This project will continue work on shoshonitic magmas from northernmost Mariana arc to test hypothesis that the enrichments result from the unroofing of metasomatically enriched mantle as a consequence of the northward propagation of the Mariana Trough. The overall objective of this project is to better understand arc magmatism. In particular, the goals are to determine: (1) the compositions of parental lavas in shoshonitic province--by examining representative lavas from selected volcanoes; (2) the spatial distribution of the source of enriched arc magmatism--by analyses of cross-chain seamount lavas; (3) the temporal distribution of shoshonites--by studying volcanic rocks from remnant and frontal arcs. %%% The investigators have obtained a very unusual suite of samples from a volcanic arc. The analyses that will be carried out in this project should address a number of question related to arc magmatism. The most important of these are the composition and early evolution of arc volcanoes. This question is important because of the possible role of arcs in the formation of continental crust.
