Two Distinct Mantle Sources for High-Ti Basalts in the Emeishan Overfall Basalt Province

In order to probe and reveal the characteristics of mantle sources for high-Ti basalts in the Emeishan overfall basalt province, major elements, trace elements and Sr-Nd-Pb isotopes of the Ertan high-Ti basalts are systemic studied. It’s indicated that they can be divided into group A and group B types. Two types of basalts shows such distinct geochemical characteristics as different concentrations of the trace elements(Rb, K, Ba, Th, Nb, Ta) and trace-element ratios(Ba/Nb, Ba/Th, Zr/Nb, Th/La, Zr/Hf) as well as different 87Sr/86Sr and 208Pb*/206Pb* ratios. The difference between group A and group B is resulted from distinct mantle sources instead of magma evolution processes (fractional crystallizztion, crustal contamination, assimilation-fractional crystallization, and partial melting). Group A, with the feature of EM II, is probably generated by partial melting of metasomatic mantle enriched pyroxenite. Group B, with the mixed features of EM I and C component, is probably derived from partial melting of mantle-derived materials with wide metasomatic spectrum.