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

Abstract

Continental Southeast A ia is dominated by Precambri an continenral blocks overlain by Late Proterozoic to Paleozoic platform successions, representing Atl an ti c-type rifted miogeocl in al margin s. All th e 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 th e distribution of Penni an Cathays ian Gigamop­ leris and Gondwana Glossop1eris floras, assisted by dated tectono-stru ctura l units, pa leoclimate ind icators, and good quality paleomagnetic data. Between th e blocks lie narrow intensely folded Ph anerozoic mobile belts, which developed on the oceanic crust of th e Paleoteth ys ocean, c haracteri zed by pela gic-turbidite flysch equences which shallowed as th e oceans narrowed. The narrowing was effected by subduction resultin g in island arcs within the oceans, and cordill eran volcano-plutonic arcs along the bl ock marg in . Extinction of th e bas in s resulted in colli s ion zones containin g S-type granites and utu re zones containin g dismembered ophi olites. Post-consolid ation pl ate readju tments res ulted in wrench and rift fa ulting in several places while convergence conti nu ed elsewhere. The tectoni c analysis has been carried out by recognizing tectonic elements (s tructural-formati onal unit~) for selected Phanerozoic time frame . We also pre ent a Phanerozoic sequence of palinspatic reconstructiors fo r the ri fti ng and drift in g of the blocks from northern Australia . These are consistent with the known ages and distribution s of th e tectono-structural units a nd th e good quality paleomagnetic data. We also present an ana lys is of the first-order re lat ionship between the di tributi on of mineral deposits and the igneous events which resulted from tectonic reactions between the Precambrian blocks and th e mobile be lt s.