PROTEROZOIC AUSTRALIA AND PLATE TECTONICS

Intraplate settings and processes have dominated interpretations of the Proterozoic evolution of the Australian plate. These interpretations are at odds with Proterozoic interpretations in other regions of the globe. Recently, the cryptic evidence for plate tectonic processes have been recognised at the margins of many Australian cratons. Arc-related magmatism occurred in the Arunta Inlier, central Australia (c. 1.8-1.7 Ga), which is interpreted to have occupied a long-lived convergent margin. This period was a major period of episodic continental growth with the Western Australian Craton and Gawler Craton amalgamating with the North Australian Craton. Intraplate basins in the interior of the North Australian Craton formed in a back arc setting at this time. Variations in the bulk crustal extension direction in these basins are attributed to a combination of roll-back of a north-dipping slab and continental break-up along the eastern margin of the North Australian Craton (c. 1.8-1.65 Ga). Thereafter, arc-related magmatism began along the western edge of the Gawler Craton between c. 1.73-1.67 Ga and oceanic crust developed to the east of the North Australian Craton at c. 1.65 Ga. Closure of this oceanic basin is recorded in a major period of orogenesis along the eastern margin of the Proterozoic Australian plate (c. 1.6-1.5 Ga). This period of crustal shortening is preserved in the Mount Isa Inlier, Georgetown Inlier, and the Broken Hill Block. Contemporaneous arc-related magmatism is recorded in the Georgetown Inlier (c. 1.55 Ga). The evolution of the Australian plate thereafter is one dominated by extensional tectonics, basin formation, and minor plate reconfiguration in which the South Australian Craton broke away from the North Australian Craton (c. 1.45 Ga) and was re-attached in its present configuration during the Grenville orogeny (c. 1.2 Ga).