Seismic anisotropy beneath the southern Ordos block and the Qinling-Dabie orogen, China: Eastward Tibetan asthenospheric flow around the southern Ordos
Seismic anisotropy beneath the southern Ordos block and the Qinling-Dabie orogen, China: Eastward Tibetan asthenospheric flow around the southern Ordos
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DOI：
10.1016/j.epsl.2016.08.026
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发表时间：
2016-12
影响因子：
5.3
通讯作者：
Yong Yu;Yongshun John Chen
中科院分区：
文献类型：
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作者：
Yong Yu;Yongshun John Chen
利用部署在鄂尔多斯地块南部和秦岭-大别造山带的180个临时地震台阵（SOSArray）记录的地震资料，进行了SKS波分裂分析，以估计上地幔的地震各向异性。最重要的发现是，大延迟时间与西北-东南快速偏振方向在西藏东北部是连续的跨越边界到鄂尔多斯块体的西南部，在那里的SKS波分裂的结果是显着不同的鄂尔多斯块体的其余部分。基于SKS波分裂结果，结合前人的研究成果，提出了一个青藏高原上地幔向东挤压的软流层流动模型。该模型由鄂尔多斯地块西南角和东南角的两个角流和沿着渭河地堑和秦岭-大别造山带的西藏上地幔向东的逃逸流组成。最后，围绕鄂尔多斯地块西南角的顺时针旋转的软流层流动目前已横向延伸到鄂尔多斯地块内部，这表明鄂尔多斯地块西南部厚冷岩石圈根部目前正在被深部的热软流层所取代，即我们观察到侧向热软流层流动正在对地幔岩石圈进行热侵蚀的过程。
SKS wave splitting analysis is performed to estimate the seismic anisotropy in the upper mantle using teleseismic data recorded by a temporary seismic array of 180 stations called SOSArray deployed in the southern Ordos block and the Qinling-Dabie orogen. The most important finding is that large delay times with NW-SE fast polarization directions in the northeastern Tibet are continuous across the boundary into the southwestern part of the Ordos block, where the SKS wave splitting results are significantly different from those in the rest of the Ordos block. Based on our SKS wave splitting results in addition to the results from previous studies, we propose an asthenospheric flow model for the eastward extrusion of the Tibetan upper mantle. The model consists of two corner flows around the southwestern corner and the southeastern corner of the Ordos block and the eastward flow along the Weihe graben and the Qinling-Dabie orogen for the escaping Tibetan upper mantle. Finally, the clockwise turning flow of the asthenosphere around the southwestern corner of Ordos block has currently extended laterally into the interior of the Ordos block, suggesting that the thick cold lithospheric root of the southwestern Ordos block there is currently being replaced with hot Tibetan asthenosphere at depths, that is, we observed an on-going process of thermal erosion of a cratonic lithosphere by lateral hot asthenospheric flow.