Constraints on the origin of alkaline and calc-alkaline magmas from the Tuxtla Volcanic Field, Veracruz, Mexico

摘要: Lavas erupted in the Tuxtla Volcanic Field (TVF) over last 7 Ma include primitive basanites and alkali basalts, mildly alkaline Hy-normative mugearites benmoreites, calc-alkaline basalts basaltic andesites. The lavas are silica-undersaturated, with high concentrations of both incompatible compatible trace elements, variable La/Yb constant Yb at 6 to 8 times chondritic, low Sr O Pb Nd isotopic ratios. magmas originated by increasing degrees melting pressure decreasing from greater than 30 kbar 20 kbar, garnet stability field. Another group hawaiites has lower Ni Cr higher Fe/Mg ratios, was derived crystal fractionation pressures several kbar. Incompatible elements these silica undersaturated show depletion field strength (HFSE) relative large ion lithophile similar subduction-related basalts. Ba/Nb ratios nearly thus HFSE cannot be result a residual HFSE-bearing phase source, but could generation source contaminated fluids or melts subducted lithosphere. silica-saturated andesites, were only between 3.3 1.0 Ma. These have element generally silica-undersaturated lavas, not been magmas. Magmas parental Melting may promoted an influx fluid Trace Sr, Nd, data suggest that three components involved TVF magmas: mantle, lithosphere, continental crust. those back-arc region MVB Japan, characteristics southern Andean volcanic arc. degree reach surface along due extensional stress allows their passage surface.