The later high alkaline, TiO2, and P2O5, and low SiO2 group, produced by central-type volcanic eruptions consisting of alkaline olivine and olivine basalts, overlies the early eruptive group. Crustal contamination may be expressed by the positive correlation between Ba/Nb and SiO2, which are higher in early eruptive basalts, possibly reflecting the involvement of crustal material, either in the source region or interaction of the melt on the way to the surface. | Vietnam Journal of Earth Sciences, 39(3), 270-288, DOI: Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) Geochemistry of late Miocene-Pleistocene basalts in the Phu Quy island area (East Vietnam Sea): Implication for mantle source feature and melt generation Le Duc Anh1,4*, Nguyen Hoang2, Renat B. Shakirov3, Tran Thi Huong2 1 Institute of Marine Geology and Geophysics, VAST, Hanoi, Vietnam Institute of Geological Sciences, VAST, Hanoi, Vietnam 3 . Il’ichev Pacific Oceanological Institute (POI), Far Eastern Branch of Russian Academy of Sciences, Vladivostok, Russia 4 Graduate University of Science and Technology, VAST, Hanoi, Vietnam 2 Received 21April 2016. Accepted 19 July 2017 ABSTRACT The chemical compositions of late Miocene - Pleistocene basalts in Phu Quy island defines two major geochemical groups that reflect the formation and development of the island. The early low alkaline, TiO2 and P2O5, and high SiO2 group, comprising olivine and tholeiitic basalts, forms the base of the island. The later high alkaline, TiO2, and P2O5, and low SiO2 group, produced by central-type volcanic eruptions consisting of alkaline olivine and olivine basalts, overlies the early eruptive group. Crustal contamination may be expressed by the positive correlation between Ba/Nb and SiO2, which are higher in early eruptive basalts, possibly reflecting the involvement of crustal material, either in the source region or interaction of the melt on the way to the surface. However, negative relationship between Ba and SiO2, and positive correlation between Nb/Y and Zr/Y observed for two basaltic series may reflect the effect of melting pressures and degrees of partial melting. Methods of calculating the primitive basaltic melts based on the principle of olivine incremental additions to the basalt until the composition is equilibrated with the residual olivine at Fo89-90 may be .
