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Australia and Gondwanaland |
Tectonics SRC, Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia ianf{at}lithos.curtin.edu.au
Three Precambrian basement provinces extend from the southern coast of Australia into East Antarctica when reconstructed in a Gondwana configuration. These are, from east to west, the Mawson Craton, and the Albany-Fraser and Pinjarra Orogens. The Mawson Craton preserves evidence for tectonic activity from the late Archaean until the earliest Mesoproterozoic. It is exposed in the Gawler Craton of South Australia, the Terre Adélie and King George V Land coastline of East Antarctica, and the Miller Range of the central Transantarctic Mountains. It may form a significant part of the ice-covered East Antarctic Shield, although insufficient data are available to constrain its lateral extent. The Mawson Craton underwent late Palaeoproterozoic tectonism along its eastern margin (the Kimban Orogeny) and the occurrence of c. 1700Ma eclogites in the Transantarctic Mountains implies that this was, in part, a collisional event, although elsewhere it was characterized by low P/T metamorphism. The western margin of the Mawson Craton collided with a continental fragment comprising the Nawa Domain of the Gawler Craton, the Coompana Block and the Nornalup Complex of Western Australia at c. 1560Ma during the Kararan Orogeny. The western edge of the Nornalup Complex later collided with the Biranup and Fraser Complexes and Yilgarn Craton to form the Albany-Fraser Orogen during two stages of tectonism at c. 1350–1260 and 1210–1140Ma. The Pinjarra Orogen truncates the western margin of the Yilgarn Craton and Albany-Fraser Orogen, and contains allochthonous 1100–1000Ma gneissic blocks transported along the craton margin during at least two stages of Neoproterozoic transcurrent movement. It divides East Gondwana into Australo-Antarctic and Indo-Antarctic domains, which are distinct continental fragments with different Proterozoic histories that were juxtaposed by oblique collision at 550–500Ma during the assembly of Gondwana. The path taken by the Pinjarra Orogen beneath the Antarctic ice sheet is unknown, but it is of similar width and length to the East African Orogen, and must have been a fundamental Neoproterozoic boundary of critical importance to supercontinent assembly and breakup.
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