International: US-Germany Doctoral Dissertation Enhancement: High-resolution Laser Ablation ICP-MS Analysis of Metamorphic Rocks from California, Germany, and the Czech Republic

俯冲带是板块构造的主要表现之一，发生在地球的两个板块相撞，一个板块在另一个板块下方滑动的地方。一个板块俯冲到另一个板块之下，是地球表面和内部之间质量转移的主要机制。了解俯冲带中流体驱动的化学循环为我们提供了发现有价值的自然资源(如金属矿石和天然气和石油储量)、开发新资源(如地热能)和了解俯冲带的地质灾害(如地震和火山喷发)的工具。本文研究了俯冲带变质作用过程中下行板块流体中微量元素的分布。这些流体负责产生产生弧形火山的岩浆。特别是，榴辉岩(俯冲洋壳)等高压变质岩是研究俯冲带深部流体生产和转移的宝贵资源。为了追踪俯冲流体中微量元素的活动性，这项研究将研究加州Franciscan杂岩环山地区以及德国和捷克ErzgeBirge(矿石山脉)地区榴辉岩中发现的单个矿物的地球化学。特别是，将详细分析石榴石和金红石，以考察稀土和高场强元素在榴辉岩中流体产生和传输过程中的行为。分析单个矿物颗粒中的多种微量元素的首选方法是激光烧蚀电感耦合等离子体质谱(LA-ICPMS)。美国宾夕法尼亚州立大学和德国美因茨大学都有补充的LA-ICP-MS设施。美因茨大学的教师们开发了尖端的方法，利用变质岩中的次要矿物相编码的信息，如金红石中的锆测温和铀-铅地质年代学。这些方法一起可以用来为我们的样品绘制温度-时间历史，以帮助我们解释发生流体运输的条件。宾夕法尼亚州立大学的博士生Alicia Cruz-Uribe将在美因茨的LA-ICP-MS实验室呆上六周，从她的东道主兼导师Thomas Zack博士那里学习如何实施这些专门的分析技术。克鲁兹-乌里韦将在顾问莫琳·费尼曼博士的指导下，带着她对这些技术的了解返回美国，在宾夕法尼亚州立大学的LA-ICP-MS设施实施。学生将受益于直接接触新的方法和新的思维方式，以及在她回来后将这些方法教给其他学生。这两个研究所都受益于合作的国际研究项目。该项目由国际科学与工程办公室和地球科学部联合资助。

Subduction zones are one of the primary manifestations of plate tectonics, occuring where two of Earth's plates collide and one slips beneath the other. Subduction of one plate beneath another functions as the primary mechanism for mass transfer between the surface and interior of the Earth. An understanding of fluid-driven chemical cycling in subduction zones provides us with the tools to discover valuable natural resources such as metal ores and natural gas and oil reserves, to develop new resources such as geothermal energy, and to understand the geologic hazards of subduction zones such as earthquakes and volcanic eruptions. This study focuses on the distribution of trace elements in fluids produced in the down-going plate during subduction zone metamorphism. These fluids are responsible for generating the magmas that produce arc volcanoes. In particular, high-pressure metamorphic rocks such as eclogite (subducted oceanic crust) are valuable resources for studying fluid production and transfer within the deeper parts of the subduction zone. In order to track the mobility of trace elements in subduction fluids, this study will examine the geochemistry of individual minerals found in eclogite from the Ring Mountain locality of the Franciscan Complex in California, and the Erzgebirge (Ore Mountains) region of Germany and the Czech Republic. In particular, garnet and rutile will be analyzed in detail to examine the behavior of rare earth and high field strength elements during the production and transport of fluids in eclogitic rocks.The preferred method for analyzing a broad spectrum of trace elements in individual mineral grains is laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Complementary LA-ICP-MS facilities exist at Pennsylvania State University in the US and the University of Mainz in Germany. Faculty at Mainz have developed cutting edge methods that make use of information encoded in minor mineral phases in metamorphic rocks, such as Zr-in-rutile thermometry and U-Pb geochronology. Together these methods can be used to develop a temperature-time history for our samples to help us interpret the conditions under which fluid transport occurred. Penn State PhD student Alicia Cruz-Uribe will spend six weeks at the LA-ICP-MS laboratory in Mainz learning how to implement these specialized analytical techniques from her host and mentor, Dr. Thomas Zack. Cruz-Uribe will return to the US with her knowledge of these techniques to be implemented at the LA-ICP-MS facility at Penn State, under the guidance of advisor Dr. Maureen Feineman. The student will benefit both by direct exposure to new methods and new ways of thinking as well as by teaching those methods to other students upon her return. Both institutes benefit by virtue of the collaborative international research project. This project is funded jointly by the Office of International Science and Engineering and the Division of Earth Sciences.