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首页> 外文期刊>Journal of geophysical research. Solid earth: JGR >Crustal structures across the western Weihe Graben, North China: Implications for extrusion tectonics at the northeast margin of Tibetan Plateau
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Crustal structures across the western Weihe Graben, North China: Implications for extrusion tectonics at the northeast margin of Tibetan Plateau

机译：华北西部渭河格拉本地区的地壳结构：对青藏高原东北缘挤压构造的启示

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摘要

The stable Ordos Plateau, extensional Weihe Graben, and Qinling orogenic belt are located at the northeast margin of the Tibetan Plateau. They have been thought to play different roles in the eastward expanding of the Tibetan Plateau. Peking University deployed a linear seismic array across the western end of the Weihe Graben to investigate the crustal structures of the tectonic provinces of this structure. Receiver function analyses revealed low-to-moderate Poisson's ratios and anticorrelations between Poisson's ratios and topography beneath the Qinling Orogen. These features may indicate a tectonic thickening of the felsic upper crust by folding and thrusting within the Qinling Orogen. We observed a strong horizontal negative signal at the midcrust beneath the Ordos Plateau which may indicate a low-velocity zone. This observation would suggest the stable cratonic Ordos Plateau had been modified due to the compression between the Tibetan Plateau and the Ordos Plateau. We also observed an abrupt 4km Moho offset across the Weihe Fault, changing from similar to 44km beneath the Ordos Plateau to similar to 40km beneath the Qinling Orogen. We conclude that the Weihe Fault is a lithosphere-scale fault/shear zone, which extends into the upper mantle beneath the Weihe Graben. It acts as the major boundary separating the stable Ordos Plateau and the active Qinling Orogen.
机译：稳定的鄂尔多斯高原，延伸的渭河格拉本和秦岭造山带位于青藏高原的东北边缘。人们认为它们在青藏高原的东扩中起着不同的作用。北京大学在Weihe Graben的西端部署了线性地震阵列，以研究这种构造省份的地壳结构。接收器功能分析显示，秦岭造山带下方的泊松比为中低至中等，泊松比与地形之间的反相关。这些特征可能表明在秦岭造山带中通过褶皱和逆冲作用，使长英质上地壳构造变厚。我们在鄂尔多斯高原下面的中地壳上观察到一个强烈的水平负信号，这可能表明是一个低速带。这一观察结果表明，由于青藏高原和鄂尔多斯高原之间的压缩作用，稳定的克拉通鄂尔多斯高原已被修改。我们还观察到整个渭河断裂带突然出现了4 km的莫霍偏移，从鄂尔多斯高原以下的大约44 km变为秦岭造山带以下的大约40 km。我们得出的结论是，渭河断裂带是一个岩石圈规模的断层/剪切带，延伸到渭河格拉本下面的上地幔。它是分隔稳定的鄂尔多斯高原和活跃的秦岭造山带的主要边界。

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