阿尔金断裂新生代构造活动的两阶段性——来自地震属性分析的证据

Two-stage activity of the Altyn Tagh Fault during the Cenozoic: Evidence from seismic attributes analysis

自新生代以来,柴达木盆地西北缘各构造单元受青藏高原持续挤压和阿尔金断裂走滑的影响,构造变形复杂,发育有多种不同性质,不同规模的断裂。地震属性技术是三维(3D)地震资料解释和构造分析的可靠依据,有助于客观、准确的揭示断裂的空间分布情况,是复杂地区地质解释的重要工具。本文利用地震属性技术,对位于阿尔金断裂南侧柴达木盆地西部的小梁山背斜深、浅层进行详细的断裂解译,发现该地区深部发育早期EW向逆冲断层;晚期由于阿尔金断裂大规模走滑的作用,形成由深部引发的NW向"楔形"逆冲断层,深部NW向断层的活动引发浅层的滑脱褶皱。综合分析认为阿尔金断裂新生代的活动分为早期隆升形成EW向斜向逆冲断层,晚期走滑运动发育控制现今背斜形态的NW向断层,具有两阶段活动的特点。

The structure units of northwestern margin of the Qaidam Basin had experienced complex structural deformation with the Tibetan Plateau continuous extrusion and Altyn Tagh strike-slip since Cenozoic,faults widely developed. It is difficult to clarify the spatial distribution of variety faults in the original three-dimensional （3D） seismic data. Seismic attributes analysis provides a method to get an accurate and unbiased view of fault features,especially in the geological interpretation process of complex region. This paper analyzes the faults of different depth in Xiaoliangshan anticline in the western part of the Qaidam Basin,located in south side of the Altyn Tagh Fault,found early EW-trending thrust faults in the deep,and with the Altyn Tagh Fault strike-slip in the late,forming NW-trending wedge-shaped thrust fault from deep to shallow,the activity of deep NW-trending fault triggered shallow detachment fault. Through comprehensive analysis,we can infer that the Altyn Tagh early uplift led to the formation of the EW-trending oblique thrust fault,and the Altyn Tagh Fault strike-slip movement in the late formed the NW-trending thrust fault in the limbs of Xiaoliangshan anticline since Cenozoic. The activity of faults had two stages.