Tectonic evolution of Proterozoic Australia

Proterozoic Australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic. This paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes. The assembly was completed between 1300 and 1100 Ma when the crustal fragments were combined as an early component of the Rodinian supercontinent. Rifting and fragmentation of Archaean continents began in the late Archaean and continued into the Proterozoic. Passive margin deposits, such as those of the Hamersley Basin, accumulated on isolated fragments of Archaean crust. These numerous fragments were subsequently assembled into three cratons by ∼ 1830 Ma. A West Australian Craton was established by collision of the Archaean Pilbara and Yilgarn cratons, which were joined along the Capricorn Orogen. Similarly, a South Australian Craton developed by amalgamation of the proto-Gawler and proto-Curnamona cratons along the Kimban Orogen. A North Australian Craton appears to have formed by accretion of numerous crustal fragments, including the Kimberley, Pine Creek, Lucas, and Altjawarra cratons, with sutures marked by the King Leopold, Halls Creek, Tennant Creek and proto-Isan orogens. The southern margin of the North Australian Craton was the site of repeated terrane accretion and orogenic activity between ∼ 1880 Ma and 1400 Ma. This included an orogenic event at ∼ 1880 – 1850 Ma; the Strangways (1780 – 1730 Ma), Argilke (1680 – 1650 Ma), and Chewings (1620 – 1580 Ma) orogenies; and the intracratonic Anmatjira uplift (1500 – 1400 Ma). Intracratonic rifting at ∼ 1750 to 1710 Ma and ∼ 1640 to 1600 Ma produced the McArthur Basin and related minor basins, parts of which were deformed by the Isan Orogeny at ∼ 1600 and ∼ 1530 Ma. Rifting along the line of the Capricorn Orogen led to deposition in the overlying intracratonic Bangemall Basin between 1630 and 1300 Ma. Along the eastern margin of the South Australian Craton, the 1670 to 1600 Ma Olarian Orogeny marks interaction with now obscured continental crust to the east. Tectonic activity between 1300 and 1100 Ma led to the assembly of Proterozoic Australia as an early component of the supercontinent of Rodinia. This first involved the amalgamation of the West Australian and North Australian cratons, followed by collision with the South Australian Craton. The Centralian Superbasin developed over the junction of the North, South, and West Australian cratons between ∼ 830 and 750 Ma. Rifting to the east formed the “Adelaide Geosyncline” at ∼ 830 Ma. This was followed by the breakup of Rodinia, with the rifting apart of Laurentia and Gondwanaland along the eastern margin of Proterozoic Australia at ∼ 750 Ma, and the subsequent formation of the Palaeo-Pacific Ocean. After the breakup of Rodinia, a series of northeast-southwest compressional events followed by periods of relaxation, reflect the assembly of a new supercontinent. Old lines of weakness were reactivated, culminating in the intracratonic King Leopold, Paterson, Petermann Ranges, and Pinjarra orogenies between 620 and 540 Ma. Subsequent reactivation continued into the Phanerozoic, with the widespread eruption of continental flood basalts and the formation of intracratonic basins (540 – 530 Ma).