Finite frequency tomography in southeastern Tibet: Evidence for the causal relationship between mantle lithosphere delamination and the north–south trending rifts
Finite frequency tomography in southeastern Tibet: Evidence for the causal relationship between mantle lithosphere delamination and the north–south trending rifts
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DOI：
10.1029/2008jb005615
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发表时间：
2008-10
影响因子：
--
通讯作者：
Yong Ren;Yang Shen
中科院分区：
文献类型：
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作者：
Yong Ren;Yang Shen
[1]虽然已经提出了几种机制来解释青藏高原的演化，但对深部岩石圈过程的观测限制很少，以前的地震研究大多是沿着垂直于印度和欧亚板块碰撞前沿的剖面沿着进行的。在这项研究中，我们显示层析成像证据的地幔岩石圈拆沉下西藏东南部，整个地幔岩石圈剥离的过程中，从地壳沿着莫霍面，因此是一种机制，快速减薄的岩石圈。我们的P波和S波速度模型表明，在西藏东南部的南北向裂谷带下，地壳和上地幔中存在一个低速异常，深度可达300 km。这个低速异常位于延伸到上地幔过渡带的板状、大倾角、高速异常之上。这种高速异常的VP/VS比表明，温度变化不是唯一的原因异常和高度熔融亏损地幔是必需的。这些观测结果表明，地幔岩石圈拆沉作用与藏东南南北向裂谷的形成有因果关系。
[1] While several mechanisms have been suggested to explain the evolution of the Tibetan Plateau, observational constraints on the deep lithospheric processes have been sparse, and previous seismic studies were mostly along profiles perpendicular to the collision front of the Indian and Eurasian plates. In this study, we show tomographic evidence for the delamination of the mantle lithosphere beneath southeastern Tibet, a process in which the entire mantle lithosphere peels away from the crust along the Moho and thus is a mechanism for rapid thinning of the lithosphere. Our P and S wave velocity models show the presence of a low-velocity anomaly in the crust and upper mantle down to ∼300 km depth beneath a north–south trending rift zone in southeastern Tibet. This low-velocity anomaly is situated above a tabular, high-dipping-angle, high-velocity anomaly that extends into the upper mantle transition zone. The VP/VS ratio of this high-velocity anomaly suggests that temperature variations are not the only cause of the anomaly and a highly melt-depleted mantle is required. These observations suggest a causal relationship between the delamination of mantle lithosphere and the formation of the north–south trending rift in southeastern Tibet.