扬子地块西侧米仓山基底卷入式冲断带的结构分析

米仓山基底卷入的巨型背斜带位于扬子地块的西北侧,西与龙门山薄皮冲断体系斜列状错位连接,东与大巴山弧形薄皮冲断带相互叠加,北侧为南秦岭造山带与扬子地块之间重要的大地构造界线——勉略缝合带。作为与周围大地构造和变形特征完全不同的构造样式,其结构的精细分析非常重要,本文利用现代构造地质学的几何解析技术对于这一特殊的基底背斜进行了研究。通过3条大型综合剖面的建立,本文对该巨型背斜的形成及空间分布进行了研究,探索性的解决米仓山背斜所卷入层序、层序的分布和彼此的接触关系问题;解决控制褶皱形成的断层分布、卷入深度、几何特点和彼此的交接关系问题;解决变形分析的构造样式问题和褶皱形成的平衡恢复问题。

Structural analysis of the Micang Shan basement-involved thrust belt in the western edge of the Yangtze Block.

The Micang Shan, located in the northwest of the Yangtze block, is a huge basement-involved anticline with the Longmen Shan thin-skinned thrust belts to the west, the Daba Shan thin-skinned thrust belts to the east and the Mianlue suture, the boundary between the South Qinling Orogen and the Yangtze block, to the north. Because the structural characteristics and deformation style of the Micang Shan anticline are quite different from those of the surrounding tectonic units, to make clear its geological structures appears fairly important for the evolution of the Qinling Orogen and the Yangtze block. In this paper, we use geometric analysis technology to decipher this special basement-involved anticline. Through the construction of three synthetical geological sections across the Micang Shan based on geophysical data and field investigation, we study the formation and the spatial distribution of this huge anticline, and focus on the questions such as (1) the sequences involved and their distribution and mutual contact, (2) the extension of faults that controlled the anticline and their distribution, detachment depth, geometric characteristic and mutual relation, (3) the structural styles and section restoration.