青藏高原错那—沃卡裂谷中部电性结构及其动力学意义

doi:10.13745/j.esf.sf.2022.2.3

地学前缘 ›› 2022, Vol. 29 ›› Issue (2): 393-401.DOI: 10.13745/j.esf.sf.2022.2.3

• “印度-欧亚大陆碰撞及其远程效应”专栏之四 • 上一篇下一篇

青藏高原错那—沃卡裂谷中部电性结构及其动力学意义

薛帅¹(), 卢占武¹^,^*(), 李文辉¹, 王光文¹, 王海燕¹, 梁宏达²

1.中国地质科学院地质研究所自然资源部深地动力学重点实验室, 北京 100037
2.中国地质科学院地球物理地球化学勘查研究所, 河北廊坊 065000

收稿日期:2022-01-10 修回日期:2022-02-14 出版日期:2022-03-25 发布日期:2022-03-31
通讯作者: 卢占武
作者简介:薛帅(1988—),男,助理研究员,主要从事大地电磁法及其应用研究。E-mail: xueshuai1211@163.com
基金资助:
国家自然科学基金项目(41804090);国家自然科学基金项目(42174124);国家自然科学基金项目(42174094);国家自然科学基金项目(91962109);中国地质调查局地质调查项目(DD20190016);中国地质科学院基本科研业务费项目(J2015)

Electrical resistivity structure beneath the central Cona-Oiga rift, southern Tibet, and its implications for regional dynamics

XUE Shuai¹(), LU Zhanwu¹^,^*(), LI Wenhui¹, WANG Guangwen¹, WANG Haiyan¹, LIANG Hongda²

1. Key Laboratory of Deep Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
2. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Science, Langfang 065000, China

Received:2022-01-10 Revised:2022-02-14 Online:2022-03-25 Published:2022-03-31
Contact: LU Zhanwu

摘要/Abstract

摘要：

藏南裂谷作为青藏高原最显著的伸展构造样式之一,是研究高原生长过程的重要窗口,但目前其深部成因机制仍存在较大争议。本文利用沿错那—沃卡裂谷中部的大地电磁数据,分析裂谷区域的大地电磁测深曲线特征和相位张量,并通过三维大地电磁反演获得邛多江地堑和沃卡地堑深部电性结构。三维大地电磁反演结果显示,沃卡地堑和邛多江地堑深部存在一条连续的显著高导异常,并呈现“俯冲”形态,且上覆高阻结构体,而在邛多江地堑两侧浅部则分布低阻异常。结合早期的研究结果,本文支持错那—沃卡裂谷深部的高导异常为地壳部分熔融,可能与南向地壳流相关,并研究认为在南北向持续挤压作用下,裂谷下方的弱地壳层,通过解耦上地壳和下部地壳,促进了藏南裂谷系的发育。

关键词: 错那—沃卡裂谷, 大地电磁, 藏南裂谷, 电性结构, 地壳流, 伸展构造

Abstract:

As one of the most significant extensional structural styles of the Tibetan Plateau, the rifts in southern Tibet are an important window for studying the growth of the plateau. However, the formation mechanism of these deep rifts remains controversial. In this paper, magnetotelluric data from the central part of the Cona-Oiga rift were used to study the rifts in southern Tibet. The Magnetotelluric sounding curves and phase tensors were calculated and analyzed, and the electrical resistivity structure beneath the Qiongduojiang and Oiga grabens was obtained through 3D MT inversion. The 3D inversion result showed that an obvious continuous high-conductivity anomaly develops beneath the Cona-Oiga rift in a “subduction” pattern overlaying with high-resistivity structures, while low-resistivity anomalies distribute in the relatively shallow parts beneath either side of the Qiongduojiang graben. Combined with the previous studies, the continuous high-conductivity anomaly beneath the Cona-Oiga rift is believed to be originated from crustal partial melting, probably related to the southward crustal flow. We suggest that, under the N-S compression driven by the India-Eurasia collision, the weakened crust promotes the development of the rifts in southern Tibet by decoupling the upper crust and the lower lithosphere.

Key words: Cona-Oiga rift, magnetotelluric, rifts in southern Tibet, electrical resistivity structure, crustal flow, extensional structures

中图分类号:

薛帅, 卢占武, 李文辉, 王光文, 王海燕, 梁宏达. 青藏高原错那—沃卡裂谷中部电性结构及其动力学意义[J]. 地学前缘, 2022, 29(2): 393-401.

XUE Shuai, LU Zhanwu, LI Wenhui, WANG Guangwen, WANG Haiyan, LIANG Hongda. Electrical resistivity structure beneath the central Cona-Oiga rift, southern Tibet, and its implications for regional dynamics[J]. Earth Science Frontiers, 2022, 29(2): 393-401.

图/表 4

图1 藏南喜马拉雅造山带地质简图和错那—沃卡裂谷地形和地质简图(a据文献[19]修改;b据文献[19,38]修改)

Fig.1 (a) Geological sketch maps of the Himalayan orogenic belt (modified from [19]) and the Cona-Oiga rift (modified from [19,38]) in southern Tibet

图2 典型测点大地电磁测深曲线(033、048、055和061,测点位置见图1b) 图中红色空心圆和蓝色空心菱形分别为观测的xy和yx模式, 红色和蓝色实线则为相应的反演模拟结果。

Fig.2 Typical MT sounding curves for the Cuonadong dome (see Fig.1b for locations of sites 033, 048, 055, 061). Red hollow circles and blue hollow rhombi represent observation modes xy and yx. Red and blue solid lines denote the corresponding inversion results.

图3 研究区域大地电磁相位张量

Fig.3 MT phase tensors in the research area

图4 南北向大地电磁测线三维反演结果 C1、C2和LR1、LR2代表高导或低阻异常,R1和R2代表高阻结构。

Fig.4 N-S vertical cross section 3D inversion result. C1/C2, LR1/LR2, R1/R2 indicate high conductivity and low- and high-resistivity features, respectively.

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青藏高原错那—沃卡裂谷中部电性结构及其动力学意义

Electrical resistivity structure beneath the central Cona-Oiga rift, southern Tibet, and its implications for regional dynamics

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