Mantle transition zone structure beneath the Central Asian Orogenic Belt  

作　　者：Jing HE Qingju WU 

机构地区：[1]Key Laboratory of Crustal Dynamics,Institute of Crustal Dynamics,China Earthquake Administration,Beijing 100085,China [2]Key Laboratory of Seismic Observation and Geophysical Imaging,Institute of Geophysics,China Earthquake Administration,Beijing 100081,China

出　　处：《Science China Earth Sciences》2020年第4期548-560,共13页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grants Nos.41704054 and 41674094);National Key R&D Plan of China(Grants Nos.2017YFC0601406 and 2017YFC0601505);the International Cooperation Project of the Ministry of Science and Technology of China(Grants No.2011DFB20210);the Central Public-interest Scientific Institution Basal Research Fund from the Institute of Crustal Dynamics,China Earthquake Administration(Grants No.ZDJ2017-04)。

摘　　要：Over the past decades, there have been hot debates in the geodynamic community regarding to the deep evolution mechanisms of Cenozoic volcanism in the Central Asian Orogenic Belt(CAOB). Of all the constraints available, high resolution structure of upper mantle discontinuities, especially the discontinuities at depths of 410 km(D410) and 660 km(D660), is of the most important, which may provide reliable clues on the magma channel as well as its evolution. In this work, we adopt the common conversion point stacking technique with teleseismic radial P-wave receiver functions to examine the D410 and D660 discontinuities. The primary results exhibit that the major characteristics of the mantle transition zone(MTZ) obtained by different velocity models are largely consistent. Obviously elevated D410 and slightly depressed D660 are observed beneath the Hannuoba Volcano, suggesting possible delamination of the local lithosphere deposited at the D410. This process may induce upwelling of the asthenospheric materials filling the space left by the delaminated lithosphere, and subsequently trigger volcanic eruptions. Strong depressions are observed at both D410 and D660 depths beneath west of the Dariganga Volcano, and the depression of D660 is more pronounced. It leads to the apparently thickened MTZ, indicating the presence of cold material at the D660. This cold material is speculated as a stagnant slab from the subducted Pacific Plate or the remains of a detached island arc system from the collision and formation of the CAOB. Slightly thinner MTZ is found beneath the Hentey Mountains and the Middle Gobi Volcano. Apparently, this thinner MTZ is not significant enough to support the existence of high thermal anomalies,which may rule out the possibility of large-scale hot material upwelling from either the local MTZ or even the lower mantle.

关 键 词：Central ASIAN OROGENIC BELT CENOZOIC VOLCANO MANTLE transition zone Receiver function 

分 类 号：P548[天文地球—构造地质学]