Primary and secondary internal structures observed in zircons from granites from the Late Archaen Darling Range Batholith record stages in the evolutionary history of the granites and provide a basis for a SHRIMP U–Pb study on the timing of granite evolution. Many granite zircons contain cores. A few low-U cores retain concordant to slightly discordant U–Pb ages of 2.8 Ga, some sow discordant intermediate ages but most have nearly concordant ages within the range 2690–2650 Ma. these ages are interpreted as dating the source rocks of the Darling Range granites, or as representing different degrees of isotopic resetting owing to recrystallization of protolith zircon during prograde metamorphism and subsequent melting. The zircon cores are enclosed by inner rims of oscillatory zoned zircon, which are interpreted as zircon growth during the main crystallization phase of the granite magma. SHRIMP ages of zoned zircon, of between 2648 and 2626 Ma, suggest an extended period of granite crystallization. The oscillatory zoned inner rims are surrounded by weakly zoned to unzoned outer rims which transgress primary zoning of the inner rim, suggesting corrosion followed by new zircon deposition. However, the preservation of weak zoning in the outer rim and the euhedral nature of external zircon faces, which are identical to those developed in the inner rim, suggests that the outer rims are in fact recrystallized outer parts of inner rims. This conclusion is supported by the younger ages (2628–2616 Ma) determined for outer rims. These results indicate that formation of outer rims and accompanying loss of radiogenic Pb occurred during or soon after granite crystallization and before zircons had time to accumulate significant radiation damage, suggesting that the recrystallization process is independent of the degree of metamictization. The history of formation of the Darling Range granites contained with the zircon crystals suggests initial magma formation between 2690 and 2650 Ma, crystallization and emplacement of the granite magma at 2648–2626 Ma, and slow cooling, indicated by marginal recrystallization and continued Pb loss from the zircons, until 2628–2616 Ma.

Introduction

The origin and evolution of large granitoid masses is a major problem in Archaean geology. Were they derived exclusively from mantle material, from mixtures of mantle and older sialic crust, or were they derived entirely from older crustal rocks? Also, what were the processes leading to melting and emplacement of these granitoids on a scale of thousands of square kilometres? Were there a series of granitoid-forming events with a systematic pattern of emplacement ages or was emplacement of granitoids essentially contemporaneous over wide areas? How does generation of granitoids relate to high-grade regional metamorphism and what was the cooling history of the granitoids after crystallization?

The ability of the ion microprobe SHRIMP to make micro-scale U–Pb isotopic analyses on the polished surfaces of sectioned zircon crystals provides a means to explore some of the questions posed above. However, the potential for a SHRIMP zircon study to provide answers depends on a careful integration of the analytical programme with structural information contained within the zircon grains. Recent studies have shown that zircons in granitoids can preserve information on their pre-magmatic history as well as providing a record of zirconium saturation and undersaturation during magma evolution (Vavra & Hansen, 1991). There is also evidence that zircons provide information on late- to post-crystallization processes during cooling (Pidgeon, 1992). The present study represents a case history where we have applied SHRIMP analysis to complex zircons from the Archaean Darling Range Batholith using zircon structure as a basis for analytical spot selection and interpretation of results. We also make use of SHRIMP Th–U–Pb concentration data to provide information on chemical changes associated with events identified from the zircon morphology. The results reveal a complex and extended evolutionary history for the batholith.

Summary of the Geology of the Batholith

The Darling Range Batholith is situated in the Southwest Yilgarn Craton of Western Australia (Fig. 1). It is bordered to the east by the Jimperding Metamorphic belt and to the south by the Proterozoic Albany–Fraser Province. The batholith is composed of granodiorites, alkali feldspar granites and less extensive gneissic granitoids, and contains two volcanic belts, the Saddleback Greenstone Belt and the Morangup Greenstone Belt (Wilde & Low, 1978, 1980; Wilde & Walker, 1982). In the present study we report results on granites from the northern part of the batholith, including the Logue Brook granite (Fig. 1).

Fig. 1.

Simplified geological map of the Southwestern Yilgarn Craton.

Fig. 1.

Simplified geological map of the Southwestern Yilgarn Craton.

Although extensive, the batholith is not well exposed, and detailed mapping of relationships between different types of granitoids forming the batholith is not possible. Wilde & Low, (1978) recognized massive and gneissic granitoids in the batholith. These workers commented that ‘the various textural types are irregularly interdeveloped’, suggesting that relative age relationships are inconsistent. In our sampling programme we have identified three major granite types, a fine-grained grey monzogranite to granodiorite, a medium- to coarse-grained light grey granite to adamellite and an alkali feldspar porphyritic granite. Geochemical studies, which will be reported elsewhere, support our textural subdivision of the granitoids into the above three types. Because of poor exposure it is rare to observe contact relationships between the granite types. However, in Stathams Quarry near Perth the fine-grained granite clearly transgresses and contains xenoliths of the coarse-grained granite. The fine-grained granite appears to form a second pulse of granite magma injection, which may reflect either the addition of magma from a new protolith, or a reactivation of the initial magma chamber.

The three granite types are cut by aplite dykes and pegmatite veins with aplite centres. The batholith is also cut by Proterozoic doleritic dykes. The locations of granitoid samples are shown in Fig. 1.

Previous Geochronology of the Batholith

A number of geochronological investigations of the Darling Range granites have been published, beginning with the classic Rb–Sr whole-rock study by Compston & Jeffery, (1959), who reported an age of 2400 Ma for granites from Canning Dam near the western margin of the batholith. Rb–Sr studies have been made on whole rock (Compston & Arriens, 1968; Arriens, 1971) and biotite (Libby & de Laeter, 1979; de Laeter & Libby, 1993) from granites within the batholith. The biotites record Early Palaeozoic Rb–Sr ages suggesting a Palaeozoic heating along the western margin of the batholith, whereas the whole-rock ages of ∼2600 Ma have large uncertainties and are not discussed further in this paper. Relevant to the present study are the few zircon U–Pb studies reported for the batholith. Conventional multigrain zircon U–Pb ages of 2677 ± 50 Ma (Mortigup granite) and 2642+242166 Ma (Monday Hill granite) were reported by Nieuwland & Compston, (1981) for undeformed granitoids from the eastern margin of the batholith. More recently, Compston et al., (1986) reported a SHRIMP zircon age of 2612 ± 5 Ma for the Logue Brook granite from the western part of the batholith (Fig. 1) and argued that this age dates the crystallization of the granite. These results raise the possibility of an extended history for granite emplacement in the batholith. Fletcher et al., (1985) determined Sm–Nd CHUR model ages of 2.9–3.0 Ga on four whole-rock samples, including one sample from the same quarry in the Logue Brook granite sampled by Compston et al., (1986), and interpreted these ages as evidence that the granites were derived from ∼3.0 Ga crustal source rocks. Compston et al., (1986) suggested that the variation of 0 to −4 in ɛCHUR initially, calculated with the Logue Brook zircon age, provides evidence that the granite formed by mixing of older continental crust with younger mantle-derived crust.

Analytical Method

Zircons were separated using conventional heavy liquid and magnetic techniques. Grains were sized and +100 µm sieve size grains were mounted in epoxy resin, polished and etched with HF to show internal structure, and studied by reflected and transmitted light microscopy. Zircon internal structures were also investigated using cathodoluminescence (JEOL 6400 at the University of Western Australia). However, it was found that the granite zircons had very weak luminescence and this technique did not give a clear picture of the internal structures of the zircons except for some zircon cores. The weak luminescence of these zircons was kindly confirmed by Dr G. Vavra at the ETH in Zürich. Williams et al., (1995) suggested that luminescence is suppressed by radiation damage of the zircon lattice. This is supported by our empirical observations that the more metamict the zircon the greater its susceptibility to HF etching and the weaker its cathodoluminescence. Backscattered electron images show similar features to those revealed by HF etching; however, for the present zircons HF etching provides excellent resolution of internal structural features, as shown by the detail in photomicrographs (Figs 2, 3 and 4). Although the cathodoluminescence was unable to resolve structural complexities in the zircon rims, it was able to show, albeit weakly, internal structures in the zircon cores that were not evident from etching (Fig. 2).

Fig. 2.

Comparison of the cathodoluminescence image (a) with photomicrograph of the etched zircon (b) from the coarse-grained granite sample W332. Cathodoluminescence shows different features of the complex zircon structure compared with the HF etching.

Fig. 2.

Comparison of the cathodoluminescence image (a) with photomicrograph of the etched zircon (b) from the coarse-grained granite sample W332. Cathodoluminescence shows different features of the complex zircon structure compared with the HF etching.

Fig. 3.

Photomicrographs of HF-etched zircons from the Darling Range granite showing different types of zircon cores (reflected light; length of the photographs represents ∼300 µm). (a) Zircon grain from the fine-grained granite W323. The granular, etched central core is surrounded by an inner zoned rim and an outer weakly zoned rim. (b) Zircon grain from the fine-grained granite W323. The granular, etched central core is partly replaced by clear unetched zircon and surrounded by an inner zoned rim and an outer weakly zoned rim. (c) Zircon grain from the fine-grained granite W323. Etched zircon is preserved as remnants in the clear central core, which is surrounded by an inner zoned rim and an outer weakly zoned rim. The [121] and [011] pyramids are developed in the inner part of the inner rim, whereas [121] pyramid is absent in the outer part of the zoned rim. (d) Zircon grain from the fine-grained granite sample W323. The clear central core is surrounded by an inner zoned rim and an outer weakly zoned rim. The boundary between core and inner rim is irregular but smooth, which can be interpreted as corrosion (Vavra, 1994). The [121] and [011] pyramids are developed in the inner part of the inner rim. (e) Zircon grain from porphyritic granite sample W382. This shows a remnant of oscillatory zoned zircon within clear core, which is surrounded by a thin zoned rim. (f) Zircon grain from the coarse-grained granite W327. Clear central core is surrounded by zoned rim. Boundary between core and zoned rim is rounded, which can be attributed to the dissolution of the core (Vavra, 1994) before overgrowth by the oscillatory zoned rim.

Fig. 3.

Photomicrographs of HF-etched zircons from the Darling Range granite showing different types of zircon cores (reflected light; length of the photographs represents ∼300 µm). (a) Zircon grain from the fine-grained granite W323. The granular, etched central core is surrounded by an inner zoned rim and an outer weakly zoned rim. (b) Zircon grain from the fine-grained granite W323. The granular, etched central core is partly replaced by clear unetched zircon and surrounded by an inner zoned rim and an outer weakly zoned rim. (c) Zircon grain from the fine-grained granite W323. Etched zircon is preserved as remnants in the clear central core, which is surrounded by an inner zoned rim and an outer weakly zoned rim. The [121] and [011] pyramids are developed in the inner part of the inner rim, whereas [121] pyramid is absent in the outer part of the zoned rim. (d) Zircon grain from the fine-grained granite sample W323. The clear central core is surrounded by an inner zoned rim and an outer weakly zoned rim. The boundary between core and inner rim is irregular but smooth, which can be interpreted as corrosion (Vavra, 1994). The [121] and [011] pyramids are developed in the inner part of the inner rim. (e) Zircon grain from porphyritic granite sample W382. This shows a remnant of oscillatory zoned zircon within clear core, which is surrounded by a thin zoned rim. (f) Zircon grain from the coarse-grained granite W327. Clear central core is surrounded by zoned rim. Boundary between core and zoned rim is rounded, which can be attributed to the dissolution of the core (Vavra, 1994) before overgrowth by the oscillatory zoned rim.

Fig. 4.

Photomicrographs of HF-etched zircons from the Darling Range granite showing different types of outer rims (reflected light; length of the photographs represents ∼300 µm). (a) Zircon grain from the porphyritic granite W427. The grain apparently was broken before the overgrowth by the outer rim. However, in this grain a remnant of the inner zoned rim is evident within the outer weakly zoned rim. On the other side of the grain, zoning of the inner rim is disrupted and rotated from its original orientation. (b) Zircon grain from the porphyritic granite W427. The grain consists almost entirely of zoned inner rim. Only a small central part of clear zircon can be interpreted as the core. An outer weakly zoned rim is developed around the grain. Small patches of clear zircon several microns in size are developed within the zoned inner rim near the ends of the grain. Locally, these patches become larger (up to 10–20 µm in size). (c) Zircon grain from the fine-grained granite W323. Rounded patches of unzoned zircon of 20–30 mm are developed within the inner zoned rim near the boundary with the outer rim. (d) Zircon grain from porphyritic granite sample W427. The veinlet of clear unzoned zircon cuts the zoned inner rim and clear core and is terminated by the boundaries with the outer rim on both sides of the crystal. (e) Zircon grain from porphyritic granite sample W427. The internal structure of the zoned inner rim is extensively broken by patches of clear unzoned zircon. (f) Zircon grain from the coarse-grained granite W332. Weakly zoned zircon, developed on one side of the grain, deeply penetrates the zoned inner rim.

Fig. 4.

Photomicrographs of HF-etched zircons from the Darling Range granite showing different types of outer rims (reflected light; length of the photographs represents ∼300 µm). (a) Zircon grain from the porphyritic granite W427. The grain apparently was broken before the overgrowth by the outer rim. However, in this grain a remnant of the inner zoned rim is evident within the outer weakly zoned rim. On the other side of the grain, zoning of the inner rim is disrupted and rotated from its original orientation. (b) Zircon grain from the porphyritic granite W427. The grain consists almost entirely of zoned inner rim. Only a small central part of clear zircon can be interpreted as the core. An outer weakly zoned rim is developed around the grain. Small patches of clear zircon several microns in size are developed within the zoned inner rim near the ends of the grain. Locally, these patches become larger (up to 10–20 µm in size). (c) Zircon grain from the fine-grained granite W323. Rounded patches of unzoned zircon of 20–30 mm are developed within the inner zoned rim near the boundary with the outer rim. (d) Zircon grain from porphyritic granite sample W427. The veinlet of clear unzoned zircon cuts the zoned inner rim and clear core and is terminated by the boundaries with the outer rim on both sides of the crystal. (e) Zircon grain from porphyritic granite sample W427. The internal structure of the zoned inner rim is extensively broken by patches of clear unzoned zircon. (f) Zircon grain from the coarse-grained granite W332. Weakly zoned zircon, developed on one side of the grain, deeply penetrates the zoned inner rim.

Most samples were etched by HF before SHRIMP analysis, to identify exact locations for analysis spots. However, all etched samples were repolished before the analyses to remove the etched surface. Two samples were analysed in separate SHRIMP sessions, one before etching and the second after etching. For sample W330, session one, made without etching, resulted in a high number of analyses being located on boundaries between the inner rims and the centres. During the second analytical session, after etching, for sample W390, an attempt was made to locate several analytical spots exactly in places where analyses were performed during the previous session (see, e.g. analyses W390–6-1 vs W390–6-4 and W390–6-2 vs W390–6-3 in Table 1). Results of these analyses indicate that the etching did not affect the SHRIMP analytical results.

Table 1

SHRIMP data for the Darling Range granitoids

Labels U (p.p.m.) Th (p.p.m.) Th/U Total Pb 206Pb/204Pb 207Pb/206Pb* 208Pb/206Pb* 206Pb/238U* 207Pb/235U* 208Pb/232Th* 207Pb/206Pb* age (Ma) 
W323 fine-grained granite 
clear cores 
W323-1-1 272 270 0.99 173 4980 0.1822 ± 13 0.2786 ± 28 0.502 ± 15 12.60 ± 41 0.1411 ± 47 2673 ± 12† 
W323-1-2 215 143 0.66 128 2380 0.1776 ± 17 0.1791 ± 35 0.500 ± 15 12.23 ± 41 0.1348 ± 51 2630 ± 16 
W323-1-4 328 218 0.66 190 2260 0.1752 ± 14 0.1892 ± 29 0.482 ± 15 11.63 ± 38 0.1375 ± 48 2607 ± 13 
W323-3-1 525 283 0.54 310 7940 0.1812 ± 7 0.1504 ± 13 0.511 ± 16 12.78 ± 40 0.1425 ± 46 2664 ± 7 
W323-3-2 408 219 0.54 239 5640 0.1820 ± 10 0.1477 ± 19 0.506 ± 15 12.70 ± 40 0.1397 ± 47 2671 ± 9 
W323-4-4 477 262 0.55 276 7450 0.1812 ± 8 0.1562 ± 15 0.500 ± 15 12.48 ± 39 0.1423 ± 46 2664 ± 7 
W323-4-5 651 313 0.48 384 12600 0.1757 ± 6 0.1298 ± 9 0.523 ± 16 12.68 ± 39 0.1414 ± 45 2613 ± 6 
W323-5-1 476 257 0.54 281 2350 0.1829 ± 10 0.1240 ± 19 0.512 ± 16 12.91 ± 41 0.1175 ± 40 2679 ± 9 
W323-5-2 574 282 0.49 332 3640 0.1794 ± 8 0.1183 ± 15 0.510 ± 15 12.62 ± 39 0.1228 ± 41 2647 ± 7 
W323-5-3 291 141 0.48 175 3320 0.1799 ± 11 0.1331 ± 20 0.524 ± 16 13.00 ± 41 0.1444 ± 50 2652 ± 10 
W323-6-1 1774 1782 1.00 1123 12600 0.1823 ± 4 0.2864 ± 8 0.498 ± 15 12.53 ± 38 0.1421 ± 43 2674 ± 3 
W323-9-2 1224 324 0.26 682 20700 0.1861 ± 4 0.0781 ± 5 0.511 ± 15 13.12 ± 40 0.1510 ± 47 2708 ± 4 
W323-10-2 4767 512 0.11 2640 29600 0.1857 ± 2 0.0303 ± 2 0.528 ± 16 13.53 ± 41 0.1490 ± 46 2704 ± 2 
W323-11-1 398 232 0.58 237 3040 0.1850 ± 10 0.1628 ± 20 0.506 ± 15 12.90 ± 41 0.1415 ± 47 2698 ± 9 
W323-12-1 1421 355 0.25 809 9520 0.1817 ± 5 0.0722 ± 6 0.525 ± 16 13.16 ± 40 0.1517 ± 48 2668 ± 4 
W323-13-1 543 230 0.42 290 2160 0.1800 ± 10 0.1210 ± 20 0.466 ± 14 11.58 ± 36 0.1334 ± 47 2653 ± 10 
W323-14-1 666 357 0.54 382 3430 0.1877 ± 9 0.1498 ± 16 0.490 ± 15 12.69 ± 39 0.1371 ± 45 2722 ± 8 
weakly zoned outer rims 
W323-1-3 2095 117 0.06 1072 23300 0.1757 ± 4 0.0151 ± 3 0.499 ± 15 12.08 ± 37 0.1356 ± 51 2613 ± 3 
W323-1-5 2267 147 0.06 1140 7430 0.1727 ± 4 0.0171 ± 5 0.488 ± 15 11.62 ± 35 0.1289 ± 54 2584 ± 4 
W323-3-3 1511 1540 1.02 842 1360 0.1736 ± 8 0.0410 ± 15 0.512 ± 15 12.24 ± 38 0.0206 ± 10 2593 ± 7 
W323-4-1 1797 125 0.07 937 5200 0.1765 ± 4 0.0152 ± 7 0.503 ± 15 12.25 ± 37 0.1094 ± 58 2620 ± 4 
W323-4-6 1872 189 0.10 995 1880 0.1727 ± 6 0.0250 ± 10 0.501 ± 15 11.92 ± 36 0.124 ± 64 2584 ± 5 
W323-5-4 2416 293 0.12 1249 7830 0.1764 ± 3 0.0177 ± 4 0.500 ± 15 12.15 ± 37 0.0730 ± 29 2619 ± 3 
W323-6-2 2103 119 0.06 1070 16340 0.1751 ± 3 0.0144 ± 3 0.496 ± 15 11.96 ± 36 0.1257 ± 48 2607 ± 3 
W323-6-3 1902 135 0.07 1037 22200 0.1750 ± 3 0.0161 ± 3 0.531 ± 16 12.81 ± 39 0.1201 ± 42 2606 ± 3 
W323-9-1 2116 181 0.09 849 16200 0.1787 ± 3 0.0197 ± 3 0.388 ± 12 9.56 ± 29 0.0893 ± 31 2641 ± 3 
W323-10-3 1813 83 0.05 921 7550 0.1793 ± 4 0.0113 ± 5 0.492 ± 15 12.17 ± 37 0.1210 ± 68 2646 ± 4 
W323-11-2 2296 419 0.18 1193 2800 0.1777 ± 4 0.0306 ± 8 0.490 ± 15 12.00 ± 36 0.0821 ± 32 2631 ± 4 
W323-13-2 1997 302 0.15 932 7110 0.1794 ± 4 0.0149 ± 6 0.451 ± 14 11.16 ± 34 0.0444 ± 21 2648 ± 4 
metamict cores 
W323-7-1 3089 1494 0.48 1821 28800 0.1814 ± 3 0.1354 ± 4 0.519 ± 16 12.98 ± 39 0.1453 ± 44 2666 ± 3 
W323-8-1 11142 2952 0.26 5013 36200 0.1590 ± 2 0.0811 ± 2 0.421 ± 13 9.23 ± 28 0.1289 ± 39 2445 ± 2 
W330 coarse-grained granite 
clear cores 
W330-7-1 930 434 0.47 543 63000 0.1811 ± 4 0.1262 ± 5 0.518 ± 4 12.94 ± 12 0.1400 ± 14 2663 ± 4 
W330-7-2 907 405 0.45 523 275000 0.1809 ± 4 0.1202 ± 5 0.515 ± 4 12.84 ± 12 0.1385 ± 14 2661 ± 4 
W330-7-3 960 655 0.68 549 3460 0.1812 ± 5 0.1600 ± 9 0.488 ± 4 12.20 ± 11 0.1146 ± 12 2664 ± 5 
W330-13-1 639 112 0.17 339 159000 0.1820 ± 7 0.0471 ± 6 0.502 ± 8 12.59 ± 22 0.1354 ± 30 2671 ± 6 
W330-13-2 529 73 0.14 233 34400 0.1845 ± 9 0.0376 ± 9 0.418 ± 7 10.62 ± 19 0.1146 ± 35 2694 ± 8 
W330-10-1 737 207 0.28 412 15700 0.1798 ± 6 0.0758 ± 7 0.515 ± 8 12.78 ± 22 0.1395 ± 27 2651 ± 5 
W330-16-1 513 251 0.49 220 1530 0.1831 ± 18 0.0746 ± 35 0.382 ± 6 9.65 ± 20 0.0582 ± 29 2681 ± 17 
W330-15-2 1355 1884 1.39 992 45400 0.1865 ± 5 0.3752 ± 11 0.544 ± 9 13.97 ± 24 0.1466 ± 25 2711 ± 5 
W330-5-1 1468 56 0.04 754 28600 0.1657 ± 4 0.0089 ± 3 0.508 ± 8 11.60 ± 20 0.1191 ± 51 2515 ± 4 
W330-5-2 1217 55 0.04 604 34600 0.1705 ± 5 0.0128 ± 4 0.487 ± 8 11.45 ± 19 0.1388 ± 50 2563 ± 5 
W330-5-3 2628 79 0.03 1411 69700 0.1641 ± 3 0.0070 ± 2 0.533 ± 9 12.05 ± 20 0.1230 ± 44 2498 ± 3 
W330-6-2 661 972 1.47 410 508000 0.1808 ± 4 0.4049 ± 11 0.454 ± 7 11.33 ± 19 0.1251 ± 21 2661 ± 4 
cores mixed with inner rims 
W330-15-1 960 1030 1.07 624 2140 0.1778 ± 8 0.2629 ± 16 0.512 ± 8 12.55 ± 22 0.1254 ± 23 2633 ± 8 
W330-1-3 1366 1411 1.03 863 9300 0.1788 ± 6 0.2823 ± 13 0.500 ± 8 12.32 ± 21 0.1365 ± 24 2642 ± 5 
W330-11-1 932 241 0.26 514 30500 0.1792 ± 5 0.0704 ± 5 0.512 ± 8 12.65 ± 21 0.1394 ± 26 2646 ± 5 
W330-11-2 875 246 0.28 489 96000 0.1784 ± 5 0.0752 ± 5 0.518 ± 8 12.74 ± 21 0.1384 ± 25 2638 ± 5 
W330-12-2 1527 1556 1.02 991 40800 0.1777 ± 4 0.2813 ± 7 0.516 ± 8 12.64 ± 21 0.1424 ± 24 2631 ± 4 
W330-3-2 1930 3302 1.71 1364 9410 0.1770 ± 5 0.4590 ± 15 0.499 ± 8 12.18 ± 21 0.1339 ± 23 2625 ± 5 
W330-12-1 2778 716 0.26 1621 763000 0.1769 ± 3 0.0702 ± 3 0.544 ± 9 13.26 ± 22 0.1481 ± 25 2624 ± 3 
zoned inner rims 
W330-9-2 1475 2744 1.86 1034 41000 0.1767 ± 4 0.4976 ± 10 0.485 ± 8 11.82 ± 20 0.1298 ± 21 2622 ± 4 
W330-9-3 2412 4977 2.06 1746 90800 0.1762 ± 3 0.5493 ± 8 0.486 ± 8 11.82 ± 19 0.1295 ± 21 2618 ± 3 
W330-2-3 1750 395 0.23 938 8800 0.1774 ± 5 0.0601 ± 7 0.500 ± 8 12.24 ± 21 0.1332 ± 28 2629 ± 5 
W330-2-4 5099 2591 0.51 3221 5400 0.1730 ± 3 0.1385 ± 5 0.554 ± 9 13.22 ± 22 0.1511 ± 25 2587 ± 3 
W330-10-2 2810 911 0.32 1393 22100 0.1657 ± 3 0.0886 ± 3 0.458 ± 7 10.47 ± 17 0.1252 ± 21 2514 ± 3 
W330-15-3 2611 4630 1.77 2226 9370 0.1794 ± 4 0.4742 ± 9 0.596 ± 10 14.73 ± 24 0.1592 ± 26 2648 ± 4 
W330-14-2 1192 1780 1.49 810 20300 0.1787 ± 5 0.4091 ± 11 0.495 ± 8 12.20 ± 21 0.1357 ± 23 2641 ± 5 
W330-8-2 1068 1509 1.41 732 110000 0.1781 ± 4 0.3871 ± 8 0.508 ± 8 12.47 ± 21 0.1392 ± 23 2635 ± 4 
W330-8-3 3454 4926 1.43 2314 386000 0.1776 ± 2 0.3847 ± 5 0.497 ± 8 12.18 ± 20 0.1342 ± 22 2631 ± 2 
W330-2-1 2762 3908 1.41 1910 18300 0.1789 ± 4 0.3958 ± 10 0.509 ± 8 12.54 ± 21 0.1423 ± 24 2643 ± 3 
W330-2-2 1296 1559 1.20 812 1590 0.1750 ± 9 0.3201 ± 22 0.472 ± 8 11.40 ± 21 0.1257 ± 23 2606 ± 9 
W330-1-4 2531 5609 2.22 2062 10400 0.1780 ± 4 0.6084 ± 13 0.527 ± 8 12.93 ± 22 0.1446 ± 24 2635 ± 4 
weakly zoned outer rims 
W330-14-1 612 569 0.93 378 42800 0.1746 ± 7 0.2471 ± 11 0.505 ± 8 12.15 ± 21 0.1341 ± 24 2602 ± 6 
W330-6-3 1123 89 0.08 541 5600 0.1760 ± 7 0.0162 ± 10 0.466 ± 7 11.29 ± 20 0.0952 ± 63 2615 ± 6 
W330-1-1 698 99 0.14 380 1330 0.1613 ± 10 0.0302 ± 19 0.510 ± 8 11.33 ± 21 0.1089 ± 72 2469 ± 10 
W330-1-2 671 112 0.17 351 4130 0.1782 ± 10 0.0295 ± 18 0.496 ± 8 12.19 ± 23 0.0876 ± 57 2636 ± 10 
metamict cores 
W330-8-1 1054 131 0.12 572 26000 0.1772 ± 4 0.0334 ± 4 0.520 ± 84 12.71 ± 21 0.1393 ± 29 2627 ± 4 
W330-16-2 5356 2279 0.43 3177 3220000 0.1813 ± 3 0.1102 ± 3 0.534 ± 86 13.34 ± 22 0.1382 ± 23 2665 ± 2 
W330-6-1 1048 1489 1.42 675 3520 0.1678 ± 8 0.3724 ± 19 0.479 ± 8 11.09 ± 20 0.1255 ± 22 2536 ± 8 
W330-9-1 1480 3173 2.14 1155 180000 0.1769 ± 4 0.5803 ± 10 0.515 ± 8 12.56 ± 21 0.1394 ± 23 2624 ± 3 
W332 coarse-grained granite 
clear cores 
W332-2-1 338 61 0.18 165 1120 0.1786 ± 16 0.1190 ± 33 0.417 ± 21 10.26 ± 53 0.2744 ± 160 2640 ± 15 
W332-3-1 282 127 0.45 189 817 0.1805 ± 17 0.1539 ± 38 0.548 ± 28 13.63 ± 71 0.1882 ± 106 2657 ± 16 
W332-8-1 1223 382 0.31 594 1110 0.1802 ± 8 0.1577 ± 17 0.403 ± 20 10.01 ± 51 0.2034 ± 105 2655 ± 8 
W332-9-1 438 262 0.60 276 9080 0.1835 ± 7 0.1616 ± 13 0.541 ± 27 13.69 ± 70 0.1465 ± 5 2685 ± 7 
W332-10-1 953 566 0.59 579 16500 0.1826 ± 5 0.1605 ± 8 0.524 ± 26 13.18 ± 67 0.1415 ± 72 2676 ± 5 
W332-11-1 267 122 0.46 162 4160 0.1805 ± 11 0.1208 ± 21 0.535 ± 27 13.32 ± 69 0.1418 ± 76 2657 ± 10 
W332-12-1 219 109 0.50 127 1570 0.1804 ± 15 0.1512 ± 32 0.489 ± 25 12.17 ± 63 0.1484 ± 82 2657 ± 14 
W332-13-1 527 285 0.54 334 12300 0.1830 ± 6 0.1472 ± 11 0.551 ± 28 13.90 ± 70 0.1496 ± 76 2681 ± 6 
W332-16-1 250 100 0.40 154 3050 0.1831 ± 12 0.1353 ± 22 0.534 ± 27 13.47 ± 69 0.1795 ± 96 2681 ± 10 
W332-17-1 147 68 0.46 88 1740 0.1828 ± 17 0.1264 ± 34 0.518 ± 26 13.06 ± 69 0.1416 ± 82 2678 ± 16 
W332-19-1 458 261 0.57 278 7720 0.1816 ± 7 0.1543 ± 12 0.525 ± 26 13.15 ± 67 0.1425 ± 73 2668 ± 6 
zoned inner rims 
W332-4-2 1618 859 0.53 995 14900 0.1771 ± 3 0.1488 ± 6 0.537 ± 27 13.12 ± 66 0.1506 ± 76 2626 ± 3 
W332-14-3 4606 1393 0.30 2486 10700 0.1595 ± 2 0.0853 ± 3 0.501 ± 25 11.02 ± 55 0.1414 ± 71 2450 ± 2 
W332-15-2 4270 2217 0.52 2322 14000 0.1628 ± 2 0.1396 ± 4 0.483 ± 24 10.85 ± 54 0.1300 ± 65 2485 ± 2 
W332-24-1 1602 695 0.43 911 7400 0.1765 ± 3 0.1187 ± 6 0.507 ± 25 12.33 ± 62 0.1385 ± 70 2620 ± 3 
W332-24-2 2746 1664 0.61 1620 18800 0.1777 ± 2 0.1648 ± 4 0.509 ± 25 12.47 ± 63 0.1385 ± 69 2631 ± 2 
weakly zoned outer rims 
W332-1-1 1180 84 0.07 636 32400 0.1769 ± 4 0.0194 ± 3 0.523 ± 26 12.77 ± 64 0.1437 ± 76 2624 ± 3 
W332-4-1 979 266 0.27 566 14300 0.1774 ± 5 0.0723 ± 6 0.536 ± 27 13.11 ± 66 0.1425 ± 73 2629 ± 4 
W332-5-1 1022 42 0.04 577 19800 0.1777 ± 4 0.0121 ± 4 0.550 ± 28 13.48 ± 68 0.1608 ± 100 2631 ± 4 
W332-6-1 862 61 0.07 472 52800 0.1772 ± 5 0.0202 ± 4 0.531 ± 27 12.98 ± 65 0.1509 ± 83 2627 ± 4 
W332-7-1 1355 43 0.03 730 7800 0.1758 ± 4 0.0104 ± 5 0.524 ± 26 12.71 ± 64 0.1714 ± 122 2614 ± 4 
W332-18-1 1767 156 0.09 947 9070 0.1778 ± 4 0.0236 ± 4 0.516 ± 26 12.64 ± 64 0.1377 ± 74 2632 ± 3 
W332-20-2 1479 73 0.05 799 6850 0.1762 ± 4 0.0132 ± 5 0.524 ± 26 12.72 ± 64 0.1406 ± 90 2617 ± 4 
W332-21-1 1428 431 0.30 712 630 0.1748 ± 9 0.0849 ± 20 0.422 ± 21 10.18 ± 52 0.1189 ± 66 2604 ± 9 
W332-22-1 1542 220 0.14 758 2660 0.1767 ± 5 0.0253 ± 8 0.466 ± 23 11.35 ± 57 0.0829 ± 49 2622 ± 4 
W332-23-1 988 80 0.08 519 7170 0.1779 ± 4 0.0223 ± 6 0.505 ± 25 12.39 ± 62 0.1392 ± 80 2633 ± 4 
W332-25-1 1321 63 0.05 689 13700 0.1777 ± 3 0.0133 ± 4 0.507 ± 25 12.42 ± 63 0.1403 ± 81 2632 ± 3 
W332-25-2 975 87 0.09 634 473 0.1739 ± 11 0.1231 ± 23 0.522 ± 26 12.53 ± 64 0.7225 ± 390 2596 ± 10 
W332-26-1 1402 64 0.05 722 8140 0.1768 ± 4 0.0115 ± 4 0.500 ± 25 12.20 ± 61 0.1262 ± 81 2623 ± 3 
metamict cores 
W332-1-2 6291 4760 0.76 3572 71600 0.1536 ± 1 0.2074 ± 3 0.484 ± 24 10.26 ± 51 0.1327 ± 66 2387 ± 2 
W332-1-3 3673 1739 0.47 1936 44800 0.1607 ± 2 0.1320 ± 3 0.473 ± 24 10.48 ± 53 0.1319 ± 66 2463 ± 2 
W332-5-2 4021 1546 0.38 2187 65600 0.1641 ± 2 0.1099 ± 3 0.496 ± 25 11.22 ± 56 0.1416 ± 71 2498 ± 2 
W332-14-1 3676 1231 0.33 2214 14100 0.1705 ± 2 0.0915 ± 3 0.552 ± 28 12.99 ± 65 0.1510 ± 76 2562 ± 2 
W332-14-2 6487 3911 0.60 3704 95700 0.1572 ± 2 0.1641 ± 3 0.502 ± 25 10.88 ± 55 0.1366 ± 68 2426 ± 2 
W332-15-1 1506 682 0.45 969 1920 0.1793 ± 6 0.1424 ± 12 0.551 ± 28 13.61 ± 69 0.1731 ± 88 2646 ± 6 
W332-20-1 1608 810 0.50 967 7180 0.1791 ± 4 0.1460 ± 7 0.524 ± 26 12.93 ± 65 0.1519 ± 76 2644 ± 3 
W332-20-3 3562 1670 0.47 2148 29500 0.1686 ± 2 0.1272 ± 3 0.540 ± 27 12.55 ± 63 0.1465 ± 73 2544 ± 2 
W382 porphyritic granite 
cores 
W382-3-1 181 82 0.45 100 7880 0.1823 ± 5 0.1265 ± 9 0.486 ± 16 12.22 ± 40 0.1363 ± 45 2674 ± 5 
W383-5-1 358 179 0.5 199 18860 0.1872 ± 3 0.1377 ± 5 0.487 ± 16 12.57 ± 41 0.1342 ± 43 2718 ± 3 
W383-5-2 202 75 0.37 92 15000 0.2049 ± 5 0.1108 ± 7 0.402 ± 13 11.36 ± 37 0.1202 ± 40 2866 ± 4 
W382-9-1 243 126 0.52 135 17800 0.1813 ± 4 0.1426 ± 7 0.487 ± 16 12.17 ± 39 0.1338 ± 44 2665 ± 4 
W382-9-2 184 62 0.34 104 13100 0.1786 ± 5 0.0904 ± 8 0.517 ± 17 12.73 ± 41 0.1379 ± 46 2640 ± 5 
W382-9-3 139 46 0.33 78 12700 0.1889 ± 6 0.0943 ± 9 0.503 ± 16 13.11 ± 43 0.1440 ± 49 2733 ± 6 
W382-9-4 157 46 0.29 86 8620 0.1819 ± 6 0.0767 ± 8 0.500 ± 16 12.54 ± 41 0.1308 ± 45 2670 ± 5 
W382-15-1 291 136 0.47 165 7720 0.1831 ± 7 0.1307 ± 7 0.501 ± 10 12.66 ± 26 0.1355 ± 30 2681 ± 6 
W382-15-2 250 120 0.48 138 3720 0.1806 ± 8 0.1370 ± 8 0.483 ± 10 12.02 ± 25 0.1288 ± 30 2659 ± 7 
W382-15-3 191 85 0.45 111 4120 0.1832 ± 10 0.1292 ± 10 0.509 ± 10 12.85 ± 27 0.1377 ± 36 2682 ± 9 
W382-16-1 465 285 0.61 268 17100 0.1817 ± 5 0.1674 ± 7 0.496 ± 10 12.43 ± 25 0.1337 ± 27 2668 ± 4 
W382-16-2 417 257 0.62 246 10400 0.1827 ± 6 0.1716 ± 8 0.505 ± 10 12.73 ± 25 0.1384 ± 29 2678 ± 5 
W382-16-3 480 185 0.38 263 29400 0.1820 ± 5 0.1033 ± 6 0.496 ± 10 12.44 ± 25 0.1315 ± 28 2671 ± 5 
W382-22-1 125 82 0.66 75 4100 0.1830 ± 2 0.1942 ± 15 0.502 ± 10 12.66 ± 28 0.1425 ± 36 2681 ± 11 
W382-22-2 124 94 0.75 82 2770 0.1811 ± 1 0.2132 ± 16 0.544 ± 11 13.59 ± 30 0.1457 ± 37 2663 ± 12 
W382-23-1 122 53 0.43 67 3780 0.1863 ± 1 0.1300 ± 13 0.484 ± 10 12.42 ± 28 0.1348 ± 43 2710 ± 13 
W382-25-1 232 103 0.44 134 6280 0.1826 ± 8 0.1270 ± 8 0.509 ± 10 12.81 ± 26 0.1400 ± 33 2676 ± 7 
W382-25-2 98 35 0.36 55 2430 0.1812 ± 2 0.1125 ± 13 0.499 ± 10 12.46 ± 29 0.1364 ± 51 2664 ± 14 
W382-28-1 192 104 0.54 113 4460 0.1818 ± 9 0.1586 ± 10 0.508 ± 10 12.73 ± 26 0.1414 ± 33 2670 ± 8 
W382-28-2 489 148 0.3 282 8580 0.1819 ± 5 0.0870 ± 5 0.526 ± 10 13.21 ± 26 0.1440 ± 32 2670 ± 5 
W382-28-3 170 79 0.46 103 2340 0.1813 ± 1 0.1418 ± 10 0.525 ± 10 13.13 ± 28 0.1445 ± 38 2665 ± 9 
W382-8-2 328 197 0.60 187 14500 0.1821 ± 4 0.1644 ± 6 0.490 ± 16 12.31 ± 40 0.1342 ± 43 2672 ± 3 
W382-12-1 548 284 0.52 307 90900 0.1227 ± 3 0.1441 ± 4 0.490 ± 16 12.35 ± 39 0.1318 ± 42 2682 ± 2 
W382-13-2 108 61 0.56 64 7190 0.1846 ± 9 0.1520 ± 15 0.510 ± 16 12.99 ± 43 0.1375 ± 47 2695 ± 8 
W382-20-3 674 212 0.32 395 9970 0.1816 ± 5 0.0859 ± 8 0.534 ± 10 13.38 ± 26 0.1456 ± 32 2668 ± 5 
W382-20-1 205 86 0.42 120 2460 0.1795 ± 9 0.1125 ± 23 0.514 ± 10 12.73 ± 27 0.1371 ± 43 2648 ± 11 
W382-4-1 433 246 0.57 241 60400 0.1832 ± 3 0.1549 ± 4 0.484 ± 16 12.22 ± 39 0.1318 ± 42 2682 ± 2 
W382-4-2 1082 285 0.26 533 22800 0.1820 ± 2 0.0745 ± 2 0.455 ± 15 11.41 ± 37 0.1285 ± 41 2671 ± 2 
W382-10-2 1546 911 0.59 904 150000 0.1813 ± 2 0.1600 ± 3 0.506 ± 16 12.65 ± 41 0.1374 ± 44 2665 ± 2 
W382-17-1 528 203 0.38 299 9240 0.1804 ± 5 0.1072 ± 6 0.510 ± 10 12.67 ± 25 0.1372 ± 30 2657 ± 5 
W382-17-2 371 161 0.43 211 12300 0.1810 ± 6 0.1218 ± 7 0.506 ± 10 12.63 ± 25 0.1389 ± 30 2662 ± 5 
W382-18-1 309 176 0.57 187 6990 0.1826 ± 7 0.1579 ± 9 0.524 ± 10 13.19 ± 27 0.1407 ± 31 2677 ± 7 
W382-18-2 277 153 0.55 162 4860 0.1812 ± 8 0.1572 ± 9 0.506 ± 10 12.64 ± 26 0.1374 ± 32 2664 ± 7 
W382-19-1 205 131 0.64 126 6290 0.1788 ± 10 0.1824 ± 12 0.522 ± 10 12.87 ± 27 0.1448 ± 34 2642 ± 9 
W382-19-2 267 189 0.71 164 4380 0.1810 ± 8 0.1973 ± 11 0.516 ± 10 12.86 ± 27 0.1382 ± 31 2662 ± 8 
W382-14-1 1515 327 0.22 879 58800 0.1810 ± 2 0.0564 ± 2 0.525 ± 17 13.12 ± 42 0.1374 ± 44 2662 ± 2 
zoned rims and clear grains 
W382-2-1 1068 354 0.33 546 30900 0.1792 ± 3 0.0870 ± 3 0.469 ± 150 11.59 ± 37 0.1231 ± 40 2645 ± 2 
W382-11-1 1025 1006 0.98 616 22800 0.1779 ± 2 0.2676 ± 5 0.482 ± 154 11.81 ± 38 0.1313 ± 42 2633 ± 2 
W382-11-2 1013 226 0.22 524 156500 0.1786 ± 2 0.0609 ± 2 0.485 ± 155 11.94 ± 38 0.1321 ± 43 2640 ± 2 
W382-13-1 1852 130 0.07 938 85600 0.1792 ± 2 0.0191 ± 1 0.491 ± 157 12.14 ± 39 0.1337 ± 44 2645 ± 2 
W382-14-2 294 186 0.63 170 75200 0.1788 ± 4 0.1725 ± 7 0.495 ± 159 12.21 ± 40 0.1351 ± 44 2641 ± 4 
W382-14-3 650 309 0.48 375 29200 0.1779 ± 3 0.1317 ± 5 0.511 ± 164 12.52 ± 40 0.1415 ± 46 2633 ± 3 
W382-14-4 851 323 0.38 466 46000 0.1787 ± 3 0.1050 ± 3 0.496 ± 159 12.21 ± 39 0.1369 ± 44 2641 ± 2 
W382-21-1 410 294 0.72 267 5650 0.1790 ± 7 0.2033 ± 10 0.544 ± 106 13.44 ± 27 0.1497 ± 32 2644 ± 7 
W382-21-2 608 194 0.32 351 6020 0.1779 ± 6 0.0920 ± 5 0.526 ± 102 12.9 ± 26 0.1424 ± 32 2633 ± 5 
W382-24-1 1145 185 0.16 604 39900 0.1786 ± 3 0.0435 ± 2 0.502 ± 96 12.36 ± 24 0.1326 ± 27 2640 ± 3 
W382-24-2 688 569 0.83 420 8980 0.1789 ± 4 0.2361 ± 7 0.500 ± 10 12.32 ± 24 0.1406 ± 28 2642 ± 4 
W382-26-1 1391 434 0.31 672 19180 0.1676 ± 3 0.0863 ± 3 0.447 ± 8 10.33 ± 20 0.1212 ± 24 2534 ± 3 
W382-26-2 530 228 0.43 297 24600 0.1772 ± 4 0.1182 ± 6 0.502 ± 10 12.27 ± 24 0.1361 ± 28 2627 ± 4 
W382-6-1 208 160 0.77 119 22700 0.1786 ± 4 0.2131 ± 8 0.476 ± 15 11.72 ± 38 0.1323 ± 43 2640 ± 4 
W382-7-1 800 354 0.44 430 47600 0.1774 ± 2 0.1203 ± 3 0.502 ± 10 12.27 ± 24 0.1361 ± 28 2627 ± 4 
W382-7-2 1028 518 0.50 585 6670 0.1781 ± 4 0.1367 ± 7 0.499 ± 10 12.26 ± 24 0.1353 ± 27 2635 ± 4 
W382-7-4 813 362 0.44 473 15900 0.1781 ± 4 0.1208 ± 6 0.490 ± 10 12.03 ± 24 0.1327 ± 27 2635 ± 4 
W382-7-3 848 369 0.44 446 9580 0.1781 ± 4 0.1168 ± 6 0.497 ± 10 12.21 ± 23 0.1335 ± 27 2636 ± 4 
W382-8-1 472 211 0.45 253 5650 0.1788 ± 3 0.1267 ± 5 0.474 ± 15 11.67 ± 38 0.1338 ± 43 2641 ± 3 
metamict 
W382-10-1 3300 749 0.23 1469 2070 0.1429 ± 2 0.1618 ± 4 0.385 ± 123 7.91 ± 25 0.2741 ± 88 2337 ± 2 
W382-12-2 1030 310 0.30 530 111000 0.1741 ± 2 0.0826 ± 3 0.476 ± 152 11.42 ± 37 0.1305 ± 42 2597 ± 2 
W427 porphyritic granite 
cores 
W427-1-1 213 61 0.29 97 9350 0.1830 ± 8 0.0723 ± 13 0.565 ± 23 14.24 ± 58 0.1429 ± 64 2680 ± 7 
W427-1-3 287 98 0.34 105 15500 0.1805 ± 8 0.0916 ± 12 0.448 ± 18 11.15 ± 46 0.1207 ± 52 2657 ± 7 
W427-1-5 362 175 0.48 153 3160 0.1838 ± 7 0.1318 ± 13 0.497 ± 20 12.60 ± 51 0.1356 ± 56 2688 ± 6 
W427-3-1 216 281 1.30 102 1880 0.1818 ± 14 0.3711 ± 34 0.467 ± 19 11.70 ± 49 0.1329 ± 55 2669 ± 13 
W427-3-2 335 691 2.06 208 2370 0.1847 ± 9 0.5340 ± 26 0.555 ± 22 14.14 ± 58 0.1438 ± 59 2696 ± 8 
W327-3-3 86 40 0.47 60 19200 0.1845 ± 12 0.1287 ± 22 0.487 ± 20 12.39 ± 51 0.1345 ± 59 2694 ± 11 
W327-3-4 220 153 0.70 141 11100 0.1765 ± 6 0.1940 ± 12 0.432 ± 17 10.52 ± 43 0.1201 ± 49 2621 ± 6 
W327-3-5 112 102 0.91 82 10400 0.1824 ± 11 0.2518 ± 23 0.470 ± 19 11.82 ± 49 0.1298 ± 54 2675 ± 10 
W427-6-1 480 188 0.39 410 10200 0.1840 ± 4 0.1142 ± 7 0.607 ± 24 15.39 ± 62 0.1768 ± 72 2689 ± 4 
W427-9-1 120 93 0.78 91 1540 0.1876 ± 22 0.2361 ± 48 0.480 ± 19 12.42 ± 54 0.1459 ± 67 2722 ± 20 
W427-9-2 289 207 0.72 186 1200 0.1829 ± 14 0.1449 ± 30 0.430 ± 17 10.85 ± 45 0.0871 ± 40 2679 ± 13 
W427-10-1 80 44 0.55 87 912 0.1845 ± 20 0.1561 ± 43 0.708 ± 29 18.01 ± 78 0.2023 ± 100 2694 ± 18 
W427-14-1 6044 727 0.12 4500 26200 0.1812 ± 1 0.0387 ± 1 0.708 ± 11 17.69 ± 28 0.2281 ± 37 2663 ± 1 
W427-19-2 283 300 1.06 184 2900 0.1809 ± 6 0.2892 ± 13 0.505 ± 8 12.59 ± 21 0.1379 ± 24 2661 ± 5 
W427-20-1 117 54 0.47 70 2800 0.1858 ± 11 0.1260 ± 21 0.520 ± 9 13.32 ± 24 0.1407 ± 34 2705 ± 10 
W427-1-9 169 60 0.35 98 10700 0.1847 ± 7 0.0978 ± 11 0.523 ± 9 13.32 ± 23 0.1451 ± 30 2695 ± 6 
W427-1-10 166 68 0.41 95 7120 0.1865 ± 7 0.1169 ± 12 0.504 ± 8 12.97 ± 22 0.1428 ± 29 2712 ± 6 
zoned inner rims 
W427-1-2 4191 634 0.15 1742 11600 0.1746 ± 2 0.0368 ± 2 0.536 ± 21 12.90 ± 52 0.1304 ± 53 2602 ± 2 
W427-2-1 5291 933 0.18 1988 89600 0.1785 ± 1 0.0397 ± 1 0.484 ± 19 11.91 ± 48 0.1088 ± 44 2639 ± 1 
W427-2-2 6952 1325 0.19 2828 7990 0.1754 ± 1 0.0384 ± 2 0.522 ± 21 12.63 ± 51 0.1052 ± 42 2610 ± 1 
W427-4-1 5298 521 0.10 3404 198000 0.1733 ± 1 0.0276 ± 1 0.496 ± 20 11.86 ± 48 0.1394 ± 56 2589 ± 1 
W427-4-2 2470 1280 0.52 1378 1440 0.1712 ± 3 0.0788 ± 6 0.399 ± 16 9.42 ± 38 0.0606 ± 25 2570 ± 3 
W427-5-1 1501 359 0.24 956 39100 0.1732 ± 2 0.0726 ± 3 0.474 ± 19 11.31 ± 45 0.1438 ± 58 2589 ± 2 
W427-6-2 2784 314 0.11 2163 18100 0.1787 ± 2 0.0245 ± 2 0.597 ± 24 14.71 ± 59 0.1298 ± 53 2641 ± 2 
W427-7-1 1559 717 0.46 1293 5040 0.1754 ± 3 0.0805 ± 5 0.606 ± 24 14.65 ± 59 0.1062 ± 43 2609 ± 3 
W427-8-1 1340 320 0.24 987 24000 0.1749 ± 3 0.0709 ± 4 0.548 ± 22 13.21 ± 53 0.1624 ± 66 2606 ± 3 
W427-11-1 3882 606 0.16 2870 68800 0.1767 ± 1 0.0423 ± 1 0.562 ± 22 13.70 ± 55 0.1524 ± 61 2622 ± 1 
W427-12-1 1689 389 0.23 995 4220 0.1748 ± 3 0.0579 ± 5 0.438 ± 18 10.54 ± 42 0.1100 ± 45 2604 ± 3 
W427-13-1 3025 486 0.16 1546 27000 0.1746 ± 2 0.0424 ± 2 0.389 ± 16 9.36 ± 38 0.1026 ± 41 2602 ± 2 
W427-15-1 1998 543 0.27 1135 25600 0.1768 ± 2 0.0739 ± 2 0.527 ± 8 12.84 ± 21 0.1433 ± 24 2623 ± 2 
W427-16-1 2720 674 0.25 1615 75100 0.1763 ± 2 0.0676 ± 2 0.555 ± 9 13.48 ± 22 0.1514 ± 25 2618 ± 1 
W427-17-1 2737 628 0.23 1448 18000 0.1714 ± 1 0.0715 ± 2 0.493 ± 8 11.66 ± 19 0.1537 ± 25 2572 ± 1 
W427-18-1 1011 645 0.64 596 5800 0.1756 ± 3 0.1506 ± 5 0.512 ± 8 12.40 ± 20 0.1209 ± 20 2612 ± 3 
W427-18-2 1242 367 0.30 577 2990 0.1737 ± 3 0.0257 ± 5 0.442 ± 7 10.58 ± 17 0.0385 ± 10 2594 ± 3 
W427-19-1 2462 1043 0.42 922 772 0.1647 ± 4 0.0199 ± 8 0.342 ± 5 7.76 ± 13 0.0160 ± 7 2504 ± 4 
W427-21-1 3165 1330 0.42 1813 1220 0.1748 ± 2 0.0672 ± 5 0.513 ± 8 12.36 ± 20 0.0821 ± 14 2604 ± 2 
W427-1-7 2767 461 0.17 1610 14800 0.1765 ± 2 0.0342 ± 2 0.557 ± 9 13.55 ± 22 0.1144 ± 20 2620 ± 2 
W427-1-8 2022 366 0.18 1130 67000 0.1763 ± 2 0.0483 ± 2 0.530 ± 9 12.88 ± 21 0.1414 ± 24 2618 ± 2 
weakly zoned outer rims 
W427-1-4 2686 99 0.04 1025 103000 0.1768 ± 2 0.0093 ± 1 0.505 ± 20 12.31 ± 49 0.1269 ± 53 2623 ± 2 
W427-1-6 3116 81 0.03 1171 104000 0.1757 ± 2 0.0069 ± 1 0.498 ± 20 12.07 ± 48 0.1323 ± 56 2613 ± 2 
W427-5-2 1170 29 0.02 849 15100 0.1749 ± 3 0.0067 ± 3 0.568 ± 23 13.70 ± 55 0.1542 ± 94 2605 ± 3 
W427-17-2 2240 107 0.05 1236 71600 0.1764 ± 2 0.0134 ± 1 0.539 ± 9 13.10 ± 21 0.1514 ± 28 2619 ± 1 
W427-22-1 3625 152 0.04 2048 143000 0.1764 ± 1 0.0113 ± 1 0.553 ± 9 13.46 ± 22 0.1491 ± 26 2620 ± 1 
W427-22-2 1765 138 0.08 898 4680 0.1762 ± 2 0.0083 ± 3 0.493 ± 8 11.99 ± 19 0.0527 ± 23 2618 ± 2 
W427-1-11 2142 70 0.03 1111 43200 0.1767 ± 2 0.0084 ± 1 0.508 ± 8 12.38 ± 20 0.1308 ± 29 2622 ± 2 
W390 aplite dyke 
cores 
W390-6-4 234 80 0.34 126 4960 0.1806 ± 5 0.0927 ± 8 0.485 ± 11 12.07 ± 29 0.1309 ± 33 2659 ± 5 
W390-6-1 297 96 0.32 158 2660 0.1809 ± 6 0.0917 ± 11 0.476 ± 11 11.87 ± 28 0.1343 ± 35 2661 ± 5 
W390-6-1a 443 82 0.18 244 23400 0.1826 ± 4 0.0493 ± 5 0.518 ± 11 13.04 ± 28 0.1388 ± 33 2677 ± 3 
W390-11-2 864 237 0.27 372 10200 0.1810 ± 5 0.0750 ± 7 0.396 ± 9 9.89 ± 23 0.1083 ± 27 2662 ± 4 
W390-1-1 624 120 0.19 332 25900 0.1814 ± 3 0.0545 ± 4 0.500 ± 11 12.50 ± 27 0.1412 ± 32 2666 ± 3 
W390-1-2 987 252 0.26 544 27800 0.1813 ± 3 0.0695 ± 3 0.511 ± 11 12.78 ± 27 0.1392 ± 30 2665 ± 2 
W390-1-3 897 169 0.19 494 17700 0.1813 ± 3 0.0513 ± 4 0.519 ± 12 12.96 ± 30 0.1414 ± 34 2665 ± 3 
W390-2-2 951 43 0.04 489 17800 0.1815 ± 3 0.0111 ± 3 0.499 ± 11 12.50 ± 27 0.1226 ± 41 2667 ± 2 
old cores 
W390-6-2 464 168 0.36 274 23600 0.1944 ± 4 0.0991 ± 5 0.529 ± 11 14.19 ± 30 0.1447 ± 32 2780 ± 3 
W390-6-3 442 174 0.39 256 9920 0.1950 ± 4 0.1067 ± 5 0.515 ± 12 13.84 ± 32 0.1394 ± 33 2785 ± 3 
W390-12-1 642 366 0.57 407 1910 0.1953 ± 4 0.1586 ± 8 0.530 ± 12 14.27 ± 33 0.1474 ± 35 2787 ± 4 
W390-12-2 184 57 0.31 112 4780 0.1956 ± 7 0.0832 ± 12 0.548 ± 13 14.76 ± 35 0.1464 ± 41 2789 ± 6 
W390-9-2 483 261 0.54 337 7060 0.1960 ± 5 0.1504 ± 8 0.599 ± 14 16.19 ± 38 0.1668 ± 40 2794 ± 4 
W390-3-3 382 443 1.16 270 9930 0.1981 ± 5 0.3098 ± 11 0.541 ± 11 14.79 ± 32 0.1447 ± 31 2810 ± 4 
W390-9-1 233 219 0.94 174 737 0.1987 ± 11 0.2630 ± 25 0.557 ± 13 15.27 ± 38 0.1565 ± 40 2816 ± 9 
W390-3-1 175 163 0.93 106 2980 0.2001 ± 8 0.2340 ± 17 0.485 ± 10 13.37 ± 30 0.1218 ± 28 2827 ± 7 
W390-3-2 283 207 0.73 184 20300 0.1997 ± 5 0.1997 ± 9 0.538 ± 11 14.82 ± 32 0.1467 ± 32 2824 ± 4 
zoned inner rims 
W390-5-1 2606 701 0.27 1498 37900 0.1791 ± 1 0.0740 ± 2 0.533 ± 11 13.15 ± 28 0.1465 ± 31 2645 ± 1 
W390-5-2 1708 461 0.27 930 78600 0.1789 ± 2 0.0723 ± 2 0.506 ± 11 12.48 ± 26 0.1356 ± 29 2643 ± 2 
W390-4-1 530 103 0.19 280 72400 0.1791 ± 3 0.0539 ± 3 0.498 ± 11 12.29 ± 26 0.1383 ± 31 2644 ± 3 
W390-5-4 1182 203 0.17 663 52400 0.1794 ± 2 0.0467 ± 2 0.532 ± 11 13.15 ± 28 0.1446 ± 31 2647 ± 2 
W390-2-1 849 73 0.09 436 27300 0.1801 ± 3 0.0230 ± 3 0.496 ± 10 12.31 ± 26 0.1319 ± 33 2653 ± 3 
W390-4-2 1288 431 0.33 747 42900 0.1802 ± 2 0.0904 ± 3 0.530 ± 11 13.16 ± 28 0.1431 ± 31 2655 ± 2 
W390-10-2 612 335 0.55 343 3960 0.1805 ± 4 0.1310 ± 8 0.490 ± 11 12.19 ± 29 0.1170 ± 28 2657 ± 4 
W390-10-3 488 210 0.43 290 19700 0.1796 ± 4 0.1191 ± 6 0.530 ± 12 13.13 ± 31 0.1471 ± 35 2649 ± 4 
clear grains and outer rims 
W390-10-1 448 196 0.44 261 1330 0.1764 ± 7 0.1194 ± 14 0.502 ± 12 12.22 ± 29 0.1369 ± 36 2619 ± 7 
W390-11-1 658 91 0.14 328 6590 0.1745 ± 5 0.0333 ± 7 0.476 ± 11 11.45 ± 27 0.1149 ± 36 2601 ± 5 
W390-7-2 293 50 0.17 155 5040 0.1766 ± 6 0.0457 ± 9 0.498 ± 12 12.12 ± 29 0.1339 ± 41 2622 ± 5 
W390-7-3 243 47 0.19 132 4200 0.1771 ± 7 0.0532 ± 12 0.506 ± 12 12.35 ± 30 0.1394 ± 46 2626 ± 7 
W390-7-4 176 28 0.16 87 2540 0.1779 ± 7 0.0387 ± 12 0.465 ± 11 11.41 ± 27 0.1131 ± 46 2633 ± 7 
W390-14-1 788 263 0.33 446 27500 0.1778 ± 3 0.0909 ± 4 0.517 ± 12 12.67 ± 30 0.1410 ± 33 2633 ± 3 
W390-14-2 717 256 0.36 410 10800 0.1774 ± 3 0.0986 ± 5 0.518 ± 12 12.68 ± 30 0.1430 ± 34 2629 ± 3 
W390-9-3 514 129 0.25 320 11100 0.1780 ± 4 0.0696 ± 6 0.577 ± 13 14.16 ± 33 0.1596 ± 41 2634 ± 4 
W390-13-1 348 54 0.15 187 6070 0.1782 ± 5 0.0412 ± 8 0.508 ± 12 12.49 ± 30 0.1354 ± 43 2636 ± 5 
W390-13-2 271 140 0.52 103 487 0.1782 ± 17 0.0543 ± 35 0.320 ± 7 7.86 ± 20 0.0336 ± 23 2636 ± 15 
W390-7-1 261 58 0.22 136 6870 0.1784 ± 5 0.0620 ± 8 0.485 ± 11 11.93 ± 28 0.1357 ± 37 2638 ± 5 
metamict 
W390-5-3 2570 733 0.28 1364 25400 0.1755 ± 1 0.0768 ± 2 0.491 ± 10 11.89 ± 25 0.1324 ± 28 2611 ± 1 
W390-8-1 3129 956 0.30 1213 3000 0.1641 ± 2 0.0939 ± 4 0.352 ± 8 7.96 ± 18 0.1081 ± 25 2499 ± 2 
W390-8-2 8686 2677 0.31 4337 2300 0.1595 ± 1 0.0993 ± 3 0.450 ± 10 9.90 ± 23 0.1451 ± 34 2451 ± 1 
W390-8-3 2940 780 0.26 1485 3800 0.1741 ± 2 0.0837 ± 3 0.460 ± 11 11.04 ± 26 0.1453 ± 34 2597 ± 2 
W393 aplite dyke 
clear cores 
W393-12-1 83 46 0.56 49 2190 0.1796 ± 20 0.1459 ± 41 0.504 ± 9 12.49 ± 28 0.1318 ± 46 2649 ± 18 
W393-7-1 577 58 0.11 311 7180 0.1796 ± 8 0.0253 ± 12 0.516 ± 8 12.78 ± 23 0.1299 ± 67 2650 ± 8 
W393-12-2 101 63 0.63 61 2280 0.1801 ± 15 0.1675 ± 31 0.512 ± 9 12.72 ± 26 0.1368 ± 37 2654 ± 14 
W393-10-2 467 271 0.58 274 6810 0.1801 ± 6 0.1498 ± 11 0.509 ± 8 12.64 ± 22 0.1313 ± 24 2654 ± 6 
W393-11-2 779 360 0.46 461 8310 0.1812 ± 4 0.1214 ± 7 0.525 ± 8 13.11 ± 22 0.1381 ± 24 2664 ± 4 
W393-1-3 370 155 0.42 213 7230 0.1813 ± 7 0.1142 ± 11 0.512 ± 8 12.82 ± 22 0.1394 ± 28 2665 ± 6 
W393-9-1 355 138 0.39 211 4250 0.1815 ± 8 0.1002 ± 14 0.532 ± 8 13.30 ± 23 0.1369 ± 31 2666 ± 7 
W393-18-2 407 182 0.45 238 6960 0.1821 ± 7 0.1183 ± 12 0.519 ± 8 13.03 ± 22 0.1373 ± 28 2672 ± 6 
W393-8-1 1543 273 0.18 884 27600 0.1824 ± 3 0.0472 ± 3 0.541 ± 9 13.60 ± 22 0.1441 ± 26 2674 ± 3 
W393-10-1 254 133 0.52 156 8450 0.1823 ± 8 0.1402 ± 13 0.538 ± 9 13.51 ± 24 0.1434 ± 29 2674 ± 7 
W393-18-1 499 67 0.13 252 3830 0.1324 ± 8 0.0283 ± 14 0.498 ± 8 9.10 ± 17 0.1048 ± 56 2129 ± 10 
W393-5-2 673 1480 2.20 896 73 0.1632 ± 27 0.2645 ± 62 0.587 ± 10 13.22 ± 32 0.0706 ± 20 2489 ± 28 
W393-1-1 275 68 0.25 174 144 0.1710 ± 36 0.1519 ± 81 0.398 ± 7 9.33 ± 27 0.2416 ± 137 2568 ± 35 
W393-11-1 1790 1412 0.79 1082 630 0.1718 ± 7 0.2436 ± 16 0.460 ± 7 10.89 ± 18 0.1419 ± 25 2576 ± 7 
W393-14-1 411 408 0.99 268 133 0.1730 ± 33 0.1347 ± 74 0.401 ± 7 9.56 ± 26 0.0544 ± 32 2586 ± 32 
W393-17-2 166 93 0.56 100 1920 0.1786 ± 14 0.1526 ± 29 0.512 ± 9 12.62 ± 25 0.1400 ± 37 2640 ± 13 
zoned rims 
W393-2-1 3492 1307 0.37 1463 6410 0.1470 ± 2 0.1060 ± 4 0.385 ± 6 7.81 ± 13 0.1091 ± 18 2311 ± 2 
W393-2-2 5336 2117 0.40 2660 28600 0.1535 ± 15 0.1087 ± 2 0.458 ± 7 9.70 ± 16 0.1256 ± 20 2385 ± 2 
W393-3-2 2003 132 0.06 763 5320 0.1546 ± 3 0.0252 ± 5 0.371 ± 6 7.91 ± 13 0.1427 ± 37 2397 ± 4 
W393-5-1 3327 1220 0.37 1895 22300 0.1649 ± 2 0.0980 ± 3 0.523 ± 8 11.89 ± 19 0.1397 ± 23 2507 ± 2 
W393-1-2 3147 1349 0.43 1523 20000 0.1659 ± 2 0.1160 ± 3 0.438 ± 7 10.01 ± 16 0.1185 ± 19 2517 ± 2 
W393-17-1 2490 686 0.28 1130 7850 0.1666 ± 3 0.0758 ± 4 0.421 ± 8 9.68 ± 16 0.1160 ± 20 2523 ± 3 
W393-3-1 1476 463 0.31 690 5670 0.1710 ± 4 0.0976 ± 6 0.424 ± 7 10.00 ± 16 0.1320 ± 23 2568 ± 4 
W393-15-1 1251 703 0.56 846 397 0.1749 ± 9 0.0870 ± 20 0.545 ± 9 13.14 ± 23 0.0845 ± 24 2605 ± 9 
W393-19-1 815 329 0.40 469 3890 0.1776 ± 5 0.1091 ± 9 0.513 ± 8 12.56 ± 21 0.1389 ± 26 2630 ± 5 
W393-13-1 1809 656 0.36 1053 24400 0.1776 ± 3 0.0978 ± 4 0.529 ± 8 12.96 ± 21 0.1427 ± 24 2631 ± 2 
W393-20-3 2008 530 0.26 1110 35800 0.1779 ± 3 0.0709 ± 3 0.514 ± 8 12.60 ± 20 0.1382 ± 23 2633 ± 2 
W393-20-4 2287 667 0.29 1341 30100 0.1781 ± 3 0.0808 ± 4 0.540 ± 9 13.28 ± 22 0.1497 ± 26 2636 ± 3 
W393-20-1 1379 314 0.23 742 13500 0.1783 ± 3 0.0611 ± 4 0.503 ± 8 12.35 ± 20 0.1349 ± 24 2637 ± 3 
W393-12-3 1151 431 0.37 616 11600 0.1785 ± 3 0.0952 ± 5 0.486 ± 8 11.97 ± 20 0.1236 ± 21 2639 ± 3 
W393-20-2 1663 689 0.41 937 1480 0.1789 ± 5 0.0740 ± 9 0.504 ± 8 12.43 ± 21 0.0900 ± 18 2642 ± 4 
W393-19-2 1573 525 0.33 901 37500 0.1794 ± 3 0.0927 ± 4 0.523 ± 8 12.93 ± 21 0.1450 ± 24 2647 ± 3 
clear grains 
W393-4-1 961 136 0.14 517 17500 0.1751 ± 4 0.0391 ± 5 0.513 ± 8 12.39 ± 20 0.1422 ± 30 2607 ± 4 
W393-16-1 713 60 0.08 394 10500 0.1771 ± 4 0.0211 ± 5 0.534 ± 9 13.04 ± 22 0.1332 ± 41 2626 ± 4 
W393-6-1 128 49 0.38 75 1720 0.1775 ± 16 0.0970 ± 31 0.514 ± 9 12.58 ± 25 0.1312 ± 49 2630 ± 15 
Labels U (p.p.m.) Th (p.p.m.) Th/U Total Pb 206Pb/204Pb 207Pb/206Pb* 208Pb/206Pb* 206Pb/238U* 207Pb/235U* 208Pb/232Th* 207Pb/206Pb* age (Ma) 
W323 fine-grained granite 
clear cores 
W323-1-1 272 270 0.99 173 4980 0.1822 ± 13 0.2786 ± 28 0.502 ± 15 12.60 ± 41 0.1411 ± 47 2673 ± 12† 
W323-1-2 215 143 0.66 128 2380 0.1776 ± 17 0.1791 ± 35 0.500 ± 15 12.23 ± 41 0.1348 ± 51 2630 ± 16 
W323-1-4 328 218 0.66 190 2260 0.1752 ± 14 0.1892 ± 29 0.482 ± 15 11.63 ± 38 0.1375 ± 48 2607 ± 13 
W323-3-1 525 283 0.54 310 7940 0.1812 ± 7 0.1504 ± 13 0.511 ± 16 12.78 ± 40 0.1425 ± 46 2664 ± 7 
W323-3-2 408 219 0.54 239 5640 0.1820 ± 10 0.1477 ± 19 0.506 ± 15 12.70 ± 40 0.1397 ± 47 2671 ± 9 
W323-4-4 477 262 0.55 276 7450 0.1812 ± 8 0.1562 ± 15 0.500 ± 15 12.48 ± 39 0.1423 ± 46 2664 ± 7 
W323-4-5 651 313 0.48 384 12600 0.1757 ± 6 0.1298 ± 9 0.523 ± 16 12.68 ± 39 0.1414 ± 45 2613 ± 6 
W323-5-1 476 257 0.54 281 2350 0.1829 ± 10 0.1240 ± 19 0.512 ± 16 12.91 ± 41 0.1175 ± 40 2679 ± 9 
W323-5-2 574 282 0.49 332 3640 0.1794 ± 8 0.1183 ± 15 0.510 ± 15 12.62 ± 39 0.1228 ± 41 2647 ± 7 
W323-5-3 291 141 0.48 175 3320 0.1799 ± 11 0.1331 ± 20 0.524 ± 16 13.00 ± 41 0.1444 ± 50 2652 ± 10 
W323-6-1 1774 1782 1.00 1123 12600 0.1823 ± 4 0.2864 ± 8 0.498 ± 15 12.53 ± 38 0.1421 ± 43 2674 ± 3 
W323-9-2 1224 324 0.26 682 20700 0.1861 ± 4 0.0781 ± 5 0.511 ± 15 13.12 ± 40 0.1510 ± 47 2708 ± 4 
W323-10-2 4767 512 0.11 2640 29600 0.1857 ± 2 0.0303 ± 2 0.528 ± 16 13.53 ± 41 0.1490 ± 46 2704 ± 2 
W323-11-1 398 232 0.58 237 3040 0.1850 ± 10 0.1628 ± 20 0.506 ± 15 12.90 ± 41 0.1415 ± 47 2698 ± 9 
W323-12-1 1421 355 0.25 809 9520 0.1817 ± 5 0.0722 ± 6 0.525 ± 16 13.16 ± 40 0.1517 ± 48 2668 ± 4 
W323-13-1 543 230 0.42 290 2160 0.1800 ± 10 0.1210 ± 20 0.466 ± 14 11.58 ± 36 0.1334 ± 47 2653 ± 10 
W323-14-1 666 357 0.54 382 3430 0.1877 ± 9 0.1498 ± 16 0.490 ± 15 12.69 ± 39 0.1371 ± 45 2722 ± 8 
weakly zoned outer rims 
W323-1-3 2095 117 0.06 1072 23300 0.1757 ± 4 0.0151 ± 3 0.499 ± 15 12.08 ± 37 0.1356 ± 51 2613 ± 3 
W323-1-5 2267 147 0.06 1140 7430 0.1727 ± 4 0.0171 ± 5 0.488 ± 15 11.62 ± 35 0.1289 ± 54 2584 ± 4 
W323-3-3 1511 1540 1.02 842 1360 0.1736 ± 8 0.0410 ± 15 0.512 ± 15 12.24 ± 38 0.0206 ± 10 2593 ± 7 
W323-4-1 1797 125 0.07 937 5200 0.1765 ± 4 0.0152 ± 7 0.503 ± 15 12.25 ± 37 0.1094 ± 58 2620 ± 4 
W323-4-6 1872 189 0.10 995 1880 0.1727 ± 6 0.0250 ± 10 0.501 ± 15 11.92 ± 36 0.124 ± 64 2584 ± 5 
W323-5-4 2416 293 0.12 1249 7830 0.1764 ± 3 0.0177 ± 4 0.500 ± 15 12.15 ± 37 0.0730 ± 29 2619 ± 3 
W323-6-2 2103 119 0.06 1070 16340 0.1751 ± 3 0.0144 ± 3 0.496 ± 15 11.96 ± 36 0.1257 ± 48 2607 ± 3 
W323-6-3 1902 135 0.07 1037 22200 0.1750 ± 3 0.0161 ± 3 0.531 ± 16 12.81 ± 39 0.1201 ± 42 2606 ± 3 
W323-9-1 2116 181 0.09 849 16200 0.1787 ± 3 0.0197 ± 3 0.388 ± 12 9.56 ± 29 0.0893 ± 31 2641 ± 3 
W323-10-3 1813 83 0.05 921 7550 0.1793 ± 4 0.0113 ± 5 0.492 ± 15 12.17 ± 37 0.1210 ± 68 2646 ± 4 
W323-11-2 2296 419 0.18 1193 2800 0.1777 ± 4 0.0306 ± 8 0.490 ± 15 12.00 ± 36 0.0821 ± 32 2631 ± 4 
W323-13-2 1997 302 0.15 932 7110 0.1794 ± 4 0.0149 ± 6 0.451 ± 14 11.16 ± 34 0.0444 ± 21 2648 ± 4 
metamict cores 
W323-7-1 3089 1494 0.48 1821 28800 0.1814 ± 3 0.1354 ± 4 0.519 ± 16 12.98 ± 39 0.1453 ± 44 2666 ± 3 
W323-8-1 11142 2952 0.26 5013 36200 0.1590 ± 2 0.0811 ± 2 0.421 ± 13 9.23 ± 28 0.1289 ± 39 2445 ± 2 
W330 coarse-grained granite 
clear cores 
W330-7-1 930 434 0.47 543 63000 0.1811 ± 4 0.1262 ± 5 0.518 ± 4 12.94 ± 12 0.1400 ± 14 2663 ± 4 
W330-7-2 907 405 0.45 523 275000 0.1809 ± 4 0.1202 ± 5 0.515 ± 4 12.84 ± 12 0.1385 ± 14 2661 ± 4 
W330-7-3 960 655 0.68 549 3460 0.1812 ± 5 0.1600 ± 9 0.488 ± 4 12.20 ± 11 0.1146 ± 12 2664 ± 5 
W330-13-1 639 112 0.17 339 159000 0.1820 ± 7 0.0471 ± 6 0.502 ± 8 12.59 ± 22 0.1354 ± 30 2671 ± 6 
W330-13-2 529 73 0.14 233 34400 0.1845 ± 9 0.0376 ± 9 0.418 ± 7 10.62 ± 19 0.1146 ± 35 2694 ± 8 
W330-10-1 737 207 0.28 412 15700 0.1798 ± 6 0.0758 ± 7 0.515 ± 8 12.78 ± 22 0.1395 ± 27 2651 ± 5 
W330-16-1 513 251 0.49 220 1530 0.1831 ± 18 0.0746 ± 35 0.382 ± 6 9.65 ± 20 0.0582 ± 29 2681 ± 17 
W330-15-2 1355 1884 1.39 992 45400 0.1865 ± 5 0.3752 ± 11 0.544 ± 9 13.97 ± 24 0.1466 ± 25 2711 ± 5 
W330-5-1 1468 56 0.04 754 28600 0.1657 ± 4 0.0089 ± 3 0.508 ± 8 11.60 ± 20 0.1191 ± 51 2515 ± 4 
W330-5-2 1217 55 0.04 604 34600 0.1705 ± 5 0.0128 ± 4 0.487 ± 8 11.45 ± 19 0.1388 ± 50 2563 ± 5 
W330-5-3 2628 79 0.03 1411 69700 0.1641 ± 3 0.0070 ± 2 0.533 ± 9 12.05 ± 20 0.1230 ± 44 2498 ± 3 
W330-6-2 661 972 1.47 410 508000 0.1808 ± 4 0.4049 ± 11 0.454 ± 7 11.33 ± 19 0.1251 ± 21 2661 ± 4 
cores mixed with inner rims 
W330-15-1 960 1030 1.07 624 2140 0.1778 ± 8 0.2629 ± 16 0.512 ± 8 12.55 ± 22 0.1254 ± 23 2633 ± 8 
W330-1-3 1366 1411 1.03 863 9300 0.1788 ± 6 0.2823 ± 13 0.500 ± 8 12.32 ± 21 0.1365 ± 24 2642 ± 5 
W330-11-1 932 241 0.26 514 30500 0.1792 ± 5 0.0704 ± 5 0.512 ± 8 12.65 ± 21 0.1394 ± 26 2646 ± 5 
W330-11-2 875 246 0.28 489 96000 0.1784 ± 5 0.0752 ± 5 0.518 ± 8 12.74 ± 21 0.1384 ± 25 2638 ± 5 
W330-12-2 1527 1556 1.02 991 40800 0.1777 ± 4 0.2813 ± 7 0.516 ± 8 12.64 ± 21 0.1424 ± 24 2631 ± 4 
W330-3-2 1930 3302 1.71 1364 9410 0.1770 ± 5 0.4590 ± 15 0.499 ± 8 12.18 ± 21 0.1339 ± 23 2625 ± 5 
W330-12-1 2778 716 0.26 1621 763000 0.1769 ± 3 0.0702 ± 3 0.544 ± 9 13.26 ± 22 0.1481 ± 25 2624 ± 3 
zoned inner rims 
W330-9-2 1475 2744 1.86 1034 41000 0.1767 ± 4 0.4976 ± 10 0.485 ± 8 11.82 ± 20 0.1298 ± 21 2622 ± 4 
W330-9-3 2412 4977 2.06 1746 90800 0.1762 ± 3 0.5493 ± 8 0.486 ± 8 11.82 ± 19 0.1295 ± 21 2618 ± 3 
W330-2-3 1750 395 0.23 938 8800 0.1774 ± 5 0.0601 ± 7 0.500 ± 8 12.24 ± 21 0.1332 ± 28 2629 ± 5 
W330-2-4 5099 2591 0.51 3221 5400 0.1730 ± 3 0.1385 ± 5 0.554 ± 9 13.22 ± 22 0.1511 ± 25 2587 ± 3 
W330-10-2 2810 911 0.32 1393 22100 0.1657 ± 3 0.0886 ± 3 0.458 ± 7 10.47 ± 17 0.1252 ± 21 2514 ± 3 
W330-15-3 2611 4630 1.77 2226 9370 0.1794 ± 4 0.4742 ± 9 0.596 ± 10 14.73 ± 24 0.1592 ± 26 2648 ± 4 
W330-14-2 1192 1780 1.49 810 20300 0.1787 ± 5 0.4091 ± 11 0.495 ± 8 12.20 ± 21 0.1357 ± 23 2641 ± 5 
W330-8-2 1068 1509 1.41 732 110000 0.1781 ± 4 0.3871 ± 8 0.508 ± 8 12.47 ± 21 0.1392 ± 23 2635 ± 4 
W330-8-3 3454 4926 1.43 2314 386000 0.1776 ± 2 0.3847 ± 5 0.497 ± 8 12.18 ± 20 0.1342 ± 22 2631 ± 2 
W330-2-1 2762 3908 1.41 1910 18300 0.1789 ± 4 0.3958 ± 10 0.509 ± 8 12.54 ± 21 0.1423 ± 24 2643 ± 3 
W330-2-2 1296 1559 1.20 812 1590 0.1750 ± 9 0.3201 ± 22 0.472 ± 8 11.40 ± 21 0.1257 ± 23 2606 ± 9 
W330-1-4 2531 5609 2.22 2062 10400 0.1780 ± 4 0.6084 ± 13 0.527 ± 8 12.93 ± 22 0.1446 ± 24 2635 ± 4 
weakly zoned outer rims 
W330-14-1 612 569 0.93 378 42800 0.1746 ± 7 0.2471 ± 11 0.505 ± 8 12.15 ± 21 0.1341 ± 24 2602 ± 6 
W330-6-3 1123 89 0.08 541 5600 0.1760 ± 7 0.0162 ± 10 0.466 ± 7 11.29 ± 20 0.0952 ± 63 2615 ± 6 
W330-1-1 698 99 0.14 380 1330 0.1613 ± 10 0.0302 ± 19 0.510 ± 8 11.33 ± 21 0.1089 ± 72 2469 ± 10 
W330-1-2 671 112 0.17 351 4130 0.1782 ± 10 0.0295 ± 18 0.496 ± 8 12.19 ± 23 0.0876 ± 57 2636 ± 10 
metamict cores 
W330-8-1 1054 131 0.12 572 26000 0.1772 ± 4 0.0334 ± 4 0.520 ± 84 12.71 ± 21 0.1393 ± 29 2627 ± 4 
W330-16-2 5356 2279 0.43 3177 3220000 0.1813 ± 3 0.1102 ± 3 0.534 ± 86 13.34 ± 22 0.1382 ± 23 2665 ± 2 
W330-6-1 1048 1489 1.42 675 3520 0.1678 ± 8 0.3724 ± 19 0.479 ± 8 11.09 ± 20 0.1255 ± 22 2536 ± 8 
W330-9-1 1480 3173 2.14 1155 180000 0.1769 ± 4 0.5803 ± 10 0.515 ± 8 12.56 ± 21 0.1394 ± 23 2624 ± 3 
W332 coarse-grained granite 
clear cores 
W332-2-1 338 61 0.18 165 1120 0.1786 ± 16 0.1190 ± 33 0.417 ± 21 10.26 ± 53 0.2744 ± 160 2640 ± 15 
W332-3-1 282 127 0.45 189 817 0.1805 ± 17 0.1539 ± 38 0.548 ± 28 13.63 ± 71 0.1882 ± 106 2657 ± 16 
W332-8-1 1223 382 0.31 594 1110 0.1802 ± 8 0.1577 ± 17 0.403 ± 20 10.01 ± 51 0.2034 ± 105 2655 ± 8 
W332-9-1 438 262 0.60 276 9080 0.1835 ± 7 0.1616 ± 13 0.541 ± 27 13.69 ± 70 0.1465 ± 5 2685 ± 7 
W332-10-1 953 566 0.59 579 16500 0.1826 ± 5 0.1605 ± 8 0.524 ± 26 13.18 ± 67 0.1415 ± 72 2676 ± 5 
W332-11-1 267 122 0.46 162 4160 0.1805 ± 11 0.1208 ± 21 0.535 ± 27 13.32 ± 69 0.1418 ± 76 2657 ± 10 
W332-12-1 219 109 0.50 127 1570 0.1804 ± 15 0.1512 ± 32 0.489 ± 25 12.17 ± 63 0.1484 ± 82 2657 ± 14 
W332-13-1 527 285 0.54 334 12300 0.1830 ± 6 0.1472 ± 11 0.551 ± 28 13.90 ± 70 0.1496 ± 76 2681 ± 6 
W332-16-1 250 100 0.40 154 3050 0.1831 ± 12 0.1353 ± 22 0.534 ± 27 13.47 ± 69 0.1795 ± 96 2681 ± 10 
W332-17-1 147 68 0.46 88 1740 0.1828 ± 17 0.1264 ± 34 0.518 ± 26 13.06 ± 69 0.1416 ± 82 2678 ± 16 
W332-19-1 458 261 0.57 278 7720 0.1816 ± 7 0.1543 ± 12 0.525 ± 26 13.15 ± 67 0.1425 ± 73 2668 ± 6 
zoned inner rims 
W332-4-2 1618 859 0.53 995 14900 0.1771 ± 3 0.1488 ± 6 0.537 ± 27 13.12 ± 66 0.1506 ± 76 2626 ± 3 
W332-14-3 4606 1393 0.30 2486 10700 0.1595 ± 2 0.0853 ± 3 0.501 ± 25 11.02 ± 55 0.1414 ± 71 2450 ± 2 
W332-15-2 4270 2217 0.52 2322 14000 0.1628 ± 2 0.1396 ± 4 0.483 ± 24 10.85 ± 54 0.1300 ± 65 2485 ± 2 
W332-24-1 1602 695 0.43 911 7400 0.1765 ± 3 0.1187 ± 6 0.507 ± 25 12.33 ± 62 0.1385 ± 70 2620 ± 3 
W332-24-2 2746 1664 0.61 1620 18800 0.1777 ± 2 0.1648 ± 4 0.509 ± 25 12.47 ± 63 0.1385 ± 69 2631 ± 2 
weakly zoned outer rims 
W332-1-1 1180 84 0.07 636 32400 0.1769 ± 4 0.0194 ± 3 0.523 ± 26 12.77 ± 64 0.1437 ± 76 2624 ± 3 
W332-4-1 979 266 0.27 566 14300 0.1774 ± 5 0.0723 ± 6 0.536 ± 27 13.11 ± 66 0.1425 ± 73 2629 ± 4 
W332-5-1 1022 42 0.04 577 19800 0.1777 ± 4 0.0121 ± 4 0.550 ± 28 13.48 ± 68 0.1608 ± 100 2631 ± 4 
W332-6-1 862 61 0.07 472 52800 0.1772 ± 5 0.0202 ± 4 0.531 ± 27 12.98 ± 65 0.1509 ± 83 2627 ± 4 
W332-7-1 1355 43 0.03 730 7800 0.1758 ± 4 0.0104 ± 5 0.524 ± 26 12.71 ± 64 0.1714 ± 122 2614 ± 4 
W332-18-1 1767 156 0.09 947 9070 0.1778 ± 4 0.0236 ± 4 0.516 ± 26 12.64 ± 64 0.1377 ± 74 2632 ± 3 
W332-20-2 1479 73 0.05 799 6850 0.1762 ± 4 0.0132 ± 5 0.524 ± 26 12.72 ± 64 0.1406 ± 90 2617 ± 4 
W332-21-1 1428 431 0.30 712 630 0.1748 ± 9 0.0849 ± 20 0.422 ± 21 10.18 ± 52 0.1189 ± 66 2604 ± 9 
W332-22-1 1542 220 0.14 758 2660 0.1767 ± 5 0.0253 ± 8 0.466 ± 23 11.35 ± 57 0.0829 ± 49 2622 ± 4 
W332-23-1 988 80 0.08 519 7170 0.1779 ± 4 0.0223 ± 6 0.505 ± 25 12.39 ± 62 0.1392 ± 80 2633 ± 4 
W332-25-1 1321 63 0.05 689 13700 0.1777 ± 3 0.0133 ± 4 0.507 ± 25 12.42 ± 63 0.1403 ± 81 2632 ± 3 
W332-25-2 975 87 0.09 634 473 0.1739 ± 11 0.1231 ± 23 0.522 ± 26 12.53 ± 64 0.7225 ± 390 2596 ± 10 
W332-26-1 1402 64 0.05 722 8140 0.1768 ± 4 0.0115 ± 4 0.500 ± 25 12.20 ± 61 0.1262 ± 81 2623 ± 3 
metamict cores 
W332-1-2 6291 4760 0.76 3572 71600 0.1536 ± 1 0.2074 ± 3 0.484 ± 24 10.26 ± 51 0.1327 ± 66 2387 ± 2 
W332-1-3 3673 1739 0.47 1936 44800 0.1607 ± 2 0.1320 ± 3 0.473 ± 24 10.48 ± 53 0.1319 ± 66 2463 ± 2 
W332-5-2 4021 1546 0.38 2187 65600 0.1641 ± 2 0.1099 ± 3 0.496 ± 25 11.22 ± 56 0.1416 ± 71 2498 ± 2 
W332-14-1 3676 1231 0.33 2214 14100 0.1705 ± 2 0.0915 ± 3 0.552 ± 28 12.99 ± 65 0.1510 ± 76 2562 ± 2 
W332-14-2 6487 3911 0.60 3704 95700 0.1572 ± 2 0.1641 ± 3 0.502 ± 25 10.88 ± 55 0.1366 ± 68 2426 ± 2 
W332-15-1 1506 682 0.45 969 1920 0.1793 ± 6 0.1424 ± 12 0.551 ± 28 13.61 ± 69 0.1731 ± 88 2646 ± 6 
W332-20-1 1608 810 0.50 967 7180 0.1791 ± 4 0.1460 ± 7 0.524 ± 26 12.93 ± 65 0.1519 ± 76 2644 ± 3 
W332-20-3 3562 1670 0.47 2148 29500 0.1686 ± 2 0.1272 ± 3 0.540 ± 27 12.55 ± 63 0.1465 ± 73 2544 ± 2 
W382 porphyritic granite 
cores 
W382-3-1 181 82 0.45 100 7880 0.1823 ± 5 0.1265 ± 9 0.486 ± 16 12.22 ± 40 0.1363 ± 45 2674 ± 5 
W383-5-1 358 179 0.5 199 18860 0.1872 ± 3 0.1377 ± 5 0.487 ± 16 12.57 ± 41 0.1342 ± 43 2718 ± 3 
W383-5-2 202 75 0.37 92 15000 0.2049 ± 5 0.1108 ± 7 0.402 ± 13 11.36 ± 37 0.1202 ± 40 2866 ± 4 
W382-9-1 243 126 0.52 135 17800 0.1813 ± 4 0.1426 ± 7 0.487 ± 16 12.17 ± 39 0.1338 ± 44 2665 ± 4 
W382-9-2 184 62 0.34 104 13100 0.1786 ± 5 0.0904 ± 8 0.517 ± 17 12.73 ± 41 0.1379 ± 46 2640 ± 5 
W382-9-3 139 46 0.33 78 12700 0.1889 ± 6 0.0943 ± 9 0.503 ± 16 13.11 ± 43 0.1440 ± 49 2733 ± 6 
W382-9-4 157 46 0.29 86 8620 0.1819 ± 6 0.0767 ± 8 0.500 ± 16 12.54 ± 41 0.1308 ± 45 2670 ± 5 
W382-15-1 291 136 0.47 165 7720 0.1831 ± 7 0.1307 ± 7 0.501 ± 10 12.66 ± 26 0.1355 ± 30 2681 ± 6 
W382-15-2 250 120 0.48 138 3720 0.1806 ± 8 0.1370 ± 8 0.483 ± 10 12.02 ± 25 0.1288 ± 30 2659 ± 7 
W382-15-3 191 85 0.45 111 4120 0.1832 ± 10 0.1292 ± 10 0.509 ± 10 12.85 ± 27 0.1377 ± 36 2682 ± 9 
W382-16-1 465 285 0.61 268 17100 0.1817 ± 5 0.1674 ± 7 0.496 ± 10 12.43 ± 25 0.1337 ± 27 2668 ± 4 
W382-16-2 417 257 0.62 246 10400 0.1827 ± 6 0.1716 ± 8 0.505 ± 10 12.73 ± 25 0.1384 ± 29 2678 ± 5 
W382-16-3 480 185 0.38 263 29400 0.1820 ± 5 0.1033 ± 6 0.496 ± 10 12.44 ± 25 0.1315 ± 28 2671 ± 5 
W382-22-1 125 82 0.66 75 4100 0.1830 ± 2 0.1942 ± 15 0.502 ± 10 12.66 ± 28 0.1425 ± 36 2681 ± 11 
W382-22-2 124 94 0.75 82 2770 0.1811 ± 1 0.2132 ± 16 0.544 ± 11 13.59 ± 30 0.1457 ± 37 2663 ± 12 
W382-23-1 122 53 0.43 67 3780 0.1863 ± 1 0.1300 ± 13 0.484 ± 10 12.42 ± 28 0.1348 ± 43 2710 ± 13 
W382-25-1 232 103 0.44 134 6280 0.1826 ± 8 0.1270 ± 8 0.509 ± 10 12.81 ± 26 0.1400 ± 33 2676 ± 7 
W382-25-2 98 35 0.36 55 2430 0.1812 ± 2 0.1125 ± 13 0.499 ± 10 12.46 ± 29 0.1364 ± 51 2664 ± 14 
W382-28-1 192 104 0.54 113 4460 0.1818 ± 9 0.1586 ± 10 0.508 ± 10 12.73 ± 26 0.1414 ± 33 2670 ± 8 
W382-28-2 489 148 0.3 282 8580 0.1819 ± 5 0.0870 ± 5 0.526 ± 10 13.21 ± 26 0.1440 ± 32 2670 ± 5 
W382-28-3 170 79 0.46 103 2340 0.1813 ± 1 0.1418 ± 10 0.525 ± 10 13.13 ± 28 0.1445 ± 38 2665 ± 9 
W382-8-2 328 197 0.60 187 14500 0.1821 ± 4 0.1644 ± 6 0.490 ± 16 12.31 ± 40 0.1342 ± 43 2672 ± 3 
W382-12-1 548 284 0.52 307 90900 0.1227 ± 3 0.1441 ± 4 0.490 ± 16 12.35 ± 39 0.1318 ± 42 2682 ± 2 
W382-13-2 108 61 0.56 64 7190 0.1846 ± 9 0.1520 ± 15 0.510 ± 16 12.99 ± 43 0.1375 ± 47 2695 ± 8 
W382-20-3 674 212 0.32 395 9970 0.1816 ± 5 0.0859 ± 8 0.534 ± 10 13.38 ± 26 0.1456 ± 32 2668 ± 5 
W382-20-1 205 86 0.42 120 2460 0.1795 ± 9 0.1125 ± 23 0.514 ± 10 12.73 ± 27 0.1371 ± 43 2648 ± 11 
W382-4-1 433 246 0.57 241 60400 0.1832 ± 3 0.1549 ± 4 0.484 ± 16 12.22 ± 39 0.1318 ± 42 2682 ± 2 
W382-4-2 1082 285 0.26 533 22800 0.1820 ± 2 0.0745 ± 2 0.455 ± 15 11.41 ± 37 0.1285 ± 41 2671 ± 2 
W382-10-2 1546 911 0.59 904 150000 0.1813 ± 2 0.1600 ± 3 0.506 ± 16 12.65 ± 41 0.1374 ± 44 2665 ± 2 
W382-17-1 528 203 0.38 299 9240 0.1804 ± 5 0.1072 ± 6 0.510 ± 10 12.67 ± 25 0.1372 ± 30 2657 ± 5 
W382-17-2 371 161 0.43 211 12300 0.1810 ± 6 0.1218 ± 7 0.506 ± 10 12.63 ± 25 0.1389 ± 30 2662 ± 5 
W382-18-1 309 176 0.57 187 6990 0.1826 ± 7 0.1579 ± 9 0.524 ± 10 13.19 ± 27 0.1407 ± 31 2677 ± 7 
W382-18-2 277 153 0.55 162 4860 0.1812 ± 8 0.1572 ± 9 0.506 ± 10 12.64 ± 26 0.1374 ± 32 2664 ± 7 
W382-19-1 205 131 0.64 126 6290 0.1788 ± 10 0.1824 ± 12 0.522 ± 10 12.87 ± 27 0.1448 ± 34 2642 ± 9 
W382-19-2 267 189 0.71 164 4380 0.1810 ± 8 0.1973 ± 11 0.516 ± 10 12.86 ± 27 0.1382 ± 31 2662 ± 8 
W382-14-1 1515 327 0.22 879 58800 0.1810 ± 2 0.0564 ± 2 0.525 ± 17 13.12 ± 42 0.1374 ± 44 2662 ± 2 
zoned rims and clear grains 
W382-2-1 1068 354 0.33 546 30900 0.1792 ± 3 0.0870 ± 3 0.469 ± 150 11.59 ± 37 0.1231 ± 40 2645 ± 2 
W382-11-1 1025 1006 0.98 616 22800 0.1779 ± 2 0.2676 ± 5 0.482 ± 154 11.81 ± 38 0.1313 ± 42 2633 ± 2 
W382-11-2 1013 226 0.22 524 156500 0.1786 ± 2 0.0609 ± 2 0.485 ± 155 11.94 ± 38 0.1321 ± 43 2640 ± 2 
W382-13-1 1852 130 0.07 938 85600 0.1792 ± 2 0.0191 ± 1 0.491 ± 157 12.14 ± 39 0.1337 ± 44 2645 ± 2 
W382-14-2 294 186 0.63 170 75200 0.1788 ± 4 0.1725 ± 7 0.495 ± 159 12.21 ± 40 0.1351 ± 44 2641 ± 4 
W382-14-3 650 309 0.48 375 29200 0.1779 ± 3 0.1317 ± 5 0.511 ± 164 12.52 ± 40 0.1415 ± 46 2633 ± 3 
W382-14-4 851 323 0.38 466 46000 0.1787 ± 3 0.1050 ± 3 0.496 ± 159 12.21 ± 39 0.1369 ± 44 2641 ± 2 
W382-21-1 410 294 0.72 267 5650 0.1790 ± 7 0.2033 ± 10 0.544 ± 106 13.44 ± 27 0.1497 ± 32 2644 ± 7 
W382-21-2 608 194 0.32 351 6020 0.1779 ± 6 0.0920 ± 5 0.526 ± 102 12.9 ± 26 0.1424 ± 32 2633 ± 5 
W382-24-1 1145 185 0.16 604 39900 0.1786 ± 3 0.0435 ± 2 0.502 ± 96 12.36 ± 24 0.1326 ± 27 2640 ± 3 
W382-24-2 688 569 0.83 420 8980 0.1789 ± 4 0.2361 ± 7 0.500 ± 10 12.32 ± 24 0.1406 ± 28 2642 ± 4 
W382-26-1 1391 434 0.31 672 19180 0.1676 ± 3 0.0863 ± 3 0.447 ± 8 10.33 ± 20 0.1212 ± 24 2534 ± 3 
W382-26-2 530 228 0.43 297 24600 0.1772 ± 4 0.1182 ± 6 0.502 ± 10 12.27 ± 24 0.1361 ± 28 2627 ± 4 
W382-6-1 208 160 0.77 119 22700 0.1786 ± 4 0.2131 ± 8 0.476 ± 15 11.72 ± 38 0.1323 ± 43 2640 ± 4 
W382-7-1 800 354 0.44 430 47600 0.1774 ± 2 0.1203 ± 3 0.502 ± 10 12.27 ± 24 0.1361 ± 28 2627 ± 4 
W382-7-2 1028 518 0.50 585 6670 0.1781 ± 4 0.1367 ± 7 0.499 ± 10 12.26 ± 24 0.1353 ± 27 2635 ± 4 
W382-7-4 813 362 0.44 473 15900 0.1781 ± 4 0.1208 ± 6 0.490 ± 10 12.03 ± 24 0.1327 ± 27 2635 ± 4 
W382-7-3 848 369 0.44 446 9580 0.1781 ± 4 0.1168 ± 6 0.497 ± 10 12.21 ± 23 0.1335 ± 27 2636 ± 4 
W382-8-1 472 211 0.45 253 5650 0.1788 ± 3 0.1267 ± 5 0.474 ± 15 11.67 ± 38 0.1338 ± 43 2641 ± 3 
metamict 
W382-10-1 3300 749 0.23 1469 2070 0.1429 ± 2 0.1618 ± 4 0.385 ± 123 7.91 ± 25 0.2741 ± 88 2337 ± 2 
W382-12-2 1030 310 0.30 530 111000 0.1741 ± 2 0.0826 ± 3 0.476 ± 152 11.42 ± 37 0.1305 ± 42 2597 ± 2 
W427 porphyritic granite 
cores 
W427-1-1 213 61 0.29 97 9350 0.1830 ± 8 0.0723 ± 13 0.565 ± 23 14.24 ± 58 0.1429 ± 64 2680 ± 7 
W427-1-3 287 98 0.34 105 15500 0.1805 ± 8 0.0916 ± 12 0.448 ± 18 11.15 ± 46 0.1207 ± 52 2657 ± 7 
W427-1-5 362 175 0.48 153 3160 0.1838 ± 7 0.1318 ± 13 0.497 ± 20 12.60 ± 51 0.1356 ± 56 2688 ± 6 
W427-3-1 216 281 1.30 102 1880 0.1818 ± 14 0.3711 ± 34 0.467 ± 19 11.70 ± 49 0.1329 ± 55 2669 ± 13 
W427-3-2 335 691 2.06 208 2370 0.1847 ± 9 0.5340 ± 26 0.555 ± 22 14.14 ± 58 0.1438 ± 59 2696 ± 8 
W327-3-3 86 40 0.47 60 19200 0.1845 ± 12 0.1287 ± 22 0.487 ± 20 12.39 ± 51 0.1345 ± 59 2694 ± 11 
W327-3-4 220 153 0.70 141 11100 0.1765 ± 6 0.1940 ± 12 0.432 ± 17 10.52 ± 43 0.1201 ± 49 2621 ± 6 
W327-3-5 112 102 0.91 82 10400 0.1824 ± 11 0.2518 ± 23 0.470 ± 19 11.82 ± 49 0.1298 ± 54 2675 ± 10 
W427-6-1 480 188 0.39 410 10200 0.1840 ± 4 0.1142 ± 7 0.607 ± 24 15.39 ± 62 0.1768 ± 72 2689 ± 4 
W427-9-1 120 93 0.78 91 1540 0.1876 ± 22 0.2361 ± 48 0.480 ± 19 12.42 ± 54 0.1459 ± 67 2722 ± 20 
W427-9-2 289 207 0.72 186 1200 0.1829 ± 14 0.1449 ± 30 0.430 ± 17 10.85 ± 45 0.0871 ± 40 2679 ± 13 
W427-10-1 80 44 0.55 87 912 0.1845 ± 20 0.1561 ± 43 0.708 ± 29 18.01 ± 78 0.2023 ± 100 2694 ± 18 
W427-14-1 6044 727 0.12 4500 26200 0.1812 ± 1 0.0387 ± 1 0.708 ± 11 17.69 ± 28 0.2281 ± 37 2663 ± 1 
W427-19-2 283 300 1.06 184 2900 0.1809 ± 6 0.2892 ± 13 0.505 ± 8 12.59 ± 21 0.1379 ± 24 2661 ± 5 
W427-20-1 117 54 0.47 70 2800 0.1858 ± 11 0.1260 ± 21 0.520 ± 9 13.32 ± 24 0.1407 ± 34 2705 ± 10 
W427-1-9 169 60 0.35 98 10700 0.1847 ± 7 0.0978 ± 11 0.523 ± 9 13.32 ± 23 0.1451 ± 30 2695 ± 6 
W427-1-10 166 68 0.41 95 7120 0.1865 ± 7 0.1169 ± 12 0.504 ± 8 12.97 ± 22 0.1428 ± 29 2712 ± 6 
zoned inner rims 
W427-1-2 4191 634 0.15 1742 11600 0.1746 ± 2 0.0368 ± 2 0.536 ± 21 12.90 ± 52 0.1304 ± 53 2602 ± 2 
W427-2-1 5291 933 0.18 1988 89600 0.1785 ± 1 0.0397 ± 1 0.484 ± 19 11.91 ± 48 0.1088 ± 44 2639 ± 1 
W427-2-2 6952 1325 0.19 2828 7990 0.1754 ± 1 0.0384 ± 2 0.522 ± 21 12.63 ± 51 0.1052 ± 42 2610 ± 1 
W427-4-1 5298 521 0.10 3404 198000 0.1733 ± 1 0.0276 ± 1 0.496 ± 20 11.86 ± 48 0.1394 ± 56 2589 ± 1 
W427-4-2 2470 1280 0.52 1378 1440 0.1712 ± 3 0.0788 ± 6 0.399 ± 16 9.42 ± 38 0.0606 ± 25 2570 ± 3 
W427-5-1 1501 359 0.24 956 39100 0.1732 ± 2 0.0726 ± 3 0.474 ± 19 11.31 ± 45 0.1438 ± 58 2589 ± 2 
W427-6-2 2784 314 0.11 2163 18100 0.1787 ± 2 0.0245 ± 2 0.597 ± 24 14.71 ± 59 0.1298 ± 53 2641 ± 2 
W427-7-1 1559 717 0.46 1293 5040 0.1754 ± 3 0.0805 ± 5 0.606 ± 24 14.65 ± 59 0.1062 ± 43 2609 ± 3 
W427-8-1 1340 320 0.24 987 24000 0.1749 ± 3 0.0709 ± 4 0.548 ± 22 13.21 ± 53 0.1624 ± 66 2606 ± 3 
W427-11-1 3882 606 0.16 2870 68800 0.1767 ± 1 0.0423 ± 1 0.562 ± 22 13.70 ± 55 0.1524 ± 61 2622 ± 1 
W427-12-1 1689 389 0.23 995 4220 0.1748 ± 3 0.0579 ± 5 0.438 ± 18 10.54 ± 42 0.1100 ± 45 2604 ± 3 
W427-13-1 3025 486 0.16 1546 27000 0.1746 ± 2 0.0424 ± 2 0.389 ± 16 9.36 ± 38 0.1026 ± 41 2602 ± 2 
W427-15-1 1998 543 0.27 1135 25600 0.1768 ± 2 0.0739 ± 2 0.527 ± 8 12.84 ± 21 0.1433 ± 24 2623 ± 2 
W427-16-1 2720 674 0.25 1615 75100 0.1763 ± 2 0.0676 ± 2 0.555 ± 9 13.48 ± 22 0.1514 ± 25 2618 ± 1 
W427-17-1 2737 628 0.23 1448 18000 0.1714 ± 1 0.0715 ± 2 0.493 ± 8 11.66 ± 19 0.1537 ± 25 2572 ± 1 
W427-18-1 1011 645 0.64 596 5800 0.1756 ± 3 0.1506 ± 5 0.512 ± 8 12.40 ± 20 0.1209 ± 20 2612 ± 3 
W427-18-2 1242 367 0.30 577 2990 0.1737 ± 3 0.0257 ± 5 0.442 ± 7 10.58 ± 17 0.0385 ± 10 2594 ± 3 
W427-19-1 2462 1043 0.42 922 772 0.1647 ± 4 0.0199 ± 8 0.342 ± 5 7.76 ± 13 0.0160 ± 7 2504 ± 4 
W427-21-1 3165 1330 0.42 1813 1220 0.1748 ± 2 0.0672 ± 5 0.513 ± 8 12.36 ± 20 0.0821 ± 14 2604 ± 2 
W427-1-7 2767 461 0.17 1610 14800 0.1765 ± 2 0.0342 ± 2 0.557 ± 9 13.55 ± 22 0.1144 ± 20 2620 ± 2 
W427-1-8 2022 366 0.18 1130 67000 0.1763 ± 2 0.0483 ± 2 0.530 ± 9 12.88 ± 21 0.1414 ± 24 2618 ± 2 
weakly zoned outer rims 
W427-1-4 2686 99 0.04 1025 103000 0.1768 ± 2 0.0093 ± 1 0.505 ± 20 12.31 ± 49 0.1269 ± 53 2623 ± 2 
W427-1-6 3116 81 0.03 1171 104000 0.1757 ± 2 0.0069 ± 1 0.498 ± 20 12.07 ± 48 0.1323 ± 56 2613 ± 2 
W427-5-2 1170 29 0.02 849 15100 0.1749 ± 3 0.0067 ± 3 0.568 ± 23 13.70 ± 55 0.1542 ± 94 2605 ± 3 
W427-17-2 2240 107 0.05 1236 71600 0.1764 ± 2 0.0134 ± 1 0.539 ± 9 13.10 ± 21 0.1514 ± 28 2619 ± 1 
W427-22-1 3625 152 0.04 2048 143000 0.1764 ± 1 0.0113 ± 1 0.553 ± 9 13.46 ± 22 0.1491 ± 26 2620 ± 1 
W427-22-2 1765 138 0.08 898 4680 0.1762 ± 2 0.0083 ± 3 0.493 ± 8 11.99 ± 19 0.0527 ± 23 2618 ± 2 
W427-1-11 2142 70 0.03 1111 43200 0.1767 ± 2 0.0084 ± 1 0.508 ± 8 12.38 ± 20 0.1308 ± 29 2622 ± 2 
W390 aplite dyke 
cores 
W390-6-4 234 80 0.34 126 4960 0.1806 ± 5 0.0927 ± 8 0.485 ± 11 12.07 ± 29 0.1309 ± 33 2659 ± 5 
W390-6-1 297 96 0.32 158 2660 0.1809 ± 6 0.0917 ± 11 0.476 ± 11 11.87 ± 28 0.1343 ± 35 2661 ± 5 
W390-6-1a 443 82 0.18 244 23400 0.1826 ± 4 0.0493 ± 5 0.518 ± 11 13.04 ± 28 0.1388 ± 33 2677 ± 3 
W390-11-2 864 237 0.27 372 10200 0.1810 ± 5 0.0750 ± 7 0.396 ± 9 9.89 ± 23 0.1083 ± 27 2662 ± 4 
W390-1-1 624 120 0.19 332 25900 0.1814 ± 3 0.0545 ± 4 0.500 ± 11 12.50 ± 27 0.1412 ± 32 2666 ± 3 
W390-1-2 987 252 0.26 544 27800 0.1813 ± 3 0.0695 ± 3 0.511 ± 11 12.78 ± 27 0.1392 ± 30 2665 ± 2 
W390-1-3 897 169 0.19 494 17700 0.1813 ± 3 0.0513 ± 4 0.519 ± 12 12.96 ± 30 0.1414 ± 34 2665 ± 3 
W390-2-2 951 43 0.04 489 17800 0.1815 ± 3 0.0111 ± 3 0.499 ± 11 12.50 ± 27 0.1226 ± 41 2667 ± 2 
old cores 
W390-6-2 464 168 0.36 274 23600 0.1944 ± 4 0.0991 ± 5 0.529 ± 11 14.19 ± 30 0.1447 ± 32 2780 ± 3 
W390-6-3 442 174 0.39 256 9920 0.1950 ± 4 0.1067 ± 5 0.515 ± 12 13.84 ± 32 0.1394 ± 33 2785 ± 3 
W390-12-1 642 366 0.57 407 1910 0.1953 ± 4 0.1586 ± 8 0.530 ± 12 14.27 ± 33 0.1474 ± 35 2787 ± 4 
W390-12-2 184 57 0.31 112 4780 0.1956 ± 7 0.0832 ± 12 0.548 ± 13 14.76 ± 35 0.1464 ± 41 2789 ± 6 
W390-9-2 483 261 0.54 337 7060 0.1960 ± 5 0.1504 ± 8 0.599 ± 14 16.19 ± 38 0.1668 ± 40 2794 ± 4 
W390-3-3 382 443 1.16 270 9930 0.1981 ± 5 0.3098 ± 11 0.541 ± 11 14.79 ± 32 0.1447 ± 31 2810 ± 4 
W390-9-1 233 219 0.94 174 737 0.1987 ± 11 0.2630 ± 25 0.557 ± 13 15.27 ± 38 0.1565 ± 40 2816 ± 9 
W390-3-1 175 163 0.93 106 2980 0.2001 ± 8 0.2340 ± 17 0.485 ± 10 13.37 ± 30 0.1218 ± 28 2827 ± 7 
W390-3-2 283 207 0.73 184 20300 0.1997 ± 5 0.1997 ± 9 0.538 ± 11 14.82 ± 32 0.1467 ± 32 2824 ± 4 
zoned inner rims 
W390-5-1 2606 701 0.27 1498 37900 0.1791 ± 1 0.0740 ± 2 0.533 ± 11 13.15 ± 28 0.1465 ± 31 2645 ± 1 
W390-5-2 1708 461 0.27 930 78600 0.1789 ± 2 0.0723 ± 2 0.506 ± 11 12.48 ± 26 0.1356 ± 29 2643 ± 2 
W390-4-1 530 103 0.19 280 72400 0.1791 ± 3 0.0539 ± 3 0.498 ± 11 12.29 ± 26 0.1383 ± 31 2644 ± 3 
W390-5-4 1182 203 0.17 663 52400 0.1794 ± 2 0.0467 ± 2 0.532 ± 11 13.15 ± 28 0.1446 ± 31 2647 ± 2 
W390-2-1 849 73 0.09 436 27300 0.1801 ± 3 0.0230 ± 3 0.496 ± 10 12.31 ± 26 0.1319 ± 33 2653 ± 3 
W390-4-2 1288 431 0.33 747 42900 0.1802 ± 2 0.0904 ± 3 0.530 ± 11 13.16 ± 28 0.1431 ± 31 2655 ± 2 
W390-10-2 612 335 0.55 343 3960 0.1805 ± 4 0.1310 ± 8 0.490 ± 11 12.19 ± 29 0.1170 ± 28 2657 ± 4 
W390-10-3 488 210 0.43 290 19700 0.1796 ± 4 0.1191 ± 6 0.530 ± 12 13.13 ± 31 0.1471 ± 35 2649 ± 4 
clear grains and outer rims 
W390-10-1 448 196 0.44 261 1330 0.1764 ± 7 0.1194 ± 14 0.502 ± 12 12.22 ± 29 0.1369 ± 36 2619 ± 7 
W390-11-1 658 91 0.14 328 6590 0.1745 ± 5 0.0333 ± 7 0.476 ± 11 11.45 ± 27 0.1149 ± 36 2601 ± 5 
W390-7-2 293 50 0.17 155 5040 0.1766 ± 6 0.0457 ± 9 0.498 ± 12 12.12 ± 29 0.1339 ± 41 2622 ± 5 
W390-7-3 243 47 0.19 132 4200 0.1771 ± 7 0.0532 ± 12 0.506 ± 12 12.35 ± 30 0.1394 ± 46 2626 ± 7 
W390-7-4 176 28 0.16 87 2540 0.1779 ± 7 0.0387 ± 12 0.465 ± 11 11.41 ± 27 0.1131 ± 46 2633 ± 7 
W390-14-1 788 263 0.33 446 27500 0.1778 ± 3 0.0909 ± 4 0.517 ± 12 12.67 ± 30 0.1410 ± 33 2633 ± 3 
W390-14-2 717 256 0.36 410 10800 0.1774 ± 3 0.0986 ± 5 0.518 ± 12 12.68 ± 30 0.1430 ± 34 2629 ± 3 
W390-9-3 514 129 0.25 320 11100 0.1780 ± 4 0.0696 ± 6 0.577 ± 13 14.16 ± 33 0.1596 ± 41 2634 ± 4 
W390-13-1 348 54 0.15 187 6070 0.1782 ± 5 0.0412 ± 8 0.508 ± 12 12.49 ± 30 0.1354 ± 43 2636 ± 5 
W390-13-2 271 140 0.52 103 487 0.1782 ± 17 0.0543 ± 35 0.320 ± 7 7.86 ± 20 0.0336 ± 23 2636 ± 15 
W390-7-1 261 58 0.22 136 6870 0.1784 ± 5 0.0620 ± 8 0.485 ± 11 11.93 ± 28 0.1357 ± 37 2638 ± 5 
metamict 
W390-5-3 2570 733 0.28 1364 25400 0.1755 ± 1 0.0768 ± 2 0.491 ± 10 11.89 ± 25 0.1324 ± 28 2611 ± 1 
W390-8-1 3129 956 0.30 1213 3000 0.1641 ± 2 0.0939 ± 4 0.352 ± 8 7.96 ± 18 0.1081 ± 25 2499 ± 2 
W390-8-2 8686 2677 0.31 4337 2300 0.1595 ± 1 0.0993 ± 3 0.450 ± 10 9.90 ± 23 0.1451 ± 34 2451 ± 1 
W390-8-3 2940 780 0.26 1485 3800 0.1741 ± 2 0.0837 ± 3 0.460 ± 11 11.04 ± 26 0.1453 ± 34 2597 ± 2 
W393 aplite dyke 
clear cores 
W393-12-1 83 46 0.56 49 2190 0.1796 ± 20 0.1459 ± 41 0.504 ± 9 12.49 ± 28 0.1318 ± 46 2649 ± 18 
W393-7-1 577 58 0.11 311 7180 0.1796 ± 8 0.0253 ± 12 0.516 ± 8 12.78 ± 23 0.1299 ± 67 2650 ± 8 
W393-12-2 101 63 0.63 61 2280 0.1801 ± 15 0.1675 ± 31 0.512 ± 9 12.72 ± 26 0.1368 ± 37 2654 ± 14 
W393-10-2 467 271 0.58 274 6810 0.1801 ± 6 0.1498 ± 11 0.509 ± 8 12.64 ± 22 0.1313 ± 24 2654 ± 6 
W393-11-2 779 360 0.46 461 8310 0.1812 ± 4 0.1214 ± 7 0.525 ± 8 13.11 ± 22 0.1381 ± 24 2664 ± 4 
W393-1-3 370 155 0.42 213 7230 0.1813 ± 7 0.1142 ± 11 0.512 ± 8 12.82 ± 22 0.1394 ± 28 2665 ± 6 
W393-9-1 355 138 0.39 211 4250 0.1815 ± 8 0.1002 ± 14 0.532 ± 8 13.30 ± 23 0.1369 ± 31 2666 ± 7 
W393-18-2 407 182 0.45 238 6960 0.1821 ± 7 0.1183 ± 12 0.519 ± 8 13.03 ± 22 0.1373 ± 28 2672 ± 6 
W393-8-1 1543 273 0.18 884 27600 0.1824 ± 3 0.0472 ± 3 0.541 ± 9 13.60 ± 22 0.1441 ± 26 2674 ± 3 
W393-10-1 254 133 0.52 156 8450 0.1823 ± 8 0.1402 ± 13 0.538 ± 9 13.51 ± 24 0.1434 ± 29 2674 ± 7 
W393-18-1 499 67 0.13 252 3830 0.1324 ± 8 0.0283 ± 14 0.498 ± 8 9.10 ± 17 0.1048 ± 56 2129 ± 10 
W393-5-2 673 1480 2.20 896 73 0.1632 ± 27 0.2645 ± 62 0.587 ± 10 13.22 ± 32 0.0706 ± 20 2489 ± 28 
W393-1-1 275 68 0.25 174 144 0.1710 ± 36 0.1519 ± 81 0.398 ± 7 9.33 ± 27 0.2416 ± 137 2568 ± 35 
W393-11-1 1790 1412 0.79 1082 630 0.1718 ± 7 0.2436 ± 16 0.460 ± 7 10.89 ± 18 0.1419 ± 25 2576 ± 7 
W393-14-1 411 408 0.99 268 133 0.1730 ± 33 0.1347 ± 74 0.401 ± 7 9.56 ± 26 0.0544 ± 32 2586 ± 32 
W393-17-2 166 93 0.56 100 1920 0.1786 ± 14 0.1526 ± 29 0.512 ± 9 12.62 ± 25 0.1400 ± 37 2640 ± 13 
zoned rims 
W393-2-1 3492 1307 0.37 1463 6410 0.1470 ± 2 0.1060 ± 4 0.385 ± 6 7.81 ± 13 0.1091 ± 18 2311 ± 2 
W393-2-2 5336 2117 0.40 2660 28600 0.1535 ± 15 0.1087 ± 2 0.458 ± 7 9.70 ± 16 0.1256 ± 20 2385 ± 2 
W393-3-2 2003 132 0.06 763 5320 0.1546 ± 3 0.0252 ± 5 0.371 ± 6 7.91 ± 13 0.1427 ± 37 2397 ± 4 
W393-5-1 3327 1220 0.37 1895 22300 0.1649 ± 2 0.0980 ± 3 0.523 ± 8 11.89 ± 19 0.1397 ± 23 2507 ± 2 
W393-1-2 3147 1349 0.43 1523 20000 0.1659 ± 2 0.1160 ± 3 0.438 ± 7 10.01 ± 16 0.1185 ± 19 2517 ± 2 
W393-17-1 2490 686 0.28 1130 7850 0.1666 ± 3 0.0758 ± 4 0.421 ± 8 9.68 ± 16 0.1160 ± 20 2523 ± 3 
W393-3-1 1476 463 0.31 690 5670 0.1710 ± 4 0.0976 ± 6 0.424 ± 7 10.00 ± 16 0.1320 ± 23 2568 ± 4 
W393-15-1 1251 703 0.56 846 397 0.1749 ± 9 0.0870 ± 20 0.545 ± 9 13.14 ± 23 0.0845 ± 24 2605 ± 9 
W393-19-1 815 329 0.40 469 3890 0.1776 ± 5 0.1091 ± 9 0.513 ± 8 12.56 ± 21 0.1389 ± 26 2630 ± 5 
W393-13-1 1809 656 0.36 1053 24400 0.1776 ± 3 0.0978 ± 4 0.529 ± 8 12.96 ± 21 0.1427 ± 24 2631 ± 2 
W393-20-3 2008 530 0.26 1110 35800 0.1779 ± 3 0.0709 ± 3 0.514 ± 8 12.60 ± 20 0.1382 ± 23 2633 ± 2 
W393-20-4 2287 667 0.29 1341 30100 0.1781 ± 3 0.0808 ± 4 0.540 ± 9 13.28 ± 22 0.1497 ± 26 2636 ± 3 
W393-20-1 1379 314 0.23 742 13500 0.1783 ± 3 0.0611 ± 4 0.503 ± 8 12.35 ± 20 0.1349 ± 24 2637 ± 3 
W393-12-3 1151 431 0.37 616 11600 0.1785 ± 3 0.0952 ± 5 0.486 ± 8 11.97 ± 20 0.1236 ± 21 2639 ± 3 
W393-20-2 1663 689 0.41 937 1480 0.1789 ± 5 0.0740 ± 9 0.504 ± 8 12.43 ± 21 0.0900 ± 18 2642 ± 4 
W393-19-2 1573 525 0.33 901 37500 0.1794 ± 3 0.0927 ± 4 0.523 ± 8 12.93 ± 21 0.1450 ± 24 2647 ± 3 
clear grains 
W393-4-1 961 136 0.14 517 17500 0.1751 ± 4 0.0391 ± 5 0.513 ± 8 12.39 ± 20 0.1422 ± 30 2607 ± 4 
W393-16-1 713 60 0.08 394 10500 0.1771 ± 4 0.0211 ± 5 0.534 ± 9 13.04 ± 22 0.1332 ± 41 2626 ± 4 
W393-6-1 128 49 0.38 75 1720 0.1775 ± 16 0.0970 ± 31 0.514 ± 9 12.58 ± 25 0.1312 ± 49 2630 ± 15 
*

Corrected for Broken Hill common lead.

All errors for individual analyses are given as 1r.

SHRIMP analytical procedures were similar to those described by Compston et al., (1984). Characteristics of the Curtin Consortium SHRIMP II have been reported by Kennedy & de Laeter, (1994) and also briefly by Pidgeon et al., (1996), and the Sri Lankan gem zircon CZ-3 used as our standard has been described by Pidgeon et al., (1994). The age of this zircon, determined by conventional analysis, is 564 Ma and the concentration of U is 530–560 p.p.m. Uncertainties reported in tables and figures are given at ±1σ but final ages are quoted at the 95% confidence level. Uncertainties in Th and U concentrations are of the order of 20%, based on repeat analyses of the standard. The O2− was used as a primary beam. The SHRIMP output data for each spot analysis were reduced initially using the PRAWN program developed at the Australian National University (ANU). Calculations of element concentrations and isotopic ratios were made using WALLEAD program modified by D. Nelson from the LLEAD program used at ANU. Broken Hill lead was used as the common lead correction, assuming that most of the common lead was added in the gold coat. This assumption is not correct for analyses with high common lead concentrations. However, these analyses were not included in final calculations of zircon ages. The 204Pb corrected data were used for calculations.

Combined SHRIMP ages on unzoned centres, oscillatory zoned inner rims and weakly zoned outer rims were calculated as the mean of radiogenic 207Pb/206Pb ages for individual spots if the data are concordant within the error. However, for zircon cores and outer rims which have undergone various degrees of recrystallization and resetting, it is unlikely that there is a single correct age and the reported mean age and uncertainty indicates an age range which embraces the ages of individual SHRIMP analyses. An alternative way of reporting the spread of 207Pb/206Pb ages as a median value with upper and lower quartiles does not significantly alter the spread of results indicated by the mean and 95% limits.

Internal Structures of the Zircons

Zircons from the granites have complex internal structures involving zoned and unzoned zircon. Many grains contain a distinct central core which consists, in various proportions, of finely granular structured matrix which reacts strongly with HF vapour, and irregular, rounded patches of unzoned zircon which is inert to HF. The granular etched zircon appears to be progressively replaced by unzoned, unetched zircon, beginning with the development of irregular patches and embayments of clear zircon at the margins of the etched central areas (Fig. 3a) and continuing (Fig. 3b and c) until the centres are totally replaced by clear zircon (Fig. 3d). Another explanation of the observed pattern (Fig. 3a, b and c) is that the strongly etched (more structurally damaged) parts of the zircon cores represent movement and concentration of some elements within the cores. This has been discussed in detail by Pidgeon & Nemchin (in preparation). Some zircons have unetched, apparently unzoned cores, which, when subjected to cathodoluminescence (CL), show a residual internal structure (Fig. 2). We interpret this as indicating the presence of residual zoning in crystalline cores, which are resistant to HF etching but strongly luminescent. Conversely, in some grains zoned structures are revealed by HF etching but are not recorded by CL imaging (Fig. 2), reinforcing our conclusions that these two techniques can reveal different aspects of the internal structures of zircons. In some grains unzoned zircon cores are bounded by a rounded, irregular corrosion surface (Fig. 3e and f), which is interpreted as chemical corrosion under conditions of mild zirconium undersaturation (e.g. Vavra, 1994).

An inner rim of oscillatory zoned zircon forms a mantle around zircon cores and represents a sustained period of zircon crystallization (Figs 2, 3 and 4). Growth begins with initial plating of fine zoned zircon, with both 011 and 121 pyramid faces, at the corners of rounded cores (Fig. 3c and d, and 4c). Once corners have formed, growth of oscillatory zoned zircon proceeds with the characteristic development of simple 011 faces. Inclusions are concentrated in this zoned inner rim. We interpret this rim as having formed during crystallization of the granite magma (e.g. Vavra, 1994). The pattern of oscillatory zoning in this rim shows no evidence for a hiatus during growth. Within a zircon population the inner rim can vary in width, with respect to the core, from narrow to very broad. The width of the inner rim can also vary between zircon populations. For example, in some populations the width of the inner rim is generally <20 µm (e.g granite sample W323) and could not be satisfactorily analysed using SHRIMP. In other populations, particularly those from the porphyritic granite samples, the inner rims are strongly developed.

The inner rim is surrounded by an outer rim of weakly zoned to unzoned zircon (resistant to HF vapour). The inner rim is separated from this outer rim by an irregular, serrated boundary which cuts into the zoned zircon and sometimes extends into the zircon cores (Figs 3 and 4). There are two possible interpretations for this boundary and the genesis of the outer rim:

  1. It represents a corrosion boundary and marks a profound change in conditions of crystallization involving zircon dissolution followed by later magmatic crystallization of unzoned to weakly oscillatory zoned zircon making up the outer rim. This is supported by apparent breaking of crystals associated with the boundary in Fig. 4a, which can be taken as evidence for magma movement during crystallization. In this explanation, the age of the outer rim would represent the age of late-stage zircon crystallization.

  2. It represents a recrystallization reaction front. This explanation is supported by the delicate irregular structure of the boundary and the apparent conformity between the zoning in the inner and outer rims. Careful inspection shows that the traces of oscillatory zoned inner rim continue into the outer rim as weakly zoned zircon (Fig. 4a). Patches of unzoned zircon in the inner and outer rims can also be seen to cross-cut zoned zircon and show disruption and removal of zoned zircon (Fig. 4). Different stages in the development of these unzoned areas can be seen in zircons from the one zircon population as well as from different populations. The process starts with the development of thin unzoned areas, several microns long, disrupting a few zones from outside or inside the zoned inner rim (Fig. 4b). This is followed by the development of rounded 20–30 µm unzoned areas which transgress the inner rim (Fig. 4c). Veinlets of unzoned zircon are also seen to transgress the inner rim (Fig. 4d). At a further stage the inner rim contains a network of unzoned zircon (Fig. 4e). This patchwork development of unzoned zircon resembles structures reported by Pidgeon, (1992), who interpreted these to be due to recrystallization. The zircons appear to have largely retained their euhedral to subhedral shapes developed during magmatic crystallization, confirming suggestions that recrystallization occurred after crystallization of the zircon, and that formation of the outer rim is not due to corrosion and new zircon growth during magmatic crystallization. In summary, the model advocated here explains the zircon in the outer rim as recrystallized inner rim material. Recrystallization takes place after crystallization of the zircon in the completely or almost completely crystallized granite magma at a temperature equal to or lower than the solidus temperature. Similar outer rims were reported by Black et al., (1986) for the zircons from Enderby Land in Antarctica and explained as a result of granulite facies metamorphism. However, the Darling Range granites have not experienced metamorphism, or any visible thermal overprint, since emplacement.

One objective of the SHRIMP study was to test the validity and the significance of this interpretation of the zircon structures, which contradicts present concepts of zircon stability. Present models for the interpretation of zircon ages in granites require that once zircon crystallizes from a magma it retains its primary crystallization age and can only be disturbed (to an older apparent age) by the presence of inherited zircon or (generally to a younger age) by a later isotopic disturbance related to weakening of the zircon structure through time-integrated radiation damage (e.g. Mezger & Krogstad, 1997). The high blocking temperature for the U–Pb system in crystallized zircon, estimated as >900°C (Mezger, 1990), testifies to the robustness of the U–Pb system in non-metamict zircon.

Shrimp II Results on Individual Samples

Space constraints prevent us from reporting all granite zircon results. However, this section contains a description of SHRIMP data and zircon morphology from samples representing the following major rock types: one fine-grained granite (W323), two coarse-grained granites (W330 and W332), two porphyritic granites (W382 and W427) and two aplite dykes (W390 and W393) (Table 1).

Fine-grained granite sample W323 (32°18′S, 116°06′E)

Sample W323 is from an outcrop of medium-grained, biotite granite with megacrysts of grey K-feldspar as well as elongated areas, 2–3 cm by 0.5–1 cm, enriched in biotite. Zircons have well-developed rounded cores and complex rims. Most grains have cores of clear, possibly recrystallized zircon with minor metamict areas, whereas a few zircons contain largely metamict (high HF etched) cores. Unfortunately, the inner rim of zoned zircon in most crystals is relatively thin, <30 µm, and cannot be analysed with SHRIMP. A well-developed highly serrated unconformable boundary separates the oscillatory zoned inner rim from the weakly zoned to unzoned outer rim. SHRIMP analyses on clear cores and weakly zoned outer rims are given in Table 1 and Figs 5a and 6a. On a concordia plot (Fig. 5a) most data points are nearly concordant. Cores show a spread in 207Pb/206Pb ages from 2772 to 2607 Ma, compared with outer rim ages which range from 2648 to 2584 Ma. Three analyses of zircon cores with low 207Pb/206Pb ages can be explained in terms of recent lead loss. Four analyses have high 207Pb/206Pb ages compared with the other core analyses and are interpreted as reflecting a separate population of older zircons or as representing residual memory of a much older event. These two possibilities cannot be resolved from the present results. The mean age for most of the analysed cores is 2665 ± 7 Ma. The 7 Ma error is 1.5 times higher than the error expected from uncertainties of individual analyses, suggesting that at least some analyses were made on areas with mixed ages or a disturbed U–Pb system. Nevertheless, 2665 ± 7 Ma is interpreted as the best estimate of the age of most zircon cores from sample W323.

Fig. 5.

SHRIMP concordia plots for zircons from the Darling Range Granite samples: (a) fine-grained granite W323; (b) coarse-grained granite W330; (c) coarse-grained granite W332; (d) porphyritic granite W382; (e) porphyritic granite W427; (f) aplite dyke W390; (g) aplite dyke W393.

Fig. 5.

SHRIMP concordia plots for zircons from the Darling Range Granite samples: (a) fine-grained granite W323; (b) coarse-grained granite W330; (c) coarse-grained granite W332; (d) porphyritic granite W382; (e) porphyritic granite W427; (f) aplite dyke W390; (g) aplite dyke W393.

Fig. 6.

Th (p.p.m.) vs. U (p.p.m.) plots for zircons from the Darling Range Granite samples: (a) fine-grained granite W323; (b) coarse-grained granite W332; (c) porphyritic granite W427; (d) aplite dyke W390.

Fig. 6.

Th (p.p.m.) vs. U (p.p.m.) plots for zircons from the Darling Range Granite samples: (a) fine-grained granite W323; (b) coarse-grained granite W332; (c) porphyritic granite W427; (d) aplite dyke W390.

The 207Pb/206Pb ages for individual analyses of zircon outer rims are evenly distributed within the range of 2584–2648 Ma with a mean of 2616 ± 13 Ma. The error is much higher than expected from analytical uncertainty. This difference can be explained on the basis of our interpretation of the outer rim as recrystallized inner rim. This interpretation suggests that differential resetting of the U–Pb system results in a spread of ages between the crystallization age and the age of recrystallization.

The cores and outer rims have distinctly different U–Th chemistry. U and Th concentrations in most cores vary from 200 to 700 p.p.m. and from 140 to 500 p.p.m., respectively (Table 1, Fig. 6a). Two analyses on metamict cores have very high U and Th contents. The outer rims have a similar range of Th concentrations (80–400 p.p.m.) to the clear zircon cores, but U concentrations are significantly higher, ranging from 1500 to 2500 p.p.m.

Coarse-grained granite sample W330 (31°57′S, 116°10′E)

Sample W330 is from an outcrop of coarse-grained, biotite granite. Zircons from this sample contain well-preserved central cores and inner rims. In contrast to the previous sample, the outer zircon rims are usually thinly developed along prismatic sections but are thicker near crystal terminations.

SHRIMP results on cores, and inner and outer rims are presented in Table 1 and Fig. 5b. In Fig. 5b, data points are concordant or slightly discordant and show small but consistent differences in age between the three basic zircon subdivisions. The 207Pb/206Pb ages for the most concordant analyses of cores are within the range 2694–2651 Ma (omitting one high uranium, reversely discordant point on grain 15 and three high uranium analyses on grain 5) with an average age of 2668 ± 10 Ma. After rejection of points 16–1 and 13–2, which are statistical outliers, the average age is 2662 ± 5 Ma. This error is similar to the expected error. SHRIMP spots that were located on the boundary between core and inner rim are characterized by higher U and Th concentrations and lower ages than analyses of pure zircon cores (Table 1). Analyses of the zoned inner rims have 207Pb/206Pb ages from 2643 to 2606 Ma (omitting analyses for points 2–4 and 10–2) with an average age of 2629 ± 8 Ma. This error is also significantly higher than expected from experimental error alone, suggesting the presence of an additional factor contributing to the spread of the SHRIMP ages. Three analyses of the outer rims show 207Pb/206Pb ages of 2636, 2615 and 2602 Ma. The broad ‘non-normal’ spread of ages in the inner and outer rims can be explained in terms of a continuum of 207Pb/206Pb ages rather than two specific age events. It is suspected that Pb loss from these zircon materials during recrystallization is incomplete and that it may be unrealistic to expect the SHRIMP ages to define specific events.

The concentration of U in cores varies from 500 to 2600 p.p.m., which is generally higher than in zircon cores from fine-grained granite sample W323 (Table 1). Analyses representing mixed core–rim zircon (Table 1) have U concentrations as high as 2780 p.p.m. Th concentrations of cores range from 55 to 655 p.p.m., with one analysis (15–2) giving 1884 p.p.m., which is similar to cores of zircons from the fine-grained granite sample W323. The Th/U ratios and Th and U concentrations in zoned inner rims (Table 1) are significantly higher than cores, but U and Th contents of outer rims and cores are similar.

Coarse-grained granite sample W332 (31°59′S, 116°05′E)

Sample W332 is from a medium-grained, biotite granite. Zircons have cores composed of etched granular and zoned zircon, unzoned (in HF) recrystallized zircon and mixtures of the two. Zoned inner rims are well developed in many grains but even so it was difficult to locate SHRIMP spot-sized areas on zoned zircon that did not show evidence of recrystallization. Outer rims of weakly zoned zircon occur as thin borders, or as irregularly shaped patches which strongly transgress zoned zircon (Fig. 4f). On a concordia plot (Fig. 5c) data points of unzoned cores from nine grains are concordant and show a spread in 207Pb/206Pb ages from 2649 to 2698 Ma (omitting strongly discordant points for grains 2 and 8). Two groups of ages can be distinguished within the analyses of zircon cores. The younger group, which includes analytical points 8–1, 3–1, 11–1, 12–1 and 19–1, gives the average age of 2659 ± 5 Ma, whereas the older includes the remaining five analyses and gives an average of 2680 ± 3 Ma. The errors of these two ages are in agreement with uncertainties from individual analyses. Three measurements of zoned inner rims are concordant and tightly grouped (Fig. 5c) with a 207Pb/206Pb age of 2626 ± 6 Ma. These data points overlap those of the outer rims, which have a mean 207Pb/206Pb age of 2622 ± 7 Ma. As previously described for results from sample W330, data points for the inner and outer rims of zircons from sample W332 appear to represent an age continuum rather than an uncertainty distribution around a single age. The concentrations of U and Th, and the Th/U ratios of cores and inner rims are correlated as shown in Fig. 6b. However, outer rims fall off this trend, possibly owing to a lowering of the concentration of Th.

Porphyritic granite sample W382 (31°51′S, 116°48′E)

Sample W382 is from a medium-grained, biotite granite with megacrysts of pink K-feldspar. Zircons have conchoidally fractured cores surrounded by generally thin rims of oscillatory zoned zircon. Some cores contain remnants of zoned zircon undergoing replacement by clear zircon (Fig. 3e). Other cores consist of clear zircon broken into irregular domains bordered by conchoidal fractures and curved zones of finely striated zircon. Cores are commonly surrounded by an inner rim of zoned zircon. However, some grains appear to be composed entirely of fractured zircon identical to that present as cores in other grains. Also present are a number of clear, weakly zoned zircon grains that are not obviously related to specific parts of more complex grains. Outer rims are poorly developed on zircons from this sample.

On a concordia plot (Fig. 5d) data points are concordant and grouped according to morphological subdivision. Most 207Pb/206Pb ages of cores are between 2650 and 2685 Ma (Table 1, Fig. 5d). However, some conchoidally fractured cores, with relatively discordant data points, have 207Pb/206Pb ages up to 2870 Ma. The average 207Pb/206Pb age for the cores, excluding analyses which show significant memory (5–1, 5–2, 9–3, 23–1), is 2668 ± 4 Ma. This error is similar to that expected from analytical uncertainty alone. Zoned rims and clear, transparent, weakly zoned grains show a spread of 207Pb/206Pb ages from 2625 to 2645 Ma, with the average 2638 ± 3 Ma.

The range of concentrations of U and Th, and Th/U ratios, in the cores is similar to that in zircon cores from other analysed samples (Table 1). The zoned rims have higher concentrations of both elements but a similar range of Th/U ratios compared with the cores.

Porphyritic Logue Brook granite sample W427 (32°52′S, 116°00′E)

Sample W427 is from a grey porphyritic granite with 1–2 cm megacrysts of K-feldspar. Internal structures of zircons from the two porphyritic granite samples W427 and W382 are similar except that outer rims are much better developed on zircons from sample W427. Data points for zircons from sample W427, presented on a concordia plot (Fig. 5e and Table 1), are more discordant than those from sample W382. However, cores show a similar spread of 207Pb/206Pb ages from 2657 to 2722 Ma, with a mean of 2680 ± 8 Ma. The 8 Ma error is 1.5 times higher than the error expected from the analytical uncertainty. The inner rims in this sample are strongly affected by recrystallization, and the geological significance of SHRIMP analyses of this inner rim zircon is doubtful. More concordant data from zoned rims and clear, transparent, weakly zoned rims show a spread of 207Pb/206Pb ages from 2570 to 2641 Ma with an average of 2613 ± 5 Ma, which is similar to the age determined by Compston et al., (1986). However, seven analyses of outer rims are concordant within the errors and have an average age of 2618 ± 5 Ma. An average calculation using concordant analyses gives an age of 2613 ± 8 Ma for the inner rims, which is indistinguishable within error from the outer rims. The extensive recrystallization of zircon in this sample raises the possibility that ages determined on the inner zoned rims are minimum ages for crystallization of the inner rims. Nevertheless, the distribution of Th and U in the cores and rims is similar to that in zircons from other granite samples (Fig. 6c). Cores are low in U and Th whereas inner rims have higher concentrations of these elements. Outer rims have Th concentrations similar to cores and U concentrations similar to inner rims (Fig. 6c).

Aplite dyke sample W390 (32°22′S, 116°58′E)

Sample W390 is from an aplite dyke which intrudes coarse-grained granite. Most zircons consist of clear, or sometimes metamict, cores overgrown by a zoned inner rim. Outer weakly zoned rims are rare and generally developed as patches on only one side of the grains. These grains are similar to those observed in zircons from the major granite types and are interpreted as inherited. Elongated grains, with length/breadth ratios up to ten, and relatively simple morphology, are also common. Some of these grains are metamict and apparently high in U, as revealed by HF etching. Most of the elongated grains are unzoned or weakly zoned.

SHRIMP analyses are generally concordant (Fig. 5f), except for high-U metamict grains. Two ages for cores are clearly identified. Nine data points show a distribution of 207Pb/206Pb ages from 2780 to 2827 Ma (Table 1) with an average of 2801 ± 12 Ma. Eight analyses are distributed within the range 2659–2677 Ma (Table 1) and have an average 207Pb/206Pb age of 2665 ± 4 Ma. Strongly zoned inner rims show a narrow spread of 207Pb/206Pb ages from 2643 to 2657 Ma with an average of 2648 ± 4 Ma. Outer rims and clear elongate grains are indistinguishable in age distribution and Th–U geochemistry (Fig. 6d), and were combined into one group with a spread of 207Pb/206Pb ages from 2601 to 2638 Ma with an average of 2628 ± 7 Ma.

Aplite dyke sample W393 (31°42′S, 116°35′E)

Unlike the previous aplite sample (W390), which was collected from a dyke <2 m thick, sample W393 represents a relatively large body of at least 20–30 m width where sampled in a road cutting. Zircons from this aplite contain cores similar to those described for major phases of the granite. Cores are overgrown by an oscillatory zoned rim. The outer weakly zoned rim is not developed as a continuous layer around the grains, but is represented by irregularly shaped weakly zoned areas in the oscillatory zoned rim.

SHRIMP analyses of clear cores show a distribution of 207Pb/206Pb ages from 2649 to 2674 Ma (Table 1), averaging 2663 ± 7 Ma (Fig. 5g). Nearly concordant analyses of zoned rims show a spread of 207Pb/206Pb ages from 2630 to 2647 Ma (Table 1) with an average age of 2633 ± 8 Ma (Fig. 5g). Three analyses of clear grains give ages of 2607, 2626 and 2630 Ma. Approximately half of the zoned rim analyses are strongly discordant (Table 1) and have been excluded from the calculation. U concentrations in cores are generally <700 p.p.m., whereas in zoned rims they are 1000–5000 p.p.m. (Table 1).

Discussion

Time span of events recorded in the zircons

The proportion of cores to rims

The cores present in all zircons represent either inherited restite from the granite precursor or zircon developed at an early stage in the formation of the granite magma. This is distinct from the oscillatory zoned zircon that formed around cores during magma crystallization. We have estimated the amount of core to rim in zircons from the studied granites by measuring lengths and widths of 30 zircon grains and their cores from each sample. Assuming zircon shapes are ellipsoidal and that polished grains represent half crystals, the proportion of cores to rims can be calculated as

 
Vr/Vc=(34πAB234πab2)/34πab2

where Vr and Vc are the volumes of rim and core, A and B are the length and width of a zircon crystal, and ab are the length and width of the core.

Overall the ratio of core to rim volumes in any zircon population is between 1:2 and 1:4; indicating that significant zircon existed in the granite magma before crystallization. This zircon is considered to be restite derived from the immediate granite source rocks. The presence of zircon constrains the composition and conditions of the source, which must be saturated in Zr, but is not suitable for redissolving zircon under conditions of extreme metamorphism and melting (see later discussion on constraints on the temperature of the granite magma).

Age distribution within cores

The 80 most concordant analyses of zircon cores were combined and plotted on a concordia plot (Fig. 7a) and a 207Pb/206Pb age histogram (Fig. 7b). These data show a skewed distribution (Fig. 7b). Most points are distributed between 2690 and 2650 Ma, although cores in some grains show older 207Pb/206Pb ages (Fig. 7).

Fig. 7.

SHRIMP data for zircon cores from the Darling Range granite samples: (a) concordia diagram; (b) histogram plot of 207Pb/206Pb ages.

Fig. 7.

SHRIMP data for zircon cores from the Darling Range granite samples: (a) concordia diagram; (b) histogram plot of 207Pb/206Pb ages.

The geological significance of the core ages depends on the stability of the U–Pb system in zircons that have survived conditions of magma formation and a subsequent residence period in granitic magma. This is a different question from that of the stability of zircon itself, which has been discussed in detail by Watson & Harrison, (1983). The robustness of the U–Pb systems of zircon in granite magmas has been described by Gulson & Krogh, (1973) and also in a number of SHRIMP studies. In a study of the origin of the S-type Cooma granite, in the Lachlan Fold Belt of SE Australia, Williams, (1995) found that the age distribution of detrital zircons from metasediments, proposed as a source of the granite, was exactly reproduced by xenocryst zircon cores in the granite itself. A SHRIMP study of zircon from four samples of Scottish Caledonian granites (Pidgeon & Compston, 1992) also found that cores have concordant ages and provide a robust memory of their Proterozoic source rocks. These studies suggest that zircon xenocrysts in granite magmas will retain a strong memory of their original age. Therefore, the simplest interpretation of the spread of core ages obtained for the Darling Range granite samples is that they reflect the different ages of the granite source rocks. The age population of ∼2.8 Ga obtained for zircon cores in the granite dyke sample W390 appears to be concordant, and suggests that the age of one of the source rocks is close to 2.8 Ga. Ages distributed in the interval of 2650–2690 Ma may date a second and younger source of the granites. This interpretation is in agreement with the suggestion of Compston et al., (1986) that the granite magma was formed by mixing of older crust with younger mantle-derived crust. However, the range 2650–2690 Ma can be broadly subdivided into two groups. The first has 207Pb/206Pb ages between 2650 and 2670 Ma with a maximum at 2660 Ma, whereas the second shows the range from 2670 to 2690 Ma with the maximum at about 2680 Ma. This suggests the possible existence of two younger sources for the Darling Range granite, with ages of ∼2660 and ∼2680 Ma, respectively.

An alternative explanation for the core ages is suggested by the observation that data points for zircon cores with high 207Pb/206Pb ages are distributed along a reverse discordia line (Fig. 7). This suggests that the U–Pb systems in zircon cores have not remained closed, but represent strongly isotopically disturbed zircons of an unknown but older age. The observation that different 207Pb/206Pb ages occur in the same core (see, e.g. W382 grain 9 in Fig. 8, and also W382 grain 5, W427 grains 1, 3 and 9, and W390 grain 6 in Table 1) is a strong argument for this interpretation. If the range of 207Pb/206Pb ages in zircon cores reflects different source ages, different 207Pb/206Pb ages should not be found in one zircon core because it is hard to infer that two parts of the same core represent different sources. Consequently, the occurrence of different ages within the same core in some zircon grains suggests that the distribution of the zircon core ages represents almost complete resetting of an original U–Pb system. The two interpretations of the core ages presented above propose significant differences in the ages of the sources and early formation history of the granites. Present SHRIMP precision is not sufficient to resolve the question of whether core ages can be explained as dating the granite parent rocks, or reflect different degrees of resetting of U–Pb systems from a single parent during a younger event, such as a prograde metamorphism leading to partial melting and formation of granite magma. In this case, the actual time of resetting could be close to the time of first zircon crystallization from the granite melt, which is represented by the oscillatory zoned inner rim.

Fig. 8.

Zircon grain from the porphyritic granite sample W382. Four SHRIMP analyses show a wide spread of 207Pb/206Pb ages within the same core, which supports resetting of the U–Pb system in the cores. Beam impact points appear as dark round spots.

Fig. 8.

Zircon grain from the porphyritic granite sample W382. Four SHRIMP analyses show a wide spread of 207Pb/206Pb ages within the same core, which supports resetting of the U–Pb system in the cores. Beam impact points appear as dark round spots.

The inner rims

The inner rims of oscillatory zoned zircon are interpreted as magmatic zircon formed during crystallization of the granite magma. The age of 2628 ± 7 Ma for clear elongate grains from the aplite dyke which cuts the coarse-grained granite (sample W388), is interpreted as the emplacement age of the dyke and provides a minimum age for the crystallization of the inner rims in the coarse-grained granite. As noted earlier, the 2613 ± 8 Ma age obtained for the inner rim of zircon from porphyritic granite sample W427 is suspect in that it may reflect late-stage recrystallization. Therefore, the most probable range of crystallization of the Darling Range granites is considered to be 2648–2626 Ma (age of inner rim in sample W332). The precision of the data and the possible influence of recrystallization Pb loss on some samples limits our ability to refine the age of crystallization any further, and to determine whether crystallization occurred over the entire 20 Ma interval or whether it took place over short stages within this interval. It is also impossible to determine whether there is a difference in crystallization age for different types of granitoids.

Outer rims

The average ages of outer rims of the Darling Range granite zircons are distributed within the range 2628–2616 Ma. Our interpretation from observations of the internal structures is that this zircon recrystallized from the magmatic inner rim and the younger age of this zircon reflects this process which took place late in the crystallization history of the granite. The U–Th compositions of the outer rims provide further support for this origin, as, compared with the inner oscillatory zoned rims, the outer rims generally have slightly lower U and significantly lower Th concentrations, which are similar in range to the unzoned cores. A strong relative decrease in Th was described by Pidgeon, (1992) as characteristic of changes in Th–U chemistry during zircon recrystallization. This contrasts with the expected increase in Th and U concentrations of zircon crystallizing in the late stages of a granite magma. This evidence, together with structural evidence discussed above, supports our interpretation that the outer rims formed by recrystallization resulting from a reaction that progressed inwards from the grain margins. It is suggested that this reaction was activated by the penetration of late magmatic solutions into the zircon crystals during cooling. As this occurred late in the crystallization history of the granite the susceptibility of the zircons to recrystallization and Th loss cannot be based on long-term radiation damage, but is explained by the proposal of Sommerauer, (1974) and Pidgeon, (1992) that the stability of zircon is strongly dependent on the trace element content.

Metamict high-U areas in the zircons

Areas of granular, highly HF etched zircon with concentrations of U of ≥3000 p.p.m. are found in cores and zoned inner rims. The 207Pb/206Pb ages of this zircon type are distributed between 2670 and 2400 Ma, with most data points lying along the concordia curve. Some of these areas of high-U, granular zircon have been described by Pidgeon & Nemchin (in preparation) as representing secondary movement and concentration of U and Th in zircon during progressive recrystallization.

U–Th–Pb geochemistry of zircons

Although uncertainties in the determinations of U and Th concentrations are of the order of ±20% it is still possible to identify systematic relationships in the concentrations of U and Th between the different parts of the zircons (Fig. 6). Unetched cores have the lowest concentrations of U, from 200 to 600 p.p.m., with rare cores over 1000 p.p.m., except for sample W330 where U varies from 600 to 2000 p.p.m. Th concentrations range from 35–285 p.p.m. in unzoned cores of zircons from the porphyritic granite sample W382 to ∼1500–5000 p.p.m. in the metamict cores of zircons from coarse-grained sample W332. Th/U ratios of cores vary from 0.2 to 1.5, except for one low-Th–high-U and discordant core (grain 5, W330). Zoned inner rims have 1000–4000 p.p.m. of U and 300–6000 p.p.m. of Th, with the exception of one grain from W332 which had a Th concentration <100 p.p.m. However, Th and U concentrations for zoned inner rims apparently lie on an extension of the trend for unzoned cores, and Th/U ratios in inner rims are similar to or slightly higher than in cores. Metamict cores in fine- and coarse-grained granite samples are characterized by even higher concentrations of U and Th and also lie close to the same trend. Outer rims for samples W323, W388 and W332 are definitely outside these trends and have concentrations of U close to that of zoned parts of grains, whereas concentrations of Th are similar to or even lower than in unzoned cores.

The Th/U ratios in both metamict and recrystallized cores are of the order of 0.5. A major change in chemistry is observed in the surrounding zoned inner rims, which contain higher concentrations of both elements relative to clear cores and an increase in Th/U in some samples. Further changes occur in the Th–U concentrations of outer rims, where the Th concentration dramatically decreases whereas U concentrations remain similar to those of zoned zircon.

Constraints on the temperature of the granite magma

Experiments reported by Harrison & Watson, (1983) and Watson & Harrison, (1983) show that zircon saturation is a function of both temperature and granite composition. The cation ratio M = (Na + K + 2Ca)/(Al × Si) was selected as characteristic of melt composition, and the ratio of Zr in stoichiometric zircon to that of the melt was related to absolute temperature and M as

 
lnDZrzircon/melt={3.80[0.85(M1)]}+12900/T.

It is assumed in this model that zircon saturation is not significantly dependent on pressure. Harrison & Watson, (1983) showed that where the H2O content in the melt is >2%, there is no effect on the solubility of zircon, but, where the H2O content of the melt is <1%, a significant decrease in zircon saturation occurs. Calculated temperatures for Zr concentrations determined in this study are shown in Table 2. Both the fine-grained and coarse-grained granite have a similar range of calculated temperatures averaging 778 ± 20°C and 793 ± 35°C (1 SD), respectively. The calculated temperature of the porphyritic granite (W382) has a value of 780°C, which is within the same range. These are maximum temperatures for the granite magma, as the calculations do not take into account zirconium in the zircon cores. Nevertheless, these results suggest that the temperature of the Darling Range granite melt did not exceed ∼800°C for a period of time sufficient to dissolve zircon cores, otherwise rounded cores observed in zircon grains would have been lost.

Table 2

Calculated M-values [M = (Na + K + 2Ca)/(Si × Al)] and temperatures of melt saturation in zircon for Darling Range granites

Sample: Si Al Ca Na Zr ln DZr zircon/melt M T (°C) 
Coarse-grained granite 
W317 69.9 14.84 2.05 3.69 4.05 232 7.67 1.45 816 
W331 72.6 14.13 1.41 3.29 5.01 165 8.01 1.39 790 
W332 70.3 14.74 1.96 3.47 4.08 269 7.52 1.39 834 
W328 72.3 14.12 1.66 3.44 4.43 185 7.90 1.40 799 
W330 70.7 14.84 2.13 3.70 3.89 240 7.64 1.44 820 
W330 72.8 13.76 1.55 2.94 4.50 214 7.75 1.32 818 
W386 73.8 14.01 1.22 3.40 4.79 93 8.58 1.34 745 
W387 74.0 14.06 1.57 3.61 3.89 89 8.63 1.33 742 
W388 74.1 13.71 1.23 3.39 5.05 143 8.15 1.39 777 
mean       7.98  793 
SD       0.40  33 
Fine-grained granite 
W325 69.9 14.35 2.59 3.55 4.00 145 8.14 1.58 765 
W324 72.2 14.73 1.94 4.04 3.77 157 8.06 1.43 782 
W335 72.0 14.05 2.27 2.97 4.14 237 7.65 1.41 820 
W384 74.7 13.56 1.34 3.84 3.93 102 8.49 1.36 751 
W380 73.8 14.05 1.46 3.86 3.97 116 8.36 1.36 761 
W321 73.1 14.20 1.66 3.48 4.28 145 8.14 1.37 780 
W323 72.9 13.58 1.76 3.74 4.09 121 8.32 1.48 757 
W326 74.3 13.13 1.15 3.27 4.5 157 8.06 1.34 789 
W337 72.3 14.34 1.84 3.60 3.67 165 8.01 1.35 792 
mean       8.13  778 
SD       0.23  20 
Porphyritic granite 
W382 68.5 15.67 3.38 4.31 3.23 152 8.09 1.45 778 
Sample: Si Al Ca Na Zr ln DZr zircon/melt M T (°C) 
Coarse-grained granite 
W317 69.9 14.84 2.05 3.69 4.05 232 7.67 1.45 816 
W331 72.6 14.13 1.41 3.29 5.01 165 8.01 1.39 790 
W332 70.3 14.74 1.96 3.47 4.08 269 7.52 1.39 834 
W328 72.3 14.12 1.66 3.44 4.43 185 7.90 1.40 799 
W330 70.7 14.84 2.13 3.70 3.89 240 7.64 1.44 820 
W330 72.8 13.76 1.55 2.94 4.50 214 7.75 1.32 818 
W386 73.8 14.01 1.22 3.40 4.79 93 8.58 1.34 745 
W387 74.0 14.06 1.57 3.61 3.89 89 8.63 1.33 742 
W388 74.1 13.71 1.23 3.39 5.05 143 8.15 1.39 777 
mean       7.98  793 
SD       0.40  33 
Fine-grained granite 
W325 69.9 14.35 2.59 3.55 4.00 145 8.14 1.58 765 
W324 72.2 14.73 1.94 4.04 3.77 157 8.06 1.43 782 
W335 72.0 14.05 2.27 2.97 4.14 237 7.65 1.41 820 
W384 74.7 13.56 1.34 3.84 3.93 102 8.49 1.36 751 
W380 73.8 14.05 1.46 3.86 3.97 116 8.36 1.36 761 
W321 73.1 14.20 1.66 3.48 4.28 145 8.14 1.37 780 
W323 72.9 13.58 1.76 3.74 4.09 121 8.32 1.48 757 
W326 74.3 13.13 1.15 3.27 4.5 157 8.06 1.34 789 
W337 72.3 14.34 1.84 3.60 3.67 165 8.01 1.35 792 
mean       8.13  778 
SD       0.23  20 
Porphyritic granite 
W382 68.5 15.67 3.38 4.31 3.23 152 8.09 1.45 778 

A temperature of 800°C may have been exceeded if the H2O content of the magma was significantly less than 2% (Harrison & Watson, 1983). However, this is not considered likely for the Darling Range granites, as there is no evidence that this was originally a ‘dry’ magma. The granitoids contain 3–8% biotite, and Clemens & Vielzeuf, (1987) and Clemens, (1990) showed that, depending on water content in the source rock, the volume of melt at 800°C can reach 30–40% at 5 kbar and 20–30% at 10 kbar. This agrees with numerous experimentally determined estimates of the temperatures of crustal melts (e.g. Wyllie, 1977; Clemens & Vielzeuf, 1987; Le Breton & Thompson, 1988; Rutter & Wyllie, 1988; Vielzeuf & Holloway, 1988; Thompson, 1990; Vielzeuf et al., 1990) and with our estimate of magma temperature from the Watson & Harrison, (1983) model.

Model for the evolution of the Darling Range batholith

The source of the granites

The age or ages of the source is a primary issue regarding the origin of granitoids in the batholith. Sm–NdCHUR model ages of ∼3.0 Ga on whole-rock samples of granites from the batholith, and the reason the CHUR model was selected to characterize the source of the granites, have been discussed by Fletcher et al., (1994). The ∼3.0 Ga CHUR age has been confirmed by unpublished Sm–Nd results of A. Nemchin (1996). However, we have not been able to confirm this age from our SHRIMP zircon measurements, where the oldest zircon ages on unzoned cores are near 2.8 Ga. This may indicate that the Sm–Nd model ages are not meaningful, or that the source rocks were in fact ∼3.0 Ga old, but no zircons of this age existed, or that isotopic memory of this age in zircon cores has been lost. Whereas ages as high as 2.8 Ga are recorded in some zircon cores most core ages fall in the range 2690–2650 Ma. One explanation is that these are the true ages of the granite source material, which is in accord with previous experience of the robustness of zircon core ages (e.g. Williams, 1992; Pidgeon & Compston, 1992). A second explanation is that the observed ages represent resetting of the zircon U–Pb systems from an older source, which may be as old as 3.0 Ga. Almost complete resetting of core ages has not been reported before but this would be in accord with the Sm–Nd results. Unfortunately, uncertainties in the SHRIMP analytical results are too high to permit a resolution of these alternatives.

On the basis of the partition coefficients (Mahood & Hildreth, 1983) and granite zircon cores with average concentrations of U (from 200 to 600 p.p.m.) and Th (from 30 to 300 p.p.m.), the concentrations of U and Th in melt coexisting with these zircon cores are expected to be between 0.7 and 2.1 p.p.m. for U and 0.4 and 3.8 p.p.m. for Th. These concentrations are 2–5 times lower than the observed concentrations in the granite samples (A. Nemchin, unpublished data, 1996), suggesting that cores could not have been in equilibrium with the granite melt. The low model U and Th concentrations, calculated from the content of U and Th in zircon cores and the reported partition coefficients, approximate those found in tonalitic rocks (Martin, 1994), which may be close to the composition of the granite source. The U–Th core data therefore give support to the proposition that the observed zircon core ages date the granite source rocks.

Magmatic crystallization

Magmatic crystallization of oscillatory zoned inner rims, enclosing unzoned zircon cores, occurred between 2648 and 2626 Ma. This stage of granite evolution represents a change of conditions from Zr undersaturation to oversaturation.

Oscillatory zoning commonly observed in magmatic zircons reflects inhomogeneities in trace element concentrations within the zircon and absence of equilibrium between the mineral and melt. Nevertheless, the average U and Th concentrations of inner zoned rims may still reflect the partition coefficients for these elements, allowing estimates to be made of average partition coefficients for Th and U between the zircon and granite melt. Average concentrations of U and Th in the coarse-grained granite are estimated from chemical analyses (Nemchin, unpublished data, 1996) as 8.73 p.p.m. and 30.7 p.p.m., respectively, and calculated average partition coefficients (for inner rims from zircons of samples W330 and W332) are 280 ± 140 (SD) for U and 78 ± 52 for Th. These results are comparable with partition coefficients between zircon and felsic melt reported by Mahood & Hildreth, (1983) as 383 ± 4 for U and 91.2 ± 0.6 for Th (early rhyolite), and 298 ± 4 for U and 62.4 ± 5 for Th (late rhyolite).

Late recrystallization of zircon and redistribution of U and Pb

The last stage of the zircon evolution is characterized by formation of weakly zoned to unzoned zircon outer rims. These are marked by a decrease in Th concentration but not U relative to the inner rims as discussed above. The outer rim is interpreted to have formed from partial recrystallization of existing zircon in the solid state. The common occurrence of outer rims on the granite zircons and the nature of its inner boundary suggests that the outer rim formed by a recrystallization reaction proceeding inward from the surface. This was probably facilitated by the penetration of late-stage granite fluids. This conclusion has implications for models for the evolution of the batholith and for interpretation of zircon ages. The ages of outer rims from all granite samples are younger than the emplacement of the aplite dykes (2628 ± 7 Ma) into the solid granite, indicating that recrystallization of zircon to form outer rims continued in the solidified granite.

Late recrystallization structures have been observed in zircons from all granite samples. Pidgeon, (1992) described similar recrystallization structures in zircons from a late granite in granitic gneiss and from a felsic dyke, elsewhere in the Yilgarn Craton. However, the occurrence of late-stage zircon recrystallization in granites throughout the Darling Range Batholith has genetic implications that have yet to be assessed. One explanation is that granitoids of the Darling Range Batholith were deep-seated intrusions, emplaced at temperatures not greatly different from that controlled by the geothermal gradient, and that temperatures of ∼600°C were maintained for a sufficient time interval for partial recrystallization of zoned zircon to occur on a regional scale.

Conclusions

Internal structures in zircons from the Late Archaean Darling Range Batholith record complexities not previously recognized in granite zircons and provide a unique opportunity for dating various stages in the evolution of the granite using SHRIMP. Results reveal a history of granite evolution, from magma formation to post-crystallization cooling, over a time span of ∼60 Ma.

Many zircons have unzoned centres, which in some cases represent rounded cores. Such cores have rare discordant ages up to 2860 Ma and concordant U–Pb ages of 2800 Ma (in zircon cores from a granite dyke), but most ages fall within the range 2690–2650 Ma. These ages may date the original granite source rocks or alternatively they may represent the profound resetting of U–Pb systems of zircons inherited from a single older source, during formation of the granitic magma at ∼2650 Ma.

Zircon cores are enclosed within an inner rim of oscillatory zoned zircon which is attributed to growth of zircon during cooling and crystallization of the granite magma. Ages of inner rims fall within the range 2648–2626 Ma. Inner rims are surrounded by outer rims of weakly zoned zircon, which are of variable thickness and have an irregular transgressive boundary with inner rims. Formation of outer rims is attributed to recrystallization of the outer parts of the magmatic zoned zircon by inward penetration of granite fluids during late-stage crystallization of the granite magma. Recrystallization is accompanied by loss of radiogenic Pb and Th. SHRIMP ages of 2628–2616 Ma for the outer rims demonstrate continued fluid activity and date final closure of the recrystallized zircon and consolidation of the granite magma as the batholith cools. The formation of outer rims indicates instability of the zircon structure under conditions of granite cooling. One explanation is that the granites were emplaced under deep-seated conditions at temperatures not greatly different from the geothermal gradient. The question of whether secondary structures observed in zircons from the Darling Range Batholith are unique, indicating a special cooling history for this batholith, or are relatively common in Archaean batholiths, is an important avenue for future research.

Acknowledgements

We thank Dr G. Vavra (ETH, Zurich) for cathodoluminescence imagery of a number of zircon samples. We are also grateful to Drs N. Oliver, S. Wilde, D. Nelson, F. Corfu and Yu. Amelin for discussion and comments on versions of this manuscript. The paper also benefited from constructive comments by Drs I. S. Williams, S. D. Weaver and A. Ewart. This work was supported by an Overseas Postgraduate Research Scholarship to A. Nemchin.

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