ABSTRACT
Some elemental and U-Pb. Sm-Nd and Rb-Sr isotopic results are presented for Palaeozoic and Mesozoic bimodal volcanic suites from Hainan Island. S.China and low reaches of Yangtze River, E.China, respectively. The two bimodal suites were continental rifting products at various periods. Tholeiites of Hainan Isl. have characteristics of typical depleted mantle basalts; but the mafic volcanics from Lower Yangtze region are relatively enriched in LIL and LREE, owing to marked contamination of Proterozoic crust rocks. Felsic volcanics of the two bimodal suites developed from anatectic melting of continental crust rocks. So that, twin magma source model for the bimodal volcanic suites are suggested in the study.
