Multiple episodes of continental subduction during India/Asia convergence: Insight from seismic tomography and tectonic reconstruction
Multiple episodes of continental subduction during India/Asia convergence: Insight from seismic tomography and tectonic reconstruction
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DOI：
10.1016/j.tecto.2009.10.007
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发表时间：
2010-03
期刊：
影响因子：
2.9
通讯作者：
A. Replumaz;A. Negredo;S. Guillot;A. Villaseñor
中科院分区：
文献类型：
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作者：
A. Replumaz;A. Negredo;S. Guillot;A. Villaseñor
印度/亚洲碰撞带下浅于1100 km的高波速层析成像异常被解释为大陆板片在碰撞过程中俯冲。结合异常的位置与古地理重建的印度，我们约束的时空演化的多个情节的大陆俯冲可能与这些异常。这项研究突出了碰撞带的西部和东部在岩石圈尺度上的不同演化。西部的演化以印度北方边缘的两次俯冲为特征。第一幕发生于40-30 Ma，以板片断裂过程结束，横向延伸范围达1500 km。第二幕发生于18 Ma，俯冲于兴都库什山脉之下。在碰撞带以东，没有发现与印度北方边缘沿着陡峭俯冲有关的异常，我们解释了印度板块东部边界以下、缅甸和安达曼海以下的两个层析异常，这是两个连续的东南向挤压和俯冲的结果。我们认为，这两个挤出部分最初位于沿着印度北方边缘，他们周围的东部结滑动，然后向南沿着印度板块的东部边界。这两个部分都沿着印度东部边界，在东部构造结以南俯冲。我们对这些俯冲和挤压事件期间印度岩石圈的消耗量进行了粗略估计。通过比较这一数量与印度岩石圈的总量在碰撞开始时，我们得出结论，这些过程容纳了大部分的印度/亚洲会聚在碰撞期间。
High wavespeed tomographic anomalies shallower than 1100km beneath the India/Asia collision zone are interpreted as continental slabs subducted during collision. Combining anomaly positions with paleogeographic reconstructions of India, we constrain the spatio-temporal evolution of multiple episodes of continental subduction likely related to these anomalies. This study highlights the different evolution at lithospheric scales of the western and eastern parts of the collision zone. The evolution of the western part is characterized by two episodes of steep subduction of the northern margin of India. The first episode, involving an area with a lateral extent as large as 1500km, started at about 40–30 and ended by a slab break-off process at ∼15Ma, The second episode consists on subduction beneath the Hindu Kush mountains since ∼8Ma. To the east of the collision zone, no anomaly related to steep subduction along the northern edge of India is found. We interpret two tomographic anomalies beneath the eastern border of the Indian plate, beneath Burma and beneath the Andaman Sea, as the result of two successive episodes of southeastward extrusion followed by subduction. We suggest that both extruded portions were initially located along the northern margin of India, and that they slid around the eastern syntaxis, then southward along the eastern boundary of Indian plate. Both portions subducted along the eastern border of India, south of the eastern syntaxis. We provide a rough estimate of the amount of Indian lithosphere consumed during these subduction and extrusion episodes. By comparing this amount with the total amount of Indian lithosphere at the onset of collision, we conclude that these processes accommodated most of the India/Asia convergence during collision.