NATURE AND EVOLUTION OF THE YOUJIANG BASIN

The study of sedimentation, tectonism and magmatism shows that the Hercynian-Indosinian Youjiang Basin may be ascribed to a passive rift basin which was controlled during its formation and evolution by the opening and closing of the palaeo-Tethys. The basin consists of several regional fault-related secondary NW-and NE-trending basins in which lithofacies and tectonic framework are quite variable in character. The NW-trending basins were formed largely by extensional faulting, whereas the NE-trending ones have the characteristics of the strike-slip basins. The following five stages have been distinguished for the evolution of the Youjiang Basin:(1) intracontinental rifting stage; (2) passive marginal rifting stage; (3) back-arc rifting stage; (4) strongly subsiding stage, and (5) filling-closing stage.