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

大陆边缘火山弧是巨大的地壳生长工厂的所在地，是广泛的矿藏形成的地点，也是广泛的造山地区。它们也是危险的火山喷发的地点，可以在任何时候和在大范围内扰乱数百万人的生活。尽管对火山喷发有了基本的了解，但对喷发的不同行为，如喷发的地点、数量和频率，还没有很好的了解。部分问题是，火山只是地表以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延伸的岩浆管道系统中，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在火山场中最有记录的时空重点，表现为从最初的低容量、成分不均匀和空间扩散的火山活动转变为往往导致大规模火山喷发的高容量、均匀和空间重点的火山活动。如果岩浆聚焦开始于更深的地壳水平，是什么过程控制了这种现象，它是如何在样式、位置、体积和火山喷发频率上表现出来的？为了回答这个问题，我们必须了解岩浆活动在垂直输送过程中通过地壳柱集中的机制，以及火山和更深的岩浆系统是如何相互联系的。了解导致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。在加利福尼亚州内华达山脉中部的初步研究导致了三项重要发现：(1)在位于焦点中心的约塞米蒂国家公园内的白垩纪侵入杂岩(TIC)中，存在明显的时空和地球化学岩浆集中模式；(2)该地区的一些寄主岩石悬垂保存了与深成岩体具有相同的时间和地球化学集中特征的火山岩；(3)该地区出现了一些次火山斑岩“火山馈送系统”，将同一时代的火山岩和深成岩田连接起来。这些发现为研究中上地壳岩浆集中的潜在原因和过程提供了机会，这些原因和过程导致了集中火山系统的产生，如科罗拉多州圣胡安火山场或智利奥坎奎尔查火山群中建立的火山系统。拟议的研究将审查两个尺度：1)研究大型硅质岩体外围边界火山和深成单元的广泛时空地球化学模式；2)以关键的深成-斑岩-火山“三位一体”为目标，检查聚焦期间的火山-深成联系。这项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内6-11公里深度的岩浆活动的空间/时间/成分集中，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阿迪尔和加州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。来自西班牙裔服务的CSU Fullerton的几名本科生和一名研究生将参与其中。将与加州大学富勒顿分校助理教授Natalie Bursztyn博士合作开发一个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，并通过带领他们穿越内华达山脉岩浆弧进行一次虚拟实地考察来吸引公众。该项目强调在国内和合作设施进行分析方法培训。帕特森和梅梅蒂将继续与约塞米蒂国家公园进行长达12年的合作。

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.