青藏高原东北缘玛沁—兰州—靖边剖面地壳上地幔电性结构研究  

Electrical conductivity structure of the crust and upper mantle in the northeastern margin of the Qinghai_Tibet plateau along the profile Maqên-Lanzhou-Jingbian

作　　者：汤吉[1] 詹艳[1] 赵国泽[1] 邓前辉[1] 王继军[1] 陈小斌[2] 赵俊猛[3] 宣飞[1] 

机构地区：[1]中国地震局地质研究所,北京100029 [2]北京大学地球物理学系,北京100871 [3]中国科学院青藏高原研究所,北京100085

出　　处：《地球物理学报》2005年第5期1205-1216,共12页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展规划973项目(G19980407:95-130202)资助.

摘　　要：在青藏高原东北缘至鄂尔多斯地块沿玛沁—兰州—靖边剖面进行62个测点的大地电磁观测,采用Robust技术对观测数据进行了处理和张量阻抗分解.分析了视电阻率和阻抗相位曲线、二维偏离度、区域走向.采用RRI二维反演技术进行了资料的反演解释,二维剖面的电性结构显示:(1)玛沁断裂带、兰州深断裂带、马家滩—大水坑断裂带将剖面分为4个电性区块:巴颜喀拉地块、秦祁地块、边界带和鄂尔多斯地块.(2)区块1、2和4的地壳电性结构有类似特点:上地壳为高阻层,下地壳上部为低阻带,下地壳下部到上地幔电阻率随深度逐渐升高.区块3电性成层性差、结构复杂,是现今构造活动较强烈的地区.(3)玛沁断裂带、海原断裂带和罗山—云雾山断裂带为较陡立的超壳断裂带;西秦岭北缘断裂带为壳内断裂带.Magnetotelluric （MT） measurements have been carried out at 62 sites in the junction area between the northeastern margin of the Qinghai-Tibet plateau and the Ordos block along the profile Maqên-Lanzhou- Jingbian. The Robust data processing technique and Bahr＇ s tensor decomposition were used to remove 3-D effect. Apparent resistivity, impedence phase curves, skewness and regional strike were analysed. RRI 2-D inversion has been used for data interpretation. The results are as follows. （1） The target area can be divided into four electrical conductivity blocks by 3 fault zones named Maqên, Lanzhou and Majiatan-Dashuikeng fault zone. The four blocks are named Bayan Har block, Qinling-Qilian block, margin belt and Ordos block, respectively. （2） The electrical conductivity structure in block 1, 2 and 4 has similar characteristics. There is a high resistivity layer in the upper crust, a lower resistivity layer in the top of the lower crust, and the resistivity rises gradually from the lower crust to the upper mantle. The characteristic of electrical conductivity layer is not well and is complex in the structure in block 3 which is very active in tectonics. （3） The Maqên fault belt, the Haiyuan fault belt and the Luoshan-Yunwushan fault belt extend through the crust with high dip angles and the fault on the northern brim of the Qinling mountains is confined inside the crust.

关 键 词：大地电磁测深 玛沁—兰州—靖边 电性结构 反演 

分 类 号：P631[天文地球—地质矿产勘探]