Middle–Late Paleozoic Australia–Asia convergence and tectonic extrusion of Australia

Abstract

Recent and new paleomagnetic data from ignimbrite-rich Carboniferous successions of the western Tamworth Belt, Southern New England Orogen, eastern Australia, show a northward excursion over ~30°. Paleozoic data from the Australian craton and Tasman Orogenic System (TOS) suggest an Early Devonian start. At the middle-late Visean peak, the central New Guinean promontory of the Australian craton reached 30°–40°N, within the latitude range of the western Central Asian Orogenic Belt (CAOB). Devonian–Carboniferous convergence of Australia/northeastern Gondwana with the CAOB, across the Paleoasian–Rheic Ocean, is proposed as a major driver for contemporaneous tectonism throughout Australia and the CAOB. This implies a substantial Variscan, Pangea-forming, influence on Australian Devonian–Carboniferous tectonics — Alice Springs Orogeny (ASO) and Quilpie and Kanimblan Orogenies. Convergence-related compressional deformation of Australia is largely confined to a “compression box”, extending southward from the New Guinean promontory and bounded westward by the Lasseter Shear Zone and eastward by the East Australian Rift System. Comparable characteristics of Paleozoic Australia–Asia and Cenozoic India–Asia convergence — north–south compression, weak and heated crust (Larapintine Graben and TOS/Tibetan Plateau), eastern “free oceanic boundary” (Paleopacific/Pacific) — do link Paleozoic Australia–Asia convergence to Cenozoic tectonic extrusion of Tibet. Tectonic extrusion of ductile lower crust from the Larapintine Graben led to eastward displacement of the Thomson and Northern New England Orogens, with upper crustal displacement bounded northward by Arunta Block shear zones, the Diamantina River Lineament, the Clarke River Fault Zone and the Townsville Trough, and southward by the Darling River/Cobar-Inglewood Lineaments and Cato Fracture Zone with the Lake Blanche-Olepoloko Fault Zones and Lachlan Transverse Zone as a subsidiary. Recognition of ASO-related tectonic extrusion opens novel, provocative, insights into puzzling aspects of Australian Middle–Late Paleozoic evolution.