塔里木盆地-西昆仑山结合带三维电性结构及其地球动力学意义

The piedmont of West Kunlun Mt. and the southwest margin of Tarim Basin is located at the west-end of the Himalaya-Tibet Orogen, where the area that he India plate and Tarim plate are closest to each other. Most of the existed data support that the Tarim plate is subducting to West Kunlun Mt. southward. However, long debates still stand regarding the regime of the subduction system, the distance of the subducted plates and their deep collision relationship. Long-period magnetotelluric (LPMT) data are very sensitive to conductive fluids and melts which are tightly related to the subducting processes and all the involved plates. We propose to collect 34 LPMT sites, covering the southwest margin of Tarim Basin and the West Kunlun Mt., to construct the three-dimensional electrical resistivity structure of the study area by inverting the MT data from the collected sites by this project and other more than 200 broadband MT sites by other historical projects. The latest parallel inversion system for three-dimension MT data will be employed, with combing other geologic and geophysical data to do the joint interpretation. By tracing the large-scale features, e.g. faults, boundaries and the distribution of the fluids and melts in depth, this project will provide new constraints for studying the contact of the India plate and Tarim plate in depth, the collision regime of the Tarim plate and India plate underneath West Kunlun Mt.

喜马拉雅造山带西端的塔里木盆地-西昆仑山结合带是印度板块与塔里木板块距离最近的区域，现有证据多数支持塔里木板块在西昆仑山前向南俯冲，但是俯冲的样式、俯冲的距离及板块间碰撞挤压关系存在较大争议。长周期大地电磁数据对深部的低阻流体分布十分敏感，而流体的分布往往与俯冲过程及俯冲板片与上覆板块之间关系密切。本项目拟在西昆仑山和塔里木盆地西南缘布置长周期大地电磁测网，采集34个基本覆盖塔西南-西昆仑山区域的大地电磁测点，结合塔里木盆地内已收集到的200多个宽频带大地电磁测点数据，综合其他地质地球物理资料，应用最新的三维大地电磁并行反演技术，构建塔里木-西昆仑山结合带三维电性结构模型。通过追踪深大构造和流体分布，为厘清印度板块和塔里木板块在研究区的对接模式，推断研究区内塔里木板块、印度板块在西昆仑山深部的俯冲碰撞关系，提供新的重要证据。

塔里木盆地-西昆仑山结合带是印度板块与塔里木板块距离最近的区域。现有证据多数支持塔里木板块在西昆仑山前向南俯冲，但是俯冲的样式、俯冲的距离及板块间碰撞挤压关系存在较大争议。长周期大地电磁数据对深部的低阻流体分布十分敏感，而流体的分布往往与俯冲过程及俯冲板片与上覆板块之间关系密切。本项目在西昆仑山南麓和塔里木盆地西南缘布设了长周期大地电磁测网，采集了53个长周期大地电磁测点和9个宽频大地电磁测点，数据质量优良。结合塔里木盆地西南缘已收集到的200多个宽频带大地电磁测点数据，应用了最新的三维大地电磁并行反演技术，构建了塔里木-西昆仑山结合带三维电性结构模型。电性结构模型显示：塔里木板块向南插入到了昆仑山下方，呈现连续的低阻区域；在昆仑山南麓，存在与昆仑山近似平行的低阻条带，可能与印度板块俯冲引起的软流圈上涌或者火山弧相关的岩浆活动有关。