Authors / CoAuthors
Brown, D.D. | Purdy, D. | Carr, P.R. | Cross, A.J. | Kositcin, N.
Abstract
The Neoproterozoic to Palaeozoic Thomson Orogen occupies a large portion of eastern Australia but is poorly known due to extensive cover. Currently, models for the tectonic evolution of the Thomson Orogen and its relationship to surrounding elements largely focus on the exposed areas. The long and complex structural and thermal history interpreted from these outcropping rocks raises many questions as to the age and origin of rocks in the vast undercover portion of the Thomson Orogen. Glimpses of the undercover Thomson Orogen are revealed in basement intersections of petroleum drill cores throughout central and south-western Queensland. These are dominated by low grade metasedimentary rocks (dominantly turbidites) with minor volcanic rocks and granites. New in-situ zircon analysis for U-Pb (SHRIMP) and Lu-Hf (Laser ablation multi-collector ICP-MS) isotopes are presented here and provide new temporal and provenance information for the rocks occurring beneath cover. Two distinct detrital zircon signatures are identified. A 'Pre-Gondwana' signature is identified in two drill holes on the north-western margin of the Thomson Orogen, adjacent to the North Australian Craton (GSQ Machattie 1, HPP Goleburra 1). These samples both have near-unimodal zircon age peaks at ~1180 Ma. -Hf (900-1300Ma) values from HPP Goleburra 1 display a range of -Hf(t) between 0 and 9 representing a moderately juvenile source. These sediments were possibly derived from the Musgrave Province in central Australia during the Cambrian Petermann Orogeny. Comparable detrital zircon age spectra from the Amadeus and Officer Basins suggests that the Thomson Orogen was connected and formed part of the greater Centralian Superbasin during this period. The second detrital zircon signature is identified extensively throughout the Thomson Orogen in basement drill cores (GSQ Eromanga 1, AAO Beryl 1, GSQ Maneroo 1, DIO Naryilco 1, DIO Betoota 1) and the outcropping Puddler Creek Formation and Les Jumelles Beds. This signature is remarkably consistent and characterised by a dominant age peak at ~570 Ma, a lesser population between ~1300-900 Ma and maximum depositional ages of ~495 Ma. This pattern is termed the 'Pacific Gondwana' detrital zircon signature and is widely recognised in eastern and central Australia and Antarctica. -Hf(500-700) data for Thomson Orogen rocks with this signature is highly variable with -Hf(t) values between -20 and 8 suggesting input from multiple source regions. Our isotopic work suggests connectivity between the Centralian Superbasin and the Thomson Orogen during and after the ~570-530 Ma, Petermann Orogeny. Parts of the uplifted Musgrave Province remained the dominant source of sediments until at least the late Cambrian when the Pacific Gondwana signature became dominant in the Thomson Orogen and central Australian basins.
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79236
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- External PublicationAbstract
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- QLD
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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2014-01-01T00:00:00
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