Coexisting late Cenozoic potassic and sodic OIB-like basalts in NE China: Role of Recycled Oceanic Components in Intraplate Magmatism and Mantle Heterogeneity

This study presents an integrated geochemical study of the Wudalianchi-Erkeshan potassic basalts (WEPBs) and the Halaha sodic basalts (HSBs) of NE China, and uses these data to further understanding of the petrogenetic relationships between the coeval potassic and sodic OIB-like basalts in this region. The WEPBs contain high concentrations of K₂O, have arc-like trace element compositions, and enriched Sr-Nd-Hf isotopic compositions with unradiogenic ²⁰⁶Pb/²⁰⁴Pb values (16.77-16.90). In contrast, the HSBs contain high concentrations of Na₂O, have OIB-like trace element compositions, and depleted Sr-Nd-Hf isotopic compositions with radiogenic ²⁰⁶Pb/²⁰⁴Pb values (18.27-18.40). These data suggest that the WEPBs and HSBs are derived from mixed depleted mid-ocean ridge basalt mantle (DMM) and enriched mantle source end-members, where the enriched end-members are ancient sediment for the WEPBs and Pacific oceanic crust for the HSBs. Recent seismic tomographic images of the mantle beneath NE China suggest the presence of a subducted slab in the mantle transition zone (MTZ). Combining these geophysical and geochemical data indicates that these two enriched end-members are most likely located in the MTZ. We propose that partial melting of upwelling asthenospheric mantle comprising the ambient DMM and recycled materials shifting from the ancient sediment to that of Pacific oceanic crust could produce the coeval potassic and sodic OIB-like basalts in NE China. The proposed mantle sources for the WEPBs and HSBs may indicate that the upper mantle beneath NE China was highly heterogeneous