Authors / CoAuthors
Champion, D.C. | Budd, A.R. | Schofield, A. | Meixner, A.J. | Lambert, I.B.
Abstract
Valuable new insights into the distribution and geological settings of U, Th and K rich (HHP) granites in Australia have come from interrogation of national datasets, supplemented by wide-ranging regional studies and inversion modelling conducted under a major Government energy security initiative. The increasing attention being paid to these granites in Australia reflects their importance in relation to geothermal energy and uranium mineralisation, which will be outlined. The oldest HHP granites in Australia are potassic, siliceous I-type late Archean (2.85 and 2.65-2.63 Ga) granites in the Pilbara and Yilgarn Cratons, Western Australia. These were produced by melting of Archean TTG-rich crust. The HHP granites were produced on a massive craton-wide scale in a geodynamic environment that is poorly understood, although high geothermal gradients appear necessary. This magmatism effectively redistributed U and Th into the middle and upper crust and stabilized the Pilbara and Yilgarn Cratons. The Proterozoic in Australia, particularly in the age range 1.8-1.5 Ga, is typified by granites with high K and, locally, very high U and Th abundances. In general, these HHP granites were also emplaced late in the evolution of the Proterozoic crust and are considered to be the result of crustal reworking, under high geothermal gradients. It is probable that there was associated crustal thinning, and mantle contributions of heat and some material. I- and S-type HHP granites also occur within the Australian Paleozoic. Their chemical compositions, including the elevated U and Th contents in the majority of these rocks, reflect extensive and efficient fractional crystallisation processes in magmas derived predominantly by crustal melting. Geodynamic environments are considered to range from late syn-tectonic, to post-collisional and back-arc extension.
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nonGeographicDataset
eCat Id
68576
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
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2601
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Keywords
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- External Publication
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- geothermal
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- geodynamics
- ( Theme )
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- geology
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2008-01-01T00:00:00
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geoscientificInformation
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