Crustal and uppermost mantle velocity structure beneath the Mid-lower Yangtze metallogenic belt and its adjacent regions from joint inversion of receiver function and surface wave

    The Middle-Lower Yangtze River Metallogenic Belt, known as the eastern “industrial corridor”, is an important polymetallic mineral resource base in eastern China. It has a significant influence on economic development in eastern China and its deep dynamic process has been the focus of debate for deposit scientists.

    Why does such a narrow zone contain so rich mineral resources? What is the deep dynamics? Many scholars put forward different explanations, such as “ continental extension mode ”, “ subduction mode ” and “ reverse L-shaped collision mode ”. Although these views reach a consensus in some aspects, they are different essentially. Thus, the deep structure information has become the key to distinguish such different views.

    In this study, we conduct teleseismic P wave receiver function, ambient noise tomography and teleseismic two-plane-wave tomography to probe the crustal and uppermost mantle structures in the Middle-Lower Yangtze River region. The data include (1) continuous seismic data from June 2012 to July 2013 recorded from Chinese provincial networks; (2) seismic event data from 2010 to 2011 recorded from Chinese provincial networks; (3) continuous seismic data from November 2009 to August 2010 deployed by Chinese Academy of Geological Sciences; (4) continuous seismic data from June 2012 to July 2013, from August 2014 to June 2015 and from July 2015 to November 2015 deployed by China University of Geosciences(Beijing). First, we apply receiver function to get the Moho depth below 191 seismic stations and the results are in good accordance with previous researches. We then conduct joint inversion of receiver function and surface wave dispersion to generate shear wave velocity structures below 191 seismic stations. The result shows that in the upper crust, the basin regions, including the JiangHan, HeHuai, SuBei, HeFei and NanYang basin, are all featured with low velocities, and the mountain regions with high velocities. In the northeastern of the Middle-Lower Yangtze River Metallogenic Belt, the result shows ore districts are clearly characterized with the strongest low velocity anomaly in the uppermost mantle at ~70km depth. The depth extent of the low-velocity zone becomes shallower and the amplitude of low velocity anomaly becomes larger from the northeast to southwest.