Coexisting Late Cenozoic Potassic and Sodic Basalts in NE China: Role of Recycled Oceanic Components in Intraplate Magmatism and Mantle Heterogeneity

Abstract

This study presents an integrated geochemical study of the Wudalianchi-Erkeshan potassic basalts and Halaha sodic basalts of NE China, and uses these data to further our understanding of the petrogenetic relationships between the coeval potassic and sodic basalts in this region. The potassic basalts with 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 sodic basalts with 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 potassic and sodic basalts were 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 potassic basalts and Pacific oceanic crust for the sodic basalts. The combined geophysical and geochemical data indicate that these two enriched end-members are located in the mantle transition zone. We propose that partial melting of upwelling asthenospheric mantle comprising ambient DMM and recycled materials shifting from the ancient sediment to the Pacific oceanic crust could have produced the coeval potassic and sodic basalts in NE China. The proposed mantle sources for the potassic and sodic basalts indicate that the upper mantle beneath NE China was highly heterogeneous during late Cenozoic.