阿尔金南缘咸水泉推覆构造

Nappe tectonic of Xianshuiquan on southern edge of Altun, Qinghai, China

柴达木盆地咸水泉构造中3井在打穿70m的N12地层后钻遇基岩,而位于该井南侧华岩山高点上的中9井、中6井,钻达千米尚在N1上部地层中,基岩高程相差极大。研究认为,咸水泉构造石油沟高点中3井附近,存在着NW方向推挤而来的推覆体,这种推覆体属于原地推覆,是沿阿尔金山前一系列断层,包括F9,F8及山前断裂带形成的叠瓦状推覆构造,其前缘位于石油沟高点的中3井附近,依据重磁资料所得出的基底埋深和断层倾角分析,推覆距离约为9km,成型于N1晚期。正是该推覆体为中9井上新统上段边缘相沉积提供了物源。该推覆构造已得到平衡剖面结果的验证。推覆构造观念的提出,对该区构造给出了合理解释,对油气勘探有重要指导意义。

Well Zhong 3 is located in the Xianshuiquan structure of Qaidam Basin and comes across the bedrock when drilled through 70 m thickness N~~1__2 formation. Well Zhong 9 and Well Zhong 6 stand in the south of Well Zhong 3 and in the high position of Huayan mountain. They are still in the upper of N_1 formation when drilled more than 1 000 m. So the bedrock elevation varies very much. According to this study, near Well Zhong 3 in the top position of the Shiyougou of the Xianshuiquan structure, there exists nappe tectonic formed from NW pression. This kind of nappe belongs to the former place nappe consisting of a series of faults along the foreland of Altun, including F_9, F_8 and the imbricated nappe structure formed from the faults in the foreland. Its front edge is situated near Well Zhong 3 at the top part of the Shiyougou. By the analysing bedrock buried depth data come from magnetic information and fault tilt angle, the author points out that the nappe translation was about 9 km and came into being in latter N_1 period. It is just the nappe that supplies the sediments to the upper formation of N_2. This nappe is proved by the balanced cross-section result. The standpoint of nappe gives a reasonable interpretation to the structure style in this area and has the guide meaning for the petroleum exploration in this area.