CAREER: Salt, Experiments, and Mass Transfer in Subduction Settings

俯冲带是地球化学反应的基本引擎。在俯冲带中，一个构造板块俯冲到另一个构造板块之下，并在下降到地球内部深处的过程中被加热。随着热量的增加，下沉板块中的含水矿物分解产生富含水的流体。这些流体具有浮力，并会上升到地表，沿着它们的路径推动化学反应。由这些流体驱动的重要地质现象包括点缀在太平洋火环上的猛烈火山，大陆边缘的关键元素的经济集中，大陆地壳的产生，以及地球内部气体的添加和补充。该项目的研究工作集中在实验研究卤素元素如何追踪流体通过俯冲带的路径，并改变深度富水流体的化学性质。该项目的教育工作包括开发课程，以更好地吸引对STEM感兴趣的学生，并在研究生和本科生阶段培训学生掌握尖端研究技术。 该项目将支持三项具体的研究任务。第一个任务是在适用的压力和温度条件下，实验测量板状矿物和富水流体之间的卤素元素分配。这些数据将被应用于预测不同板坯条件下流体和残余矿物的卤素化学。然后将预测与弧火山和地幔源的观测结果进行比较，以限制卤素如何通过俯冲带移动。第二个任务是测量氯如何有效地增加了适用于板流体相互作用的条件下的富水流体的溶质浓度。收集的数据将告知如何确定俯冲带流体的化学性质。第三个任务是量化如何通过加入氯来增加岩石的流体饱和熔点。结果将被应用于了解俯冲带的热结构和相关的倾向板熔化。研究任务的共同努力将产生一个系统的调查，卤素如何跟踪和修改俯冲设置中的质量传递。该项目还将支持主要的教育工作。第一个是开发一个以行星科学为重点的入门课程。该课程将通过杜兰科学学者计划提供，该计划针对路易斯安那州南部的高中学生，并使150名学生的多样化队列在夏季参加STEM课程，以获得大学学分。目前没有地球科学类通过这个程序提供，新开发的行星科学类将填补目前课程的这一关键漏洞。第二个是改造地球材料类在杜兰的实验室活动，向学生介绍了广泛的分析技术，通常应用于地球化学。这次改造的影响将通过与教授地球材料课程的其他机构合作来加强，以帮助改进实验室活动。改进后的活动将张贴到社区课程库。第三项教育工作将为三名博士生提供材料合成和材料表征技术方面的培训。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Subduction zones are fundamental engines for chemical reactions in the Earth. In a subduction zone, one tectonic plate dives beneath another and is heated during its descent into Earth’s deep interior. With heat, the hydrous minerals in the down-going plate breakdown to produce water-rich fluids. These fluids are buoyant and rise back to the surface, driving chemical reactions along their path. Important geological phenomena driven by these fluids include the violent volcanoes that dot the Pacific Ring of Fire, the economic concentration of critical elements along the edges of continents, the production of continental crust, and the addition and replenishment of gasses in Earth’s interior. Research efforts of this project center on experimental investigations of how the halogen elements trace the path of fluids through subduction zones and modify the chemical properties of water-rich fluids at depth. Educational efforts of this project include developing curricula to better engage students interested in STEM and training students in cutting edge research techniques at the graduate and undergraduate level. This project will support three specific research tasks. The first task is to experimentally measure the elemental partitioning of halogens between slab minerals and water-rich fluids under applicable pressure and temperature conditions. These data will be applied towards predicting the halogen chemistry of fluids and residual minerals for different slab conditions. Predictions will then be compared to observations from arc volcanoes and mantle sources to constrain how halogens are mobilized through subduction zones. The second task is to measure how efficiently chlorine increases the solute concentrations of water-rich fluids under conditions applicable to slab-fluid interactions. The collected data will inform how the chemistry of subduction zone fluids are determined. The third task is to quantify how the fluid-saturated melting point of rocks is increased by the addition of chlorine. Results will be applied towards understanding the thermal structure of subduction zones and the associated propensity for slab melting. The combined efforts of the research tasks will yield a systematic investigation for how halogens trace and modify mass transfer in subduction settings. This project will also support major educational efforts. The first is to develop an introductory class focused on planetary science. The class will be offered through the Tulane Science Scholars Program, a program that targets southern Louisiana high school students and enables a diverse cohort of ~150 students to take a STEM class over the summer for college credit. No geosciences class is currently offered through this program, and the newly developed planetary science class will fill this crucial hole in the current curriculum. The second is to revamp the laboratory activities of the Earth Materials class at Tulane to introduce students to a wide range of analytical techniques commonly applied within geochemistry. The impact of this revamping will be enhanced by partnering with other institutions that teach Earth Materials courses to help refine the laboratory activities. The refined activities will be posted to community repositories for curricula. The third educational effort will provide training for three PhD students in materials synthesis and materials characterization techniques. Within this effort, undergraduate students will be recruited from the New Orleans metro area to join the research efforts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.