Sr-Nd-Pb isotopic compositions of submarine alkali basalts recovered from the South Korea Plateau, East Sea

Abstract

We present geochemical and isotope results (Sr, Nd, Pb) on submarine basalts dredged from the southeastern margin of the South Korea Plateau. The present data are the first geochemical result obtained on submarine basaltic lavas recovered from the Korea Plateau, which is considered to be one of rifted remnants of continent in the East Sea (Sea of Japan) and partially segmented from the Korean Peninsula. The South Korea Plateau basalts (SKPB) show alkali affinities and are characterized by Ocean Island Basalts (OIB)-like trace element compositions relatively enriched in Ba, Nb and Pb. They display relatively flatter [(Ce/Yb)n = 4.49 similar to 5.46] and less fractionated HREE [(Dy/Yb)n = 1.11 similar to 1.29] patterns compared to average OIB, implying that the SKPB were derived from a relatively shallower mantle depth with a larger degree of partial melting. The Sr, Nd and Pb isotopic compositions of the SKPB display a range of values for (87)Sr/(86)Sr (0.70378 to 0.70409), (143)Nd/(144)Nd (0.512846 to 0.512860) and (206)Pb/(204)Pb (17.88-18.44). They show a considerably high range of (207)Pb/(204)Pb (15.48-15.62) and (208)Pb/(204)Pb (37.86-38.46) values, indicating the involvement of a DUPAL-like MORB source. According to our two-stage magma mixing model, the isotopic compositions of SKPB can be explained by magma source mixing by the addition of an EMII-like mantle component (up to 2%) to the DUPAL-like MORB source embedded with endogenous EMI-like material (about 2%).