 0·21 0·27 86·3 99·02 
08HN-24B-34-C 39·42 46·97 12·99 0·19 0·27 0·31 86·6 100·16 
Euhedral olivine 
08HN-1A-8 40·60 48·26 8·78 0·14 0·15 0·38 90·7 98·31 
08HN-1A-9 41·55 47·10 9·76 0·11 0·21 0·38 89·6 99·10 
08HN-1A-10 40·19 43·44 15·31 0·12 0·28 0·3 83·5 99·64 
08HN-1A-11 39·92 42·36 16·57 0·34 0·23 0·16 82·0 99·58 
08HN-1A-12 39·78 44·53 13·86 0·11 0·33 0·36 85·1 98·97 
08HN-1A-13 39·49 45·28 14·19 0·34 0·16 0·35 85·0 99·81 
08HN-1A-14 39·04 44·66 14·36 0·24 0·21 0·27 84·7 98·78 
08HN-1A-10 40·84 48·74 9·11 0·10 0·23 0·41 90·5 99·43 
08HN-2B-23 38·58 34·50 26·65 0·53 0·35 0·06 69·8 100·67 
08HN-2B-24C 40·26 48·74 10·21 0·17 0·06 0·41 89·5 99·85 
08HN-2B-24R 40·33 41·21 17·76 0·31 0·11 0·30 80·5 100·01 
08HN-2B-25 40·45 47·07 10·87 0·15 0·28 0·41 88·5 99·23 
08HN-2B-26C 40·62 49·30 9·18 0·14 0·05 0·37 90·5 99·64 
08HN-2B-26R 39·40 42·62 16·31 0·33 0·14 0·28 82·3 99·08 
08HN-16A-1 39·51 41·87 17·87 0·25 0·45 0·18 80·7 100·13 
08HN-16A-2 39·27 40·57 19·78 0·25 0·22 0·22 78·5 100·31 
08HN-24B-1 40·64 45·23 13·98 0·19 0·22 0·26 85·2 100·52 
08HN-24B-2 40·45 43·49 15·73 0·25 0·25 0·23 83·1 100·40 
08HN-24B-3 40·12 42·55 16·60 0·20 0·25 0·30 82·0 100·02 
08HN-24B-4 40·84 44·66 13·84 0·22 0·27 0·26 85·2 100·10 
Probe no. SiO2 MgO FeO MnO CaO NiO Fo Total 
08HN-24B-5 38·56 34·87 25·74 0·38 0·25 0·18 70·7 99·99 
08HN-24B-6 41·29 44·82 13·64 0·17 0·24 0·29 85·4 100·45 
08HN-24B-7 39·94 44·30 14·29 0·21 0·21 0·24 84·7 99·18 
08HN-24B-8 40·02 44·62 14·03 0·20 0·27 0·32 85·0 99·46 
08HN-24B-11 38·14 35·22 25·36 0·35 0·39 0·15 71·2 99·62 
08HN-24B-12 39·46 46·22 14·03 0·17 0·26 0·25 85·4 100·39 
08HN-24B-13 37·78 36·33 24·58 0·34 0·23 0·20 72·5 99·46 
08HN-24B-18 39·88 44·59 13·78 0·22 0·23 0·30 85·2 98·99 
08HN-24B-19 39·41 38·06 22·75 0·29 0·25 0·18 74·9 100·94 
08HN-24B-20 39·79 39·61 20·79 0·27 0·23 0·14 77·3 100·83 
08HN-24B-21 38·84 35·84 25·42 0·35 0·30 0·12 71·5 100·87 
08HN-24B-22 37·96 33·18 28·54 0·46 0·32 0·15 67·5 100·60 
08HN-24B-23 38·06 35·40 26·04 0·37 0·26 0·17 70·8 100·29 
08HN-24B-24 38·37 36·22 24·89 0·38 0·29 0·14 72·2 100·29 
08HN-24B-26 40·52 44·73 14·00 0·16 0·24 0·27 85·1 99·92 
08HN-24B-27 40·47 44·83 14·07 0·21 0·26 0·32 85·0 100·15 
08HN-24B-28 39·22 41·39 18·48 0·25 0·27 0·22 80·0 99·83 
08HN-14B-11 37·74 31·13 30·82 0·34 0·26 0·17 64·3 100·45 
08HN-14B-13 37·59 32·06 29·93 0·32 0·26 0·14 65·6 100·30 
08HN-14B-15 38·79 33·15 27·65 0·30 0·27 0·11 68·1 100·29 
08HN-14B-16 37·77 32·78 28·77 0·35 0·22 0·17 67·0 100·06 
08HN-14B-17 37·83 31·75 29·84 0·34 0·25 0·09 65·5 100·10 
08HN-14B-18 37·67 32·40 29·49 0·30 0·25 0·08 66·2 100·18 
08HN-14B-19 37·67 32·51 29·51 0·36 0·25 0·10 66·3 100·39 
08HN-14B-20 37·39 32·44 29·50 0·36 0·27 0·09 66·2 100·05 
08HN-14B-26 36·82 30·55 31·10 0·38 0·27 0·11 63·6 99·23 
08HN-14B-33 37·88 32·33 29·16 0·34 0·27 0·13 66·4 100·11 
08HN-14B-35 37·93 32·50 28·65 0·33 0·27 0·13 66·9 99·81 
08HN-14B-36 37·16 31·71 30·19 0·36 0·23 0·17 65·2 99·82 
Probe no. SiO2 MgO FeO MnO CaO NiO Fo Total 
08HN-24B-5 38·56 34·87 25·74 0·38 0·25 0·18 70·7 99·99 
08HN-24B-6 41·29 44·82 13·64 0·17 0·24 0·29 85·4 100·45 
08HN-24B-7 39·94 44·30 14·29 0·21 0·21 0·24 84·7 99·18 
08HN-24B-8 40·02 44·62 14·03 0·20 0·27 0·32 85·0 99·46 
08HN-24B-11 38·14 35·22 25·36 0·35 0·39 0·15 71·2 99·62 
08HN-24B-12 39·46 46·22 14·03 0·17 0·26 0·25 85·4 100·39 
08HN-24B-13 37·78 36·33 24·58 0·34 0·23 0·20 72·5 99·46 
08HN-24B-18 39·88 44·59 13·78 0·22 0·23 0·30 85·2 98·99 
08HN-24B-19 39·41 38·06 22·75 0·29 0·25 0·18 74·9 100·94 
08HN-24B-20 39·79 39·61 20·79 0·27 0·23 0·14 77·3 100·83 
08HN-24B-21 38·84 35·84 25·42 0·35 0·30 0·12 71·5 100·87 
08HN-24B-22 37·96 33·18 28·54 0·46 0·32 0·15 67·5 100·60 
08HN-24B-23 38·06 35·40 26·04 0·37 0·26 0·17 70·8 100·29 
08HN-24B-24 38·37 36·22 24·89 0·38 0·29 0·14 72·2 100·29 
08HN-24B-26 40·52 44·73 14·00 0·16 0·24 0·27 85·1 99·92 
08HN-24B-27 40·47 44·83 14·07 0·21 0·26 0·32 85·0 100·15 
08HN-24B-28 39·22 41·39 18·48 0·25 0·27 0·22 80·0 99·83 
08HN-14B-11 37·74 31·13 30·82 0·34 0·26 0·17 64·3 100·45 
08HN-14B-13 37·59 32·06 29·93 0·32 0·26 0·14 65·6 100·30 
08HN-14B-15 38·79 33·15 27·65 0·30 0·27 0·11 68·1 100·29 
08HN-14B-16 37·77 32·78 28·77 0·35 0·22 0·17 67·0 100·06 
08HN-14B-17 37·83 31·75 29·84 0·34 0·25 0·09 65·5 100·10 
08HN-14B-18 37·67 32·40 29·49 0·30 0·25 0·08 66·2 100·18 
08HN-14B-19 37·67 32·51 29·51 0·36 0·25 0·10 66·3 100·39 
08HN-14B-20 37·39 32·44 29·50 0·36 0·27 0·09 66·2 100·05 
08HN-14B-26 36·82 30·55 31·10 0·38 0·27 0·11 63·6 99·23 
08HN-14B-33 37·88 32·33 29·16 0·34 0·27 0·13 66·4 100·11 
08HN-14B-35 37·93 32·50 28·65 0·33 0·27 0·13 66·9 99·81 
08HN-14B-36 37·16 31·71 30·19 0·36 0·23 0·17 65·2 99·82 

C, M and R after probe numbers indicate core, mantle and rim of Ol phenocrysts, respectively.

Xenocrystic olivines may be discriminated from phenocrystic olivines by their physical characteristics including deformation banding (e.g. kink bands), resorption, and small grain sizes (<2 mm) (e.g. Garcia, 1996). Kink bands have been identified in samples 08HN-1A and 08HN-4D. This kind of deformed olivine is characterized by low CaO (<0·1 wt %), MnO (<0·14 wt %) and FeO (<10 wt %), and high MgO (>46 wt %), which suggests that they were probably derived from disaggregated peridotite xenoliths.

Figure 9a shows results of the single microprobe analyses as functions of the Mg# of the host basalts. We calculated the whole-rock Mg# with 10% of total Fe as Fe3+. The Fe–Mg exchange partition coefficient between olivine and basaltic liquid is well constrained by experiments, varying from 0·3 at 1 atm in equilibrium with a basaltic melt with about 8 wt % MgO (Roeder & Emslie, 1970) to 0·31–0·34 at 5–15 kbar (Ulmer, 1989). Olivine–melt equilibrium relations of this kind are best shown in a plot of whole-rock Mg# versus the forsterite content of olivine (Fo) (e.g. Garcia, 1996). As shown in Fig. 9a, the bold curves indicate the theoretical range of olivine compositions that would be in equilibrium with a given melt composition. Horizontal arrows in Fig. 9a indicate the effect of crystal accumulation. Only two compositions of olivine cores in samples 08HN-8A and 16A fall within or near the equilibrium field. Olivine core compositions for samples 08HN-14B, 17A, and 19C fall significantly below the equilibrium field, suggesting that the analysed olivines are not equilibrium phenocrysts, but late-crystallizing groundmass grains. The remaining five samples (08HN-1A, 2B, 4D, 24B, and 25A) contain three populations of olivines including an Mg-rich group, an Mg-depleted group, and an equilibrium group, which plot respectively above, within, and below the equilibrium field. The Mg-rich group can be divided into xenocrystic and phenocrystic olivines. All xenocrystic olivines from 08HN-1A, 2B, and 4D, recognized by their physical characteristics, are much more Mg-rich and plot significantly higher in the equilibrium field. The Mg-rich phenocrystic olivines (08HN-1A, 2B, 24B, and 25A) also plot above the equilibrium field. These Mg-rich olivines probably crystallized earlier from hotter, higher-MgO melts and were entrained in the ascending magma. The Mg-rich phenocrystic olivines have Fo contents ranging from 89·6 to 90·7, which suggest Mg# values of 72–75 for the equilibrium melts using a KD = 0·3. Such Mg# values indicate that the equilibrium melts should have ∼16 wt % MgO based on the correlations of Mg# vs MgO in the Hainan basalts.

Fig. 9.

Mineral–melt Fe/Mg equilibrium diagrams for olivine and clinopyroxene. (a) Whole-rock mg-number (Mg#) vs Fo content (Mg#) of olivine, where mg-number = Mg2+/(Mg2+ + Fe2+) calculated assuming Fe2+/Fetotal = 0·9 for whole rock and total Fe as Fe2+ in olivine. The Fe/Mg exchange partition coefficient between olivine and basaltic liquid is well constrained by experiments to vary from 0·3 at 1 atm equilibrium for a basaltic melt with about 8 wt % MgO (Roeder & Emslie, 1970), to 0·31–0·34 at 5–15 kbar (Ulmer, 1989). Arrows indicate the relative effects of olivine accumulation, high-Mg xenocryst addition, and groundmass crystallization on Fe/Mg equilibrium. (b) Whole-rock Mg# vs clinopyroxene Mg#. The Fe–Mg KD is slightly dependent on pressure, and probably falls between 0·27 ± 0·05 (Putirka, 1999) and 0·23 ± 0·05 (Toplis & Carroll, 1995).

Fig. 9.

Mineral–melt Fe/Mg equilibrium diagrams for olivine and clinopyroxene. (a) Whole-rock mg-number (Mg#) vs Fo content (Mg#) of olivine, where mg-number = Mg2+/(Mg2+ + Fe2+) calculated assuming Fe2+/Fetotal = 0·9 for whole rock and total Fe as Fe2+ in olivine. The Fe/Mg exchange partition coefficient between olivine and basaltic liquid is well constrained by experiments to vary from 0·3 at 1 atm equilibrium for a basaltic melt with about 8 wt % MgO (Roeder & Emslie, 1970), to 0·31–0·34 at 5–15 kbar (Ulmer, 1989). Arrows indicate the relative effects of olivine accumulation, high-Mg xenocryst addition, and groundmass crystallization on Fe/Mg equilibrium. (b) Whole-rock Mg# vs clinopyroxene Mg#. The Fe–Mg KD is slightly dependent on pressure, and probably falls between 0·27 ± 0·05 (Putirka, 1999) and 0·23 ± 0·05 (Toplis & Carroll, 1995).

Clinopyroxene

The chemical compositions of analyzed clinopyroxenes (Cpx) are presented in Table 5. Cations were calculated on a six-oxygen basis following the procedure of Lindsley (1983) and ferric iron was calculated from charge-balance considerations. Interestingly, although large compositional variations in single samples exist (Table 5), all the analyses in cores and rims fall in the diopside to Mg-augite field in terms of En–Fs–Wo nomenclature with an end-member composition of En24·3–47·3Fs38·3–1·6Wo37·4–51·1 (Fig. 10a). All the analyzed clinopyroxenes plot within the Ca–Mg–Fe pyroxene (Quad area) field in the Q–J diagram (Fig. 10b) where Q = Ca + Mg + Fe2+, and J = 2Na. Some clinopyroxenes contain a high proportion of calculated jadeite (up to 14·4%).

Fig. 10.

Compositional variations in clinopyroxenes in the Hainan basalts. (a) The pyroxene quadrilateral; (b) Q–J diagram. Abbreviations and compositions of the end-members are after Morimoto (1988).

Fig. 10.

Compositional variations in clinopyroxenes in the Hainan basalts. (a) The pyroxene quadrilateral; (b) Q–J diagram. Abbreviations and compositions of the end-members are after Morimoto (1988).

Table 5:

Representative electron probe analyses of clinopyroxene from the Hainan basalts

Host rock: 08HN-1A
 
08HN-2A
 
08HN-2B 08HN-2B
 
08HN-8A
 
Probe no.: 1A-1R 1A-1M 1A-1C 1A-2R 1A-2M 1A-2C 2A-1M 2A-1C 2A-2M 2A-2R 2A-3R 2A-3C 2A-3M 2B-1M 2B-1R 2B-2R 2B-2M 2B-2C 8A-1M 8A-1R 8A-1C 8A-2C 
SiO2 50·9 49·35 52·18 49·89 53·15 51·83 49·53 51·53 52·28 49·81 50·42 53·2 51·78 51·7 53·5 53·3 51·1 53·2 52·18 49·21 50·39 51·35 
TiO2 1·35 1·97 0·92 1·78 0·72 0·03 2·09 0·54 0·51 0·65 1·04 0·72 1·23 0·73 0·69 0·38 0·78 0·4 1·28 1·89 1·47 1·18 
Al2O3 2·41 4·31 2·08 3·59 6·81 3·37 4·85 7·35 7·42 10·74 2·2 6·81 2·52 2·02 0·14 0·11 6·19 6·2 2·69 4·49 2·98 4·11 
Cr2O3  0·24 0·46 0·13 0·27 0·77 0·7 0·64 0·66 0·25 0·32 0·27 0·11 0·79 0·04 0·89 0·91 0·25 0·26 0·2 0·77 
FeOT 8·08 7·43 6·95 8·39 4·59 4·87 6·08 3·51 3·5 5·45 7·05 4·59 8·8 7·36 9·02 9·26 5·37 2·57 7·32 7·59 7·51 5·93 
MnO 0·19 0·29 0·15 0·24 0·05 0·14 0·1 0·13 0·08 0·14 0·05 0·14 0·15 0·2 0·2 0·11 0·1 0·2 0·12 0·15 0·1 
MgO 15·5 14·82 16·46 14·33 13·53 18·79 13·99 14·87 14·81 14·28 15·91 13·5 14·38 16·4 13·4 12·9 14·9 15·2 15·13 13·72 14·64 15·29 
CaO 20·5 20·79 20·84 21·14 19·32 18·74 21·12 19·18 18·52 17·48 21·73 19·3 19·88 20·1 21·6 22 18·8 19·4 20·92 21·29 21·34 20·37 
Na20·3 0·42 0·27 0·36 1·52 0·54 0·74 1·68 1·72 1·54 0·49 1·52 0·58 0·71 0·7 0·69 1·64 1·64 0·51 0·45 0·37 0·57 
Total 99·2 99·62 100·3 99·85 99·96 98·94 99·23 99·4 99·54 100·3 99·3 100 99·43 99·9 99·2 98·9 99·7 99·6 100·5 99·02 99·06 99·66 
Cations based on 6 oxygens per formula unit 
Si 1·900 1·835 1·916 1·859 1·922 1·875 1·844 1·873 1·891 1·794 1·922 1·88 1·862 1·91 2·01 2·01 1·87 1·92 1·919 1·846 1·886 1·892 
Ti 0·040 0·055 0·025 0·05 0·02 0·001 0·058 0·015 0·014 0·018 0·02 0·03 0·029 0·02 0·02 0·01 0·02 0·01 0·035 0·053 0·041 0·033 
Al 0·110 0·189 0·09 0·158 0·29 0·186 0·213 0·315 0·316 0·456 0·29 0·1 0·096 0·09 0·01 0·01 0·27 0·26 0·116 0·199 0·131 0·178 
AlIV 0·100 0·165 0·084 0·141 0·078 0·125 0·156 0·127 0·109 0·206 0·078 0·1 0·096 0·09 0·14 0·08 0·081 0·154 0·114 0·108 
AlVI 0·010 0·024 0·006 0·017 0·212 0·062 0·057 0·187 0·208 0·25 0·212 0·01 0·01 0·13 0·18 0·036 0·045 0·017 0·07 
Cr 0·000 0·007 0·013 0·004 0·008 0·022 0·021 0·019 0·019 0·007 0·008 0·01 0·009 0·02 0·03 0·03 0·007 0·008 0·006 0·022 
Fe3+ 0·030 0·04 0·025 0·035 0·058 0·012 0·008 0·015 0·06 0·064 0·07 0·01 0·02 0·04 0·003 0·021 0·026 
Fe2+ 0·220 0·191 0·188 0·226 0·139 0·09 0·178 0·099 0·106 0·149 0·139 0·16 0·154 0·16 0·28 0·27 0·13 0·08 0·223 0·217 0·209 0·183 
Mn 0·010 0·009 0·005 0·008 0·004 0·003 0·004 0·003 0·004 0·01 0·01 0·01 0·006 0·004 0·005 0·003 
Mg 0·860 0·821 0·901 0·796 0·729 1·013 0·776 0·805 0·799 0·767 0·729 0·88 0·93 0·9 0·75 0·72 0·81 0·82 0·829 0·767 0·817 0·839 
Ca 0·820 0·828 0·82 0·844 0·749 0·727 0·842 0·747 0·718 0·674 0·749 0·87 0·86 0·79 0·87 0·89 0·73 0·75 0·824 0·856 0·856 0·804 
Na 0·020 0·03 0·019 0·026 0·107 0·038 0·054 0·119 0·121 0·107 0·107 0·04 0·035 0·05 0·05 0·05 0·12 0·12 0·036 0·033 0·027 0·041 
Sum 4·010 4·007 4·007 4·007 3·963 4·01 4·003 4·002 3·988 4·015 3·963 4·03 4·043 4·01 3·99 3·99 4·01 3·98 4·001 4·004 4·004 3·996 
End-member (%) 
Wo 43·5 45·5 43·4 45·7 46·3 40·4 47·1 45·4 44·2 43·7 47·3 46·3 42·5 43·7 45·8 46·7 44·5 45·7 48·5 46·8 45·8 44 
En 45·5 45·1 47·7 43·1 45·1 56·3 43·4 48·9 49·2 49·6 48·2 45·1 42·8 49·5 39·3 37·9 49·2 49·6 40·1 42 43·7 46 
Fs 11 9·4 8·9 11·2 8·6 3·4 9·5 5·7 6·5 6·7 4·5 8·6 14·7 6·8 14·9 15·3 6·3 4·7 11·3 11·2 10·5 10 
Mg# 79·4 81·1 82·7 77·9 84 91·9 81·4 89·1 88·3 83·7 84 85 85·8 85 72·9 72·9 86·5 91·3 78·8 77·9 79·6 82·1 
Host rock: 08HN-1A
 
08HN-2A
 
08HN-2B 08HN-2B
 
08HN-8A
 
Probe no.: 1A-1R 1A-1M 1A-1C 1A-2R 1A-2M 1A-2C 2A-1M 2A-1C 2A-2M 2A-2R 2A-3R 2A-3C 2A-3M 2B-1M 2B-1R 2B-2R 2B-2M 2B-2C 8A-1M 8A-1R 8A-1C 8A-2C 
SiO2 50·9 49·35 52·18 49·89 53·15 51·83 49·53 51·53 52·28 49·81 50·42 53·2 51·78 51·7 53·5 53·3 51·1 53·2 52·18 49·21 50·39 51·35 
TiO2 1·35 1·97 0·92 1·78 0·72 0·03 2·09 0·54 0·51 0·65 1·04 0·72 1·23 0·73 0·69 0·38 0·78 0·4 1·28 1·89 1·47 1·18 
Al2O3 2·41 4·31 2·08 3·59 6·81 3·37 4·85 7·35 7·42 10·74 2·2 6·81 2·52 2·02 0·14 0·11 6·19 6·2 2·69 4·49 2·98 4·11 
Cr2O3  0·24 0·46 0·13 0·27 0·77 0·7 0·64 0·66 0·25 0·32 0·27 0·11 0·79 0·04 0·89 0·91 0·25 0·26 0·2 0·77 
FeOT 8·08 7·43 6·95 8·39 4·59 4·87 6·08 3·51 3·5 5·45 7·05 4·59 8·8 7·36 9·02 9·26 5·37 2·57 7·32 7·59 7·51 5·93 
MnO 0·19 0·29 0·15 0·24 0·05 0·14 0·1 0·13 0·08 0·14 0·05 0·14 0·15 0·2 0·2 0·11 0·1 0·2 0·12 0·15 0·1 
MgO 15·5 14·82 16·46 14·33 13·53 18·79 13·99 14·87 14·81 14·28 15·91 13·5 14·38 16·4 13·4 12·9 14·9 15·2 15·13 13·72 14·64 15·29 
CaO 20·5 20·79 20·84 21·14 19·32 18·74 21·12 19·18 18·52 17·48 21·73 19·3 19·88 20·1 21·6 22 18·8 19·4 20·92 21·29 21·34 20·37 
Na20·3 0·42 0·27 0·36 1·52 0·54 0·74 1·68 1·72 1·54 0·49 1·52 0·58 0·71 0·7 0·69 1·64 1·64 0·51 0·45 0·37 0·57 
Total 99·2 99·62 100·3 99·85 99·96 98·94 99·23 99·4 99·54 100·3 99·3 100 99·43 99·9 99·2 98·9 99·7 99·6 100·5 99·02 99·06 99·66 
Cations based on 6 oxygens per formula unit 
Si 1·900 1·835 1·916 1·859 1·922 1·875 1·844 1·873 1·891 1·794 1·922 1·88 1·862 1·91 2·01 2·01 1·87 1·92 1·919 1·846 1·886 1·892 
Ti 0·040 0·055 0·025 0·05 0·02 0·001 0·058 0·015 0·014 0·018 0·02 0·03 0·029 0·02 0·02 0·01 0·02 0·01 0·035 0·053 0·041 0·033 
Al 0·110 0·189 0·09 0·158 0·29 0·186 0·213 0·315 0·316 0·456 0·29 0·1 0·096 0·09 0·01 0·01 0·27 0·26 0·116 0·199 0·131 0·178 
AlIV 0·100 0·165 0·084 0·141 0·078 0·125 0·156 0·127 0·109 0·206 0·078 0·1 0·096 0·09 0·14 0·08 0·081 0·154 0·114 0·108 
AlVI 0·010 0·024 0·006 0·017 0·212 0·062 0·057 0·187 0·208 0·25 0·212 0·01 0·01 0·13 0·18 0·036 0·045 0·017 0·07 
Cr 0·000 0·007 0·013 0·004 0·008 0·022 0·021 0·019 0·019 0·007 0·008 0·01 0·009 0·02 0·03 0·03 0·007 0·008 0·006 0·022 
Fe3+ 0·030 0·04 0·025 0·035 0·058 0·012 0·008 0·015 0·06 0·064 0·07 0·01 0·02 0·04 0·003 0·021 0·026 
Fe2+ 0·220 0·191 0·188 0·226 0·139 0·09 0·178 0·099 0·106 0·149 0·139 0·16 0·154 0·16 0·28 0·27 0·13 0·08 0·223 0·217 0·209 0·183 
Mn 0·010 0·009 0·005 0·008 0·004 0·003 0·004 0·003 0·004 0·01 0·01 0·01 0·006 0·004 0·005 0·003 
Mg 0·860 0·821 0·901 0·796 0·729 1·013 0·776 0·805 0·799 0·767 0·729 0·88 0·93 0·9 0·75 0·72 0·81 0·82 0·829 0·767 0·817 0·839 
Ca 0·820 0·828 0·82 0·844 0·749 0·727 0·842 0·747 0·718 0·674 0·749 0·87 0·86 0·79 0·87 0·89 0·73 0·75 0·824 0·856 0·856 0·804 
Na 0·020 0·03 0·019 0·026 0·107 0·038 0·054 0·119 0·121 0·107 0·107 0·04 0·035 0·05 0·05 0·05 0·12 0·12 0·036 0·033 0·027 0·041 
Sum 4·010 4·007 4·007 4·007 3·963 4·01 4·003 4·002 3·988 4·015 3·963 4·03 4·043 4·01 3·99 3·99 4·01 3·98 4·001 4·004 4·004 3·996 
End-member (%) 
Wo 43·5 45·5 43·4 45·7 46·3 40·4 47·1 45·4 44·2 43·7 47·3 46·3 42·5 43·7 45·8 46·7 44·5 45·7 48·5 46·8 45·8 44 
En 45·5 45·1 47·7 43·1 45·1 56·3 43·4 48·9 49·2 49·6 48·2 45·1 42·8 49·5 39·3 37·9 49·2 49·6 40·1 42 43·7 46 
Fs 11 9·4 8·9 11·2 8·6 3·4 9·5 5·7 6·5 6·7 4·5 8·6 14·7 6·8 14·9 15·3 6·3 4·7 11·3 11·2 10·5 10 
Mg# 79·4 81·1 82·7 77·9 84 91·9 81·4 89·1 88·3 83·7 84 85 85·8 85 72·9 72·9 86·5 91·3 78·8 77·9 79·6 82·1 
Host rock: 08HN-8A
 
08HN-14B 08HN-14B
 
08HN-16A
 
  
Probe no.: 8A-2M 8A-2R 8A-3R 8A-3C 8A-3M 14B-1R 14B-1M 14B-1C 14B-2C 14B-2R 14B-3R 14B-4C 14B-5C 16A-1R 16A-1M 16A-2C 16A-2R 16A-3R 16A-3C 16A-4C   
SiO2 49·9 50·59 51·24 51·8 50·38 50·23 52·7 51·86 52·03 52·63 50·61 52·12 51·97 50·22 50·44 49·29 51·44 51·78 50·98 50·1   
TiO2 1·88 1·86 1·43 0·94 1·66 1·92 0·75 0·96 0·9 0·87 2·27 1·05 0·99 1·69 1·23 0·85 1·13 1·23 0·7 1·16   
Al2O3 5·02 4·62 3·27 3·57 4·56 1·99 1·83 2·91 2·22 0·87 2·89 1·97 1·77 4·02 2·6 2·48 3·24 2·52 2·32 3·46   
Cr2O3 0·81 0·61 0·15 0·44 0·36 0·52 0·53 0·58 0·01 0·28 0·22 0·2 0·2 0·5 0·73 0·11 0·18 0·28   
FeOT 6·33 6·52 7·97 6·34 6·53 9·1 8·25 7·73 7·71 14·32 10·69 8·28 8·37 7·7 7·51 8·58 7·49 8·8 9·16 7·85   
MnO 0·15 0·13 0·16 0·13 0·12 0·2 0·16 0·21 0·12 0·36 0·19 0·14 0·18 0·09 0·14 0·2 0·16 0·14 0·19 0·14   
MgO 14·3 14·34 14·68 15·8 14·4 14·79 16·1 16·29 16·79 12·69 12·54 14·9 15·92 13·76 15·48 17·78 14·95 14·38 17·85 16·65   
CaO 21·1 21·31 20·21 19·6 21·07 20·71 18·8 19·32 19·2 17·25 20·12 19·89 19·84 20·96 20·97 19·94 19·75 19·88 19·08 19·22   
Na20·51 0·42 0·41 0·58 0·42 0·49 0·42 0·45 0·38 0·64 0·63 0·4 0·35 0·47 0·44 0·37 0·45 0·58 0·46 0·58   
Total 100 100·4 99·53 99·2 99·5 99·43 99·5 100·3 99·93 99·63 99·94 99·04 99·61 99·11 99·01 99·98 99·32 99·43 100·9 99·43   
Cations based on 6 oxygens per formula unit 
Si 1·84 1·862 1·906 1·91 1·869 1·889 1·95 1·906 1·917 1·993 1·901 1·947 1·93 1·88 1·883 1·832 1·912 1·932 1·867 1·854   
Ti 0·05 0·051 0·04 0·03 0·046 0·054 0·02 0·027 0·025 0·025 0·064 0·03 0·028 0·048 0·034 0·024 0·031 0·034 0·019 0·032   
Al 0·22 0·2 0·144 0·16 0·2 0·088 0·08 0·126 0·096 0·039 0·128 0·087 0·077 0·177 0·115 0·109 0·142 0·111 0·1 0·151   
AlIV 0·16 0·138 0·094 0·09 0·131 0·088 0·05 0·094 0·083 0·007 0·099 0·053 0·07 0·12 0·115 0·109 0·088 0·068 0·1 0·146   
AlVI 0·06 0·062 0·049 0·07 0·068 0·03 0·032 0·013 0·031 0·029 0·034 0·007 0·057 0·054 0·043 0·005   
Cr 0·02 0·018 0·004 0·01 0·011 0·02 0·015 0·017 0·008 0·006 0·006 0·006 0·015 0·021 0·003 0·005 0·008   
Fe3+ 0·015 0·02 0·023 0·019 0·057 0·073 0·089 0·083   
Fe2+ 0·19 0·201 0·248 0·2 0·203 0·271 0·26 0·218 0·215 0·454 0·336 0·259 0·241 0·241 0·177 0·194 0·233 0·275 0·192 0·16   
Mn 0·01 0·004 0·005 0·004 0·006 0·01 0·006 0·004 0·012 0·006 0·005 0·006 0·003 0·005 0·006 0·005 0·004 0·006 0·004   
Mg 0·79 0·786 0·814 0·87 0·796 0·829 0·89 0·892 0·922 0·716 0·702 0·83 0·881 0·768 0·861 0·985 0·828 0·8 0·974 0·918   
Ca 0·84 0·84 0·805 0·78 0·837 0·835 0·75 0·761 0·758 0·7 0·81 0·796 0·79 0·841 0·839 0·794 0·787 0·795 0·749 0·762   
Na 0·04 0·03 0·03 0·04 0·03 0·036 0·03 0·032 0·027 0·047 0·046 0·029 0·025 0·034 0·032 0·026 0·032 0·042 0·033 0·042   
Sum 3·993 3·995 3·995 4·024 4·004 4·004 3·989 3·994 3·991 4·003 3·998 4·01 4·061 3·991 3·997 4·033 4·014   
End-member (%) 
Wo 46 46 43·1 42·1 45·6 44·8 39·5 40·9 40·3 37·4 43·8 42·2 41·5 45·4 45·4 44·3 42·6 42·5 41·2 42·4   
En 43·4 43 43·6 47·3 43·4 44·5 47 48 49 38·3 38 44 46·3 41·5 46·6 55 44·8 42·8 53·7 51·1   
Fs 10·6 11 13·3 10·6 11 10·7 13·5 11·1 10·8 24·3 18·2 13·7 12·1 13 0·7 12·6 14·7 5·1 6·6   
Mg# 80·3 79·7 76·7 81·7 79·7 75·4 77·7 80·4 81·1 61·2 67·7 76·2 78·5 76·1 82·9 83·5 78·1 74·4 83·5 85·2   
Host rock: 08HN-8A
 
08HN-14B 08HN-14B
 
08HN-16A
 
  
Probe no.: 8A-2M 8A-2R 8A-3R 8A-3C 8A-3M 14B-1R 14B-1M 14B-1C 14B-2C 14B-2R 14B-3R 14B-4C 14B-5C 16A-1R 16A-1M 16A-2C 16A-2R 16A-3R 16A-3C 16A-4C   
SiO2 49·9 50·59 51·24 51·8 50·38 50·23 52·7 51·86 52·03 52·63 50·61 52·12 51·97 50·22 50·44 49·29 51·44 51·78 50·98 50·1   
TiO2 1·88 1·86 1·43 0·94 1·66 1·92 0·75 0·96 0·9 0·87 2·27 1·05 0·99 1·69 1·23 0·85 1·13 1·23 0·7 1·16   
Al2O3 5·02 4·62 3·27 3·57 4·56 1·99 1·83 2·91 2·22 0·87 2·89 1·97 1·77 4·02 2·6 2·48 3·24 2·52 2·32 3·46   
Cr2O3 0·81 0·61 0·15 0·44 0·36 0·52 0·53 0·58 0·01 0·28 0·22 0·2 0·2 0·5 0·73 0·11 0·18 0·28   
FeOT 6·33 6·52 7·97 6·34 6·53 9·1 8·25 7·73 7·71 14·32 10·69 8·28 8·37 7·7 7·51 8·58 7·49 8·8 9·16 7·85   
MnO 0·15 0·13 0·16 0·13 0·12 0·2 0·16 0·21 0·12 0·36 0·19 0·14 0·18 0·09 0·14 0·2 0·16 0·14 0·19 0·14   
MgO 14·3 14·34 14·68 15·8 14·4 14·79 16·1 16·29 16·79 12·69 12·54 14·9 15·92 13·76 15·48 17·78 14·95 14·38 17·85 16·65   
CaO 21·1 21·31 20·21 19·6 21·07 20·71 18·8 19·32 19·2 17·25 20·12 19·89 19·84 20·96 20·97 19·94 19·75 19·88 19·08 19·22   
Na20·51 0·42 0·41 0·58 0·42 0·49 0·42 0·45 0·38 0·64 0·63 0·4 0·35 0·47 0·44 0·37 0·45 0·58 0·46 0·58   
Total 100 100·4 99·53 99·2 99·5 99·43 99·5 100·3 99·93 99·63 99·94 99·04 99·61 99·11 99·01 99·98 99·32 99·43 100·9 99·43   
Cations based on 6 oxygens per formula unit 
Si 1·84 1·862 1·906 1·91 1·869 1·889 1·95 1·906 1·917 1·993 1·901 1·947 1·93 1·88 1·883 1·832 1·912 1·932 1·867 1·854   
Ti 0·05 0·051 0·04 0·03 0·046 0·054 0·02 0·027 0·025 0·025 0·064 0·03 0·028 0·048 0·034 0·024 0·031 0·034 0·019 0·032   
Al 0·22 0·2 0·144 0·16 0·2 0·088 0·08 0·126 0·096 0·039 0·128 0·087 0·077 0·177 0·115 0·109 0·142 0·111 0·1 0·151   
AlIV 0·16 0·138 0·094 0·09 0·131 0·088 0·05 0·094 0·083 0·007 0·099 0·053 0·07 0·12 0·115 0·109 0·088 0·068 0·1 0·146   
AlVI 0·06 0·062 0·049 0·07 0·068 0·03 0·032 0·013 0·031 0·029 0·034 0·007 0·057 0·054 0·043 0·005   
Cr 0·02 0·018 0·004 0·01 0·011 0·02 0·015 0·017 0·008 0·006 0·006 0·006 0·015 0·021 0·003 0·005 0·008   
Fe3+ 0·015 0·02 0·023 0·019 0·057 0·073 0·089 0·083   
Fe2+ 0·19 0·201 0·248 0·2 0·203 0·271 0·26 0·218 0·215 0·454 0·336 0·259 0·241 0·241 0·177 0·194 0·233 0·275 0·192 0·16   
Mn 0·01 0·004 0·005 0·004 0·006 0·01 0·006 0·004 0·012 0·006 0·005 0·006 0·003 0·005 0·006 0·005 0·004 0·006 0·004   
Mg 0·79 0·786 0·814 0·87 0·796 0·829 0·89 0·892 0·922 0·716 0·702 0·83 0·881 0·768 0·861 0·985 0·828 0·8 0·974 0·918   
Ca 0·84 0·84 0·805 0·78 0·837 0·835 0·75 0·761 0·758 0·7 0·81 0·796 0·79 0·841 0·839 0·794 0·787 0·795 0·749 0·762   
Na 0·04 0·03 0·03 0·04 0·03 0·036 0·03 0·032 0·027 0·047 0·046 0·029 0·025 0·034 0·032 0·026 0·032 0·042 0·033 0·042   
Sum 3·993 3·995 3·995 4·024 4·004 4·004 3·989 3·994 3·991 4·003 3·998 4·01 4·061 3·991 3·997 4·033 4·014   
End-member (%) 
Wo 46 46 43·1 42·1 45·6 44·8 39·5 40·9 40·3 37·4 43·8 42·2 41·5 45·4 45·4 44·3 42·6 42·5 41·2 42·4   
En 43·4 43 43·6 47·3 43·4 44·5 47 48 49 38·3 38 44 46·3 41·5 46·6 55 44·8 42·8 53·7 51·1   
Fs 10·6 11 13·3 10·6 11 10·7 13·5 11·1 10·8 24·3 18·2 13·7 12·1 13 0·7 12·6 14·7 5·1 6·6   
Mg# 80·3 79·7 76·7 81·7 79·7 75·4 77·7 80·4 81·1 61·2 67·7 76·2 78·5 76·1 82·9 83·5 78·1 74·4 83·5 85·2   

Cations were calculated on six-oxygen basis following the procedure of Lindsley (1983). Fe2+ and Fe3+ were calculated based on charge-balance considerations using clinopyroxene formula spreadsheet Cpx_formula.V2 (http://serc.carleton.edu/files/research_education/equilibria/cpx_formula.v2.xls). C, M and R after probe numbers indicate core, mantle and rim of Cpx phenocrysts, respectively. FeOT total iron as FeO.

The Fe–Mg exchange partition coefficient between clinopyroxene and basaltic melts is less well constrained than that for olivine–melt, principally because of the presence of ferric iron in clinopyroxene and in the melt (Putirka et al., 2003; Putirka, 2008). The Fe–Mg KD is slightly dependent on pressure, and probably falls between 0·27 ± 0·05 (Putirka, 1999) and 0·23 ± 0·05 (Toplis & Carroll, 1995). Figure 9b shows the relationship between Cpx Mg# and whole-rock Mg# using an Fe–Mg KD of 0·23, 0·25, and 0·27. Four samples (e.g. 08HN-2A, 2A, 16A and 17A) contain equilibrium composition clinopyroxenes. However, three samples (08HN-1A, 2A and 2B) contain phenocrysts that are too Mg-rich to be considered as equilibrium compositions. High-Mg clinopyroxenes can crystallize at high pressure from less evolved magmas with high Al/Ti and Na/Ti ratios (e.g. Damasceno et al., 2002). Clinopyroxenes in samples 08HN-4B, 8A and 19C are characterized by low Mg#, all plotting below the equilibrium field. Sample 08HN-1A contains two populations of clinopyroxenes—an Mg-rich group that plots significantly above the equilibrium field and an Mg-depleted group that plots below the equilibrium field.

The Mg# values [100Mg/(Mg + Fe2+), cations] vary from 91·3 to 61·2; reverse zoning is never observed. The Mg# values correlate moderately positively with Al2O3/TiO2 (r = 0·51), Na2O/TiO2 (r = 0·48), and Al6+/Al4+ (r = 0·52), suggesting that the high Mg# clinopyroxenes are the result of high-pressure crystallization (e.g. Damasceno et al., 2002). These clinopyroxenes are characterized by high Al contents (up to 10·7 wt %). The Cr2O3 contents in the clinopyroxenes decrease rapidly from ∼0·8 at an Mg# of 80 to 0–0·3 wt % at an Mg# of 75 (Fig. 11a). MnO contents correlate negatively with Mg# (Fig. 11d). TiO2, Na2O, CaO, and SiO2 do not systematically correlate with Mg# and show curves or kinks on the trends of Mg#–X (Fig. 11).

Fig. 11.

Chemical variations of clinopyroxene phenocrysts. The grey bands highlight the kinks in the trends of the major elements vs Mg# in clinopyroxene. The continuous-line and dotted-line arrows indicate the trends of clinopyroxenes hosted by tholeiites and alkali basalts, respectively.

Fig. 11.

Chemical variations of clinopyroxene phenocrysts. The grey bands highlight the kinks in the trends of the major elements vs Mg# in clinopyroxene. The continuous-line and dotted-line arrows indicate the trends of clinopyroxenes hosted by tholeiites and alkali basalts, respectively.

DISCUSSION

Multiphase and polybaric crystallization and fractionation

At the outset of this discussion, it is necessary to establish what dominant process was responsible for the large range of chemical variations in the studied samples, including the variation of MgO between 2 and 11 wt % and the equally wide ranges of Ni (315–83 ppm) and Cr (387–114 ppm) contents (Table 3). Although both mantle melting and fractional crystallization processes could cause such variations in Mg-rich basalts, the depletions of MgO, Ni and Cr in the basalts requires fractional crystallization from more magnesian parent magmas to be the main factor in their genesis. The strong positive Mg#–Ni–Cr correlations (Fig. 4k and l) also suggest fractional crystallization of olivine from the bulk-rock samples. This is consistent with the correlated Fo–NiO–MnO–CaO variations in olivine phenocryst compositions (Fig. 8). However, the high-Mg olivine phenocrysts (Fo ≥ 89) are not in equilibrium with the whole-rock compositions of the host basalts (Fig. 9a). This implies that the high-Mg olivine phenocrysts may have crystallized from early high-magnesian melts, whereas the low-Mg phenocrysts are probably in equilibrium with the host melt prior to or during eruption.

Except for a few samples, the tholeiites have similar FeOT, CaO, and CaO/Al2O3 contents (highlighted by the grey band in Fig. 4c, d, and i). This implies that clinopyroxene is not a predominant phase in the fractionating mineral assemblage. Clinopyroxene fractionation can significantly increase the Zn/Fe ratios in the remaining melt because DZn/Fe for olivine/melt is nearly unity, but much less than unity between clinopyroxene and melt (Le Roux et al., 2010). Except for three samples, all the tholeiite samples are characterized by a narrow range of Zn/Fe ratios (Zn/Fe × 104 = 10–13; Fig. 4h) over a large range of Mg# (65–50). This implies that the effect of clinopyroxene fractionation on the composition of the tholeiites is insignificant. In contrast, the alkali basalt samples define a highly negative correlation of Zn/Fe with Mg# at Mg# <61, indicating that clinopyroxene fractionation strongly affected the compositions of the alkali basalts at Mg# <61. However, high Mg# (>61) alkali basalts have nearly constant Zn/Fe ratios, similar to the tholeiites (Fig. 4h). This implies a negligible effect of clinopyroxenes fractionation on the compositions of high Mg# alkali basalts.

The kinks in the trends of SiO2, Al2O3, Na2O, and K2O with Mg# (Fig. 4a, b, f, and i) imply that plagioclase began to crystallize at Mg# = 58, following crystallization of olivine + clinopyroxene. Extensive removal of plagioclase occurred at Mg# < 55, resulting in depletions of SiO2, Al2O3, Na2O and K2O.

Figure 11 provides another independent constraint on the assemblage of liquidus phases. The TiO2 contents in alkali basalt-hosted clinopyroxenes decreases from about 3 wt % to <1 wt % at Mg#Cpx ≤ 75 (Fig. 11c), perhaps owing to Fe–Ti oxide crystallization from the melt (e.g. Stone & Niu 2009). This is consistent with increases in SiO2 with falling Mg# at Mg#Cpx ≥ 75 (Mg#melt ≈ 43) (Fig. 11g) because crystallization of Fe–Ti oxides can lead to an SiO2 jump in the residual melt. The FeOT contents in both the tholeiites and alkali basalt-hosted clinopyroxenes increase sharply at Mg#Cpx ≥ 77 but decline gently and eventually flatten out at Mg#Cpx < 77 (Fig. 11h). This suggests that Fe–Ti oxides possibly begin to crystallize at Mg#Cpx = 77 (Mg#melt ≈ 44).

The Na2O contents in the tholeiite-hosted clinopyroxenes decrease slightly with decreasing Mg#Cpx in the Mg#Cpx range 83–77, and increase from about 0·1 to 0·4 wt % with decreasing Mg#Cpx in the Mg#Cpx range 77–75 (Fig. 11b). In the lower Mg#Cpx range (<75), Na2O in clinopyroxenes decreases again with falling Mg#Cpx (Fig. 11b). This may reflect crystallization of Na-rich plagioclase, which makes Na2O less available in the melt for clinopyroxene (e.g. Stone & Niu, 2009). Except for one high CaO analysis, CaO increases with falling Mg#Cpx at Mg#Cpx >80 and reaches maximum values at Mg#Cpx = 80–75 (Fig. 11f). At low Mg#Cpx (<75), CaO decreases sharply with falling Mg#Cpx (Fig. 11f). This indicates that initial fractional crystallization of clinopyroxene occurred at Mg#Cpx = 80–75 (Mg#melt ≈ 50–43), because clinopyroxene fractionation can sharply reduce the CaO content in the residual melt, which makes CaO less available for later crystallized clinopyroxene. The Al2O3 contents increase with falling Mg#Cpx at Mg#Cpx >80 and then decrease at Mg#Cpx < 80 (Fig. 11e), indicating that plagioclase fractionation began at Mg#Cpx ≈ 80 (Mg#melt ≈ 50).

Crystallization pressure and temperature

The CIPW norms of the Hainan basalts have been plotted on a Ne–Ol–Di–Hy–Qz projection and compared with cotectics for basaltic liquids in equilibrium with olivine, plagioclase and clinopyroxene at different pressures within the crust (Fig. 3a). Figure 3a shows that the majority of the Hainan basalts lie above and along the 9 (±1·5) kbar cotectic, with a few samples plotting significantly below the 9 kbar cotectic, suggesting that the basalts fractionated mainly at high pressure (≥9 kbar). Below we use three independent approaches (bulk-rock composition, clinopyroxene composition only and clinopyroxene–liquid) to constrain the crystallization pressure and temperature.

The crystallization pressure of dry tholeiitic liquids can be estimated using whole-rock compositions and the Ca–Mg barometer of Villiger et al. (2007), which reflects CaO–MgO equilibria for dry tholeiitic melts co-saturated in clinopyroxene and plagioclase. The results show a crystallization pressures range of 1–24 kbar (mostly between 7 and 14 kbar) with a peak at 10–14 kbar (Fig. 12a).

Fig. 12.

Crystallization pressure and temperature estimates for the Hainan basalts based on (a) tholeiitic whole-rock data; (b) clinopyroxene only; (c, d) equilibrium clinopyroxene–liquid; (e, f) all clinopyroxene–host rock.

Fig. 12.

Crystallization pressure and temperature estimates for the Hainan basalts based on (a) tholeiitic whole-rock data; (b) clinopyroxene only; (c, d) equilibrium clinopyroxene–liquid; (e, f) all clinopyroxene–host rock.

The empirical approach of Soesoo (1997) uses principal component analysis of the major-element composition of clinopyroxenes crystallized from melting experiments to construct eigenvector grids for P and T. On Soesso's plots (Fig. 12b), clinopyroxenes predict a large range of pressure (2–15 kbar) and temperature conditions (1100–1300°C).

Putirka et al. (1996, 2003) and Putirka (1999, 2008) established a series of thermodynamic equations based on experimental work that relate temperature and pressure to equilibrium constants and allow for the construction of clinopyroxene–liquid thermobarometers. We carried out two calculations using these equations. First, we used only clinopyroxene compositions that fell well within the Fe–Mg equilibrium field in Fig. 9b. In this case, the whole-rock compositions of the host-rocks were regarded as liquid compositions. The thermobarometers from Putirka et al. (2003) were used to constrain the crystallization pressure and temperature (Fig. 12c and d). The calculated temperatures range from 1062 to 1322°C and have two main populations of 1120–1150°C and 1240–1350°C (Fig. 12c). The calculated pressures range from 2 to 25 kbar with three populations of 1–7, 10–19 and 22–25 kbar (Fig. 12d). Second, we employed the equations T1 and P1 from Putirka et al. (1996), equations 31, 32c and 33 from Putirka (2008), and thermobarometers from Putirka et al. (2003) to calculate the crystallization pressures and temperatures of all analysed clinopyroxene compositions. The host whole-rock compositions were adjusted to be in equilibrium with clinopyroxenes using an Fe–Mg partition coefficient of 0·25 for clinopyroxene/melt, by adding or subtracting clinopyroxene. The results are presented in Fig. 12e and f. The majority of the calculated temperatures range from 1100 to 1250°C with two populations of 1100–1180°C and 1200–1280°C. A few temperatures fell within the field >1300°C. The majority of the calculated pressures fall in the range of 7–15 kbar with a peak of 10–14 kbar. A few clinopyroxenes predict pressures of 2–4 and 22–24 kbar. Overall, the two model calculations gave similar crystallization T–P ranges: the magma initially crystallized at high pressure (20–25 kbar) and high temperature (1300–1350°C) and then mainly fractionated at 10–15 kbar and moderate temperatures of 1100–1250°C. The results also indicate that the parental magma cooled from at least 1350°C to 1100°C.

Primary melt compositions

Primary melt compositions have been widely used as probes of the thermal state of their mantle sources (e.g. McKenzie & Bickle, 1988; Albarède, 1992; Langmuir et al., 1992; Putirka, 2005; Herzberg et al., 2007; Putirka et al., 2007). The discussion above shows that clinopyroxene fractionation has little effect on high Mg# (>61) alkali basalts and most tholeiites. Furthermore, the trend of CaO–Mg#Cpx indicates that clinopyroxene in the tholeiites most probably began to crystallize at Mg# < 50. Available data for the Hainan basalts allow us to produce a regression equation of MgO = 0·0051 × (Mg#)2 – 0·2669 × Mg# + 5·805 (R2 = 0·88, n = 146). Using this equation, Mg# = 61 corresponds to MgO ≈ 8·5 wt %. Thus, the effect of clinopyroxene fractionation on samples with MgO > 8·5 wt % is negligible, if any.

To minimize the effect of clinopyroxene fractionation, only samples with MgO ≥ 9 wt % and CaO > 8 wt % were chosen as starting compositions. A series of olivine and basalt compositions were then calculated from these starting materials as follows: (1) the composition of equilibrium olivine was obtained using KD(Fe/Mg)oliv/liq = 0·31 (Putirka, 2005) and DNioliv/liq (Beattie et al., 1991), assuming that Fe2+/(Fe2+ + Fe3+) = 0·90 in the melt; (2) a more primitive basalt composition was calculated as a mixture of the basalt and equilibrium olivine in a weight ratio of 99·9:0·1; (3) steps (1) and (2) were repeated using the calculated primitive basalt to obtain a more primitive basalt. For the Hainan basalts, the most high-magnesian phenocrystic olivines have values of Fo90·7 and 0·38 wt % NiO. Therefore, the calculations of olivine and basalt compositions were repeated until the calculated equilibrium olivines had a value of Fo90·7. The amount of olivine addition required to achieve liquid Mg# values consistent with a Fo90·7 source is typically between 17 and 25% for the Hainan basalts (Table 6).

Table 6:

Estimated primary melt compositions, mantle potential temperatures and melting conditions for late Cenozoic Hainan basalts

Starting sample: 08HN-1A 08HN-2A 08HN-2B 08HN-3 08HN-8A 08HN-22D 08HN-24A 08HN-24B 08HN-24D HN9907 
Reference: Z10 
Rock type: QT AB AB QT QT AB AB AB QT QT 
Olivine add (%): 18 23 25 21 24 25 20 20 19 17 
NiO (wt %): 0·39 0·4 0·4 0·39 0·28 0·27 0·31 0·3 0·3  
wt %           
SiO2 47·25 46·65 46·92 46·58 48·21 45·84 47·18 47·01 47·3 48·46 
TiO2 2·38 2·26 2·19 1·78 2·07 1·98 1·94 1·98 
Al2O3 10·41 10·39 10·49 10·34 10·13 10·16 10·74 10·71 10·99 11·51 
FeO 10·42 11·05 10·95 11·18 10·72 11·11 10·38 10·53 10·33 9·54 
MnO 0·11 0·11 0·11 0·12 0·14 0·13 0·12 0·12 0·12 0·23 
MgO 16·8 18·11 17·92 18·29 17·64 18·17 16·95 17·3 16·86 15·64 
CaO 7·08 6·29 6·35 7·67 7·58 7·74 7·83 7·68 7·88 8·15 
Na21·8 2·64 2·18 2·57 2·39 2·45 2·34 2·27 2·2 
K21·06 1·09 1·08 0·78 1·07 1·18 0·76 0·87 1·19 
Fe2O3 1·03 1·06 1·03 1·1 1·01 1·04 1·02 1·03 1·02 0·97 
P2O5 0·53 0·46 0·48 0·51 0·35 0·31 0·48 0·36 0·35 0·39 
H2O1 1·28 1·19 1·18 0·83 0·73 1·37 1·07 0·92 0·9 1·07 
H2O2 1·38 1·42 1·4 1·02 1·39 1·54 1·3 0·99 1·13 1·54 
F14 16 16 17 19 14 15 16 15 15 
Pf1 31·2 32·3 31·1 32 27·1 34·7 27·9 28·8 26·8 21·6 
Pf2 22·7 26·6 25·3 27·1 20·8 29·9 23·1 24·1 22·6 17·9 
Pf3 27·6 27·8 26·6 28·1 20·9 31·3 25·5 26·2 24·9 19·9 
Pf4 27·3 27·6 26·9 27 24·2 28·2 24·2 24·7 23·3 19·4 
Pf5 27·2 28·6 27·5 28·5 23·3 31 25·2 26 24·4 19·7 
SD 3·5 2·5 2·5 2·3 2·7 2·1 1·9 1·5 
Pi 32·4 36·3 35·8 37·5 35·9 36 33·1 34·4 37·6 29·3 
T1 1466 1498 1506 1514 1498 1509 1474 1484 1469 1429 
T2 1494 1528 1522 1533 1505 1537 1498 1507 1495 1457 
T3 1526 1527 1519 1533 1500 1543 1492 1502 1487 1441 
T4 1495 1518 1516 1527 1501 1529 1488 1498 1483 1442 
SD 30 17 11 18 12 12 13 14 
Tp1 1503 1532 1528 1536 1522 1534 1506 1514 1504 1475 
Tp2 1555 1600 1594 1606 1584 1602 1560 1572 1557 1512 
Tp3 1534 1586 1579 1594 1568 1589 1540 1554 1537 1490 
Tp4 1505 1555 1546 1565 1529 1559 1502 1514 1498 1441 
Tp5 1570 1597 1600 1611 1625 1556 1578 1589 1413  
Tp6 1534 1574 1569 1582 1566 1568 1538 1549 1502 1480 
SD 30 30 31 31 42 27 33 34 55 30 
Starting sample: 08HN-1A 08HN-2A 08HN-2B 08HN-3 08HN-8A 08HN-22D 08HN-24A 08HN-24B 08HN-24D HN9907 
Reference: Z10 
Rock type: QT AB AB QT QT AB AB AB QT QT 
Olivine add (%): 18 23 25 21 24 25 20 20 19 17 
NiO (wt %): 0·39 0·4 0·4 0·39 0·28 0·27 0·31 0·3 0·3  
wt %           
SiO2 47·25 46·65 46·92 46·58 48·21 45·84 47·18 47·01 47·3 48·46 
TiO2 2·38 2·26 2·19 1·78 2·07 1·98 1·94 1·98 
Al2O3 10·41 10·39 10·49 10·34 10·13 10·16 10·74 10·71 10·99 11·51 
FeO 10·42 11·05 10·95 11·18 10·72 11·11 10·38 10·53 10·33 9·54 
MnO 0·11 0·11 0·11 0·12 0·14 0·13 0·12 0·12 0·12 0·23 
MgO 16·8 18·11 17·92 18·29 17·64 18·17 16·95 17·3 16·86 15·64 
CaO 7·08 6·29 6·35 7·67 7·58 7·74 7·83 7·68 7·88 8·15 
Na21·8 2·64 2·18 2·57 2·39 2·45 2·34 2·27 2·2 
K21·06 1·09 1·08 0·78 1·07 1·18 0·76 0·87 1·19 
Fe2O3 1·03 1·06 1·03 1·1 1·01 1·04 1·02 1·03 1·02 0·97 
P2O5 0·53 0·46 0·48 0·51 0·35 0·31 0·48 0·36 0·35 0·39 
H2O1 1·28 1·19 1·18 0·83 0·73 1·37 1·07 0·92 0·9 1·07 
H2O2 1·38 1·42 1·4 1·02 1·39 1·54 1·3 0·99 1·13 1·54 
F14 16 16 17 19 14 15 16 15 15 
Pf1 31·2 32·3 31·1 32 27·1 34·7 27·9 28·8 26·8 21·6 
Pf2 22·7 26·6 25·3 27·1 20·8 29·9 23·1 24·1 22·6 17·9 
Pf3 27·6 27·8 26·6 28·1 20·9 31·3 25·5 26·2 24·9 19·9 
Pf4 27·3 27·6 26·9 27 24·2 28·2 24·2 24·7 23·3 19·4 
Pf5 27·2 28·6 27·5 28·5 23·3 31 25·2 26 24·4 19·7 
SD 3·5 2·5 2·5 2·3 2·7 2·1 1·9 1·5 
Pi 32·4 36·3 35·8 37·5 35·9 36 33·1 34·4 37·6 29·3 
T1 1466 1498 1506 1514 1498 1509 1474 1484 1469 1429 
T2 1494 1528 1522 1533 1505 1537 1498 1507 1495 1457 
T3 1526 1527 1519 1533 1500 1543 1492 1502 1487 1441 
T4 1495 1518 1516 1527 1501 1529 1488 1498 1483 1442 
SD 30 17 11 18 12 12 13 14 
Tp1 1503 1532 1528 1536 1522 1534 1506 1514 1504 1475 
Tp2 1555 1600 1594 1606 1584 1602 1560 1572 1557 1512 
Tp3 1534 1586 1579 1594 1568 1589 1540 1554 1537 1490 
Tp4 1505 1555 1546 1565 1529 1559 1502 1514 1498 1441 
Tp5 1570 1597 1600 1611 1625 1556 1578 1589 1413  
Tp6 1534 1574 1569 1582 1566 1568 1538 1549 1502 1480 
SD 30 30 31 31 42 27 33 34 55 30 
Starting sample: HN9910 HN9911 HN9912 HN9914 HN9908 HN9910 220B-3 220B-4 219Bl 219B4 
Reference: Z10 Z10 Z10 Z10 Z10 F04 F04 F04 F04 F04 
Rock type: AB AB AB QT AB AB QT QT QT QT 
Olivine add (%): 20 19 21 17 20 24 18 19 19 18 
NiO (wt %):      0·26     
wt %           
SiO2 45·45 45·97 45·27 49·06 45·22 45·39 47·34 47·4 46·87 46·9 
TiO2 2·31 2·39 2·31 1·88 2·35 2·19 1·97 1·99 2·03 2·02 
Al2O3 10·88 11·23 10·74 12·02 10·72 10·31 11·04 11·05 11·64 11·07 
FeO 10·52 9·97 10·47 9·03 10·58 11·06 10·18 10·22 10·29 10·24 
MnO 0·26 0·16 0·17 0·13 0·17 0·25 0·13 0·12 0·11 0·12 
MgO 17·25 16·3 17·19 14·8 17·32 18·1 16·71 16·8 16·86 16·85 
CaO 9·05 9·02 8·8 8·12 8·83 8·57 8·38 8·2 8·28 8·48 
Na22·03 2·55 2·63 2·7 2·38 1·92 1·95 1·82 1·97 
K21·08 1·25 1·23 0·8 1·23 1·22 1·09 1·13 0·96 1·17 
Fe2O3 1·05 1·01 1·05 0·92 1·06 1·07 1·04 1·02 1·03 1·04 
P2O5 0·64 0·61 0·62 0·35 0·67 0·6 0·38 0·4 0·4 0·46 
H2O1 1·96 1·86 1·84 0·72 1·96 1·84     
H2O2 1·4 1·63 1·6 1·04 1·6 1·59 1·41 1·47 1·25 1·53 
F12 11 11 15 11 13 15 16 14 14 
Pf1 31·9 29·5 34·1 19·8 34 34 25·7 25·7 26·3 27·1 
Pf2 30 26·4 30·7 15·6 31·1 31·8 22·3 22·2 24 23·9 
Pf3 33 30·8 33·8 17·2 34·1 33·3 24·8 24·5 26·8 26·7 
Pf4 25·7 24·8 27·6 18·6 27·3 27·1 22·2 22·3 22·5 23·2 
Pf5 30·2 27·9 31·6 17·8 31·6 31·6 23·7 23·7 24·9 25·2 
SD 3·2 2·8 3·1 1·8 3·2 3·1 1·8 1·7 
Pi 32·5 30·1 32·4 27·3 32·6 35 32·6 32·9 33 33 
T1 1467 1449 1478 1414 1477 1492 1459 1462 1459 1464 
T2 1519 1493 1520 1433 1523 1539 1491 1492 1498 1498 
T3 1520 1488 1524 1414 1527 1547 1482 1483 1489 1490 
T4 1502 1476 1507 1420 1509 1526 1477 1479 1482 1484 
SD 30 24 25 11 28 30 17 16 20 18 
Tp1 1513 1491 1512 1454 1515 1532 1501 1503 1504 1504 
Tp2 1570 1537 1569 1481 1573 1600 1552 1555 1557 1556 
Tp3 1552 1515 1550 1459 1555 1586 1531 1535 1537 1536 
Tp4 1513 1472 1509 1407 1517 1555 1487 1490 1495 1492 
Tp5 1483 1478 1466 1540 1463 1508 1577 1582 1570 1570 
Tp6 1526 1504 1521 1468 1525 1556 1530 1533 1533 1532 
SD 35 28 40 49 42 38 36 37 32 33 
Starting sample: HN9910 HN9911 HN9912 HN9914 HN9908 HN9910 220B-3 220B-4 219Bl 219B4 
Reference: Z10 Z10 Z10 Z10 Z10 F04 F04 F04 F04 F04 
Rock type: AB AB AB QT AB AB QT QT QT QT 
Olivine add (%): 20 19 21 17 20 24 18 19 19 18 
NiO (wt %):      0·26     
wt %           
SiO2 45·45 45·97 45·27 49·06 45·22 45·39 47·34 47·4 46·87 46·9 
TiO2 2·31 2·39 2·31 1·88 2·35 2·19 1·97 1·99 2·03 2·02 
Al2O3 10·88 11·23 10·74 12·02 10·72 10·31 11·04 11·05 11·64 11·07 
FeO 10·52 9·97 10·47 9·03 10·58 11·06 10·18 10·22 10·29 10·24 
MnO 0·26 0·16 0·17 0·13 0·17 0·25 0·13 0·12 0·11 0·12 
MgO 17·25 16·3 17·19 14·8 17·32 18·1 16·71 16·8 16·86 16·85 
CaO 9·05 9·02 8·8 8·12 8·83 8·57 8·38 8·2 8·28 8·48 
Na22·03 2·55 2·63 2·7 2·38 1·92 1·95 1·82 1·97 
K21·08 1·25 1·23 0·8 1·23 1·22 1·09 1·13 0·96 1·17 
Fe2O3 1·05 1·01 1·05 0·92 1·06 1·07 1·04 1·02 1·03 1·04 
P2O5 0·64 0·61 0·62 0·35 0·67 0·6 0·38 0·4 0·4 0·46 
H2O1 1·96 1·86 1·84 0·72 1·96 1·84     
H2O2 1·4 1·63 1·6 1·04 1·6 1·59 1·41 1·47 1·25 1·53 
F12 11 11 15 11 13 15 16 14 14 
Pf1 31·9 29·5 34·1 19·8 34 34 25·7 25·7 26·3 27·1 
Pf2 30 26·4 30·7 15·6 31·1 31·8 22·3 22·2 24 23·9 
Pf3 33 30·8 33·8 17·2 34·1 33·3 24·8 24·5 26·8 26·7 
Pf4 25·7 24·8 27·6 18·6 27·3 27·1 22·2 22·3 22·5 23·2 
Pf5 30·2 27·9 31·6 17·8 31·6 31·6 23·7 23·7 24·9 25·2 
SD 3·2 2·8 3·1 1·8 3·2 3·1 1·8 1·7 
Pi 32·5 30·1 32·4 27·3 32·6 35 32·6 32·9 33 33 
T1 1467 1449 1478 1414 1477 1492 1459 1462 1459 1464 
T2 1519 1493 1520 1433 1523 1539 1491 1492 1498 1498 
T3 1520 1488 1524 1414 1527 1547 1482 1483 1489 1490 
T4 1502 1476 1507 1420 1509 1526 1477 1479 1482 1484 
SD 30 24 25 11 28 30 17 16 20 18 
Tp1 1513 1491 1512 1454 1515 1532 1501 1503 1504 1504 
Tp2 1570 1537 1569 1481 1573 1600 1552 1555 1557 1556 
Tp3 1552 1515 1550 1459 1555 1586 1531 1535 1537 1536 
Tp4 1513 1472 1509 1407 1517 1555 1487 1490 1495 1492 
Tp5 1483 1478 1466 1540 1463 1508 1577 1582 1570 1570 
Tp6 1526 1504 1521 1468 1525 1556 1530 1533 1533 1532 
SD 35 28 40 49 42 38 36 37 32 33 
Starting sample: 212B2 QB013 QB012 QB014 II2B-2 HN9907 HN27 HN64 HN97  
Reference: F04 F04 F04 F04 F04 F04 F92 F92 F92  
Rock type: QT QT QT AB AB QT QT QT QT  
Olivine add (%): 19 25 25 24 24 19 24 24 22  
NiO (wt %):  0·28 0·25    0·3 0·3 0·36  
wt %           
SiO2 48·51 46·88 45·3 46·17 46·61 47·96 46·23 45·58 47·06  
TiO2 1·76 2·02 2·07 2·04 1·91 2·07 2·2 2·16  
Al2O3 11·45 10·85 10·93 10·47 10·74 11·1 10·91 10·67 10·55  
FeO 9·81 10·83 11·01 10·85 10·6 10·04 10·6 10·78 10·62  
MnO 0·12 0·11 0·11 0·12 0·12 0·23 0·14 0·14 0·13  
MgO 16·17 17·73 17·97 17·81 17·42 16·52 17·36 17·66 17·49  
CaO 7·62 7·88 9·22 8·14 8·16 7·86 8·01 7·67 7·15  
Na22·3 1·61 1·63 2·03 2·01 2·11 2·28 2·59 2·63  
K21·15 0·96 1·12 1·2 1·19 1·14 1·23 1·04 0·74  
Fe2O3 0·98 1·03 1·05 1·04 1·02 1·02 1·01  
P2O5 0·33 0·47 0·46 0·5 0·47 0·38 0·46 0·52 0·44  
H2O1  1·42 1·42 1·45   1·51 1·22 0·49  
H2O2 1·5 1·24 1·46 1·56 1·54 1·49 1·6 1·35 0·96  
F (%) 17 16 13 15 15 16 16 15 18  
Pf1 22·7 28 32·2 31·8 29·5 24·3 31 35 29·5  
Pf2 18·3 25·2 31·9 28 25·7 20·2 27 30·2 24·2  
Pf3 19·7 26·8 33·7 29·9 28 22·1 29·6 32·5 26  
Pf4 20·6 23·6 25·6 26·2 24·8 21·4 26 28·8 25·5  
Pf5 20·3 25·9 30·9 29 27 22 28·4 31·6 26·3  
SD 1·8 1·9 3·6 2·4 2·1 1·7 2·3 2·7 2·3  
Pi 31 34·9 35·1 34·9 34·8 32·1 33·6 34·6 35·9  
T1 1447 1479 1482 1491 1484 1456 1481 1502 1496  
T2 1469 1518 1537 1526 1513 1481 1515 1528 1511  
T3 1455 1514 1543 1527 1510 1470 1513 1531 1507  
T4 1457 1504 1521 1515 1502 1469 1503 1520 1505  
SD 11 21 34 20 16 13 19 16  
Tp1 1488 1524 1529 1526 1517 1497 1516 1522 1519  
Tp2 1532 1587 1595 1590 1577 1545 1574 1585 1579  
Tp3 1510 1571 1581 1574 1559 1524 1556 1568 1562  
Tp4 1460 1537 1551 1538 1519 1477 1519 1533 1521  
Tp5 1575 1588 1503 1562 1582 1581 1548 1522 1611  
Tp6 1513 1561 1552 1558 1551 1525 1543 1546 1558  
SD 44 29 37 26 31 41 25 29 40  
Starting sample: 212B2 QB013 QB012 QB014 II2B-2 HN9907 HN27 HN64 HN97  
Reference: F04 F04 F04 F04 F04 F04 F92 F92 F92  
Rock type: QT QT QT AB AB QT QT QT QT  
Olivine add (%): 19 25 25 24 24 19 24 24 22  
NiO (wt %):  0·28 0·25    0·3 0·3 0·36  
wt %           
SiO2 48·51 46·88 45·3 46·17 46·61 47·96 46·23 45·58 47·06  
TiO2 1·76 2·02 2·07 2·04 1·91 2·07 2·2 2·16  
Al2O3 11·45 10·85 10·93 10·47 10·74 11·1 10·91 10·67 10·55  
FeO 9·81 10·83 11·01 10·85 10·6 10·04 10·6 10·78 10·62  
MnO 0·12 0·11 0·11 0·12 0·12 0·23 0·14 0·14 0·13  
MgO 16·17 17·73 17·97 17·81 17·42 16·52 17·36 17·66 17·49  
CaO 7·62 7·88 9·22 8·14 8·16 7·86 8·01 7·67 7·15  
Na22·3 1·61 1·63 2·03 2·01 2·11 2·28 2·59 2·63  
K21·15 0·96 1·12 1·2 1·19 1·14 1·23 1·04 0·74  
Fe2O3 0·98 1·03 1·05 1·04 1·02 1·02 1·01  
P2O5 0·33 0·47 0·46 0·5 0·47 0·38 0·46 0·52 0·44  
H2O1  1·42 1·42 1·45   1·51 1·22 0·49  
H2O2 1·5 1·24 1·46 1·56 1·54 1·49 1·6 1·35 0·96  
F (%) 17 16 13 15 15 16 16 15 18  
Pf1 22·7 28 32·2 31·8 29·5 24·3 31 35 29·5  
Pf2 18·3 25·2 31·9 28 25·7 20·2 27 30·2 24·2  
Pf3 19·7 26·8 33·7 29·9 28 22·1 29·6 32·5 26  
Pf4 20·6 23·6 25·6 26·2 24·8 21·4 26 28·8 25·5  
Pf5 20·3 25·9 30·9 29 27 22 28·4 31·6 26·3  
SD 1·8 1·9 3·6 2·4 2·1 1·7 2·3 2·7 2·3  
Pi 31 34·9 35·1 34·9 34·8 32·1 33·6 34·6 35·9  
T1 1447 1479 1482 1491 1484 1456 1481 1502 1496  
T2 1469 1518 1537 1526 1513 1481 1515 1528 1511  
T3 1455 1514 1543 1527 1510 1470 1513 1531 1507  
T4 1457 1504 1521 1515 1502 1469 1503 1520 1505  
SD 11 21 34 20 16 13 19 16  
Tp1 1488 1524 1529 1526 1517 1497 1516 1522 1519  
Tp2 1532 1587 1595 1590 1577 1545 1574 1585 1579  
Tp3 1510 1571 1581 1574 1559 1524 1556 1568 1562  
Tp4 1460 1537 1551 1538 1519 1477 1519 1533 1521  
Tp5 1575 1588 1503 1562 1582 1581 1548 1522 1611  
Tp6 1513 1561 1552 1558 1551 1525 1543 1546 1558  
SD 44 29 37 26 31 41 25 29 40  

H2O1 and H2O2 water contents in primary melts were estimated by fractionation correction of Ce and K2O (equilibrium with Fo90·7 olivines), respectively. F, degree of melting, estimated by equation A2 of Putirka et al. (2007). Pf1 to Pf5 are effective melting pressures in kbar. Pf1 is as defined by Lee et al. (2009); Pf2 as defined by Albarède (1992); Pf3 as defined by Haase (1996); Pf4 as defined by equation 42 of Putirka (2008); Pf5 is the average of Pf1 to Pf4. SD, standard deviation. Pi is the initial melting pressure by Putirka et al. (2007) in kbar. T1 to T4 are the melting temperatures (°C) of the melt segregation: T1 is according to equation 14 of Putirka (2008); T2 according to Albarède (1992); T3 according to Lee et al. (2009). Tp1 to Tp6 are the mantle potential temperatures in °C: Tp1 to Tp3 were estimated using the MgO contents in the primary melts following Herzberg et al. (2007), McKenzie & Bickle (1988) and Langmuir et al. (1992), respectively; Tp4 is defined by FeO contents in the primary melt according to equation 12 of Kelley et al. (2006); Tp5 is estimated following Putirka (2005); Tp6 is the average of Tp1 to Tp5. Sources for the starting samples: T, this study; Z10, Zou et al. (2010); F04, Fan et al. (2004); F92, Flower et al. (1992).

An independent constraint on the extent of olivine addition can be obtained by comparing the compositions of calculated olivines and real phenocrystic olivines (e.g. Tamura et al., 2000; Leeman et al., 2005). As shown in Fig. 13, the NiO contents in calculated olivines are similar to those of real phenocrystic olivines, suggesting that the calculated primary magmas represent the primary melt composition.

Fig. 13.

Variation of NiO vs Fo [100Mg/(Fe2+ + Mg)] for measured olivines (black filled circles) and calculated equilibrium olivines (open circles) for four basalt lavas. The calculated olivines were determined from the bulk composition of each lava, as described in the text. Grey symbols show all the measured olivine compositions from the Hainan basalts. Measured olivine compositions overlap those of the calculated equilibrium olivines (e.g. 08HN-1A, 08HN-2B and 08HN-24B). Although the measured olivine compositions are more iron-rich than calculated equilibrium olivines (e.g. 08HN-8A), the trends of NiO vs Fo defined by measured olivines extend towards or pass through the calculated equilibrium olivines. The calculated equilibrium olivine compositions fall within the distribution of all measured olivines from the Hainan basalts.

Fig. 13.

Variation of NiO vs Fo [100Mg/(Fe2+ + Mg)] for measured olivines (black filled circles) and calculated equilibrium olivines (open circles) for four basalt lavas. The calculated olivines were determined from the bulk composition of each lava, as described in the text. Grey symbols show all the measured olivine compositions from the Hainan basalts. Measured olivine compositions overlap those of the calculated equilibrium olivines (e.g. 08HN-1A, 08HN-2B and 08HN-24B). Although the measured olivine compositions are more iron-rich than calculated equilibrium olivines (e.g. 08HN-8A), the trends of NiO vs Fo defined by measured olivines extend towards or pass through the calculated equilibrium olivines. The calculated equilibrium olivine compositions fall within the distribution of all measured olivines from the Hainan basalts.

Twenty-eight samples (Table 6) were selected as starting materials to calculate the primary melts for the Hainan basalts. The tholeiites and alkali basalts have similar estimated primary melt compositions except for their SiO2 contents. The tholeiites are characterized by highly variable SiO2 contents of 50–45 wt %, whereas the alkali basalts show relatively low SiO2 contents of 47–45 wt %. Compared with ocean island basalts (OIB), the calculated primary melt compositions are similar to those of fractionation-corrected EM-1 and EM-2 type OIB (Fig. 14). The estimated primary melt compositions plot within the overlap of experimental fields defined by partial melting of silica-deficient eclogite and peridotite (Fig. 14).

Fig. 14.

Comparison of fractionation-corrected Hainan basalts (compositions in equilibrium with Fo90·7, corrected by olivine addition; Table 6), with experimental partial melts. Also shown for reference are the estimated compositions of primary melts of HIMU, EM1, and EM2 mantle end-members. The fields of experiment partial melts and the primary melt compositions for the HIMU, EM1, and EM2 mantle end-members are modified from Dasgupta et al. (2010).

Fig. 14.

Comparison of fractionation-corrected Hainan basalts (compositions in equilibrium with Fo90·7, corrected by olivine addition; Table 6), with experimental partial melts. Also shown for reference are the estimated compositions of primary melts of HIMU, EM1, and EM2 mantle end-members. The fields of experiment partial melts and the primary melt compositions for the HIMU, EM1, and EM2 mantle end-members are modified from Dasgupta et al. (2010).

Melting conditions and mantle thermal state

Melting conditions and mantle potential temperatures can be estimated using primary melt compositions (e.g. McKenzie & Bickle, 1988; Langmuir et al., 1992; Putirka, 2005, 2008; Herzberg et al., 2007; Putirka et al., 2007; Lee et al., 2009). The calculated results are presented in Table 6.

The estimated melting temperature (T) at which melts separate from the melting column varies from 1420 to 1520°C for the tholeiites and from 1480 to 1530°C for the alkali basalts (Table 6). Effective melting pressure (Pf), an average equilibration pressure, is 25–32 kbar (with a weighted average of 28·3 ± 1·4 kbar) for the alkali basalts, and 18–32 kbar (with a weighted average of 23·8 ± 1·8 kbar) for the tholeiites. This is consistent with the presence of significant (18–32%) 230Th excess in the Holocene Hainan basalts that requires a melting depth >75 km (∼25 kbar) (Zou & Fan, 2010). The initial melting pressure (Pi), at the bottom of the melting column, is calculated by the intersection of convective geotherms with the mantle solidus (Putirka et al., 2007). Estimated Pi values for the tholeiites and alkali basalts are similar, typically between 30 and 38 kbar (Table 6). As the mantle source ascends above the solidus, the total melt fraction F increases until the pressure at which the mantle source ceases to ascend adiabatically (Pf) and therefore ceases to melt. The degree of melting is proportional to the length of the melting column, except at relatively shallow depth (e.g. Asimow et al., 1997). F may also be a function of melting pressure, temperature and melt composition (e.g. McKenzie, 1984; Putirka et al., 2007). In this study, F was estimated using an experimental regression equation [equation A2 in the appendix of Putirka et al. (2007)]. The estimated F values are presented in Table 6.

Mantle potential temperature (Tp) is a key parameter for describing the thermal state of the upper mantle (e.g. McKenzie & Bickle, 1988; Albarède, 1992; Langmuir et al., 1992; Thompson & Gibson, 2000; Putirka, 2005, 2008; Campbell, 2007; Herzberg et al., 2007; Wang et al., 2007, 2009). There are two main approaches for modeling Tp: (1) calculating Tp using melt composition, as FeO, Na2O (e.g. Kelley et al., 2006) and MgO contents (e.g. Herzberg et al., 2007, and references therein), based on the pooled, accumulated fractional melting model; (2) using the equation Tp = T + F(Hfus/Cp) – ∂T/∂P (e.g. Putirka et al., 2007). The calculated Tp values using the two approaches are comparable, and we take the average Tp as the final result (Table 6). The tholeiites and alkali basalts have similar Tp ranging from about 1500 to 1580°C with a weighted average of 1541 ± 10°C.

To evaluate the significance of this result, it is important to consider the uncertainties involved in obtaining melting conditions and mantle potential temperatures. These mainly concern the value of KD, redox state (Fe3+/total Fe), mantle Mg#, and water content. Variations in Fe3+/∑Fe can introduce significant differences in the estimated compositions of the parental liquids, notably Mg#. For a given lava, increasing Fe3+/∑Fe from 0·1 to 0·2 would result in a decrease of about 1·5 wt % MgO for the primary melts, ∼60°C for the melting temperature and mantle potential temperature, and ∼4 kbar for the melting pressure. KD values increase slightly with increasing pressure (e.g. Putirka, 2005, 2008) and melt composition (Tamura et al., 2000; Herzberg & O'Hara, 2002) (typically within the range of 0·30–0·35). For the given original basalts, increasing KD from 0·30 to 0·33 would result in an increase of about 2 wt % MgO for the primary magma, ∼5 kbar for melting pressures, ∼40°C for melting temperature, and ∼100°C for mantle potential temperature. Thus, the net effect of variations in Fe3+/∑Fe and KD are negligible. Typical mantle Mg# [Mg# = Mg/(Mg + Fe2+) molar ratio] values are 89–90, but the values vary. The maximum Mg# value for the residual mantle of the Hainan basalts can be constrained by the maximum Fo values in phenocrystic olivines. Decreasing mantle Mg# values from 90·7 to 90 would reduce in decreases of about 1·4 wt % for the MgO content of the calculated primary magma, <20°C for melting temperature and mantle potential temperature, and 3 kbar for melting pressure for a given original basalt. Considering the compounded effects of the uncertainties in Fe3+/∑Fe ratios, KD values, and mantle Mg#, the final uncertainties are about ±4 kbar for pressure and ±50°C for melting temperature and potential temperatures. This is on a par with calibration errors associated with the thermobarometers used (i.e. ±50–70°C, ±3–5 kbar).

Water (H2O) content is another factor controlling the melting temperatures and pressure. The H2O concentrations in the melts were estimated using their primary Ce or K2O contents (olivine fraction correction), assuming that the Hainan basalts have the same H2O/Ce ratios of ∼200 as oceanic basalts (Herzberg et al., 2007) or H2O/K2O ratios of 1·3 like typical Hawaiian tholeiitic magmas (e.g. Wallace & Anderson, 1998). The two methods predict similar H2O contents for the primary melts of the Hainan basalts, varying in the range of 1·28–1·42 wt %, which is slightly higher than that for typical Hawaiian tholeiitic magmas (0·5–1·0 wt %; Ren et al., 2004). The calculated temperatures listed in Table 6 have the effect of H2O contents taken into account.

Figure 15 is a plot of the effective melting pressure vs temperature. We find that the temperatures (1420–1530°C) and pressures (18–32 kbar) for the primary melts of the Hainan basalts plot systematically above the dry lherzolite solidus but below the spinel garnet transition (∼50–60 km depth) and the base of the lithosphere (∼55 km; Wu et al., 2004). The PfT data form an array (Pf = 0·0105 × e0·0052T, R2 = 0·81) that begins at about 18 kbar (∼60 km) and intersects the dry peridotite solidus at ∼50 kbar or ∼160 km. This intersection translates into a mantle potential temperature beneath Hainan Island of ∼1500–1600°C, which is ∼200°C hotter than average MORB mantle (e.g. Herzberg et al., 2007; Lee et al., 2009) but typical of thermal mantle plumes such as the Hawaiian and Iceland plumes (Putirka, 2005; Herzberg et al., 2007; Lee et al., 2009).

Fig. 15.

Temperatures and pressures calculated for the Hainan basalts. The lherzolite solidus and melt fraction isopleths are from Katz et al. (2003). Curved lines represent melting adiabats where F(%) represents the fraction of melting. Near-vertical lines represent solid mantle adiabats. Fields for MORB and Hawaiian OIB are from Lee et al. (2009). The lithosphere–asthenosphere boundary (LAB) for Hainan Island is at about 55 km depth as constrained by geophysical data (Wu et al., 2004). Garnet-in and spinel-out occur at ∼60 and 80 km in peridotite for a steady-state geotherm (McKenzie & O'Nions, 1991). The pressure (P) is the average of the effective melting pressure (Pf5 from Table 6), and melting temperature (T) is the average value of T4 (Table 6).

Fig. 15.

Temperatures and pressures calculated for the Hainan basalts. The lherzolite solidus and melt fraction isopleths are from Katz et al. (2003). Curved lines represent melting adiabats where F(%) represents the fraction of melting. Near-vertical lines represent solid mantle adiabats. Fields for MORB and Hawaiian OIB are from Lee et al. (2009). The lithosphere–asthenosphere boundary (LAB) for Hainan Island is at about 55 km depth as constrained by geophysical data (Wu et al., 2004). Garnet-in and spinel-out occur at ∼60 and 80 km in peridotite for a steady-state geotherm (McKenzie & O'Nions, 1991). The pressure (P) is the average of the effective melting pressure (Pf5 from Table 6), and melting temperature (T) is the average value of T4 (Table 6).

The olivine fractionational correction element contents (SiO2, TiO2, MgO, Al2O3, and FeO) and ratios (Al2O3/TiO2, Sm/Nd, Zr/Y, and Nb/Y) correlate well with the effective melting pressure (Pf) (Fig. 16). This suggests that melting pressure is one of the controlling factors for the compositions of the primary melts.

Fig. 16.

Plots of major element contents and ratios vs effective melting pressure. The element contents and ratios were adjusted to be in equilibrium with olivine Fo90·7. The pressure Pf5 is from Table 6.

Fig. 16.

Plots of major element contents and ratios vs effective melting pressure. The element contents and ratios were adjusted to be in equilibrium with olivine Fo90·7. The pressure Pf5 is from Table 6.

Magma source mineralogy

The correlation trends in Fig. 17 could have been affected by post-solidification alteration, assimilation–fractionation–crystallization processes, residual mineral assemblages (source composition), and melting processes. The following lines of evidence show that these trends are mainly controlled by the melting degree and the residual mineral assemblage. First, it has been demonstrated that the effect of crustal contamination on the compositions of the Hainan basalts is insignificant (e.g. Tu et al., 1991; Fan et al., 2004; Zou & Fan, 2010). Second, the contribution of post-magmatic alteration is also negligible, because most of the studied samples are fresh. Third, fractionation crystallization processes could not explain the variations in trends in Fig. 17. After stripping off the effect of olivine fractionation, the Hainan basalts still have large variations in Th content, which would require extremely large-scale fractional crystallization of clinopyroxene and plagioclase (forumla50%; dashed-line arrows in Fig. 17). This is inconsistent with the major element compositions. The fractional crystallization trends are also inconsistent with the evolutionary trends of the Hainan basalts (Fig. 17). For example, fractional crystallization processes should produce positive correlations of Ti/Eu–Th and Sc/V–Th, but the Hainan basalts show negative correlations (Fig. 17b). Our analysis shows that the fractionating mineral assemblages in the Hainan basalts were controlled by olivine plus clinopyroxene and plagioclase at a late stage. Such crystal fractionation would have increased the silica and incompatible trace element contents of the remaining melts, resulting in positive correlations of SiO2–Th, whereas the Hainan basalts define a negative SiO2–Th trend. Therefore, the trends shown in Fig. 17 can be used to evaluate the residual source mineralogy.

Fig. 17.

(a) Abundance ratios of incompatible elements vs concentrations of Th adjusted to be in equilibrium with Fo90·7 for the Hainan basalts. (b) Abundance ratios (Zr/Hf, Zr/Sm, Zr/Tb, Ti/Eu and Sc/V) and major and trace element (SiO2, TiO2, Al2O3, CaO, K2O, Sc and Zr) contents vs Th content for the Hainan basalts. The element contents (SiO2, TiO2, Al2O3, CaO, K2O, Sc, Zr and Th) were adjusted to be in equilibrium with Fo90·7. The continuous-line arrows indicate the trends of element contents and ratios with respect to Th. The dashed-line arrows indicate the effect of 50 wt % fractionation of 70% clinopyroxene + 30% plagioclase on the melt compositions. The partition coefficients are from Supplementary Data Appendix Table R2.

Fig. 17.

(a) Abundance ratios of incompatible elements vs concentrations of Th adjusted to be in equilibrium with Fo90·7 for the Hainan basalts. (b) Abundance ratios (Zr/Hf, Zr/Sm, Zr/Tb, Ti/Eu and Sc/V) and major and trace element (SiO2, TiO2, Al2O3, CaO, K2O, Sc and Zr) contents vs Th content for the Hainan basalts. The element contents (SiO2, TiO2, Al2O3, CaO, K2O, Sc, Zr and Th) were adjusted to be in equilibrium with Fo90·7. The continuous-line arrows indicate the trends of element contents and ratios with respect to Th. The dashed-line arrows indicate the effect of 50 wt % fractionation of 70% clinopyroxene + 30% plagioclase on the melt compositions. The partition coefficients are from Supplementary Data Appendix Table R2.

Garnet and olivine control on compositional variations

Thorium contents (adjusted to be in equilibrium with olivine Fo90·7) were employed as an index of the degree of melting (e.g. Frey et al., 2000; Ren et al., 2004). The positive correlations of Tb/Yb–Th and negative correlation of Lu/Yb–Th in tholeiites and low-Th (<4 ppm) alkali basalts (Fig. 17a), require bulk solid/melt DTb/Yb < 1 and DYb/Lu < 1. Because the experimentally determined DTb/Yb and DYb/Lu ratios for clinopyroxene/melt, amphibole/melt and phlogopite/melt partitioning are near unity (e.g. LaTourrette et al., 1995; Dalpé & Baker, 2000; Adam & Green, 2006), these phases cannot effectively fractionate Tb from Yb. In contrast, it is well established that DTb/Yb ratios for garnet/melt partitioning are as low as 0·23 and DYb/Lu ratios are <1 (e.g. van Westrenen et al., 2000; Adam & Green, 2006). Therefore, the correlations between Tb/Yb, Lu/Yb and Th reflect the control of residual garnet. None the less, three high-Th (>4 ppm) alkali basalt samples have near constant Tb/Yb and Lu/Yb ratios (Fig. 17a), suggesting the presence of clinopyroxene (and/or amphibole, phlogopite) in their generation.

The high-Th alkali basalts have near constant Sc/V ratios whereas the Sc/V ratios in low-Th alkali basalts and tholeiites correlate negatively with Th (Fig. 17b). This implies that DSc/V is nearly unity for the high-Th alkali basalts, but DSc/V is >1 for low-Th alkali basalts and tholeiites. Experimentally determined DSc/V values for clinopyroxene/melt, garnet/melt, and amphibole/melt are nearly unity, but >2 for olivine/melt (Geochemical Earth Reference Model: http://earthref.org/GERM). Thus, olivine is most probably a predominant phase in the residual mineral assemblage during the generation of the tholeiites and most alkali basalts (low-Th) in Hainan.

The effect of residual K-bearing minerals on K, Rb, Sr and Ba

Amphibole and phlogopite are the major hosts for K, Rb, Sr, and Ba, which could have an effect on the concentrations and related ratios of these elements in equilibrium melts (e.g. Class & Goldstein, 1997; Yang et al., 2003). The following evidence suggests the presence of residual amphibole and phlogopite in the source during the generation of the Hainan basalts.

First, the tholeiites and low-Th alkali basalts exhibit broad negative correlations of Sr/Ce and Sr/Nd with Th (Fig. 17a), suggesting that DSr/Ce and DSr/Nd are >1. Experimental work shows that DSr/Ce and DSr/Nd for garnet/melt are <1 (e.g. Hauri et al., 1994; Gaetani et al., 2003; Bennett et al., 2004). Although experimentally determined values of DSr/Nd for clinopyroxene/melt range from <1 (0·4 ± 0·2; Blundy et al., 1998) to ≥1 (Bennett et al., 2004; Adam & Green, 2006), all available experimental data show DSr/Ce <1 for clinopyroxene/melt (http://earthref.org/GERM). Thus, residual garnet and/or clinopyroxene could not have produced these trends. On the other hand, Yang et al. (2003) showed that the relatively high compatibility of Sr relative to Ce and Nd signifies the presence of residual K-bearing minerals such as phlogopite and/or amphibole in Hawaiian basalts.

Second, the tholeiites define a broad positive correlation of Ba/La vs Th and negative correlations of Rb/La, Rb/Ba and K/Ce with Th (Fig. 17a), indicating DBa < DLa < DRb and DK > DCe. The alkali basalts define broad negative correlations of Ba/La and Rb/La with Th and nearly constant ratios of Rb/Ba, indicating DBa ≈ DRb > DLa. The K/Ce ratios in the high-Th alkali basalts are nearly constant and in most alkali basalts (low-Th alkali basalts) correlate negatively with Th. These trends suggest DK ≥ DCe for the alkali basalts, a diagnostic indicator of the presence of residual amphibole and/or phlogopite in the mantle source (e.g. Class & Goldstein, 1997; Yang et al., 2003).

Rb usually shows incompatible behavior in calcic amphibole but Dalpé & Baker (2000) found that it might be also slightly compatible (DRb = 1·04), whereas Ba is highly incompatible in amphibole (Tiepolo et al., 2007). The experimentally determined DRb/Ba for amphibole/melt in some cases is >1 (e.g. Brenan et al., 1995; LaTourrette et al., 1995; Dalpé & Baker, 2000; Adam & Green, 2006). However, both Ba and Rb usually are strongly compatible in phlogopite with DBa = 3·3–3·7 and DRb = 2·5–6 (e.g. LaTourrette et al., 1995; Foley et al., 1996). Thus, a bulk DBa < DRb indicates that the residual K-bearing mineral for the tholeiites is amphibole. A bulk DBa ≈ DRb > DLa implies that the K-bearing residual phase for the alkali basalts is most probably phlogopite.

Variations of HFSE: implications for source characteristics

Nb/La, Zr/Hf, Zr/Sm and Zr/Tb ratios in the tholeiites are positively correlated with Th contents, whereas Zr/Nb and Ti/Eu ratios are inversely correlated with Th content (Fig. 17). In addition, Hf/Sm ratios remain constant with falling Th (not shown). These trends imply DNb < DLa, DNb < DZr < DHf ∼ Dsm < DTb and DTi > DEu, similar to the pattern for typical OIB (e.g. David et al., 2000).

The positive correlations of Zr/Hf vs Th and Nb/Ta vs Th in the tholeiites (Fig. 17b) indicate a bulk DZr/Hf < 1 and DNb/Ta < 1. This is a typical characteristic of partial melts derived from predomintly peridotitic sources (e.g. David et al., 2000; Pfänder et al., 2007).

The increasing evidence suggests the presence of residual garnet during the generation of the alkali basalts. First, the alkali basalts have nearly constant Zr/Hf ratios (42–45) with falling Th from about 11 to 4 ppm (Fig. 17b), implying a bulk DZr/Hf ≈ 1. In the experiments of Hauri et al. (1994) and Van Westrenen et al. (1999), Zr and Hf are compatible in eclogitic garnet with DZr/Hf ≥ 1·5. On the other hand, the calculated bulk DZr/Hf values are about 0·3–0·4 for peridotitic sources using the partition coefficients of Horn et al. (1994), Salters & Longhi (1999), Salters et al. (2002) and McDade et al. (2003), and typical modal proportions of the mantle phases (in the garnet and spinel stability fields) after Kelemen et al. (2004). Therefore, the nearly unity value of DZr/Hf suggests the likely presence of residual eclogitic garnet in the source of Hainan basalts that elevated the DZr/Hf value from that of a peridotitic source. Second, the alkali basalts define a negative correlation of Nb/Ta vs Th (Fig. 17a), implying a bulk DNb/Ta >1. This is a typical characteristic of an eclogitic source because DNb/Ta for eclogitic garnet (grossular-rich garnet) is >1, with DNb/Ta values ranging between about 1·2 and 2·0 (e.g. Stalder et al., 1998; van Westrenen et al., 1999; Klemme et al., 2002; Pertermann et al., 2004). Third, the alkali basalts also exhibit negative correlations of Nb/La vs Th (Fig. 17a), indicating a bulk DNb/La > 1. Experimental data show that eclogitic garnet has DNb/La >1, with DNb/La values ranging from 1·3 to 7·5 (e.g. Van Westrenen et al., 1999; Pertermann et al., 2004). HFSE are also compatible in rutile, whereas the LREE are highly incompatible (e.g. Schmidt et al., 2004; Klemme et al., 2005; Xiong et al., 2005). A small amount of rutile could cause strong fractionation of Nb from La. A bulk DNb/La >1 thus suggests the presence of residual eclogitic garnet and possibly rutile in the generation of alkali basalts.

In summary, the residual source region for the Hainan tholeiites was dominated by olivine with the involvement of garnet and possibly amphibole, whereas the source region for the alkali basalts was dominated by clinopyroxene, phlogopite, and eclogitic garnet, with the possible involvement of rutile (i.e. a typical garnet-pyroxenite or eclogite lithology).

Characterizing the source region

Excluding crustal contamination, the Lu/Hf–X and Sm/Nd–X trends (Figs 18 and 19) indicate that generation of the Hainan basalts may have involved two end-member melts. The correlations of silica contents (corrected for olivine fractionation) with element ratios further suggest that the two end-members are high- and low-silica melts (Fig. 20a). The trends shown in Figs 17–20 were employed to estimate the composition of the high- and low-silica melts (Table 7). The low- and high-silica melts probably represent the end-members of the alkali basalts and tholeiites in the Hainan province, respectively. The plots of effective Pf versus estimated primary major element and trace element ratios from samples with MgO > 9·0 wt % and CaO > 8·0 wt % also indicate two end-members (Fig. 16). One end-member is characterized by low Pf with high SiO2, Al2O3, Al2O3/TiO2 and Sm/Nd, and low TiO2, FeO, Zr/Y and Nb/Y, which is similar to the high-silica melt (Table 7 and Figs 18–20). The other is characterized by high Pf with low SiO2, Al2O3, Al2O3/TiO2 and Sm/Nd, and high TiO2, FeO, Zr/Y and Nb/Y, which is similar to the low-silica melt (Table 7 and Figs 18–20).

Fig. 18.

Major and trace element ratios vs (a) Lu/Hf and (b) Sm/Nd for the Hainan basalts.

Fig. 18.

Major and trace element ratios vs (a) Lu/Hf and (b) Sm/Nd for the Hainan basalts.

Fig. 19.

Olivine fractionation-corrected major and trace element contents (in equilibrium with Fo90·7) vs Sm/Nd.

Fig. 19.

Olivine fractionation-corrected major and trace element contents (in equilibrium with Fo90·7) vs Sm/Nd.

Fig. 20.

(a) Abundance ratios and SiO2 vs Sr/Sr*. Sr* = SrN/(CeN × NdN)0·5 (primitive mantle normalized values). (b) Abundance ratios vs SiO2 for the Hainan basalts. The SiO2 contents were adjusted to be in equilibrium with Fo90·7.

Fig. 20.

(a) Abundance ratios and SiO2 vs Sr/Sr*. Sr* = SrN/(CeN × NdN)0·5 (primitive mantle normalized values). (b) Abundance ratios vs SiO2 for the Hainan basalts. The SiO2 contents were adjusted to be in equilibrium with Fo90·7.

Table 7:

Estimated compositions for the low- and high-silica melts

 Low-silica melt High-silica melt 
SiO2 (wt %) 45 >49 
TiO2 (wt %) 2·5 1·5 
FeO (wt %) 11 9·8 
Al2O3 (wt %) 10·7 11·5 
Th (ppm) >5 <1 
Sm/Nd 0·18 0·3 
Lu/Hf 0·01 >0·06 
Nb/Ta 14 18 
Sm/Yb >7 
Zr/Hf >42 32 
Zr/Y 30 
Nb/Y >4 
Zr/Nb 
La/Sm 
Al2O3/TiO2 
CaO/TiO2 3·5 
Al2O3/Na2
K2O/Na2>0·5 <0·3 
 Low-silica melt High-silica melt 
SiO2 (wt %) 45 >49 
TiO2 (wt %) 2·5 1·5 
FeO (wt %) 11 9·8 
Al2O3 (wt %) 10·7 11·5 
Th (ppm) >5 <1 
Sm/Nd 0·18 0·3 
Lu/Hf 0·01 >0·06 
Nb/Ta 14 18 
Sm/Yb >7 
Zr/Hf >42 32 
Zr/Y 30 
Nb/Y >4 
Zr/Nb 
La/Sm 
Al2O3/TiO2 
CaO/TiO2 3·5 
Al2O3/Na2
K2O/Na2>0·5 <0·3 

The concentrations are adjusted to equilibrate with olivine Fo90·7. The compositions of low- and high-silica melts are estimated based on trends in Figs 17–20.

The low- and high-silica end-member melts can be produced by partial melting of (1) peridotite at different degrees of partial melting (e.g. McKenzie & O'Nions, 1991) or (2) mixture of a mafic component and a normal mantle peridotite (e.g. Kogiso et al., 2004). Partial melting of a uniform mantle source cannot generate the kinks in the trends of K/Ce, Zr/Hf, Nb/Ta, Al2O3, Zr, Sc, CaO, TiO2 and SiO2 vs Th (Fig. 17) and Sm/Nd–X and Lu/Hf–X (Figs 18 and 19). Thus, generation of the Hainan basalts requires partial melting of a heterogeneous mantle source. The most pronounced characteristics of the Hainan tholeiites are the significant positive Sr anomalies (Sr/Sr* = 1· 0–1· 6, mostly >1·1), whereas the alkali basalts display insignificant Sr anomalies (Sr/Sr* = 0·8–1·1). The tholeiites and alkali basalts exhibit correlations of Sr/Sr* with SiO2 (adjusted to equilibrium olivine Fo90·7), Lu/Hf, La/Sm, Sm/Nd, Sr/Ce, Sr/Nd, Al2O3/TiO2, and CaO/TiO2 (Fig. 20a). The trends suggest that the significant positive Sr anomalies reflect the characteristics of their source region. Positive Sr anomalies are a typical characteristic of oceanic gabbro, which is a distinctive component in recycled oceanic crust (up to 50%; Stracke et al., 2003). Experimental and olivine-hosted melt inclusion studies have shown that positive Sr anomalies coupled with saturation to oversaturation in silica in the melt is a diagnostic feature of recycled oceanic gabbro in the source of plume-related magmas (e.g. Sobolev et al., 2000; Kogiso et al., 2003; Yaxley & Sobolev, 2007; Stroncik & Devey, 2011). Thus, the significant positive Sr anomalies coupled with silica-saturated to -oversaturated characteristics in the Hainan tholeiites strongly suggests the presence of recycled oceanic gabbro in the source of the tholeiites. However, the experimental study of Yaxley & Sobolev (2007) showed that partial melts of oceanic gabbro and eclogite derived from oceanic gabbro are highly siliceous dacitic melts (up to 61–65 wt % SiO2), similar to partial melts of MORB-like eclogites (Fig. 14). Therefore, these melts alone cannot satisfy the estimated primary melt composition of the tholeiites (Fig. 14). Furthermore, the inferred residual mineral assemblages indicate that the source of the tholeiites should be dominated by peridotite. Thus, we prefer a mixture of predominantly mantle peridotite with some recycled oceanic crust as the source for the tholeiites. The nature of the estimated primary melt compositions is consistent with such a conclusion. The estimated primary melts are similar to those of EM1- and EM2-type OIB (Fig. 14), which have been demonstrated to be produced by partial melting of a mixture of garnet-bearing mafic rock with normal mantle peridotite (e.g. Hofmann, 1997; Hirschmann et al., 2003; Kogiso et al., 2003, 2004).

The following evidence suggests that the source region of the alkali basalts most probably contains silica-poor eclogites (or garnet pyroxenite). First, by comparison with experimental melt compositions, the estimated primary melts for the alkali basalts plot within or close to the field defined by partial melts of silica-poor eclogite (Fig. 14). Second, the residual mineral assemblage of the alkali basalts most probably contains typical eclogite (or garnet pyroxenite) minerals, such as clinopyroxene, phlogopite and eclogitic garnet, and possibly rutile. The predominance of residual olivine, however, suggests that the source for most of the alkali basalts should be dominated by peridotite. Thus, a mixture of peridotite with K-bearing eclogite (or garnet pyroxenite) is proposed to be the source for most of the alkali basalts. Only a few high-Th alkali basalts may have been produced mainly by melting of low-silica eclogite (or garnet pyroxenite).

The presence of recycled garnet-bearing mafic rocks in the source region of the Hainan basalts is further supported by their high Fe/Mn and Zn/Fe ratios. There are two factors that control the Fe/Mn ratio: crystal fractionation (olivine and clinopyroxene) and source composition. Olivine fractionation reduces the Fe/Mn ratio in the residual melts (Liu et al., 2008, and references therein). Although clinopyroxene fractionation increases the Fe/Mn ratio in the residual melt, as DFe/Mn between clinopyroxene and basaltic melt is <1, fractional crystallization of clinopyroxene cannot satisfy the observed high Fe/Mn ratios in the Hainan basalts. On the other hand, there is evidence suggesting that the high Fe/Mn ratios record the contribution of source components rather than the effects of magmatic differentiation. First, clinopyroxene fractionation should produce a positive correlation of Fe/Mn vs Yb in the residual melts, whereas a negative trend is observed in the Hainan basalts (Fig. 6c). Second, clinopyroxene fractionation would result in a negative correlation of Fe/Mn vs Mg#, but the Hainan basalts show no such a correlation (Fig. 6d). Third, 50% clinopyroxene crystal fractionation from MORB-like melts with Fe/Mn ratios of 59 (average of MORB with 11–15 wt % MgO; Liu et al., 2008) would only cause an increase in Fe/Mn ratios from 59 to 70, which is still lower than that in the majority of the Hainan basalt samples (Figs 5 and 6).

Experimental studies have shown that high Fe/Mn ratios (>60) in basaltic melts can be generated by partial melting of garnet pyroxenite or hydrous peridotite at high degrees of melting (Liu et al., 2008, and references therein; Fig. 21). Zou & Fan (2010) demonstrated that it would be impossible to produce the Hainan basalts by partial melting of hydrous peridotite. The Fe/Mn ratios in the Hainan basalts are similar to those of partial melts of pyroxenite, but significantly higher than those of partial melts of hydrous and anhydrous peridotites at given MnO contents (Fig. 21). Thus, the high Fe/Mn ratios may be attributed to partial melting of garnet-pyroxenites (eclogites) in the source of the Hainan basalts.

Fig. 21.

Variation of Fe/Mn ratios vs MnO contents of the Hainan basalts and basaltic melts formed by partial melting of pyroxenite, dry peridotite and hydrous peridotite. The inset shows that the Hainan basalts have higher Fe/Mn ratios at given MnO contents compared with experimental melts derived by partial melting of dry peridotite, suggesting that such high Fe/Mn ratios in the Hainan basalts could not have been generated only by partial melting of a dry peridotite source. The fields of experimental melts were modified from Liu et al. (2008).

Fig. 21.

Variation of Fe/Mn ratios vs MnO contents of the Hainan basalts and basaltic melts formed by partial melting of pyroxenite, dry peridotite and hydrous peridotite. The inset shows that the Hainan basalts have higher Fe/Mn ratios at given MnO contents compared with experimental melts derived by partial melting of dry peridotite, suggesting that such high Fe/Mn ratios in the Hainan basalts could not have been generated only by partial melting of a dry peridotite source. The fields of experimental melts were modified from Liu et al. (2008).

Zn/Fe ratios are also sensitive to the contribution of eclogite and garnet pyroxenite in the generation of OIB (Le Roux et al., 2010). The less-evolved Hainan basalts (Mg# > 60) display relatively high Zn/Fe ratios, with Zn/Fe × 104 of about 12 (Fig. 4h), which are significantly higher than average upper mantle values (∼8·5; Le Roux et al., 2010). According to Le Roux et al. (2010), this characteristic also signifies the presence of eclogite and/or garnet pyroxenite in the source.

Origin of the garnet-bearing mafic component in the source region

Our geochemical data suggest that the garnet-bearing mafic component in the source region of the tholeiites was recycled oceanic crust, including MORB and oceanic gabbros, trapped by an upwelling mantle flow (e.g. a plume). However, the silica-undersaturated characteristics of the alkali basalts suggest that the garnet-bearing mafic component in their source was not directly derived from recycled oceanic crust because direct partial melting of recycled oceanic crust produces silica-saturated to -oversaturated melts (e.g. Kogiso et al., 2003; Sobolev et al., 2005). Figure 15 shows that partial melting occurred below the asthenosphere–lithosphere boundary. Significant 230Th excesses in the Holocene Hainan basalts indicate that they were produced by melting of a mantle source at >75 km depth (Zou & Fan, 2010). Because the asthenosphere–lithosphere boundary is at about 55 km depth here (Wu et al., 2004), the melting event must have occurred within the asthenosphere. Thus, the inferred garnet-bearing mafic component could not have originated from the sub-continental lithospheric mantle. The lack of continental crust-derived signatures (low Nb/La, Nb/U and negative Nb–Ta–Ti anomalies) and long-term enriched isotope characteristics (Zou & Fan, 2010) is inconsistent with an origin from delaminated ancient lower continental crust. Another possibility is that the recycled mafic component was derived from delaminated mafic rocks that were emplaced at the base of the crust by plume magmatism at an earlier stage. The contribution of such a delaminated mafic component would produce silica-saturated to -oversaturated melts in the later stages of the volcanism. This is inconsistent with the fact that late-stage Hainan volcanism is dominated by alkali basalts and there is no clear correlation between age and geochemical signature.

On the other hand, subduction processes (dehydration and partial melting) and interaction of the subducted slab with the surrounding peridotite in upwelling plumes could convert some silica-excess oceanic crust to silica-poor garnet pyroxenite and/or eclogite (e.g. Kogiso et al., 2003). The presence of residual K-bearing minerals, eclogitic garnet, clinopyroxene and rutile indicates that the low-silica garnet-bearing mafic component in the asthenospheric mantle source of the alkali basalts may have originated from interactions between silica-excess recycled oceanic crust and the ambient peridotite in an upwelling mantle plume (e.g. Sobolev et al., 2000, 2005; Yaxley & Sobolev, 2007; Stroncik & Devey, 2011).

Constraints on the Hainan plume model

The high-magnesian olivine phenocrysts (Fo90·7), high mantle potential temperature (1541 ± 10°C) and the presence of recycled oceanic crust in the source region consistently argue for a plume-origin model for the Hainan basalts. Zou & Fan (2010) proposed that the enriched Sr–Nd–Pb isotopic signatures of the basalts may have originated from the mantle Transition Zone, or more likely, the lower mantle. The magma supply of the Hainan flood basalt province is 0·1–0·25 km3 a−1, similar to that of plume-induced continental flood basalt provinces (e.g. Flower et al., 1992). Such an interpreted plume origin for the geochemical and petrological characteristics of the Hainan basalts is consistent with the geophysical observations. The plume model also best explains why the extensive and voluminous late Cenozoic basaltic volcanism in the South China Sea and surrounding regions started after the cessation of the South China Sea opening (e.g. Hoang & Flower, 1998; Ho et al., 2000; Zou & Fan, 2010). It also explains the high mantle potential temperature (∼1440°C) estimated for the synchronous Vietnam flood basalt province in the nearby Indochina Block (Hoang & Flower, 1998).

However, the rate of mantle upwelling for the hypothesized Hainan plume, estimated using the (230Th/238U) disequilibrium dataset, is <1 cm a−1 (Zou & Fan, 2010). This estimated upwelling rate is significantly slower than that for the Hawaiian plume. Thus, if the seismic low-velocity structure indeed represents a mantle plume, it may signify a dying plume (Zou & Fan, 2010). It should be cautioned that the estimated mantle upwelling rate was mainly based on the Holocene alkali basalts. These basalts represent a melting event with a slower rate than the other events, and consequently may lead to an underestimation of the mantle upwelling rate. Therefore, independent estimates of the mantle upwelling rate, particularly based on the tholeiites, are called for to further test the Hainan plume hypothesis.

The conclusion that the low-velocity structure beneath Hainan Island may indeed represent a thermal mantle plume is provocative because such a plume would potentially provide a rare example of a young mantle plume close to a deep slab subduction zone rather than a lower mantle superplume. Regional and global seismic tomographic studies suggest that the plume-like mantle low-velocity structure beneath Hainan Island sits close to the subduction of the Pacific and Philippine Sea slabs to the east, and the Indian slab to the west (Zhao, 2004, 2007; Huang & Zhao, 2006; Huang et al., 2010; Zhao et al., 2011). This is unusual in that subducting slabs and a potential hotspot occur within about 1000 km of one another (Zhao et al., 2011). Globally, these two geological components are commonly separated by far greater distances (Davaille et al., 2005). Thus, the hypothesized Hainan plume could potentially provide a key insight into the possible interrelation between plumes and slab subduction. The origin of the inferred garnet-bearing mafic component in the source region of the basalts, and the question of whether the source also contains lower mantle materials, will probably bring further insight to this issue. This may be achieved through further in-depth isotopic studies (especially He and Os isotopes)

CONCLUSIONS

New 40Ar/39Ar dating indicates that Cenozoic volcanism in Hainan Island started in the late Miocene (about 13 Ma), peaked during the late Pliocene to middle Pleistocene, and terminated in the Holocene.

Geochemical analyses show that crystal fractionation of olivine, clinopyroxene and plagioclase probably occurred during the magmatic evolution of the Hainan basalts. The effect of clinopyroxene fractionation is negligible for samples with MgO >8·5 wt %. Clinopyroxenes are estimated to have crystallized over a wide range of pressures (2–25 kbar) with a dominant pressure range of 10–15 kbar. The clinopyroxene and clinopyroxene–liquid thermometry results reveal that the magma cooled from about 1350°C to 1100°C in the process.

Using the most forsteritic olivine (Fo90·7), a constant Fe–Mg exchange partition coefficient KD = 0·31, and the least evolved basaltic samples (MgO > 9·0 wt % and CaO > 8·0 wt %) from Hainan Island, we constrained the primary melt compositions. The estimated melting temperature (T) and effective melting pressure (Pf) are slightly different for the tholeiites and alkali basalts: for the tholeiites, T = 1420–1520°C, Pf = 18–32 kbar with a weighted average of 23·8 ± 1·8 kbar; for the alkali basalts, T = 1480–1530°C, Pf = 25–32 kbar with a weighted average of 28·3 ± 1·4 kbar. The T–Pf array plots systematically above the dry lherzolite solidus and beneath the spinel–garnet transition depth (∼50–60 km) and the asthenosphere–lithosphere boundary (∼55 km). The PfT data form an array that intersects the dry peridotite solidus at about 50 kbar. The mantle potential temperatures for the estimated primary melts range from about 1500 to 1580°C with a weighted average of 1541 ± 10°C, which is similar to that of typical thermal mantle plumes.

The geochemical characteristics of the Hainan basalts are hard to reconcile with partial melting of a peridotitic mantle alone. This study suggests that the source for the tholeiites was a mixture of peridotite with a minor recycled oceanic crust component, whereas the source for most of the alkali basalts (Th < 4 ppm) was a mixture of peridotite with a low-silica eclogite (or garnet pyroxenite). Only the minor occurrence of high-Th (>4 pm) alkali basalts may be related to partial melting of low-silica garnet pyroxenite or eclogite.

The high mantle potential temperature and melting pressures, the presence of high-magnesian olivine phenocrysts in the basalts, and the presence of recycled oceanic crust in the source region provide independent support for the Hainan basalts being the manifestation of a thermal mantle plume, a model previously established largely on geophysical observations. The hypothesized Hainan plume could potentially provide a rare example of a young mantle plume closely associated with a deep slab subduction system.

FUNDING

This work was supported by the National Natural Science foundation of China (grants 40803010 and 40973044) and Australian Research Council (ARC) Discovery Project grant (DP0770228). This is TIGeR (The Institute for Geoscience Research, Curtin University) Publication 265, and contribution 24 from the ARC Centre of Excellence for Core to Crust Fluid Systems.

SUPPLEMENTARY DATA

Supplementary data for this paper are available at Journal of Petrology online.

ACKNOWLEDGEMENTS

We thank reviewers Cin-Ty Lee, Zhong-Yuan Ren and Nicholas Schmerr, and editor Gerhard Wörner for their constructive and helpful reviews. We are grateful to Y. H. Ling for help during the field work, G. Q. Hu for assistance in geochemical analyses, L. K. Yang for assistance in 40Ar/39Ar dating, and Marion Grange for proofreading.

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Supplementary data