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的造山地区。它们也是危险的火山爆发地点，随时可能在大范围内扰乱数百万人的生活。虽然对火山喷发有了基本的认识，但对火山喷发的不同行为，如喷发的位置、喷发量和喷发频率还不太了解。部分问题在于，火山只是地表下复杂的物理和化学过程的表面表现，这些过程发生在垂直扩展的岩浆管道系统中，这些岩浆管道系统为火山提供养分。一种重要但鲜为人知的火山行为类型是这些系统的时空聚焦，这些系统在火山场中得到了最好的记录，表现为从最初的小体积、成分不均匀和空间分散的火山作用到大体积、均匀和空间集中的火山作用的变化，往往导致大规模的火山喷发。如果岩浆集中开始于更深的地壳水平，是什么过程控制了这种现象，它是如何在火山喷发的风格、位置、体积和频率上表现出来的？为了回答这个问题，我们必须了解岩浆活动在通过地壳柱的垂直运输过程中集中的机制，以及火山和更深的岩浆系统是如何相互联系的。了解岩浆聚集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。在加州内华达山脉中部进行的初步研究取得了三个重要发现：(1)白垩纪岩体具有清晰的时空和地球化学岩浆聚焦模式，尤塞米蒂国家公园内的95 ~ 85马图伦侵入杂岩（TIC）位于聚焦中心；(2)该区许多寄主岩石垂坠保存着火山岩，它们与岩体具有相同的时间和地球化学聚焦；(3)区内发育多处次火山斑岩“火山支线系统”，连接着同一时代的火山与深成田。这些发现为研究岩浆在中上部地壳聚集的潜在原因和过程提供了机会，这些岩浆聚集导致了集中火山系统的产生，就像在科罗拉多州圣胡安火山场或智利的Aucanquilcha火山群中建立的那样。本研究将从两个尺度上进行：1)研究大型硅质岩体外围边界火山-深部单元的广泛时空地球化学格局；2)在聚焦过程中，以关键的深部-斑岩-火山“三合一”为目标，考察火山-深部联系。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弧6-11公里深处岩浆活动的空间/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。该项目支持两名早期职业女性，南加州大学的博士生Ardill和科罗拉多州立大学富勒顿分校的助理教授Memeti，以及南加州大学的Paterson教授。来自加州州立大学富勒顿分校的几名本科生和一名研究生将参与其中。科罗拉多州立大学富勒顿分校助理教授Natalie Bursztyn博士将与他们合作开发一款免费的移动应用程序，该应用程序将加强学生在地球科学方面的学习，并通过带领他们进行穿越内华达山脉岩浆弧的虚拟实地考察来吸引公众。该项目强调在家庭和合作设施进行分析方法培训。Paterson和Memeti将继续与约塞米蒂国家公园长达12年的合作。