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

资金将允许对千岛岛弧上的弧火山活动进行广泛、系统的放射性成因、u系列和微量元素地球化学研究。目的是描述在整个岛弧的典型岛弧环境下的各种岩浆过程。放射性成因同位素变化将用于表征整个弧上长期存在的地壳/地幔源的差异，微量金属变化将用于追踪与熔化或流体相互作用有关的更近期的过程。铀系不平衡也将用于追踪熔化过程中的流体参与（238U过量），并对地幔中的熔体输送时间（226Ra过量）施加限制。地幔楔的沉积物输入将通过测量放射性成因同位素、宇宙成因10Be和ODP岩心中的主要/微量元素来获得。这项工作将测试千岛岛弧的以下假设：1)板块在火山锋下产生一种流体，来自沉积物和改变的海洋地壳，这种流体在后弧下转变为沉积物融化；2)印度地幔软流圈延伸至千岛群岛和堪察加半岛；3)弧后熔岩代表地幔较低程度的熔融，与火山锋下相似，流体通量较小；4)弧后熔岩对元素通量的影响较小，尤其是对U-Th-Pb、Rb-Sr、Sm-Nd、Lu-Hf同位素系统的亲子对。研究生和本科生将获得资助。

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.