Crustal structure of Hubei Province of China from teleseismic receiver functions: Evidence for lower crust delamination
Crustal structure of Hubei Province of China from teleseismic receiver functions: Evidence for lower crust delamination
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来自远震接收函数的中国湖北省地壳结构：下地壳拆沉的证据
DOI：
10.1016/j.tecto.2014.09.001
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发表时间：
2014-12
期刊：
影响因子：
2.9
通讯作者：
Yixian Xu
中科院分区：
文献类型：
--
作者：
Rong Huang;Lupei Zhu;Yixian Xu
鄂西地处中国兴安岭-太行山-武陵山3000公里南北走向阶梯的南端，西部为高原和山脉，东部为低海拔平原。本文计算了湖北省32个永久宽频带地震台站的地震P接收函数，并利用H-κ方法估算了它们下面的地壳厚度。我们还获得了详细的地壳结构图像沿着三个剖面使用CCP叠加方法。结果表明，在研究区域，东西地壳厚度在不到20公里的水平距离内从30-35公里增加到45-50公里，很可能是以阶梯方式增加的。鄂东南翔盆地和江汉盆地下的薄地壳延伸到鄂西武陵隆起和黄陵地块内部。莫霍面与地表地形之间缺乏镜像对称性，表明鄂西部分山脉要么受到非Airy型均衡模型的补偿，要么不处于均衡平衡状态，而是受到岩石圈强度的支持。下地壳/上地幔的脆性或局部韧性变形与上地壳的脆性变形是不耦合的。CCP图像还揭示了武当山下明显的双莫霍面。这可能是由于中生代晚期中国东部原始地幔岩石圈被温暖的水化地幔物质所取代后，下地壳部分榴辉岩化的结果。莫霍面台阶是榴辉岩化下地壳的一部分在重力作用下变得不稳定并沉入地幔而形成的。
Western Hubei Province is at the southern end of the 3000-km-long north-south-oriented Xing'anling–Taihangshan–Wulingshan topographic step in China, which separates high-rising plateaus and mountain ranges in the west from low-elevation plains in the east. We calculated teleseismicPreceiver functions of 32 permanent broadband seismic stations in Hubei Province and estimated crustal thicknesses under them using theH-κmethod. We also obtained detailed crustal structural images along three profiles using the CCP stacking method. The results show an east-west crustal thickness increase in the study area from 30–35 km to 45–50 km in less than 20 km of horizontal distance, most likely in a step-wise fashion. The thin crust beneath the Nanxiang and Jianghan basins in eastern Hubei extends into the interior of the Wuling Uplift and the Huangling Massif in western Hubei. The lack of mirror symmetry between the Moho and surface topography suggests that part of the mountain ranges in western Hubei is either compensated by non-Airy-type isostasy models or is not in isostatic equilibrium but supported by the strength of the lithosphere. The brittle or localized ductile deformation in the lower crust/uppermost mantle as indicated by the abrupt Moho steps seems to be decoupled with brittle deformation in the upper crust. The CCP images also reveal an apparent double Moho beneath the Wudang Mts. which is interpreted to be due to a partially eclogitized lower crust after the original cratonic mantle lithosphere was replaced by warm and hydrated mantle materials in eastern China in the Late Mesozoic. The Moho steps were formed when a segment of eclogitized lower crust became gravitationally unstable and foundered into the mantle.
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