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，发生在地球上两个板块碰撞，一个板块滑到另一个板块下面的地方。一个板块在另一个板块之下的俯冲作用是地球表面和内部之间质量传递的主要机制。对俯冲带中流体驱动的化学循环的理解为我们提供了发现有价值的自然资源（如金属矿石、天然气和石油储备）、开发新资源（如地热能）以及了解俯冲带的地质灾害（如地震和火山爆发）的工具。本文研究了俯冲带变质作用下下行板块流体中微量元素的分布。这些液体产生了岩浆，形成了弧状火山。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运移的宝贵资源。为了追踪俯冲流体中微量元素的流动性，本研究将检查在加利福尼亚方济各杂岩的环山地区以及德国和捷克共和国的Erzgebirge（矿石山）地区的榴辉岩中发现的单个矿物的地球化学。特别是对石榴石和金红石进行了详细的分析，以研究稀土和高场强元素在榴辉岩流体产生和运移过程中的行为。分析单个矿物颗粒中广谱微量元素的首选方法是激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）。互补的LA-ICP-MS设备存在于美国宾夕法尼亚州立大学和德国美因茨大学。美因茨大学的教师们已经开发出了最先进的方法，利用变质岩石中微量矿物相的编码信息，如金红石中的锆温度测量和U-Pb地质年代学。这些方法可以用来为我们的样品建立一个温度-时间历史，以帮助我们解释流体输送发生的条件。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实验室度过六个星期，从她的主人和导师Thomas Zack博士那里学习如何实施这些专业的分析技术。Cruz-Uribe将在导师Maureen Feineman博士的指导下，带着她对这些技术的了解回到美国，在宾夕法尼亚州立大学的LA-ICP-MS设施中实施。学生将受益于直接接触新方法和新思维方式，并在回国后将这些方法传授给其他学生。两个研究所都受益于国际合作研究项目。本项目由国际科学与工程办公室和地球科学司联合资助。

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.