Tomography Imaging of Near-Surface Velocity Structure Experiment and Its Application in the Ore Concentrate Area of the Lower and Middle Yangtze River

Four cross-deep seismic reflection profiles at the Luzhong iron-polymetallic deposits in the Lower and Middle Yangtze Reaches were performed by the Chinese Academy of Geological Sicences(CAGS) before the Chinese New Year of 2007.The near-surface(~1000m) velocity model for the Luzhong volcanoic rock basin was established for the first time using the first break-arrivals of these long-offset shot records and tomography method.The various fine imaging results show the height and undulated shape of blind syenite,discovering there is corresponding relation between positions of top interface and change of the syenite,and distribution of ore bodies,with Luohe,Xiaoling,Longqiao,and Mabianshan iron deposits all situating at the salient sections in high-speed top interface.The Luohe fault presents an obvious horizontal velocity transformation interface in line lz06-1 and line lz06-3.The research results indicate that the long-offset first arrival travel-time tomography method can provide abundant crustal shallow structure information(0~1000m) for the study of prospect for the deep concealed deposits and the potential prospecting direction for iron-polymetallic deposits in the Luzhong area,Anhui province.