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| | | | Geological Survey of Western Australia |
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| | | | HM Howard, RH Smithies, R Quentin de Gromard, and CL Kirkland | | | | | Event type | tectonic: orogeny | Parent event | _Top of Event list | Child events | | Tectonic units affected | | Tectonic setting | orogen: intracratonic orogen | Metamorphic facies | | Metamorphic/tectonic features | –– |
| | | Summary | The Musgrave Orogeny is the oldest orogenic event to have affected the whole of the Musgrave Province in western Australia, South Australia and the Northern Territory. It produced the widespread granitic rocks of the Pitjantjatjara Supersuite that form the dominant component of the province. The Musgrave Orogeny was also responsible for ultra-high temperature (UHT) metamorphism that affected the basement rocks, such as the Wirku Metamorphics and Wankani Supersuite. Geochronological studies show that the combined magmatic and metamorphic events related to the Musgrave Orogeny occurred between c. 1219 and 1124 Ma. | | | Distribution | The Musgrave Orogeny is the oldest orogenic event to have affected all areas of the Musgrave Province. The magmatic expression of the orogeny, the Pitjantjatjara Supersuite, is extensive in the northeastern part of the west Musgrave Province, and in the Northern Territory and South Australian parts of the Musgrave Province. Metamorphism during the Musgrave Orogeny affected older basement rocks of the Wirku Metamorphics and Wankanki Supersuite. The Musgrave Orogeny is the equivalent of Stage 2 of the Albany–Fraser Orogen and was synchronous with magmatism in the Eucla basement. | | | Description | The Musgrave Orogeny is the oldest orogenic event to have affected the whole of the Musgrave Province. Its expression is dominated by the magmatism that produced the voluminous felsic magmatic rocks of the Pitjantjatjara Supersuite (Edgoose et al., 2004). Evidence for deformation during this event is uncommon, most likely overprinted by subsequent events such as the Giles Event or Petermann Orogeny. The Pitjantjatjara Supersuite intruded throughout the province but decreases in abundance from northeast to southwest. The rocks are typically metaluminous and ferroan, ranging from alkali-calcic to calc-alkalic, with A-type granite affinities, and include charnockite and rapakivi granite. The anhydrous Ti- and P-enriched composition suggests very high-temperature magmatism requiring a significant mantle contribution for both the heat and source material. Smithies et al. (2010) suggested that a lower crustal MASH (melting, assimilation, storage, homogenization) domain, in which crustal melts and mantle-derived magma mixed into a crystal mush zone, provided the source region for the Pitjantjatjara Supersuite.
Most rocks of the Pitjantjatjara Supersuite were metamorphosed under granulite-facies conditions either during the Musgrave Orogeny itself, or during the 1085–1030 Ma Giles Event or the 630–520 Ma Petermann Orogeny. Pressure–temperature (P–T) conditions during the Musgrave Orogeny are preserved in pelitic rocks of the Wirku Metamorphics to the south (e.g. south of the Mann Fault) and outside the areas significantly affected by Petermann Orogeny metamorphism. Thermobarometric studies combined with U–Pb dating of both zircon and monazite have established that peak mineral assemblages of garnet–sillimanite–spinel–quartz equilibrated at conditions of ~1000°C and 7–8 kbar from at least 1220–1120 Ma throughout the entire 700 km strike length of the Musgrave Province (Kelsey et al., 2009; Smithies et al., 2010). Patterns of lead diffusion in dated zircon crystals also indicate that UHT metamorphic conditions occurred at the preserved level of exposure during several events throughout the Musgrave Orogeny, until at least c. 1120 Ma (Kelsey et al., 2009; Smithies et al., 2010). This c. 100 Ma history of UHT metamorphism, including more-or-less continuous high-temperature charnockitic magmatism, chronicles an extremely unusual tectonothermal regime which almost certainly involved extensive crust–mantle interaction. | | | | | | Geochronology | | | Musgrave Orogeny | Maximum age | Minimum age | Age (Ma) | 1219 | 1149 | Age | Mesoproterozoic | Mesoproterozoic | Age data type | Inferred | | References | | |
| SHRIMP U–Pb dates on zircons from over 100 samples of rocks that belong to the Pitjantjatjara Supersuite (see Smithies et al., 2010) include ages interpreted to reflect crystallization of the granite magma, as well as ages interpreted to reflect growth during metamorphism. The oldest Musgravian granitic rock identified is from the Walpa Pulka Zone (BATES) and is dated at 1219 ± 12 Ma (GSWA 174737, Bodorkos et al., 2008). The youngest rocks are a granite from the Mamutjarra Zone, dated at 1149 ± 5 Ma (GSWA 189522, Kirkland et al., 2013b) and a metanorite dyke with an age of 1149 ± 10 Ma (GSWA 194376, Kirkland et al., 2010). These dates indicate an age range for the Pitjantjatjara Supersuite of 1219–1149 Ma; however, zircon rim growth may have continued until c. 1124 Ma (GSWA 187113, Kirkland et al., 2009a).
The youngest Pitjantjatjara Supersuite granitic rock in the Walpa Pulka Zone (BATES) has been dated at 1157 ± 9 Ma (GSWA 189523, Kirkland et al., 2009c), and is an unfoliated granite dyke that cuts an early Musgrave Orogeny foliation. Most Pitjantjatjara Supersuite granitic rocks in the Mamutjarra Zone have magmatic crystallization ages between 1179 ± 10 Ma (GSWA 189452, Kirkland et al., 2013a) and 1148 ± 6 Ma (GSWA 189522, Kirkland et al., 2013b).
The northeastern part of the Tjuni Purlka Tectonic Zone contains deformed granitic plutons with early Pitjantjatjara Supersuite ages similar to those in the western part of the adjacent Walpa Pulka Zone. In the southwest, the Tjuni Purlka Tectonic Zone contains late Pitjantjatjara Supersuite granitic rocks similar to those in the adjacent part of the Mamutjarra Zone. Apart from these occurrences, Pitjantjatjara Supersuite granitic rocks in the Tjuni Purlka Tectonic Zone consist of schlieric biotite–orthopyroxene leucogranites, which provided dates ranging from 1200 ± 5 Ma (GSWA 185339, Kirkland et al., 2009b) to 1156 ± 3 Ma (GSWA 183509, Kirkland et al., 2007).
Mafic magmatism did not form a significant component of the Musgrave Orogeny, as observed at the present outcrop level. Mafic dykes of this age are extremely rare, and the granitic rocks themselves do not typically contain mafic enclaves. Nevertheless, rare leucogabbro intruded the Walpa Pulka Zone during the late Musgrave Orogeny at 1190 ± 9 Ma (GSWA 174594, Bodorkos and Wingate, 2008), and rare norite dykes cut the Mamutjarra Zone at 1149 ± 10 Ma (GSWA 194376, Kirkland et al., 2010). | | | Tectonic Setting | The time by which the amalgamation of the North, South, and West Australian Cratons was complete is debated (e.g. Li, 2000; Giles et al., 2004; Betts and Giles, 2006; Wade et al., 2006, 2008; Cawood and Korsch, 2008), although most models of Australian continental amalgamation have the major cratonic components in place by at least c. 1290 Ma (e.g. Cawood and Korsch, 2008). This means that, during the Musgrave Orogeny, a large portion (possibly as much as 60 000 km²) of central Australia overlying the point where the cratonic elements of the continent join was subjected to unusually high heat flow for up to 100 million years (Smithies et al., 2010).
Taylor et al. (2010) reviewed various models proposed to explain regional episodes of low- to medium-pressure, high-temperature metamorphism, typically with isobaric cooling paths, similar to the Musgrave Orogeny. Common to these models is a substantial amount of advective mantle heat, and significant crustal thinning and extension. Currie and Hyndmann (2006) and Kelsey (2008) suggested that one possible setting for UHT metamorphism is in the thin, weak crust of back-arc basins, and Brown (2006) noted that many Ediacaran–Cambrian aged UHT belts resemble inverted and thickened back-arc basins.
Whereas a compressional regime may have existed locally, or at some stages, during the Musgrave Orogeny (e.g. Aitken and Betts, 2008), the evidence from the west Musgrave Province is that the major northeasterly shortening (folding) pre-dates the main stage of the Musgrave Orogeny, that the onset of UHT metamorphism coincided with significant thinning of the lower crust, and that this thin crust was sustained throughout the orogeny. The Musgrave Orogeny appears more compatible with an intracratonic extensional regime (e.g. Wade et al., 2006, 2008; Smithies et al., 2010), in terms of both sustained UHT conditions and granite geochemistry. | | | | References | Aitken, ARA and Betts, PG 2008, High-resolution aeromagnetic data over central Australia assist Grenville-era (1300-1100 Ma) Rodinia reconstructions: Geophysical Research Letters, v. 35, doi:10.1029/2007GL031563. | Betts, PG and Giles, D 2006, The 1800-1100 Ma tectonic evolution of Australia: Precambrian Research, v. 144, p. 92–125. | Bodorkos, S and Wingate, MTD 2008, 174594.1: metamorphosed leucogabbro, Mirturtu Camp; Geochronology Record 716: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Bodorkos, S, Wingate, MTD and Kirkland, CL 2008, 174737.1: foliated metamonzogranite, Mount Fanny; Geochronology Record 718: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Brown, M 2006, Duality of thermal regimes is the distinctive characteristic of plate tectonics since the Neoarchean: Geology, v. 34, no. 11, p. 961–964, doi:10.1130/G22853A.1. | Cawood, PA and Korsch, RJ (eds.) 2008, Assembling Australia: Proterozoic building of a continent, Precambrian Research v. 166, 396p. | Currie, CA and Hyndman, RD 2006, The thermal structure of subduction zone back arcs: Journal of Geophysical Research, v. 111, no. B8, doi:10.1029/2005JB004024. | Edgoose, CJ, Scrimgeour, IR and Close, DF 2004, Geology of the Musgrave Block, Northern Territory: Northern Territory Geological Survey, Report 15, 46p. | 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. | Kelsey, DE 2008, On ultrahigh-temperature crustal metamorphism: Gondwana Research, v. 13, no. 1, p. 1–29, doi:10.1016/j.gr.2007.06.001. | Kelsey, DE, Hand, M, Smithies, H, Evins, P, Clark, C and Kirkland, CL 2009, High temperature, high geothermal gradient metamorphism in the Musgrave Province, central Australia; potential constraints on tectonic setting, in Geological Society of Australia Abstracts edited by Timms, NE, Foden, J, Evans, KE and Clark, C: Biennial Conference of the Specialist Group for Geochemistry, Mineralogy and Petrology, Kangaroo Island, South Australia, 8–13 November 2009. | Kirkland, CL, Wingate, MTD and Bodorkos, S 2007, 183509.1: leucogranite dyke, Mount West; Geochronology Record 724: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Bodorkos, S 2009a, 187113.1: folded pegmatite vein, Mount Aloysius; Geochronology Record 798: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Bodorkos, S and Howard, HM 2009b, 185339.1: mylonitic granite, Hazlett Rocks; Geochronology Record 768: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Evins, PM 2010, 194376.1: norite dyke, Minnie Hill; Geochronology Record 921: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Smithies, RH 2009c, 189523.1: metagranodiorite, Lightning Rock; Geochronology Record 826: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Smithies, RH 2013a, 189452.1: metagranodiorite, Lightning Rock; Geochronology Record 1132: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Smithies, RH 2013b, 189522.1: leucogranite vein, Lightning Rock; Geochronology Record 1133: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Li, ZX 2000, Palaeomagnetic evidence for unification of the North and West Australian Cratons by ca. 1.7 Ga: New results from the Kimberley Basin of northwestern Australia: Geophysical Journal International, v. 142, p. 173–180. | Smithies, RH, Howard, HM, Evins, PM, Kirkland, CL, Kelsey, DE, Hand, M, Wingate, MTD, Collins, AS, Belousova, E and Allchurch, S 2010, Geochemistry, geochronology, and petrogenesis of Mesoproterozoic felsic rocks in the west Musgrave Province, Central Australia, and implications for the Mesoproterozoic tectonic evolution of the region: Geological Survey of Western Australia, Report 106, 73p. View Reference | Taylor, J, Stevens, G, Armstrong, R and Kisters, AFM 2010, Granulite facies anatexis in the Ancient Gneiss Complex, Swaziland, at 2.73 Ga: Mid-crustal metamorphic evidence for mantle heating of the Kaapvaal craton during Ventersdorp magmatism: Precambrian Research, v. 177, no. 1–2, p. 88–102, doi:10.1016/j.precamres.2009.11.005. | Wade, BP, Barovich, KM, Hand, M, Scrimgeour, IR and Close, DF 2006, Evidence for early Mesoproterozoic arc magmatism in the Musgrave Block, central Australia: Implications for Proterozoic crustal growth and tectonic reconstructions of Australia: The Journal of Geology, v. 114, p. 43–63. | Wade, BP, Kelsey, DE, Hand, M and Barovich, KM 2008, The Musgrave Province: Stitching north, west and south Australia, in Assembling Australia: Proterozoic building of a continent edited by Cawood, PA and Korsch, RJ, Precambrian Research v. 166, p. 370–386. |
| | | | Recommended reference for this publication | Howard, HM, Smithies, RH, Quentin de Gromard, R and Kirkland, CL 2024, Musgrave Orogeny (MMO): 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 28 May 2024. | | | | | 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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