Far-field continental backarc setting for the 1.80-1.67 Ga basins of northeastern Australia

Abstract

The 1.80–1.67 Ga volcano-sedimentary basins of northeastern Australia, preserved in the Mount Isa inlier, McArthur basin, and Georgetown inlier, have been a cornerstone of nonuniformitarian “intracontinental” tectonic models of the Australian Proterozoic. However, geochronological data show that major tectonothermal events within the basins coincided with significant tectonic events that occurred along a complex convergent plate boundary that developed on the southern margin of the proto–Australian continent. These data imply a paired evolution, whereby thermal events were shared and plate-margin stresses were propagated (to 1500 km) into the plate interior. We propose a tectonic model in which the 1.80–1.67 Ga northeastern Australian basins occupied a wide region of intermittently extending continental crust in the overriding plate of a long-lived subduction system—effectively a far-field continental backarc setting. The combined effects of slab rollback, accretion, and enhanced subcontinental convection produced an environment of episodic extension, transient shortening, elevated heat flow, and magmatism.