滇西三江地区深部电性结构特征及其意义

沿盈江一姚安布置了一条长约350 km的长周期大地电磁剖面,共观测宽频大地电磁测深点53个,长周期大地电磁测深点26个;利用多种数据处理方法对观测资料进行了预处理、定性分析和二维反演,得到沿剖面的地壳和上地幔电性结构模型.对主要地块和断裂带的电性结构进行了分析,电性结构模型揭示滇西三江地区广泛存在壳内低阻层,但沿剖面方向即东西向埋深和厚度不一,在保山地块和滇中地块地下存在较大规模的壳幔低阻带;腾冲地块地下埋深13~20 km,厚约10~17 km的壳内低阻层可能是岩浆囊的反映;初步将保山壳幔韧性剪切带作为印支地块挤出的深部东边界.

Deep electrical resistivity structure of Sanjiang Area of west Yunnan and its significance

A 350 km long-period Magnetotelluric profile is placed along Yinjiang-Yaoan. Altogether 69 broadband magnetotelluric sounding stations and 19 long-period magnetotelluric sounding stations were laid. After pre-treatment, qualitative analysis, and two-dimensional inversion of the observed field data by several data-processing methods, the crust and upper mantle electrical resistivity model along the profile is obtained. An analysis is made on the electrical resistivity structure of the main land blocks and faults, and the resistivity model reveals that there widely exist low resistivity zones in the crust in Sanjiang area at the Southeast edge of Qinghai-Tibet Plateau, the low resistivity zones differ in burial depth and thickness from east to west, and there exist massive crust-mantle low resistivity zones in Baoshan Block and central Yunnan Block. Under Tengchong block, there is a low resistivity zone in the crust with burial depth about 13~20 km and thickness about 10~17 km, which indicates there is magma chamber. Preliminarily, the ductile shear zone of Baoshan crust-mantle is taken as the deep east boundary of extrusion of the Indochina block.