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4-D Reconstruction of Magmatism at a long-lived Andesite Locus: Goat Rocks Volcanic Complex, Cascade Arc

长寿安山岩区域岩浆作用的 4 维重建：山羊岩火山群、喀斯喀特弧

基本信息

批准号：
1939347
负责人：
Anita Grunder
金额：
$ 19.4万
依托单位：
Oregon State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-04-01 至 2022-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1939347&HistoricalAwards=false
关键词：
Reconstruction Magmatism long lived Andesite

项目摘要

The large composite volcanoes that are distinctive of subduction zones are the surface expressions of the magma factory that distills mantle material to create and change the Earth’s crust. While the volcanoes themselves pose hazards to human health and property, the magma systems that drive them result in the circulation of hot water used for power and recreation, and also lead to the formation of many types of ore deposits at depth. For these reasons, the nature and development of subduction volcanoes and the magmatic underpinnings that feed them are critical. This project will investigate the long-term (~3 million year) development of the Goat Rocks Volcanic Complex, a cluster of eroded composite volcanoes in the Washington Cascade Range, to understand the origin and storage conditions of magmas erupted there and how they changed over time. Broader impacts of this study include the training of a female PhD student and undergraduate students in diverse field, laboratory, publication, and outreach skills; collaboration with the Washington Department of Natural Resources on projects and publications; and an animation of the development of the Cascade Volcanic Arc.The Goat Rocks Volcanic Complex makes a particularly good natural laboratory because it is well exposed by glacial erosion, it is relatively young, and it spans a large part of the global compositional range of subduction zone stratovolcanoes. Preliminary work at the Goat Rocks Volcanic Complex indicates that the magma system changed substantially in time, from potassium-rich magmas stored at modest depth in the crust, to low-potassium and more water-rich magmas stored at greater depth. Detailed stratigraphy and geochronology (mainly 40Ar/39Ar dating) will provide a more robust time framework for the geochemical analyses of rocks and minerals to be used in reconstructing the magmatic history (e.g., pressure, temperature and water conditions), which will be quantified using computer models that couple mass and thermal balance. The reconstruction of this volcanic complex will then be compared to the magmatic histories of other subduction volcanoes in the Cascades and in other arcs. A particular aim is to evaluate conflicting models of magma generation and storage, i.e. (1) a model wherein deep crustal magma generation is prevalent, with only transient shallow storage before eruption; vs. (2) extensive interaction between crust and magma at all levels, as suggested by exposed sections of volcanic arc crust. We posit that seen through the lens of development in time, such models may be reconciled.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

俯冲带特有的大型复合火山是岩浆工厂的表面表现，它蒸馏地幔物质以创造和改变地壳。虽然火山本身对人类健康和财产构成危害，但驱动火山的岩浆系统导致用于发电和娱乐的热水循环，并导致在深处形成许多类型的矿床。由于这些原因，俯冲火山的性质和发展以及为它们提供燃料的岩浆基础至关重要。该项目将调查山羊岩火山复合体的长期（约300万年）发展，山羊岩火山复合体是华盛顿喀斯喀特山脉的一组侵蚀复合火山，以了解那里喷发的岩浆的起源和储存条件以及它们如何随时间变化。这项研究的更广泛的影响包括在不同领域，实验室，出版和推广技能的女博士生和本科生的培训;与自然资源的华盛顿部的项目和出版物的合作;以及瀑布火山弧发展的动画。山羊岩火山复合体是一个特别好的天然实验室，因为它很好地暴露在冰川侵蚀下，它相对较年轻，而且跨越了全球俯冲带成层火山组成范围的很大一部分。在山羊岩火山复合体的初步工作表明，岩浆系统在时间上发生了很大变化，从储存在地壳适度深度的富钾岩浆，到储存在更深处的低钾和更富水的岩浆。详细的地层学和地质年代学（主要是40 Ar/39 Ar测年）将为用于重建岩浆历史的岩石和矿物的地球化学分析提供更可靠的时间框架（例如，压力、温度和水条件），这将使用耦合质量和热平衡的计算机模型来量化。这座火山复合体的重建将与喀斯喀特山脉和其他岛弧中其他俯冲火山的岩浆历史进行比较。一个特别的目的是评估岩浆生成和储存的相互冲突的模型，即（1）一个模型，其中深地壳岩浆生成是普遍的，只有短暂的浅存储在喷发前;与（2）地壳和岩浆之间的广泛的相互作用，在所有级别，如火山弧地壳的暴露部分所建议的。我们认为，通过及时发展的透镜，这些模型可能会协调一致。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。