X-ray and Spectroscopic Studies of Subduction-Related Phases: Probing the Mid-Point of Volatile Recycling in the Earth

我们水圈和大气层的主要物质，如水和二氧化碳，如何通过板块构造在固体矿物相内循环到地球深处，然后最终在高压和高温下以流体相释放，对于与俯冲相关的火山活动如何具有关键重要性。（如环太平洋“火环”）的产生，也可能是为了发生深地震（深度大于200公里）。在该项目中，研究人员计划在高压和高温条件下研究相关的含水和含碳矿物，在这些条件下，它们释放水和二氧化碳，以确定：（1）它们的性质决定水或二氧化碳何时在深度释放;（2）水或二氧化碳是逐渐释放还是突然释放。这些结果将限制最终通过水引起的融化产生环太平洋火山活动的水如何在地球深处释放，并有助于模拟深处的岩浆生产;并将探索二氧化碳如何在深处释放以及它可能被运输到表面的形式。因此，这些结果对于大陆边缘火山活动的产生，以及与深俯冲有关的地震（可能由流体润滑）是如何产生的具有根本的相关性。在进行这些实验时，该小组将率先开发一个新的设施，该设施将提供给整个科学界，该设施旨在在劳伦斯伯克利国家实验室的先进光源中进行材料的高压/高温表征。该小组广泛参与其研究工作的本科生，并由这项赠款支持的研究生包括一名退伍军人。研究结果也被纳入PI研究所的本科课程中。研究团队计划：（1）使用高精度单晶X射线衍射技术，在高压和高温条件下研究地幔中挥发物的重要载体的性质;（2）使用红外和拉曼光谱技术，在高压条件下表征与碳酸盐岩成因相关的碳酸盐的性质。在实现第一个目标的同时，这一支助将促进建立一个新的、社区可利用的、基于高压/高温同步加速器的单晶X射线衍射设施。 水和二氧化碳进出地球内部的循环是影响固体地球（通过其对融化和流变学的影响）和地球表面（通过水圈的体积和地球大气层的组成）的关键过程。该团队提议探索俯冲条件下含挥发分相的性质，以深入了解：（1）地球地幔中含挥发分相的多态性（2）高温高压下含挥发分相的结构（以检查为什么这些相保持挥发物）;和（3）已知将水携带到深度的相（特别是硬硅钙石和多硅云母）在它们接近（并且希望超过）它们的脱水条件时如何表现。 他们还将提供新的限制与地幔条件下的碳酸根离子的结合相丰富的多态性：这里的重点将是富碱碳酸盐，最近已被证明是与深碳酸盐岩熔融，并已在很大程度上在高压条件下未被审问。该团队将利用该项目部署两名研究生，以协助，工作，调整和调试一个新的，世界一流的高压单晶X射线衍射装置，该装置将于明年在劳伦斯伯克利国家实验室（LBNL）的高级光源（ALS）中安装和调试。该设施将通过ALS的一般用户计划提案过程提供给整个社区（该设施也将是ALS的COMPRES联盟批准计划的一部分，因此将为获得时间的用户提供帮助）。除了部署新的社区基础设施外，PI还将：（1）为多样化的研究生群体的教育做出贡献（目前，一名退伍军人，一名归国女性）和本科生;（2）继续出版/撰写有关地球自然史感兴趣者广泛感兴趣的专题的文献（并在适当的时候通过新闻稿宣传这些成果）;（3）将新成果纳入UCSC本科教学（通常每年约90个地球科学专业）。

How the major materials of our hydrosphere and atmosphere, such as water and carbon dioxide, are cycled into the deep Earth within solid mineral phases via plate tectonics, and then ultimately released as fluid phases at high pressures and temperatures, is of key importance for how subduction-associated volcanism (like the circum-Pacific "Ring of Fire") is produced, and also possibly for the occurrence of deep earthquakes (at depths greater than ~200 km). In this project, the investigators plan to examine water- and carbon-containing minerals of relevance under the high-pressure and high temperature conditions under which they release water and carbon dioxide to determine: (1) their properties that govern when water or carbon dioxide are released at depth; and (2) whether water or carbon dioxide are released gradually or abruptly. These results will constrain how the water that ultimately generates circum-Pacific volcanism via water-induced melting is released at depth in the planet, and help in the modeling of magma production at depth; and will explore how carbon dioxide is released at depth and the form in which it might be transported to the surface. Thus, these results have fundamental relevance for the production of volcanism at continental margins, and for how deep subduction-related earthquakes (which are likely greased by fluids) are generated. In conducting these experiments, the group will spearhead the development of a new facility, which will be available to the scientific community as a whole, which is designed to conduct high-pressure/high-temperature characterizations of materials at the Advanced Light Source at Lawrence Berkeley National Labs. The group extensively engages undergraduates in its research effort, and the graduate students supported by this grant include a military veteran. The results are also incorporated into undergraduate curricula at the PI's institution.The investigator team plans to: (1) examine the properties of important carriers of volatiles into Earth's mantle at simultaneous high pressures and high temperatures using high precision single-crystal x-ray diffraction; and (2) characterize the properties of carbonates of relevance to carbonatite petrogenesis at high pressures using infrared and Raman spectroscopy. In tandem with the first objective, the establishment of a new, community-accessible, high-pressure/high-temperature synchrotron-based single crystal x-ray diffraction facility will be facilitated by this support. The cycling of water and carbon dioxide into and out of Earth's interior are pivotal processes that impact both the properties of the solid Earth (through their effects on melting and rheology) and Earth's surface (through the volume of the hydrosphere and the composition of Earth's atmosphere). The team proposes to probe the properties of volatile-bearing phases under subduction conditions to gain insights into: (1) the polymorphism of volatile-bearing phases in Earth's mantle (or, what is degassing at depth); (2) the structures of volatile-bearing phases at high-pressures and temperatures (to examine why these phases hold volatiles); and (3) how phases that are known to carry water to depth (and particularly lawsonite and phengitic micas) behave as they approach (and hopefully exceed) their dehydration conditions. They also will provide new constraints on the rich polymorphism of phases associated with the binding of the carbonate ion under mantle conditions: the focus here will be on alkali-rich carbonates, which have recently been demonstrated to be associated with deep carbonatite melting, and which have largely been uninterrogated at high pressure conditions. The team will utilize this project to deploy two graduate students to assist, work through, shake down and debug a new, world-class high-pressure single-crystal x-ray diffraction set-up that will be set-up and commissioned over the next year at the Advanced Light Source (ALS) at Lawrence Berkeley National Labs (LBNL). This facility will be available to the community as a whole through the General User Program proposal process of the ALS (the facility will also be part of the COMPRES-Consortium's Approved Program at the ALS, and thus will have assistance for users who are awarded time). In addition to this deployment of new community infrastructure, the PI will: (1) contribute to the education of a diverse group of graduate students (currently, one military veteran, one returning female) and undergraduates; (2) continue to publish/contribute to the literature on topics of broad interest for those interested in the natural history of the planet (and promote these as appropriate with press releases); and (3) incorporate new results into UCSC undergraduate teaching (typically, to ~90 earth sciences majors per year).