云南思茅盆地基底构造电性特征研究

Study on the electric properties of basal structures in Simao basin, Yunnan

(天津华北地质勘查局地球物理勘探公司，天津300181)

Geophysical Exploration Corporation, Huabei Geological Exploration Bureau, Tianjin 300181, China

通过对思茅盆地21条剖面，共1007个测点的大地电磁测深资料的分析，采用有效视电阻率概念对剖面进行反演处理，继而从电性特征方面对坳陷的双重基底构造进行了研究。研究成果表明：坳陷内中生界侏罗系、元古界浅中变质岩是剖面构造层追踪和划分的标志层；基底平面特性上除中央凸起外，呈现自东西两侧向中央逐步下降的三级构造格局；古生界沉积变质基底的起伏与结晶基底间有一定的继承关系，但局部起伏范围、位置因多期的构造运动而表现较大区别。

magnetotelluric data along 21 profiles in Simao basin were analyzed and the profiles were processed by using the inverse modeling based on the concept of effective apparent resistivity. On this basis, the dual basal structures of the depression have been studied in the aspect of electric properties. The results show that 1) the metamorphic rocks of Jurassic, Mesozoic and Proterozoic in the depression is the marker bed for tracing and classifying the structure layers on the profiles, 2) except the center bulge, the basal plane presents threelevel descending structure frame from west and east to central, and 3) the fluctuation of diagenic metamorphism in Proterozoic has a succession relationship to crystalline basement, but the range and position of part fluctuation differs greatly for many stages of tectonic movement.