Collaborative Research: Examining Upper Mantle Volatile History Through Isotopic Variations of Carbon, Nitrogen, Hydrogen and Noble Gases in Undegassed Mid-Ocean Ridge Basalts

GSTDTAP

项目编号	1558798
	Collaborative Research: Examining Upper Mantle Volatile History Through Isotopic Variations of Carbon, Nitrogen, Hydrogen and Noble Gases in Undegassed Mid-Ocean Ridge Basalts
	David Graham
主持机构	Oregon State University
项目开始年	2016
	2016-03-15
项目结束日期	2019-02-28
资助机构	US-NSF
项目类别	Standard Grant
项目经费	225085(USD)
国家	美国
语种	英语
英文摘要	Measurements of volatiles such as carbon dioxide, water, nitrogen and noble gases in submarine basalts from mid-ocean ridges have provided considerable insight into the origin of Earth's atmosphere and oceans, and the geologic history of cycling between the surface of the Earth and its interior. However, almost all submarine basalts have lost much of their volatile inventory by degassing when they are erupted, which has led to a major loss of the reliable chemical data needed to identify pristine chemical signatures from Earth's mantle. As a result, there is significant uncertainty and controversy in our understanding of the origins of volatiles and their fluxes into and out of the Earth. This research carries out analyses of the very rare occurrences of undegassed mid-ocean ridge basalts to obtain information on the mantle isotopic composition of carbon, nitrogen, hydrogen and noble gases (helium, neon and argon). Collectively, these gases can be used synergistically to better understand how Earth's atmosphere and oceans formed and evolved. Mid-ocean ridges are fundamental geologic features of Earth's surface, and one of the most intriguing challenges in geosciences is understanding the processes by which they are created and evolve. The chemical and isotopic data resulting from this project are fundamental in this regard, and will provide benchmarks for years to come for models of degassing at ocean ridges and the origin and evolution of Earth's volatiles. Broader impacts of the work include funding an institution in Oklahoma, a state that receives comparatively little federal money (i.e., an EPSCoR state) and the development of new international collaborations with French scientists. It also uses NSF-funded analytical facilities at Oregon State University and develops new methods for analyzing noble gases in rock samples, building infrastructure for science. Findings will also be incorporated into classes taught by the investigators and used to develop a new seminar for graduate students centered on modeling of reservoirs, processes and fluxes in chemical geodynamics. The scientific goals of this research are to test the extent to which regions of the upper mantle beneath mid-ocean ridges and continental rifts are similar in their volatile abundances and isotopic compositions on a global scale. Analyses of carbon, nitrogen, hydrogen, and noble gases in undegassed mid-ocean ridge basalts will allow, for the first time, testing of the inter-relationships of noble gas and major volatile isotopes in CO2, N2, and H2O without employing degassing corrections. This allows a direct test for regional heterogeneity in the upper mantle. The research also specifically addresses the questions: (1) What proportions of the volatiles C, N and H2O in the upper mantle are primordial versus recycled; (2) do carbon stable isotopes in the ultra-depleted mid-ocean ridge basalts carry a record of earlier depletion in low degree melts that appears to be required in formation of the ultra-depleted source; (3) what is the behavior and concentration of N in the depleted upper mantle; and (4) what record of early Earth processes is preserved in the primordial isotope ratios of upper mantle noble gases.
来源学科分类	Geosciences - Ocean Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/69250
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	David Graham.Collaborative Research: Examining Upper Mantle Volatile History Through Isotopic Variations of Carbon, Nitrogen, Hydrogen and Noble Gases in Undegassed Mid-Ocean Ridge Basalts.2016.