Genesis and Evolution of Shoshonitic Volcanism in the Northern Mariana and Southern Volcano Arcs

该项目将继续研究马里亚纳弧最北端的钾玄质岩浆，以检验以下假设：富集是由于马里亚纳海槽向北扩展而使交代富集的地幔去顶所致。该项目的总体目标是更好地了解弧岩浆作用。具体而言，其目标是确定：⑴钾玄岩区母熔岩的成分-通过检查选定火山的代表性熔岩; ⑵富集弧岩浆活动来源的空间分布-通过分析跨岛链海山熔岩; ⑶钾玄岩的时间分布-通过研究残余弧和前缘弧的火山岩。研究人员从火山弧中获得了一套非常不寻常的样本。在这个项目中将要进行的分析应解决一些与弧岩浆作用有关的问题。其中最重要的是弧火山的组成和早期演化。这个问题很重要，因为弧在大陆地壳的形成中可能发挥作用。

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.