Shear structural paragenesis and its role in continental rifting of the East Asian margin

摘要

The spatial-genetic relationships between transit fault systems of the East Asian global shear zone (EAGSZ) are analyzed. It is established that the EAGSZ internal structure between the Okhotsk and South China seas is identical to that of world-known natural and experimental shear zones, which confirms its development as an integral structure. The structural-kinematic analysis included the Tan-Lu-Sikhote-Alin (TS) system of left-lateral strike-slip faults (NNE 25°-30°) and the Bohai-Amur (BA) system of updip-strike-slip faults (NE 50°-70°). It is shown that these systems were formed as structural parageneses during two stages. The first and shear-thrust stage (Jurassic-Early Cretaceous) was marked by general NNW-oriented compression with the formation of the TS system of left-lateral strike-slip faults and their structural parageneses (compression structures) such as the BA system of updip-thrusts. The second, strike-slip-pull apart stage (Late Cretaceous-Cenozoic) was characterized by SE-directed tangential compression, which was generated by the SW left-lateral displacement of the continental crust along the Central Sikhote-Alin deep-seated fault. In such dynamic settings, the updip-thrust kinematics of the BA system gave way to that of left-lateral strike-slip faults. The strike-slip faults were formed in the transtension regime (shear with extension), which determined the development of pull-apart structures, where the left-lateral shear extension component played the decisive role. Simultaneously, the extension involved the Tan-Lu strike-slip fault with the formation of the rift valley and the discrete development of sedimentary basins along the latter.