班公-怒江构造带的电性结构特征--大地电磁探测结果  

The electrical structure of Bangong-Nujiang suture:results from magnetotelluric sounding detection

作　　者：金胜[1] 魏文博[1] 叶高峰[1] 邓明[1] 谭捍东[1] Martyn Unsworth 

机构地区：[1]地下信息探测技术与仪器教育部重点实验室,中国地质大学(北京)地球物理与信息技术学院,北京100083 [2]University of Albert,Edmonton,Canada

出　　处：《地球物理学报》2009年第10期2666-2675,共10页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(4040406,40674045)资助

摘　　要：对青藏高原过班公一怒江构造带的三条大地电磁剖面进行探测,获得班公—怒江构造带及其邻区的电性结构模型,研究了班公—怒江构造带的深部结构与构造特征.研究结果表明:构造带及其两侧上地壳内广泛分布不连续高阻体,反映了岩浆岩的空间分布特征,表明构造带南北两侧岩浆的活动规律可能存在较大差别.研究区内的冈底斯及羌塘地体的中、下地壳普遍发育高导层,反映了印度大陆碰撞、俯冲过程的效应与痕迹,而高导层之下的高阻块体则可能是向北俯冲、冷的、刚性的印度大陆地壳.羌塘地体的电性结构模型可以分为南北两个区段,南羌塘块体的壳内高导层与班公—怒江构造带对印度板块俯冲的阻挡作用有关;而北羌塘块体壳内高导层与亚洲大陆对印度板块向北俯冲的"阻挡"与向南"对冲"有关.印度板块向北的俯冲与挤入,受到班公—怒江构造带及亚洲板块的阻挡,可能没有越过班公—怒江构造带,并在班公—怒江构造带附近向下插人软流圈,导致慢源物质上涌,形成壳、慢热交换与物质交换的通道和规模巨大、延伸至上地慢的高导体.班公—怒江构造带的电性结构证明了该构造带是一组产状陡立、巨型的超壳深断裂带.This paper discussed the features of electrical structure of Bangong-Nujiang tectonic belt and its adjacent zones based on three magnetotelluric sounding profiles which crossed Bangong-Nujiang suture. The results of MT detection show that discontinuous resistive bodies are widely distributed in the upper crust along the suture, which may indicate the features of magmatite distribution and the different magmatic activities in the northern and southern part of Bangong-Nujiang tectonic belt. High conductive bodies were detected in the middle and lower crust in Gangdisi and Qiangtang terrane. High conductive layer found in Gangdisi area to the south of Bangong-Nujiang tectonic belt may be the result of the Indian plate collision and underthrust; while the high resistive bodies underneath the high conductive bodies may be interpreted as the cold and rigid India continental crust that underthrusted northward. The electrical structure mode in Qiangtang terrane to the north of Bangong-Nujiang tectonic belt can be divided into two parts： the northern part and the southern part. The high conductive layer in the southern Qiangtang terrane crust is related with the Bangong-Nujiang tectonic belt resisting the India plate underthrust. Whereas the high conductive layer in the northern crust is connected with Asian continent′s resistance against the northward underthrust of India plate and the southward underthrusting of Asian continent. The northward underthrusting of the India plate may not cross the Bangong-Nujiang tectonic belt. The underthrusting of the India plate is stopped by Bangong-Nujiang tectonic belt and Asian plate, and turns down into the asthenosphere, which resulted in mantle substance flowing up, hence a channel for heat exchange between crust and mantle near the suture is formed and high conductive bodies stretching to upper mantle in large scale exist. The electrical structure of Bangong-Nujiang tectonic belt suggests that the suture is a group of high angle, super deep fault in large scale.

关 键 词：青藏高原 班公-怒江构造带 大地电磁测深 电性结构 

分 类 号：P631[天文地球—地质矿产勘探]