Marginal Basin Basalts: Isotopic Studies Bearing on Magma Genesis and Source Evolution

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In this award, the investigators would carry out a Nd, Sr, and Pb isotopic study of samples collected by ALVIN and dredged by other ships from the spreading axes in the Mariana Trough and the Lau Basin, both very important back arc basins in the western Pacific. These two sample sets are extremely valuable since they were collected at a very fine scale and at a great cost and considerable geophysical measurements were made at the sample sites. Besides, visual observational data exist with the ALVIN samples. Major element and trace element analyses are being done on these samples, as part of other NSF supported projects. The combined elemental and isotopic data set will help in understanding various magmatic processes in marginal basins, such as, nature and scale of source variability of magma, partial melting of rocks and mixing of magma, segmentation of the spreading ridge, etc. Also the study will indicate the extent of inhomogeneity in the mantle under these back arc basins. Back arc basins have been somewhat neglected by the community but they hold important clues for the overall understanding of the plate tectonic processes. //