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

GSTDTAP

项目编号	1620423
	X-ray and Spectroscopic Studies of Subduction-Related Phases: Probing the Mid-Point of Volatile Recycling in the Earth
	Quentin Williams
主持机构	University of California-Santa Cruz
项目开始年	2016
	2016-07-01
项目结束日期	2019-06-30
资助机构	US-NSF
项目类别	Continuing grant
项目经费	126000(USD)
国家	美国
语种	英语
英文摘要	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).
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/69777
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Quentin Williams.X-ray and Spectroscopic Studies of Subduction-Related Phases: Probing the Mid-Point of Volatile Recycling in the Earth.2016.