Collaborative Research: Plutons as ingredients for continental crust: Pilot study of the differences between intermediate plutons and lavas in the intra-oceanic Aleutian arc

长英质深成岩弧形成浮力相对于地幔橄榄岩在整个范围内的相关压力和温度。他们倾向于留在地球上？形成了大陆地壳的基本组成部分。在阿留申群岛，大多数长英质深成岩的成分与大陆地壳的整体成分估计重叠，并且与空间相关的熔岩明显不同。了解阿留申长英质深成岩的成因是通过弧岩浆作用了解大陆成因和演化的关键，这是MARGINS和GeoPRISMS倡议的关键科学目标。PI将解决以下问题：（1）阿留申深成岩是否有同位素不同的来源组成，附近的熔岩相比？如果是这样的话，这是非常重要的，因为通常认为喷发的玄武岩代表了从地幔进入弧壳的岩浆流。如果不是，我们将评估如何将其解释为在相同亲本熔体上操作的不同分化过程的结果。(2)阿留申岛弧的成分随时间变化了吗？深成岩和火山岩之间的差异是否代表了弧的时间演化，或者不同岩浆成分的岩浆搬运和侵位方式不同？ 高粘度长英质岩浆是否优先侵位于岩体中，而低粘度镁铁质岩浆是否优先形成熔岩？当熔岩被认为是弧岩浆过程和成分的代表时，这会引入什么样的偏见？更广泛的影响：阿留申岛弧对社会造成了许多危害。了解俯冲过程有助于预测，避免和/或减轻火山爆发，山体滑坡和地震的危险后果。在这个项目中，一名研究生将接受研究培训，并将有可能帮助设计和参与基于这个试点项目的更大的实地研究计划。

Felsic plutonic rocks formed in arcs are buoyant with respect to mantle peridotite over the entire range of relevant pressures and temperatures. They tend to remain at the Earth?s surface, to form the fundamental building blocks of continental crust. In the Aleutians, most felsic plutonic rocks have compositions that overlap estimates for the bulk composition of the continental crust, and that are distinctly different from spatially associated lavas. Understanding the genesis of Aleutian felsic plutonic rocks is a key to understanding continental genesis and evolution via arc magmatism, a key science goal for the MARGINS and GeoPRISMS Initiatives. The PIs will address the following questions: (1) Do Aleutian plutonic rocks have an isotopically distinct source composition, compared to nearby lavas? If they do, this is vitally important since it is commonly assumed that erupted basalts are representative of the magmatic flux from the mantle into arc crust. If not, we will evaluate how they can be explained as the result of different differentiation processes operating on the same parental melt. (2) Has there been compositional variation in the Aleutian arc over time? Do differences between plutonic and volcanic rocks represent temporal evolution of the arc, or different modes of magma transport and emplacement for different magma compositions? And (3) are high viscosity felsic magmas preferentially emplaced in plutons, while low viscosity, mafic magmas preferentially form lavas? What biases does this introduce, when lavas are presumed to be representative of arc magmatic processes and compositions?Broader Impacts: The Aleutian arc poses numerous hazards to society. Understanding subduction processes helps to predict, avoid, and/or mitigate the hazardous consequences of volcanic eruptions, landslides and earthquakes. During this project, a graduate student will be trained in research, and will likely be able to help design and participate in a larger field research program based on this pilot project.