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| | | | SP Johnson, FJ Korhonen, S Sheppard, and SA Occhipinti | | | | | Event type | tectonic: intracratonic orogeny | Parent event | | Child events | | Tectonic units affected | | Tectonic setting | orogen: intracratonic orogen | Metamorphic facies | | greenschist: muscovite | amphibolite: sillimanite - K-feldspar |
| Metamorphic/tectonic features | –– |
| | | Summary | The 1680–1620 Ma Mangaroon Orogeny encompasses complex and progressive deformation and metamorphism. In the Mangaroon Zone this has been divided into two discrete deformation and regional metamorphic ‘events’ (D1m/M1m, D2m/M2m), which are probably associated with the intrusion of voluminous granite plutons of the Durlacher Supersuite. Metamorphism in the Mangaroon Zone reached upper amphibolites-facies during D1m/M1m, and appears to have been low pressure and high temperature in nature, although granite magmatism throughout the province continued until c. 1619 Ma. Between c. 1670 and 1648 Ma over 55 000 km³ of granitic material was emplaced as the Davey Well batholith in the Mutherbukin Zone, making this one of the largest batholiths in the province. The Mangaroon Orogeny is therefore much younger than the 1820–1770 Ma Capricorn Orogeny, and represents an important episode of intracontinental reworking of the Capricorn Orogen (Sheppard et al., 2005). Although it is difficult to assign regional-scale transport directions to both the D1m and D2m events, due to a distinct lack of shear sense indicators, the low-pressure, high-temperature nature of D1m metamorphism suggest that tectonism may have been essentially extensional, or transtensional in nature.
Our understanding of the Mangaroon Orogeny in the Gascoyne Province is largely based on mapping in the Mangaroon Zone. Because of overprinting by younger orogenic events, in particular the Edmundian Orogeny and the Mutherbukin Tectonic Event, outside this zone it is difficult to be confident that any of the tectonic fabrics were formed during the Mangaroon Orogeny. Nevertheless, preliminary Ar–Ar ages of c. 1650 Ma for shear zones in the Sylvania Inlier along the northern margin of the Capricorn Orogen, and a prominent cleavage in rocks along the northern margin of the Earaheedy Basin in the southeastern part of the orogeny, indicate that the Mangaroon Orogeny is of regional significance. | | | Distribution | The structures and metamorphic assemblages related to the 1680–1620 Ma Mangaroon Orogeny are best developed in the northern Gascoyne Province, in particular in the Mangaroon Zone. The effects of this orogeny in the central part of the province (i.e. south of the Minnie Creek batholith) may have been largely obliterated by deformation and metamorphism related to the Edmundian Orogeny, although no SHRIMP U–Pb ages indicative of the Mangaroon Orogeny have been obtained. Tectonic fabrics and accompanying low-grade mineral assemblages in the Glenburgh Terrane, Errabiddy Shear Zone, and Yarlarweelor Gneiss Complex that have been attributed to the waning stages of the Capricorn Orogeny (e.g. Sheppard and Swager, 1999; Occhipinti and Sheppard, 2000; Occhipinti et al., 2001), may, at least in part, be part of the Mangaroon Orogeny. There is also evidence that deformation related to the Mangaroon Orogeny has affected other tectonic units in the Capricorn Orogen, such as the Earaheedy and Bresnahan Basins, and other units along the southern margin of the Pilbara Craton. | | | Description | The oldest fabric in the Mangaroon Zone is a regionally extensive gneissic layering or foliation (S1m) developed in metamorphic rocks of the Pooranoo Metamorphics and the Gooche Gneiss. Folds associated with D1m are difficult to identify, but local refolded folds and evidence from facings indicates the presence of F1m structures. Mineral assemblages developed during M1m are commonly well preserved in the fold hinges of macroscopic F2m folds. Pelitic gneiss and granofels contain assemblages including biotite–muscovite–quartz–plagioclase–sillimanite, quartz–biotite–cordierite–plagioclase–muscovite–(minor)sillimanite, and plagioclase–biotite–quartz–sillimanite–muscovite–cordierite. The above cordierite- and sillimanite-bearing assemblages are stable at about 600–630°C at 200 MPa or 650–700°C at 500 MPa (Spear, 1993). The appearance of sillimanite in non-migmatitic pelitic gneiss is consistent with a metamorphic grade equivalent to the amphibolite facies.
The migmatites around the Star of Mangaroon mine are associated with pelitic gneisses consisting of cordierite, biotite, quartz, microcline, sillimanite, and minor muscovite, or quartz, cordierite, biotite, microcline, sillimanite, and minor plagioclase. The major difference with non-migmatitic pelitic gneisses north of the Mangaroon Syncline is the paucity or absence of plagioclase or muscovite, and the appearance of microcline. The co-existence of sillimanite and K-feldspar is consistent with the onset of the equivalent of upper amphibolite facies conditions (Bucher and Frey, 2002).
The dominant fabric in rocks of the Pooranoo Metamorphics in the Mangaroon Zone is a pervasive, east-southeasterly striking foliation. The foliation cuts the gneissic layering (S1m) and is parallel to the axial surfaces of metre- to kilometre-scale folds. A widespread lineation defined by the crenulation of S1m by S2m plunges parallel to F2m folds. The F2m folds are upright, range from close to tight, and plunge moderately to steeply to the west-northwest or east-southeast. Metamorphism accompanying the folding (M2m) has resulted in widespread retrogression of M1m assemblages to sericite–chlorite–quartz–plagioclase–biotite schist. This assemblage, along with the absence of andalusite, chloritoid, or staurolite is consistent with greenschist facies metamorphism of a low Al bulk composition (Spear, 1993).
At the exposed southeastern end of the orogen the Earaheedy Basin is strongly folded and cut by numerous steeply north-dipping faults on its northern margin. Sinistral strike-slip and reverse faulting have been recorded, but its structural history is not well understood. However, a ⁴⁰Ar/³⁹Ar muscovite date of c. 1650 Ma has been determined for muscovite defining the main cleavage (Pirajno et al., 2009). It implies that at least some of the deformation is likely to be related to the Mangaroon Orogeny.
The Bresnahan Group along the northern margin of the Capricorn Orogen comprises siliciclastic rocks deposited unconformably on Archean and Paleoproterozoic successions along the southern margin of the Pilbara Craton. Deposition of the Bresnahan Group was controlled by a series of northeast-striking en echelon normal faults linked by sinistral transfer faults that are consistent with an overall southeast-directed extension. An ⁴⁰Ar/³⁹Ar muscovite date of c. 1650 Ma from one of these shear zones cutting the Archean Sylvania Inlier to the east (D Hollingsworth, 2006, written comm., 10 January) suggests that deposition of the Bresnahan Group is related to the Mangaroon Orogeny. Large open west-northwesterly striking folds in the Bresnahan Group, which pre-date the deposition of the Edmund Group, may be related to a later stage of the Mangaroon Orogeny. In the iron ore deposits hosted by the Hamersley Group at the northern edge of the Capricorn Orogen, monazite and xenotime which are intergrown with the hematite ore grew during multiple discrete events, including one at c. 1650 Ma (Rasmussen et al., 2007). Monazite crystals interpreted to have grown during low-grade metamorphism of sedimentary rocks in the central part of the Pilbara Craton also record ages of c. 1650 Ma (Rasmussen et al., 2006). These data suggest that fluid flow associated with the Mangaroon Orogeny may have extended over a very wide area. | | | | | | Geochronology | | | Mangaroon Orogeny | Maximum age | Minimum age | Age (Ma) | 1689 ± 6 | 1619 ± 15 | Age | Paleoproterozoic | Paleoproterozoic | Age data type | Isotopic | | References | | |
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The age of D1m/M1m in the Mangaroon Zone is tightly constrained. The oldest granitic units in the Durlacher Supersuite are schlieric monzogranites to granodiorites (P_-DU-gmbi, P_-DU-ggvs). The oldest dated sample (GSWA 208365) is a medium-grained, moderately deformed, biotite granodiorite that forms a more even-textured part of abundant, but poorly outcropping schlieric granodiorites. This sample yielded a magmatic crystallization age of 1689 ± 6 Ma (Wingate et al., 2017a). Other schlieric granitic rocks have been dated throughout the Mangaroon Zone giving ages of 1683 ± 7 Ma (GSWA 208372; Wingate et al., 2017b), 1682 ± 4 Ma (GSWA 208318; Wingate et al., 2013) and 1677 ± 5 Ma (GSWA 178027; Nelson, 2005). Abundant metasedimentary enclaves with high-grade D1m gneissic fabrics and M1m metamorphic assemblages are enclosed within the schlieric granites, suggesting that granite magmatism post-dates the peak of M1m. However, in sample GSWA 208318 (Wingate et al., 2013) the gneissic enclaves yielded zircons with an age of 1808 ± 4 Ma, indicating that they are part of the Moorarie Supersuite (P_-MO-mggn) and not the Pooranoo Metamorphics (P_-PO-md) and so the age of the gneissic fabrics is questionable. The best estimate for the timing to D1m metamorphism is provided by the age of metamorphic zircons obtained from a pelitic gneiss and granofels of the Pooranoo Metamorphics (P_-PO-mln) at 1680 ± 13 Ma (GSWA 169094, Nelson 2004). This age is also within uncertaintly of the schlieric granitic rocks that enclose and truncate S1m fabrics within the metasedimentary enclaves. These relationships suggest that the age of D1m/M1m ranges between c. 1683 and 1677 Ma.
The S2m fabric is present in some of the granitic rocks of the Durlacher Supersuite, such as the schlieric inclusion-rich granodiorite (P_-DU-ggvs) dated at 1677 ± 5 Ma. Some of the other granite units dated at c. 1675 Ma contain a magmatic foliation defined by tabular K-feldspar phenocrysts parallel to S2m. They comprise a series of sheets parallel to S2m, suggesting that they were emplaced during D2m. Geochronological data imply a very short time interval for the combined D1m-D2m event. Following D2m, deformation and metamorphism ceased in the Mangaroon Zone but magmatism continued with the emplacement of the Davey Well batholith in the Mutherbukin Zone. The oldest and youngest intrusions in the batholith have been dated at c. 1670 Ma (GSWA 195819, Wingate et al., 2013b) and c. 1648 Ma (GSWA 185945, Wingate et al., 2010), respectively, indicating batholith construction over a 20 m.y. period. The youngest magmatism associated with the Mangaroon Orogeny is recorded in the Yarlarweelor Gneiss Complex in the southern part of the province, with the emplacement of the Discretion Granite between c. 1644 and 1619 Ma (Nelson 1998, 2001).
In iron ore deposits hosted by the Hamersley Group at the northern edge of the Capricorn Orogen, monazite and xenotime that are intergrown with the hematite ore grew during multiple discrete events, including one at c. 1650 Ma (Rasmussen et al., 2007). Monazite crystals, interpreted to have grown during low-grade metamorphism of sedimentary rocks in the central part of the Pilbara Craton, also record ages of c. 1650 Ma (Rasmussen et al., 2006). Two ⁴⁰Ar/³⁹Ar muscovite dates of c. 1650 Ma in other tectonic units of the Capricorn Orogen suggest that the Mangaroon Orogeny extended over a very wide area. One date was obtained from muscovite defining the main cleavage in rocks along the northern edge of the Earaheedy Basin (Pirajno et al., 2009). The other date derives from muscovite from a sinistral transfer fault that is linked to a series of en echelon normal faults, which controlled the deposition of the Bresnahan Group (Sheppard et al., 2006).
| | | Tectonic Setting | The Mangaroon Orogeny encompassed pervasive reworking of crust in the Mangaroon Zone at 1680–1660 Ma and coeval voluminous granitic magmatism, followed by reactivation of faults and shear zones and intrusion of granite plutons over a wide area of the Gascoyne Province until c. 1620 Ma. On either side of the Mangaroon Zone, the Boora Boora Zone and the Limejuice Zone appear to have undergone a similar geological evolution, suggesting that the crust under the Mangaroon Zone is contiguous and that the zone formed roughly in its current position. The lack of any volcanic and plutonic activity immediately preceding the Mangaroon Orogeny, either within or flanking the Mangaroon Zone, also precludes that the orogeny is related to closure of an ocean. Instead, the Mangaroon Orogeny represents an episode of intracontinental reworking. Existing geochronological data suggest that D1m/M1m and D2m/M2m may have taken place over a short time, albeit followed by a prolonged period of granite intrusion. The abundance of strongly peraluminous two-mica granites in the Durlacher Supersuite, in combination with their silicic nature, suggests that they were derived largely by remelting of older crust that included a significant proportion of metasedimentary rock. This conclusion is consistent with the abundance of inherited zircon grains in the dated granites.
The absence of megascopic compressional structures during D1m may be consistent with regional metamorphism related to voluminous granite intrusion during extensional or transtensional orogenesis. In the northern half of the Mangaroon Zone pelitic rocks commonly have a hornfels texture that suggests the presence of large igneous intrusions just below the current level of exposure. Preliminary gravity modelling suggests that the small exposed gabbro intrusions are not part of much larger subsurface intrusions (GSWA, unpublished data), which suggests that the voluminous granitic rocks probably provided the heat. The Mangaroon Zone shows no substantial change in metamorphic grade along or across strike. Furthermore, there is also a change in grade across the Mangaroon Syncline, but this probably reflects differential uplift during the Neoproterozoic Edmundian Orogeny.
The Mangaroon Orogeny took place in a time frame similar to the 1710–1650 Ma Biranup Orogeny in the Albany–Fraser Orogen (Johnson 2013). This period encompassed the intrusion of voluminous granitic magmas into, and the structural reworking of the southern Yilgarn Craton margin, possibly in a back-arc setting (Kirkland et al., 2011; Spaggiari et al., 2011). This activity was also synchronous with magmatism and deformation in the southern Arunta region (Wyborn et al., 1998; Close et al., 2002; Scrimgeour et al., 2002), the Mount Isa Inlier, the McArthur Basin (Page et al., 2000) of the North Australian Craton, and the western Gawler Craton (Ferris, 2000), and Broken Hill and Olary Domains (Raetz et al., 2002) of the South Australian Craton.
The Albany–Fraser Orogen of the West Australian Craton and the Warumpi Province (southern part of the Arunta region) of the North Australian Craton (Close et al., 2002, 2003; Scrimgeour 2003) show the greatest degree of similarity to the Capricorn Orogen. Overall, they have a similar age range of tectonism, metamorphism, and igneous activity, although — not surprisingly given the distance between them — in detail there are notable differences. For example, protoliths to the Pooranoo Metamorphics are older than the sedimentary packages in the Warumpi Province — but overlap in age with those in the Barren Basin of the Albany–Fraser Orogen). Furthermore, volcanic rocks are abundant in the Warumpi Province, and the Liebig Orogeny in the Warumpi Province is characterized by high pressure (up to 900 MPa) and temperature (up to 900°C) metamorphism and is also associated with charnockites. The nature of the metamorphism during the Liebig Orogeny and the charnockitic granites contrast with the lower temperatures (<750°C) in the Mangaroon Orogeny and the peraluminous, xenocryst-rich granites of S-type or mixed S/I-type affinity in the Durlacher Supersuite.
In their plate-tectonic reconstruction of Proterozoic Australia, Myers et al. (1996) suggested that the West, North, and South Australian Cratons did not amalgamate until 1300–1000 Ma. However, recent work suggests that the three cratons were joined before c. 1500 Ma or possibly even before c. 1600 Ma (Wingate and Evans 2003; Giles et al., 2004). Giles et al. (2004) proposed a model in which north- or northeast-directed subduction and progressive accretion of material to the southern margin of the combined West and North Australian Cratons took place between c. 1800 Ma and c. 1600 Ma. The Warumpi Province in the Arunta Inlier is interpreted to have developed outboard of the craton, and to have been accreted to it during the 1640–1630 Ma Liebig Orogeny (Scrimgeour, 2003). If these interpretations of a contiguous latest Paleoproterozoic West and North Australian Craton are correct, then the Mangaroon Orogeny may be linked to tectonic events along the southern margin of the craton (Johnson 2013). | | | | References | Bucher, K and Frey, M 2002, Petrogenesis of metamorphic rocks: Springer Verlag, Berlin, 341p. | Close, D, Scrimgeour, I, Edgoose, C, Cross, A, Claoué-Long, J and Meixner, A 2002, Identification of new terrains in the southern Arunta Province, central Australia: Geological Society of Australia Abstracts, v. 67, p. 105. | Close, DF, Scrimgeour, IR, Edgoose, CJ, Claoué-Long, JC, Kinny, P and Meixner, AJ 2003, Redefining the Warumpi Province, in Annual Geoscience Exploration Seminar (AGES) 2003: Record of abstracts: Northern Territory Geological Survey; Record 2003–001. | Ferris, GM 2000, Insights into tectonic evolution of the Western Gawler Craton: MESA Journal, v. 19, p. 28–31. | Giles, D, Betts, PG and Lister, GS 2004, 1.8 - 1.5-Ga links between the North and South Australian Cratons and the Early-Middle Proterozoic configuration of Australia: Tectonophysics, v. 380, p. 27–41. | Kirkland, CL, Spaggiari, CV, Pawley, MJ, Wingate, MTD, Smithies, RH, Howard, HM, Tyler, IM, Belousova, EA and Poujol, M 2011, On the edge: U-Pb, Lu-Hf, and Sm-Nd data suggests reworking of the Yilgarn Craton margin during formation of the Albany-Fraser Orogen: Precambrian Research, v. 187, no. 3–4, p. 223–247, doi:10.1016/j.precamres.2011.03.002. | Myers, JS, Shaw, RD and Tyler, IM 1996, Tectonic evolution of Proterozoic Australia: Tectonics, v. 15, p. 1431–1446. | Nelson, DR 1998, 142855.1: porphyritic monzogranite, Anderson Well; Geochronology Record 371: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Nelson, DR 2001, 168751.1: biotite monzogranite, Round Yard Bore; Geochronology Record 219: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Nelson, DR 2004, 169094.1: quartz–plagioclase–biotite–sillimanite gneiss, Woorkadjia Pool; Geochronology Record 88: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Nelson, DR 2005, 178027.1: biotite–muscovite granodiorite, Mangaroon Homestead; Geochronology Record 536: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Occhipinti, SA and Sheppard, S 2000, Glenburgh, WA Sheet 2147: Geological Survey of Western Australia, 1:100 000 Geological Series. View Reference | Occhipinti, SA, Sheppard, S, Myers, JS, Tyler, IM and Nelson, DR 2001, Archaean and Palaeoproterozoic geology of the Narryer Terrane (Yilgarn Craton) and the southern Gascoyne Complex (Capricorn Orogen), Western Australia - a field guide: Geological Survey of Western Australia, Record 2001/8, 70p. View Reference | Page, RW, Jackson, MJ and Krassay, AA 2000, Constraining sequence stratigraphy in north Australian basins: SHRIMP U-Pb zircon geochronology between Mt Isa and McArthur River: Australian Journal of Earth Sciences, v. 47, p. 431–459. | Pirajno, F, Hocking, RM, Reddy, SM and Jones, JA 2009, A review of the geology and geodynamic evolution of the Palaeoproterozoic Earaheedy Basin, Western Australia: Earth-Science Reviews, v. 94, p. 39–77. | Raetz, M, Krabbendam, M and Donaghy, AG 2002, Compilation of U-Pb zircon data from the Willyama Supergroup, Broken Hill region, Australia: Evidence for three tectonostratigraphic successions and four magmatic events: Australian Journal of Earth Sciences, v. 49, p. 965–983. | Rasmussen, B, Fletcher, IR and Muhling, JR 2007, In situ U–Pb dating and element mapping of three generations of monazite: unravelling cryptic tectonothermal events in low-grade terranes: Geochimica et Cosmochimica Acta, v. 71, no. 3, p. 670–690. | Rasmussen, B, Fletcher, IR, Muhling, JR, Thorne, WS and Broadbent, GC 2007, Prolonged history of episodic fluid flow in giant hematite ore bodies: Evidence from in situ U-Pb geochronology of hydrothermal xenotime: Earth and Planetary Science Letters, v. 258, p. 249–259. | Scrimgeour, I, Kinny, PD, Edgoose, C and Close, D 2002, The Liebig Event -- 1640-1630 Ma deformation, magmatism and high grade metamorphism in the southern Arunta province: Geological Society of Australia Abstracts, v. 67, p. 189. | Scrimgeour, IR 2003, Developing a revised framework for the Arunta region, in Annual Geoscience Exploration Seminar (AGES) 2003: Record of abstracts: Northern Territory Geological Survey; Record 2003–001, p. 1–3. | Sheppard, S, Farrell, TR, Bodorkos, S, Hollingsworth, D, Tyler, IM and Pirajno, F 2006, Late Paleoproterozoic (1680-1620 Ma) sedimentation, magmatism, and tectonism in the Capricorn Orogen, in GSWA 2006 extended abstracts: promoting the prospectivity of Western Australia: Geological Survey of Western Australia, Record, p. 11–12. View Reference | Sheppard, S, Occhipinti, SA and Nelson, DR 2005, Intracontinental reworking in the Capricorn Orogen, Western Australia: The 1680–1620 Ma Mangaroon orogeny: Australian Journal of Earth Sciences, v. 52, p. 443–460, doi:10.1080/08120090500134589. | Sheppard, S and Swager, CP 1999, Geology of the Marquis 1:100 000 sheet: Geological Survey of Western Australia, 1:100 000 Geological Series Explanatory Notes, 21p. View Reference | Spaggiari, CV, Kirkland, CL, Pawley, MJ, Smithies, RH, Wingate, MTD, Doyle, MG, Blenkinsop, TG, Clark, C, Oorschot, CW, Fox, LJ and Savage, J 2011, The geology of the east Albany-Fraser Orogen - a field guide: Geological Survey of Western Australia, Record 2011/23, 97p. | Spear, FS 1993, Metamorphic phase equilibria and pressure-temperature-time paths: Mineralogical Society of America, Monograph, 799p. | Wingate, MTD and Evans, DAD 2003, Palaeomagnetic constraints on the Proterozoic tectonic evolution of Australia, in Proterozoic East Gondwana: Supercontinent Assembly and Breakup edited by Yoshida, M, Windley, BF and Dasgupta, S: The Geological Society of London, Special Publication 206, p. 77–91. | Wingate, MTD, Kirkland, CL and Johnson, SP 2013b, 195819.1: metamonzogranite, Bee Well Creek; Geochronology Record 1098: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Wingate, MTD, Kirkland, CL and Korhonen, FJ 2013a, 208318.1: metagranite, Brown Well; Geochronology Record 1174: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Wingate, MTD, Kirkland, CL, Sheppard, S and Johnson, SP 2010, 185945.1: pegmatite lenses in metamonzogranite, Yinnetharra Homestead; Geochronology Record 901: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Wingate, MTD, Lu, Y, Johnson, SP and Korhonen, FJ 2017, 208365.1: biotite metagranodiorite, Kimbers Well; Geochronology Record 1356: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Wyborn, LAI, Hazell, M, Page, R, Idnurm, M and Sun, S-S 1998, A newly discovered major Proterozoic granite-alteration system in the Mount Webb region, central Australia, and implications for Cu-Au mineralisation: Australian Geological Survey Organisation, Research Newsletter 28, 7p. |
| | | | Recommended reference for this publication | Johnson, SP, Korhonen, FJ, Sheppard, S and Occhipinti, SA 2022, Mangaroon Orogeny (MA): Geological Survey of Western Australia, WA Geology Online, Explanatory Notes extract, viewed 05 August 2025. <www.dmp.wa.gov.au/ens> |
| | | This page was last modified on 24 February 2022. | | | | | Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zones 49 to 52. All locations are quoted to at least the nearest 100 m. Capitalized names in text refer to standard 1:100 000 map sheets, unless otherwise indicated. WAROX is GSWA’s field observation and sample database. WAROX site IDs have the format ‘ABCXXXnnnnnnSS’, where ABC = geologist username, XXX = project or map code, nnnnnn = 6 digit site number, and SS = optional alphabetic suffix (maximum 2 characters). All isotopic dates are based on U–Pb analysis of zircon and quoted with 95% uncertainties, unless stated otherwise. U–Pb measurements of GSWA samples were conducted using a sensitive high-resolution ion microprobe (SHRIMP) in the John de Laeter Centre at Curtin University, Perth, Western Australia. Digital data related to WA Geology Online, including geochronology and digital geology, are available online at the Department’s Data and Software Centre and may be viewed in map context at GeoVIEW.WA. | | | Further details of geological publications and maps produced by the Geological Survey of Western Australia are available from: Information Centre Department of Mines, Industry Regulation and Safety 100 Plain Street EAST PERTH, WA 6004 Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444 |
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