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

合作研究：岩体作为大陆地壳的成分：对大洋内阿留申弧中的中间岩体和熔岩之间差异的初步研究

• 批准号: 1144648
• 负责人: Matthew Rioux
• 金额: $ 3.5万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144648&HistoricalAwards=false
• 关键词: Collaborative; Research; Plutons; ingredients; continental

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.

在弧形中形成的长英质深成岩在整个相关压力和温度范围内相对于地幔橄榄岩是有浮力的。它们往往留在地球表面，形成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整体成分的估计重叠，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，也是 MARGINS 和 GeoPRISMS 计划的关键科学目标。 PI 将解决以下问题：(1) 与附近的熔岩相比，阿留申深成岩是否具有同位素不同的源成分？如果确实如此，那就至关重要，因为通常认为喷发的玄武岩代表了从地幔到弧地壳的岩浆通量。如果不是，我们将评估如何将它们解释为在同一亲本熔体上运行的不同分化过程的结果。 (2) 随着时间的推移，阿留申岛弧的成分是否发生了变化？深成岩和火山岩之间的差异是否代表了弧的时间演化，或者代表了不同岩浆成分的不同岩浆输送和侵位模式？ (3) 是否是高粘度长英质岩浆优先侵位于岩体中，而低粘度镁铁质岩浆优先形成熔岩？当熔岩被认为是弧岩浆过程和成分的代表时，这会带来什么偏见？更广泛的影响：阿留申群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。在该项目期间，一名研究生将接受研究培训，并可能能够帮助设计和参与基于该试点项目的更大的实地研究计划。