Bilateral Heterogeneity in an Upwelling Mantle via Double Subduction of Oceanic Lithosphere

Vietnam is a major field of Cenozoic volcanism in Southeast (SE) Asia. Two contrasting models have been proposed to explain the mantle upwelling and this region; collision Indian Eurasian continents or subduction Pacific Indo-Australian oceanic lithosphere. To place constraints on origin intraplate SE Asia, new geochronological geochemical data for basalts are presented. Based largely Sr-Nd-Pb isotope systematics, it was found that sources from Central Southern chemically distinct forming sharp boundary at 13.5°N. The north show isotopic features similar Enriched Mantle type 2 (EM2) ocean island basalts. Whereas south 1 (EM1) EM1 EM2 display positive Sr anomalies elevated Pb/Ce Th/La ratios, respectively. Such suggest origins through recycling deeply-subducted crustal lithologies. Furthermore, dense lithosphere can induce convecting cell upper mantle. Therefore, we different represent surface expression melting two cells, one driven by plate other plate.