STRUCTURE OF BACK THRUST BLOCK ON THE NORTH PART OF TARIM BASIN AND HYDROCARBON ACCUMULATION

Back thrust block structures reffered to two or more serieses of back thrust faults with opposite inclination in space and in-between blocks, which were dominant in the deformational forms in the vast area of northern part of Tarim basin. Six major structural belts of back thrust blocks were determined in the area, which, according to the structural features of the basement, properties of petrology and the evolution of stress field, can be divided into four types, i.e, compressed back, basal control, strike-slip fracture control and faulted fold thrusts. Compressional environment used to dominate over the tectonics of the area, resulted in back thrust to anti-thrust, with mountain range and rising belt being held between the former, while basin and depressing area being placed in the latter. Major sourced depressions were controlled by anti-thrust, and the rises of back thrust block were favourable for hydrocarbon accumulation. With the basis of tectonic and sedimentary evolutions of Tarim basin, the author considered that eight types of hydrocarbon pools may exist, thus the area is of petroleum prospects.