Collaborative Research: RUI: Examining the Temporal, Spatial and Geochemical Focusing of Magmatism During a Continental Arc Flare-up

合作研究：RUI：检查大陆弧爆发期间岩浆作用的时间、空间和地球化学聚焦

• 批准号: 1624854
• 负责人: Valbone Memeti
• 金额: $ 15万
• 依托单位: CSU Fullerton Auxiliary Services Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624854&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Examining; Temporal

Continental margin volcanic arcs are locations of vast crustal growth factories, sites of extensive ore deposit formation and areas of widespread mountain building. They are also locations of dangerous volcanic eruptions that can disrupt the lives of millions of people at any time and over large regions. Although a basic understanding of volcanic eruptions exists, the different behaviors of eruption such as location, volumes and frequency are not well understood. Part of the problem is that volcanoes are only the surface expression of the complex physical and chemical processes that occur below the Earth's surface in vertically extensive magma plumbing systems that feed the volcanoes. One important but poorly understood type of volcanic behavior is the spatial and temporal focusing of these systems best documented in volcanic fields, as expressed through the change from initially low volume, compositionally heterogeneous and spatially spread-out volcanism to high volume, homogeneous and spatially focused volcanism often leading to large volcanic eruptions. If magma focusing begins at deeper crustal levels, what processes control this phenomenon, and how does it manifest itself in style, location, volume, and the frequency of volcanic eruptions? To answer this, it is essential that we understand the mechanisms by which magmatism is focused during vertical transport through the crustal column and how volcanic and deeper magmatic systems are linked to one another. Understanding the processes causing magma focusing will also help us understand ore deposit formation and aspects of mountain building and the growth of continents. Preliminary research in the central Sierra Nevada, California, has led to three important discoveries: (1) a clear pattern of spatiotemporal and geochemical magmatic focusing in a field of Cretaceous plutons with the large 95 to 85 Ma Tuolumne Intrusive Complex (TIC), in Yosemite National Park occurring at the center of the focus; (2) a number of host rock pendants in this area preserve volcanic rocks that mimic the same temporal and geochemical focusing as the plutons; (3) a number of subvolcanic porphyry "volcanic feeder systems" occur in this area, linking volcanic and plutonic fields of the same age. These discoveries provide the opportunity to investigate the potential causes and processes facilitating magma focusing in the mid-upper crust that leads to the generation of focused volcanic systems, like those established in the San Juan volcanic field in Colorado or the Aucanquilcha volcanic cluster in Chile. The proposed study will examine two scales: 1) Studying the broad spatiotemporal geochemical pattern of volcanic and plutonic units at the peripheral boundaries of a large silicic pluton; 2) Targeting key plutonic-porphyry feeder-volcanic "triads" to examine volcanic-plutonic links during the focusing. The proposed research will use field mapping, geochemical analyses and geochronology to explore spatial/temporal/compositional focusing of magmatism at 6-11 km depths in an ancient arc, and compare to similar phenomena established in modern volcanic systems. This project supports two early career women, PhD student Ardill at USC and assistant professor Memeti at CSU Fullerton, and professor Paterson from USC. Several undergraduates and one graduate student from Hispanic-Serving CSU Fullerton will be involved. A free mobile application will be developed in collaboration with CSU Fullerton assistant professor Dr. Natalie Bursztyn that will enhance student learning in the geosciences and engage the general public by taking them on a virtual field trip back in time through the Sierra Nevada magmatic arc. The project emphasizes training in analytical methods at home and at collaborating facilities. Paterson and Memeti will continue a 12 yr collaboration with Yosemite National Park.

大陆边缘火山弧是巨大的地壳生长工厂、广泛的矿床形成地点和广泛造山的地区。它们也是危险的火山喷发地点，随时可能扰乱大片地区数百万人的生活。尽管人们对火山喷发有了基本的了解，但人们对喷发的不同行为（例如位置、数量和频率）还没有很好的了解。部分问题在于，火山只是复杂物理和化学过程的表面表现，这些过程发生在地球表面以下垂直延伸的岩浆管道系统中，这些岩浆管道系统为火山提供水源。一种重要但知之甚少的火山行为类型是这些系统的空间和时间集中，这在火山田中得到了最好的记录，表现为从最初的低体积、成分异质和空间分散的火山活动到高体积、均匀和空间集中的火山活动的变化火山活动常常导致大规模火山喷发。如果岩浆聚焦从更深的地壳层面开始，那么什么过程控制着这种现象，它如何在火山喷发的类型、位置、体积和频率方面表现出来？ 为了回答这个问题，我们必须了解岩浆作用在地壳柱垂直输送过程中集中的机制，以及火山和更深的岩浆系统如何相互联系。了解导致岩浆聚焦的过程也将有助于我们了解矿床的形成以及造山和大陆生长的各个方面。加利福尼亚州内华达山脉中部的初步研究取得了三项重要发现：（1）在白垩纪岩体区域中存在清晰的时空和地球化学岩浆聚焦模式，其中包括大型 95 至 85 Ma Tuolumne 侵入杂岩（TIC），优胜美地国家公园位于焦点的中心； (2) 该地区的一些主岩悬垂物保存了模拟与岩体相同的时间和地球化学聚焦的火山岩； (3)该区发育大量的火山下斑岩“火山供给系统”，连接同龄的火山田和深成岩田。 这些发现提供了研究促进岩浆集中在中上地壳的潜在原因和过程的机会，从而导致集中火山系统的产生，例如科罗拉多州圣胡安火山场或智利奥坎基尔查火山群中建立的火山系统。拟议的研究将检查两个尺度：1）研究大型硅质岩体外围边界的火山和岩体单元的广泛时空地球化学模式； 2) 以关键的深成岩-斑岩供给源-火山“三合一”为目标，在聚焦过程中检查火山-深成联系。拟议的研究将利用野外测绘、地球化学分析和地质年代学来探索古代弧内 6-11 公里深度的岩浆作用的空间/时间/成分聚焦，并与现代火山系统中建立的类似现象进行比较。该项目支持两位早期职业女性，南加州大学的博士生阿迪尔和科罗拉多州立大学富勒顿分校的助理教授梅梅蒂，以及南加州大学的帕特森教授。来自科罗拉多州立大学富勒顿分校西班牙裔服务的几名本科生和一名研究生将参与其中。我们将与科罗拉多州立大学富勒顿分校助理教授 Natalie Bursztyn 博士合作开发一款免费移动应用程序，该应用程序将增强学生在地球科学方面的学习，并通过带他们穿越内华达山脉岩浆弧进行虚拟实地考察来吸引公众。该项目强调在国内和合作机构进行分析方法培训。 Paterson 和 Memeti 将继续与优胜美地国家公园长达 12 年的合作。