Cathaysia, Gondwanaland, and the Paleotethys in the evolution of continental Southeast Asia

Abstract

Continental Southeast A ia is dominated by Precam brian continenral blocks overlain by Late Proterozoic to Paleozoic platform successions, representing Atlantic-type rifted miogeocl inal margins. All the blocks appear to have rifted and drifted from the Australian part of Gondwanaland. The timing and ex tent of their eparati on is ana lysed by the distribution of Penni an Cathays ian Gigamop-leris and Gondwana Glossop1eris floras, assisted by dated tectono-structura l units, pa leoclimate ind icators, and good quality paleomagnetic data. Between the blocks lie narrow intensely folded Phanerozoic mobile belts, which developed on the oceanic crust of the Pal eotethys ocean, characteri zed by pelagic-turbidite flysch equences which shallowed as the oceans narrowed. The narrowing was effected by subduction resulting in island arcs within the oceans, and cordilleran volcano-p lutonic arcs along the block marg in. Extinction of the bas ins resulted in co llision zones containing S-type granites and utu re zones containin g dismembered ophi olites. Post-consolidation pl ate readju tments resulted in wrench and rift fa ulting in several places while convergence conti nued elsewhere. The tectonic analysis has been carried out by recognizing tectonic elements (structural-formati onal unit~) for selected Phanerozoic time frame. We also pre ent a Phanerozoic sequence of palinspatic reconstructiors for the ri fti ng and drift ing of the blocks from northern Australia. These are cons istent with the known ages and distributions of the tectono-structural units and the good quality paleomagnetic data. We also present an ana lys is of the first-order relationship between the di tribution of mineral deposits and the igneous events which resulted from tectonic reactions between the Precambrian blocks and the mobile be lts.