The sources of island arcs as indicated by Nd and Sr isotopic studies

摘要: Island arc lavas from New Britain and the Marianas have ^(143)Nd/^(144)Nd similar to other oceanic basalts distinctly different continental flood thus appear be derived a high Sm/Nd, light-REE-depleted reservoir. Consideration of both Nd Sr isotopes suggests seawater involvement in generation some island indicates that they may altered subducted crust. Other show no evidence mantle reservoirs with affinities sources ocean basalts. Andesite rhyolite an Andean volcano reflect assimilation old basaltic ultrapotassic rocks indicate mafic magmas regions low-Sm/Nd or are heavily contaminated crustal material. Fish debris floor provides estimate light-REE marine environment mainly continents. Basalts erupted above sea level areas isotopically distinct those on floor, suggesting relationship between parental hydrostatic head.