Electrical resistivity structure of the Xiaojiang fault system (SW China) and its tectonic implications
Electrical resistivity structure of the Xiaojiang fault system (SW China) and its tectonic implications
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小江走滑断裂系电阻率结构及其构造意义
DOI：
10.1016/j.jseaes.2019.01.031
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发表时间：
2019
影响因子：
3
通讯作者：
Ilya Lozovsky
中科院分区：
文献类型：
--
作者：
Xin Li;Denghai Bai;Xiaobing Ma;Yun Chen;Ivan M. Varentsov;Guoqiang Xue;Shuai Xue;Ilya Lozovsky
大规模走滑断层在印度-欧亚大陆汇聚过程中起着重要的作用，但沿断层沿着的地表位移与深部变形之间的关系仍不确定。为了解决这一问题，我们在西南地区构造活动最活跃的小江断裂系上，沿两条剖面进行了沿着新的大地电磁成像。虽然两条剖面在细节上有所不同，但总体上显示出相似的地壳电阻率结构。上地壳通常是电阻性的，但被几个狭窄的、接近垂直的导体所分隔，这些导体与XJFS的表面痕迹大致一致。这些断裂带导体（FZC）被解释为代表沿XJFS由走滑断层/剪切沿着形成的断层损伤带，并填充有深源岩浆和/或变质流体。下地壳的广泛特征是导电性增强，可能与高温下的部分熔融有关。这些观测结果与该地区的其他地球物理测量结果一致，并有利于沿着XJFS发展韧性流动，尽管流动模式比以前提出的更复杂。根据这些观测结果，我们认为沿着XJFS的活动变形在脆性上地壳中可以用沿着流体弱化断层的走滑运动和部分熔融下地壳中剪切增强的韧性流动来描述。这两种机制并非相互排斥，而是可以相互补充的。
It is widely accepted that large-scale strike-slip faults play an important role in.accommodating the India‐ Eurasia convergence, but the relationships between surface.displacements and deep deformation along the faults remain largely uncertain. To.address this issue, new magnetotelluric (MT) images were obtained along two profiles.across the Xiaojiang fault system (XJFS), one of the most tectonically active areas in.southwest China. Although different in details, these two profiles show similar overall.crustal resistivity structures. The upper crust is generally resistive but separated by.several narrow, subvertical conductors that broadly coincide with the surface traces of.the XJFS. These fault zone conductors (FZCs) are interpreted to represent fault.damage zones that formed by strike-slip faulting/shearing along the XJFS and filled.with deeply-sourced magmatic and/or metamorphic fluids. The lower crust is broadly.characterized by enhanced conductivity and likely associated with partial melting at.high temperatures. These observations are consistent with other geophysical.measurements in this area and in favor of the development of ductile flow along the.XJFS, although the pattern of flow is more complex than previously suggested. Based.on these observations, we propose that active deformation along the XJFS can be.better described, in the brittle upper crust, by strike-slip motion along the.fluid-weakened faults, and by shear-enhanced ductile flow in the partially molten.lower crust. These two mechanisms are not mutually exclusive but rather may be.complementary to each other.