Basalts from Zhangzhongjing Seamount, South China Sea and Their Linkage to a Plume-Modified Mantle Reservoir

Basement rock samples were collected from the Zhangzhongjing intraplate seamount in the Southeast sub-basin of the South China Sea (SCS). These alkaline basalts are enriched in light rare earth elements (LREE). The Sr-Nd-Pb-Hf isotopic compositions of the basalts suggest that their parental melts originated from an Indian Ocean-type mantle source that was mixed with enriched EMII components. Semi-quantitative geochemical modeling indicates that the parental melts of the studied basalts formed through heterogeneous melting starts at depth in the garnet facies and, during its uprising, continue at shallow levels in the spinel facies. Furthermore, qualitative isotopic modeling indicates that the inferred EMII components were most likely derived from the nearby Hainan plume. This study provides invaluable insights into the extent to which the Hainan diapir influenced the geochemical and isotopic composition of the upper mantle beneath the East Sub-basin of the SCS.