六盘山盆地西南缘构造样式及勘探意义

Structural pattern of the southwestern margin in the Liupanshan basin and its significance of petroleum prospecting

六盘山盆地构造背景复杂,尤其是盆地西南缘,构造样式认识不清.在野外调查、重力资料及地震资料解析的基础上,分析六盘山盆地西南缘各大断层带构造特征和构造样式,提出以压扭走滑构造样式为主,结合区域地质背景探讨中新生代以来构造演化特征.结果表明:盆地西南缘构造带具有断层带地层陡直、剖面上呈花状构造、空间上见"丝带效应"、平面上各断裂雁列式排列的构造特征,划分走滑构造和压扭走滑构造相关褶皱两大类构造样式;结合区域构造应力场不断顺时针旋转的构造演化特点,确认六盘山盆地西南缘新生代以来以压扭走滑构造样式为主,走滑构造相关褶皱构造样式为次.该研究成果对六盘山盆地油气勘探具有指导意义.

Abstact:The southwestern margin in Liupanshan Basin has complex tectonic background,and little is known about its structural pattern.On the basis of abundant field investigation and the gravity and seismic data,the analysis of major faults structural characteristics and structural pattern in southwestern margin of Liupanshan Basin,we put forward compresso-shear structural pattern,combined with regional geological background of the Mesozoic-Cenozoic to study tectonic evolution characteristics.The results show that the tectonic belt in the southwestern margin of the basin has the steep fault surface,abundant distribution configuration,dolphin effect,flower structure and rapidly changing of strata thickness in two sides of a fault.The structural pattern is complied as compresso-shear and its fault-related folding;and combining with the regional tectonic stress field continuously along the tectonic evolution characteristics of clockwise rotation,we confirmed that since Cenozoic the main structural pattern is compresso-shear and the secondary is strike-slip fault related folds tectonic pattern.The results have guiding significance to the following oil and gas exploration in this area.