川西盐井沟断层传播褶皱的三维构造建模与磁组构分析

当前断层相关褶皱研究的发展方向是从二维向三维的转换。文中基于Arcgis、Discovery以及Gocad等三维软件平台,对川西盐井沟地区地震资料进行精细的解析,得出盐井沟背斜是一个典型的三剪断层传播褶皱,并建立了它的三维模型。同时考虑到单纯符合几何约束的构造解释普遍存在着多解性和不确定性,结合几何学的三维建模和动力学的有限应变分析研究断层相关褶皱。在川西盐井沟地区18个采样点钻取了184块定向岩心样品,通过磁组构的分析结果发现,盐井沟地区的磁组构基本上都是弱应变的初始变形组构,褶皱前翼应变强度比后翼略强。断层传播褶皱三剪带是有限应变最为集中的区域,在模型预测的三剪带内,磁组构反映的有限应变也较为强烈。磁组构所指示的构造应力场大致为NW-SE向挤压缩短,与断层相关褶皱的几何学与运动学模型的预测相一致。

Three dimension construction and magnetic fabric analysis of the Yanjinggou fault-propagation fold in western Sichuan

Recently, there is a transition trend of the research on the fault-related fold from 2D to 3D. Based on ARCGIS,DISCOVERY and GOCAD software platform,we built a 3D geological model of the Yanjinggou anticline using 3D seismic data in the area. It was found that Yanjinggou anticline was a typical trishear fault-propagation fold. Because the structural interpretation of the 3D model only is of non-uniqueness and uncertainty due to geometric constraint, the finite strain analysis was also applied in the structural interpretation.184 oriented samples have been drilled at 18 sampling sites in Yanjinggou, western Sichuan. AMS of these samples disclosed:(1) that most of the magnetic fabrics were the initial deformation fabric; (2) that deformation in the forelimb was relatively stronger than that in the rearlimb, and (3) that the finite strain was strong within the trishear zone of the fault-propagation fold, in accordance with demonstration in the 3D geometric model. The tectonic stress field indicated by the magnetic fabrics suggested a NW-SE compression and shortening, which was consistent with the prediction of the 3D geometric model.