商南地区商丹断裂带特征

商丹断裂带是北秦岭加里东造山带与中秦岭海西造山带的分界断裂,在空间上由韧性剪切带、逆冲推覆构造带、断陷-走滑地堑断裂带及其所夹持的岩块、岩片、褶皱所组成的大型复杂断裂带。其演化历史至少经历晋宁期海沟俯冲;加里东期陆内俯冲-碰撞;海西—印支期陆内俯冲;燕山期的逆冲-推覆和喜山期断块-走滑的复杂演化过程,而形成今日所见的复杂断裂构造。

THE STRUCTURAL CHARACTERISTICS AND EVOLUTION OF THE SHANGDAN FAULT ZONE

The Shangdan fault zone is a boundary fault between the North Qinling Caledonian and the Middle Qin-ling Hercynian erogenic zones. It is a long-developed and deepcut lithosphere fault with complicated dynamic features and the diversified structural styles. The fault zone is a trench subduction zone of Andersian-type continental margin of the North China continental block in the Sibao-Jinning period. The subduction orogenesis in the Jinning period formed thermal events, such as deformation and metamorphism, ductile shear zones and ophiolite suite and so on of the North Qinling in the Jinning period (800~1000Ma). The Caledonian period (400~450Ma) is a main stage of intra-continental subduction and collision orogeny for the North Qinling. Being affected by the subduction of the circum-pacific plate and the India plate, the Qinling orogenic zone has formed the horst and graben structure patterns involving tilled blocks combining with horizontal strike -slip, which is responsible for the grabentype strike-slip structures of the Shandan fault.