Seismic Imaging of the Crust and Upper Mantle Beneath Chinese Fujian Province and Its Implications for Deep Mineralization

Fujian Province is located in the southeast coastal region of Mainland China and belongs to the Cathaysia Block (CB). Since the Neoproterozoic, this region has experienced multi-stage tectonic activities, which have formed extensive metallogenic belts, such as the Wuyishan and Nanling metallogenic belts. To clarify deep geodynamic processes and deep metallogenic mechanisms, we determine a high-resolution three-dimensional (3-D) velocity model of the crust and upper mantle beneath the Fujian region. Two datasets are collected for the tomographic inversion. One dataset includes 70,330 P-wave and 87,057 S-wave arrival times from 6206 local earthquakes. The other dataset includes 13,714 P-wave relative travel-time residuals from 812 teleseismic events. Our tomography reveals significant low-velocity (low-V) anomalies in the upper mantle down to 500 km depth, which may represent hot ad wet upwelling flows from the mantle transition zone. We also find some low-V and high-Vp/Vs anomalies in the crust beneath major faults and the coastal area of Fujian, which are interpreted as magmatic channels. Combining with previous geological, geochemical, and geophysical results, we consider that the subduction of the Paleo-Pacific Plate in the Late Mesozoic played a crucial role in the formation of ore deposits. We propose a geodynamic model of the deep mineralization in Fujian, in which upwelling mantle flow underplated the crust and intruded into the crust along fault zones. This geodynamic model also has certain significance for the deep mineralization mechanisms of the CB and the Lower Yangtze Block.