鄂尔多斯地块西缘定边-景泰地壳和上地幔电性结构分析

给出了定边－景泰大地电磁剖面探测结果并对其进行了分析．鄂尔多斯块体内部电性结构简单，电性界面成层性好，而在其西缘弧形断裂带，电性结构复杂，电导率横向变化较大．在弧形断裂带上地幔低阻层埋藏深度加大，这与北面的银川断陷盆地上地幔结构上隆形成反照，经分析认为银川断陷盆地属于拉张性质，而弧形断裂带属于挤压性质，由于均衡调整作用，造成了两者上地幔结构的反差．深部电性结构在大罗山－惠安堡之间有一局部上隆，经分析认为此处可能为深大断裂，南北构造带仅在此通过．

ANALYSIS ON ELECTRICAL STRUCTURE OF CRUST AND UPPER MANTLE ALONG THE WESTERN BORDER OF ORDOS BLOCK

The magnetotelluric sounding results show that electrical structure is simple inside Ordos block and complex in the arcuate fault zones on the western border of the block.In the arcuate fault zones,lateral change of conductivity is severe and the low resistivity layer in upper mantle tends to deepen.This is different from Yinchuan fault basin where upper mantle structure is uplifted.It is considered that tectonics are tensional in the Yinchuan basin and compressional in the arcuate fault zones.In addition,deep electrical structure is uplifted between Daluoshan and Huianpu.It is shown that this is a deep-seated fault where the North-South tectonic belt passes through.