Mantle source heterogeneity for Hainan basalts revealed by Pb and Sr isotopic compositions in olivine-hosted melt inclusions

Olivine-hosted melt inclusions in basaltic magma provide a "window" to understand the nature of their mantle source. In this study, we first report the trace element, Pb-Sr isotope compositions of olivine-hosted melt inclusions of the Hainan basalts. These data together with the newly analyzed Sr, Nd, Pb and Hf isotope compositions of the Hainan bulk rocks combined with previous data were used to constrain the mantle source of the Hainan basalts. Compared with the bulk rocks, the melt inclusions exhibit more heterogeneous in geochemical compositions, which show that FOZO, EM2 and EM1 are the main mantle components in the Hainan mantle plume and the HIMU components play minor roles. In the process of magma mixing, the EM1 and HIMU components were diluted by other major components and are not recognized from the bulk rocks. The trace element components of the melt inclusions and bulk rocks have a positive anomaly of Nb and Ta, and the characteristics of Sr/Sr* and Eu/Eu* >1 for most of the melt inclusions and all the bulk rocks. Compared with Mantle Array, eHf values of the Hainan basalts are lower relative to a given eNd. These features suggest that recycled oceanic crust plays a significant role in the mantle source. The trace element modellings of the melt inclusions suggest that both pelagic sediments and terrigenous sediments exist in the mantle source and have a contribution to the formation of EM1 and EM2 mantle components. According to the evolution model of the eHfeNd and Pb isotope compositions, we conclude that the recycled oceanic crust and sediments in the Hainan mantle source are relatively young, and might be <1.0 Ga.