大陆俯冲板片的持续断离正在终结喜马拉雅造山作用

Fragmentation of continental subduction is ending the Himalayan orogeny

俯冲的大陆岩石圈在大陆碰撞后仍然对地表板块施加拖拽作用,使造山作用得以维持.但是大陆碰撞作用最终为何减弱乃至停止,目前存在多种解释.本文利用覆盖青藏高原的流动地震观测数据,进行地震层析成像研究,在地慢过渡带中识别出多个高地震波速度异常,认为它们是俯冲印度大陆岩石圈断离形成的碎片.俯冲板片会不断沿大陆岩石圈内部的先存薄弱带断离,该过程将持续减小俯冲岩石圈的板片拖曳力,进而导致中新世印度-欧亚板块汇聚速率降低.据此推断,俯冲大陆板片持续断离将导致印欧大陆碰撞和喜马拉雅造山作用最终结束.

After two continents collide,plate convergence and orogenesis are sustained because subducted continental lithosphere continues pulling the surface plate.It remains controversial how,why,and when continental plate convergence and collision slow down and eventually cease.We use an unprecedented data coverage and present a regional-scale seismic tomographic image of the mantle structure beneath the Tibetan Plateau.In the mantle transition zone,we identify multiple high-velocity anomalies and interpret them as detached pieces of the Indian continental slab.Facilitated by internal heterogeneity of the continental lithosphere,piecewise slab detachments could reduce the slab pull force,resulting in the Miocene slowdown of the India-Eurasia convergence and coeval diachronous potassic volcanism in southern Tibet.We propose that slab detachment is a mechanism that eventually will lead to the end of the Indo-Eurasian continental collision and the Himalayan orogeny.