HYDROCARBON ACCUMULATION IN ZENGMU PULL-APART BASIN:INSIGHTS FROM THE CONTROL OF TINJAR-WEST BARAM LINE

The Tinjar-West Baram Line of the Southern South China Sea is a northwest-trending strike-slip fault. As the boundary between the Zengmu Basin and the Beikang Basin and Nansha Trough, the strike-slip fault of the Tinjar-West Baram Line was first activated in Oligocene as a intensely dextral strike-slip fault, then turned to sinistral after late Miocene and, then turned to dextral again since Pleistocene up to present. Based upon the study of seismic profiles, gravity and magnetic data, geothermal heat flux distribution data near the Tinjar-West Baram Line, we studied the crustal nature and lithosphere thickness of the Zengmu Basin, and discussed the control of Tinjar-West Baram Line over the evolution and accumulation of hydrocarbon in the Zengmu Basin. It is concluded that the faulting of the Tinjar-West Baram Line had provided rich source of sediments for the Zengmu Basin. The strike slipping of the faults helped the formation of the good traps in the Zengmu Basin, and the reversed strike slipping in the late period led to the northward motion of the basin depocenters. The faults are important channels to the deep heat source, beneficial to the hydrocarbon generation, and the secondary faults are also the major passages for hydrocarbon migration.