TWO PHASE OF STRUCTURAL STRESS IMPACTS ON LIAOHE BASIN:NEW EVIDENCES FROM TECTONOPHYSICAL MODELING EXPERIMENTS

New results from modeling experiments and geological information analysis indicate that mechanism of the Yingkou-Tongerpu fracture zone in the Liaohe Basin, China is due to composite actions of both older extensional stresses from upwelling of the mantle during the continental rift and younger dextral shear stresses from dextral strike-slip structural movement. The evolution of the continental rift is driven by extensional stresses from upwelling of the mantle during the Fangshenpao and Shahejie phases of the Paleocene and Eocene, Paleogene times (Ef-Es1, about 63.0~37.0 Ma.BP). The dextral strike-slip structural movement occurred during the Dongying phase of Oligocene and Paleogene times (Ed, about 36.9~24.5 Ma.BP). Two phases of the structural movements led to formation and evolution of the complex fracture system in the Liaohe Basin. It is suggested that the dextral strike-slip structural movement of post-rift reactivated older extensional fractures and produced new fractures. On the basis results from modeling experiments and analysis of geological information, the displacement magnitudes of the Liaohe Basin caused by the dextral strike-slip structural movement during the Dongying phase of Paleogene times (Ed) is about 4~8km. New studies prove that complex fracture systems of the Liaohe Basin are not only strongly controlled by older extensional stresses, but also influenced by the younger dextral strike-slip structural movement. Two phase structural movement resulted in oil and gas migration and accumulation in this area.