Lithospheric rheological heterogeneity across an intraplate rift basin (Linfen Basin, North China) constrained from magnetotelluric data: Implications for seismicity and rift evolution
Lithospheric rheological heterogeneity across an intraplate rift basin (Linfen Basin, North China) constrained from magnetotelluric data: Implications for seismicity and rift evolution
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DOI：
10.1016/j.tecto.2017.07.014
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发表时间：
2017-10
期刊：
影响因子：
2.9
通讯作者：
Yaotian Yin;Sheng Jin;Wenbo Wei;G. Ye;J. Jing;Letian Zhang;Hao Dong;C. Xie;Hongda Liang
中科院分区：
文献类型：
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作者：
Yaotian Yin;Sheng Jin;Wenbo Wei;G. Ye;J. Jing;Letian Zhang;Hao Dong;C. Xie;Hongda Liang
本文以山西裂谷新生代活动最活跃的吕梁盆地为例，介绍了如何利用大地电磁资料反演板内构造带岩石圈流变非均匀性。电阻率模型结合流变数值模拟结果表明，电阻率与流变强度之间具有良好的相关性，表明电导率的提高也可能是粘度降低的原因。吕梁盆地地壳在电阻率和流变学方面均表现出整体的层状特征。地壳最上层导电层以摩擦滑动型脆性破裂为主。高阻中地壳是被深断裂包裹的高粘变质基底。塑性下地壳表现出明显的高导特征。地震活动似乎是由地壳流变学的不均匀性。微地震主要分布在脆-韧性过渡带，如高-低电阻率界面或高孔隙压力断裂带，而两个巨大的破坏性历史地震的震中发生在高电阻率，因此高强度块体附近推断的流变界面。岩石圈尺度的横向流变学沿剖面沿着的不均匀性也可以说明。鄂尔多斯地块、吕梁山和太行山下的地壳和上地幔具有高流变强度，表现为大规模的高阻带，而吕梁盆地东缘则存在明显的高导岩石圈规模的软弱带。根据以往的地球动力学模拟工作，我们认为这种横向流变学不均匀性可能在印度-欧亚碰撞远场效应下为山西裂谷的形成演化、区域岩石圈变形和地震活动提供了重要的驱动力。
We take the Linfen Basin, which is the most active segment of the Cenozoic intraplate Shanxi Rift, as an example, showing how to use magnetotelluric data to constrain lithospheric rheological heterogeneities of intraplate tectonic zones. Electrical resistivity models, combined with previous rheological numerical simulation, show a good correlation between resistivity and rheological strength, indicating the mechanisms of enhanced conductivity could also be reasons of reduced viscosity. The crust beneath the Linfen Basin shows overall stratified features in both electrical resistivity and rheology. The uppermost crustal conductive layer is dominated by friction sliding-type brittle fracturing. The high-resistivity mid-crust is inferred to be high-viscosity metamorphic basement being intersected by deep fault. The plastic lower crust show significantly high-conductivity feature. Seismicity appears to be controlled by crustal rheological heterogeneity. Micro-earthquakes mainly distribute at the brittle-ductile transition zones as indicated by high- to low-resistivity interfaces or the high pore pressure fault zones while the epicenters of two giant destructive historical earthquakes occur within the high-resistivity and therefore high-strength blocks near the inferred rheological interfaces. The lithosphere-scale lateral rheological heterogeneity along the profile can also be illustrated. The crust and upper mantle beneath the Ordos Block, Lüliang Mountains and Taihang Mountains are of high rheological strength as indicated by large-scale high-resistivity zones while a significant high-conductivity, lithosphere-scale weak zone exists beneath the eastern margin of the Linfen Basin. According to previous geodynamic modeling works, we suggest that this kind of lateral rheological heterogeneity may play an essential role for providing driving force for the formation and evolution of the Shanxi Rift, regional lithospheric deformation and earthquake activities under the far-field effects of the India-Eurasian Collision.