Collaborative Research: Variations of sedimentary input to magma genesis across the Kurile arc

资金将允许对千岛弧弧上的弧火山作用进行广泛、系统的放射成因、U系列和微量元素地球化学研究。其目的是描述典型岛弧下横跨整个弧段的各种岩浆过程。放射性成因的同位素变化将被用来表征整个弧区长寿命地壳/地幔来源的差异，而痕量金属变化将追踪与熔化或流体相互作用有关的更新的过程。铀系列不平衡也将被用来追踪熔融过程中的流体参与(238U过剩)，并对地幔中的熔体运输时间(226Ra过剩)施加限制。地幔楔体的沉积物输入将通过测量ODP型钻芯中的放射性同位素、宇宙成因10Be和主量/微量元素获得。这项工作将在千岛弧验证下列假设：1)板块在火山前缘以下产生流体，来自沉积物和洋壳蚀变，在弧后转变为沉积物熔融；2)印度地幔软流圈延伸到千岛和堪察加山脉；3)弧后熔岩代表与火山前缘类似的地幔较低程度的熔融，具有较小的流体通量；4)弧后熔岩对元素通量几乎没有影响，特别是对U-Th-Pb，Rb-SR，Sm-ND，Lu-Hf同位素体系的母子对影响不大。研究生和本科生将得到支持。

Funds will allow an extensive, systematic radiogenic, U-series, and trace element geochemistry study of arc volcanism on the Kurile arc. The objective is to characterize various magmatic processes beneath a typical island arc setting across the entire arc. Radiogenic isotope variations would be used to characterize differences in long-lived crust/mantle sources across the arc, and trace metal variations will trace more recent processes related to melting or fluid interactions. Uranium-series disequilibria would also be used to trace fluid involvement during melting (238U excess) and to place constraints on melt transport times in the mantle (226Ra excess). Sediment inputs to the mantle wedge would be obtained from measurements of radiogenic isotopes, cosmogenic 10Be, and major/trace elements in ODP drill cores. The work will test the following hypotheses in the Kurile arc: 1) That the slab yields a fluid beneath the volcanic front, deriving from both sediments and altered oceanic crust, which changes to a sediment melt beneath the rear arc; 2) Indian mantle asthenosphere extends into the Kuriles and Kamchatka; 3) Rear-arc lavas represent lower degree melts of a mantle that is similar to that beneath the volcanic front, with lesser fluid fluxes; and 4) Rear-arc lavas have little effect on element fluxes, particularly on the parent-daughter pairs of the U-Th-Pb, Rb-Sr, Sm-Nd, Lu-Hf isotope systematics. Graduate and undergraduate students will be supported.