利用时间域航空电磁资料再论华北地台北界的划分

A further discussion on the boundary of North China Platform's north margin based on time-domain airborne electromagnetic data

华北地台北缘矿产资源十分丰富,但其与内蒙古中部地槽褶皱系界线的划分问题历来争议不断。通过对大朝阳沟地区最新获得的大比例尺、高精度时间域航空电磁资料不同时间道电磁响应情况、时间常数特征和视电阻率变化规律的研究,精确厘定了区内华北地台的北界。平面上,该界线沿西南沟—小朝阳沟—上东三家一线呈向北凸出的弧形展布;垂向上,界面总体外倾,倾角50°~70°,在两端先内倾,后外倾,呈扭动弯曲的曲面向下延伸。上述研究成果不仅有助于区域大地构造的研究,而且对区内的地质矿产勘查具有重要意义。

The north margin of North China Platfor^ n , which possesses ver^^ rich mineral resources, is one of the important mineral pro-ducing areas in China. However, its boundar^^ with the geosyncline folded system in central Inner Mongolia has not been confirmed,and researchers have debated this problem for a long time. To get a specific definition, the authors made a detailed research on Dachaoy- angou area which is located in the south of Wengniute County on the north margin of North China Platfor^m. A large scale geological sur-vey was completed using the VTEM system, and high precision time-domain airborne electromagnetic data were obtained. With these data, the authors analyzed the electromagnetic response, time constant characteristics and the variation regularity of apparent electrical resistivity. The boundar^^ extends along the line from east to west, exhibiting a northward protruding arc in the plane. Its interface over-all leans outward with the angle 50 ° to 70 °, and it first leans inward and then outward, showing S-shaped twisting down. Objectively, the conclusions of this paper are conducive not only to the study of regional tectonics but also to the mineral resources exploration within the area.