四川阿坝——秀山地学断面

ABA-XIUSHAN GEOSCIENCE TRANSECT IN SICHUAN

四川省阿坝—秀山地学断面长约1000km,横跨上扬子地台和松潘-甘孜地槽褶皱系。在综合研究现有地质、地球物理资料的基础上,对断面及邻区划分出不同性质的三大岩石圈块体;结合表壳变形特征又区分出以四川地块为中心的东、西对冲构造体系;并进一步划分出8个次级构造带(块)。在垂向上划分出地壳、岩石圈厚度及形态,讨论了地壳次级分层及壳、幔低速层、低阻层和高阻层异常的特征,提出了初步解释。指出龙门山断裂带西部地壳缩短、增厚的主要因素。概述了地壳演化。

Aba -Xiushan geoscience transect with a longth of about 1000km traverses the Upper Yangtze platform and Songpan -Garze geosynclinal folded system. On the basis of comprehensive study of geological and geophysical data, three lithospheric blocks in the transect have been divided. Accord-ing to the surface configuration of crustal deformation,east and west ramp structural systems which take Sichuan massif as centre,and eight structural subzones(blocks)have been distinguished. Mor-phology and thickness of the crust and lithosphere,crustal architecture,characteristics of low velocty layer,low resistivity zone and high resistivity anomaly in the crust and mantle have been preliminarily explained. Main factors responsible for shortening or thickening of the crust to the west of the Longmenshan fracture zone are pointed out. The crustal evolrtion has been outlined.