塔里木盆地东北部基底拆离构造与油气领域

BASAL DETACHMENT STRUCTURES AND OIL-GAS TERRITORY IN THE NORTHEAST OF TARIM BASIN

塔里木盆地东北部的塔北隆起是发育在南倾、犁式的亚南韧性剪切带上盘的推复隆起带。是因二叠纪末期古特提斯海的开启与关闭,塔里木板块向北漂移,天山海西地槽关闭,碰撞后会聚及挤压作用促使板内古生代盆地发生了以基底拆离式构造为主的变形改造的结果。古生代地层中滑脱断层的脱顶褶皱及其上盘的牵引背斜、晚海西运动的古侵蚀面残山是区内油气聚集的主要圈闭样式。

Basal detachment structure is a major structural style of intraplate deformation. At the end of Permian, Tarim plate drifted northward as a result of the opening and closing of Tethy; on the one hand, the closing of Haixi geosycline in Tianshan was advanced; on the other hand , the convergency and pressing after the collision continued, caused the deformation reconstru-ction with basal detachment as the major structural style in Palaeozoic basin of Tarim platform. Tabei ( north Tarim ) uplift in the northeast of Tarim basin is a nappe uplift belt , being developed on the upper hanging of Yanan ductile shear belt, has a southdipping listric nature. Furthermore , a series of slip fault and decollement structures with southdip bedding plane were formed along the 'weak belts' of the Cambrian and Silurian bottom shales in Palaeozoic sedimentary cover.They may be subdivided into interlayer shear fracture cleavage , decollement folds , plastic flow belt , interlayer slip band and fault-slip front pressing belt. In the Palaeozoic strata in Tarim basin, there are the decollement folds of detachment faults , the dragging anticline on the upper hanging , and the relict on palaeo-erosion surface caused by late movement.They are the domi-nant structures for oil-gas accumulation in the study area.