西昆仑阿什库勒火山的起源:来自地震层析成像的证据

Origin of the Ashi volcano,Western Kunlun Mountains:Evidence from seismic tomography

利用中国地震台网、ISC地震台网以及布设在青藏高原临时台网记录到的地震到时数据,研究了青藏高原,阿什库勒火山群及其周边的P波速度结构。高分辨率的成像结果显示印度板块呈明显的高速异常俯冲到了青藏高原之下,该高速异常的前端到达青藏西部的北缘、青藏中部的班公湖—怒江缝合带以及青藏东部的金沙江断裂带,表明印度板块在青藏高原内部南北向的俯冲距离并不相同。成像结果显示印度板块已经俯冲到了西昆仑山阿什火山附近,其北的塔里木地块呈明显的高速异常。阿什火山的正下方存在明显低速异常及岩浆上涌的通道。在阿什火山下的地幔转换带存在明显的低速异常体,我们认为软流圈物质的减压熔融以及岩浆上涌是阿什库勒火山群形成的根本原因。

We carried out a high-resolution P-wave velocity tomography of the Tibetan Plateau,Ashikule volcano clusters and surrounding areas by using arrival-time data obtained from the nationwide seismic network,International Seismological Centre（ISC）as well as temporary seismic arrays deployed on the Tibetan Plateau.Our high-resolution tomography shows that the Indian plate is revealed as a high-velocity anomaly and it is subducted beneath the Tibetan Plateau.The northern limit of the high-velocity anomaly has reached to the northern boundary of western Tibet,to the Bangong-Nujiang suture under central Tibet and around the Jinsha River suture under eastern Tibet,suggesting the different north-south distance that the Indian plate subducted northward.Our tomographic results suggest that the Indian plate has subducted to western Kunlun,around the Ashi volcano.To the north,the Tarim block shows a prominent high velocity anomaly.We found obvious low velocity anomalies and magma upwelling path beneath the Ashi volcano.In the mantle transition zone,there is a low velocity zone beneath the Ashi volcano.The Ashikule volcano clusters could be formed by the decompression melting of asthenospheric materials and magma upwelling.