龙木错—双湖—澜沧江缝合带中段双湖地区地球物理特征

龙木错—双湖—澜沧江板块缝合带位于青藏高原羌塘中部至藏东一带,相关研究将其厘定为冈瓦纳板块的北界,对探讨青藏高原早期形成与演化历史及区域资源勘查与评价有重要的地质意义.本文结合区域重磁数据、大地电磁数据对该缝合带地球物理特征进行分析论证.首先基于WGM2012全球重力场模型网格化数据,利用垂向一阶导数计算、构造增强滤波等处理方法,推测龙木错—双湖—澜沧江缝合带异常的空间分布.计算的区域莫霍面在缝合带南北两侧深度存在较大差异.重力数据及其处理结果论证了龙木错—双湖—澜沧江缝合带存在的可能性.其次,选取了龙木错—双湖—澜沧江缝合带中段双湖地区的高质量大地电磁数据进行反演解释,电阻率反演结果表明缝合带南北存在较大的电性差异,结合区域地质情况,推测缝合带是不同地质体的分界线.最后,对缝合带地球物理响应特征和地质认识进行了讨论.通过对地球物理数据分析处理,为进一步讨论缝合带形成提供了有利的科学依据.

Geophysical characteristics of the Shuanghu District in the Lungmu Co-Shuanghu-Lancang river suture zone

Lungmu Co-Shuanghu-Lancang river suture zone is located from the middle of Qingtang area to the east of the Qinghai-Tibetan plateau. This zone was put forward and has been determined as the north edge of the Gondwanaland. It is important for the study of the early formation, evolutionary history of the Qinghai-Tibetan plateau and the exploration and evaluation of the regional resources. The geophysical characteristics of the suture are analyzed with the gravity and magnetotelluric (MT) data. Firstly, we use the vertical first derivative calculation and constrained anisotropic diffusion to process the gravity data of the World Gravitation Model 2012 (WGM2012) in this region, and get the distribution of the study zone. Meanwhile, the Moho interface depth shows the differences between the north part and south part of the Lungmu Co-Shuanghu-Lancang river suture zone. These results could show the possibility of the existence. Secondly, we do the inversion of the MT data in the Shuanghu area, which is in the middle part of the suture zone. The result shows that it is obviously different between the north part and south part. The suture zone may be the edge of the different terranes. At last, we discuss these geophysical characteristics and the related geology understanding. Through the discussion, it shows that the results will be helpful for the future discussion on the suture zone.