韦州—石沟驿拆离滑脱构造的确定及地质意义

Determination of Weizhou-Shigouyi detachment structure and its geologic meaning.

以地震反射特征为依据,结合区域地质特征,确定了鄂尔多斯地块西部南北向基底拆离形成的韦州-石沟驿拆离滑脱构造。它在地震剖面上表现为:滑脱面以上有多层平行反射,不出现逆冲推覆前缘带复杂变形造成的杂乱反射;在平面上拆离滑脱构造与周边构造有明显的不协调性;它是在晚侏罗世地块西部大规模的东西向逆冲推覆所造成的南高北低的构造背景下,因重力作用沿T9界面附近的煤系地层由南至北拆离滑脱形成的,在东、西、北均以断层与周边相接,为一外来岩席构成的复式向斜,构造变形相对简单。在鄂尔多斯地块西部构造强烈变形区,因重力作用导致从南至北的拆离滑脱,形成了构造变形相对简单并且完整的石沟驿复向斜覆盖在原地岩席之上,这对该区构造演化史研究及油气勘探部署具有重要意义。

Taking the features of seismic reflection as a basis and combining with regional geologic charac-teristic, the Weizhou-Shigouyi detachment struc-ture that was formed by basement detachment of western Ordos massif from south to north is deter-mined in the paper. On the seismic section it shows multi-layers' parallel reflections above detachment interface,and the chaotic seismic reflection resulted from complex deformation in frontal overthrust nappe has failed to appear, on the plane, the detachment structure formed clear structural discor-dance vvith neighboring areas;it came into being af-ter detachment from south to north along coal mea-sure strata nearby T9 interface under the gravity action,under such structural background that the large scale of overthrust nappe of late Jurassic west massif in east-west direction formed the south part being higher and the north part being lower, its east, west and north boundary connected vvith neighboring by faults. The structure is composite syncline consisted of exotic sheet and structural deformation is relatively simple. In strongly struc-ture-deformed area of western Ordos massif, the detachment from south to north under the gravity action formed simply structure-deformed and in-tegrite Shigouyi composite syncline overlying on the autochthonous sheets,which has importance to the study of structural history and the arrangement of oil-gas exploration in that area.