科研之友
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摘要
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 similar to 20 km and thickness about 10 similar to 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.
