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.

在整个相关的压力和温度范围内，在弧形中形成的绒毛岩石岩相对于地幔橄榄岩具有浮力。它们倾向于留在地球表面，形成大陆壳的基本构建块。在阿留申者中，大多数长英质岩石岩具有对大陆壳的整体组成的估计的组成，它们与空间相关的熔岩截然不同。了解阿留申兰氏岩石岩石的起源是通过弧岩岩岩（Arc Magmatism）理解大陆的起源和进化的关键，弧岩岩（Arc Magmatism）是边缘和地理主义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，Aleutian Plutonic Rocks是否具有同位素不同的源组成？如果这样做的话，这至关重要，因为通常假定爆发的玄武岩代表了从地幔到弧形地壳的岩浆通量。如果没有，我们将评估如何通过在同一父母熔体上运行的不同分化过程来解释它们。 （2）随着时间的流逝，阿留申弧的组成差异是否存在？岩石岩和火山岩之间的差异是否代表弧的时间演化，或不同岩浆成分的岩浆传输和降级模式？ （3）高粘度长英质岩浆优先放置在岩石中，而低粘度，黑镁岩浆优先形成熔岩？当假定熔岩代表弧形过程和构图时，这会引入哪些偏见？更广泛的影响：阿留申弧对社会构成了许多危害。了解俯冲过程有助于预测，避免和/或减轻火山喷发，滑坡和地震的危险后果。在此项目期间，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现场研究计划。