Helium isotopes and olivine geochemistry of basalts and mantle xenoliths in Jeju Island, South Korea: Evaluation of role of SCLM on the Cenozoic intraplate volcanism in East Asia

Jeju Island, South Korea, is a Cenozoic intraplate volcano located in East Asia. The basalts display ocean island basalt (OIB)-like trace element patterns and enriched mantle type 2 (EM2) radiogenic isotope compositions, but the source that remains unclear. Here we report new geochemical compositions of xenoliths, including first helium analysis olivine phenocrysts to constrain basalt. Olivines have 3He/4He ratios 3.5 7.3 Ra while olivines xenoliths are 2.9 6.3 Ra. They provide no evidence lower plume overlap range regional subcontinental lithospheric (SCLM) OIBs with low values. Olivine included show variations Mn, Ni, Ca concentrations forsterite (Fo) contents, similar trend for crystallized from pyroxenite-derived melts. Elemental Ca-Fe-Ni-Mg-Mn also indicate pyroxenite contribution. Considering our results, it suggested main SCLM containing pyroxenite. In addition, tomography image shows low-velocity zone extending asthenosphere beneath central Island. This implies localized asthenospheric upwelling caused by edge-driven convection, high-velocity zones exist around indicating thick cratonic lithosphere. Therefore, propose interaction between component rising mechanism generate basaltic magmas volcanism Asia,