The Musgrave Province is a Mesoproterozoic crystalline basement terrain that extends across the common borders of South Australian, Western Australian and Northern Territory
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- Sedimentation, volcanism and granite intrusions — Palaeoproterozoic to Mesoproterozoic (~1680–1550 Ma Birksgate Complex, ~1340– 1270 Ma Wirku Metamorphics and ~1300 Ma Wankanki Supersuite)
- Granite (Pitjantjatjara Supersuite) intrusions, deformation and amphibolite to granulite facies metamorphism by Musgravian Orogeny — ~1220–1120 Ma
- Layered ultramafic–mafic–anorthosite intrusions (Giles Complex), Alcurra Dolerite, Angatja Granite suite and bimodal volcanics and rift sediments (Bentley Supergroup and Tjauwata Group) — ~1085 – 1040 Ma
- Regional olivine dolerite (Kullal) dyke suite — ~1000 Ma
- Regional dolerite (Amata Dolerite) dyke swarms (~825–760 Ma) equivalent to the Gairdner Dyke Swarm
- Sedimentation around proto-province margins (Centralian Superbasin) — ~850 to ~540 Ma
- Petermann Orogeny (~570–530 Ma) — crustal shortening with strain distribution varying from partitioning in thrust faults, to regional penetrative, to basement and cover coupling in thrust nappes. Final thrust exhumation of the Musgrave Province and development of internal grabens (Levenger and Moorilyanna grabens)
- Significant epidote–quartz alteration and faulting during Alice Springs Orogeny (~380 Ma)
Ni, Cu, PGE, Au, Pb, Zn, chromite, V, ilmenite, REE, U, W, Sn, opal, diamonds, rubies, chrysoprase, magnesite, S, construction material (road base), ground water.
- Magmatic nickel sulphides and PGE
- Stratiform chromite cumulates
- Stratiform titaniferous magnetite cumulates
- Stratiform vanadiferous magnetite cumulates
- Laterite nickel deposits
- VHMS in basement meta-volcanics
- SEDEX in basement meta-sediments
- Diamonds in kimberlites along major structures
The Musgrave Province covers an area of approximately 120 000 km2, straddling the border between South Australia, the Northern Territory and Western Australia. The oldest exposed rocks belong to the undifferentiated Birksgate Complex and consist of amphibolite to granulite facies, felsic and minor mafic gneisses with igneous intrusive, volcanic, volcaniclastic and, less commonly, sedimentary precursors. SHRIMP U-Pb geochronology on zircons from these rocks indicate protolith ages between c. 1680–1550 Ma. Igneous protoliths typically have calc-alkaline affinities and trace element tectonic discrimination plots as well as juvenile isotopic compositions suggest the protoliths to the Birksgate Complex formed in a volcanic arc setting.
In the western Musgrave Province, the Geological Survey of Western Australia has defined a younger supracrustal package composed mostly of paragneiss, termed the Wirku Metamorphics. These metasedimentary units are interpreted to have been deposited between c. 1340 and 1270 Ma. Near synchronously, a suite of calcic to alkali-calcic granitoids, the Wankanki Supersuite, intruded and crystallised between c. 1345 to 1293 Ma during the Mount West Orogeny. Currently there is no evidence that these units are represented/present within the eastern Musgrave Province.
The Birksgate Complex, Wirku Metamorphics and Wankanki Supersuite were subsequently deformed and metamorphosed at amphibolite to granulite facies during the province-wide c. 1220-1120 Ma Musgravian Orogeny. Large volumes of predominantly felsic magma intruded during and post the Musgravian Orogeny, and have been grouped into the Pitjantjatjara Supersuite.
The Musgravian Orogeny was quickly followed by the c. 1085–1040 Ma Giles Event, which includes the variably deformed mafic-ultramafic layered intrusions of the Giles Complex, bimodal volcanics and associated rift sediments of the Bentley Supergroup and Tjauwata Group, the Alcurra Dolerite and minor granitic intrusions and felsic dykes. The Giles Event has been interpreted to form part of the Warakurna Large Igneous Province, which affected much of central and western Australia.
Subsequent to the Giles Event were the intrusion of a number of dolerite suites including the c. 1000 Ma Kullal Dyke Suite and the c. 825–760 Ma Amata Dolerite, a correlative of the Gairdner Dolerite that intrudes the Gawler Craton in central South Australia .
The 570–530 Ma Petermann Orogeny is a major intracratonic event which resulted in the reactivation of several crustal scale east-west trending shears, faults and thrusts and the development of widespread mylonitic shear fabrics, and the final exhumation of the Musgrave Province from beneath the Centralian Superbasin. Coeval with the Petermann Orogeny was the development of the Levenger and Moorliyanna grabens, which were infilled with clastic sediments derived from the locally exposed Musgrave Province basement.
The c. 400–300 Ma Alice Springs Orogeny is a significant event which is best recorded in the Arunta Province region (Northern Territory) and is associated with the uplift of the Arunta Block from beneath the Centralian Superbasin and the deposition of early Devonian syn-orogenic sediments into the Amadeus Basin. No clear evidence for the Alice Springs Orogeny has been documented from the eastern Musgrave Province but some quartz-epidote alteration described on AGNES CREEK, EATERINGINNA and TIEYON is attributed to this event.
Following the Alice Springs Orogeny the Musgrave Province has undergone at least one phase of intensive deep weathering and erosion prior to the deposition of clastic sediments of the Mesozoic Eromanga Basin along its eastern margin. Intense chemical weathering of these sedimentary deposits as well as the basement rocks resulted in a deep weathering profile that can reach up to 90 m below the present day surface. The typically composite weathering profiles are characterised by kaolinisation and mottled or varicoloured, pallid, ferruginous or siliceous zones. Multiple phases of post-Mesozoic dominantly siliceous and ferruginous induration led to the formation of widespread silcrete and ferruginous duricrust.
The Musgrave Province is still tectonically active with a number of significant earthquakes occurring in the region in the past 30 years. In 1986 a 6.0 magnitude earthquake produced a 13km long fault scarp with a maximum throw of 0.6m along the Marryat Fault zone. More recently, the community of Ernabella (Pukatja) recorded two magnitude 5.7 earthquakes in both 2012 and 2013.
Dutch, R.A., Werner, M., Krapf, C. and Rusak, T., 2013b. Geology of the Tieyon (5464) 1:100 000 mapsheet. Department for Manufacturing, Innovation, Trade, Resources and Energy, South Australia. Report Book, 2013/00011.
Edgoose, C.J., Scrimgeour, I.R. and Close, D.F., 2004. Geology of the Musgrave Block, Northern Territory. Northern Territory Geological Survey. Report 15.
Howard, H.M., Smithies, H.R., Evins, P.M., Kirkland, C.L., Werner, M., Wingate, M.T.D. and Pirajno, F., 2011. Explanatory notes for the west Musgrave Province. Geological Survey of Western Australia, Record 2011/4: 349p.
Major, R.B. and Conor, C.H.H., 1993. The Musgrave Block. In: J.F. Drexel, W.P. Preiss and A.J. Parker (Editors), The Geology of South Australia, Vol.1. The Precambrian. Geological Survey of South Australia. Bulletin 54, pp. 156-167.
Woodhouse, A. and Gum, J., 2003. Musgrave Province - geological summary and exploration history. South Australia. Department of Primary Industries and Resources. Report Book, 2003/21.
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