An Experimental Study of Solubility, Solution Mechanisms, and Stable Istope Fractionation of COHN Volatiles in Silicate Melts and Fluids in the Earth's Interior

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Intellectual merit. Characterization of the processes that govern the behavior and budget of volatiles (H2O, CO2, CO, CH4, N2, NH3, noble gases, etc.) in the Earth's interior is fundamental to our understanding of the formation and evolution of the solid Earth, its oceans, and atmosphere. Physicochemical description of melting and crystallization in the Earth's interior is central to this understanding. Experimental characterization of solubility and solution mechanisms of volatiles in silicate melts, and the distribution and stable isotope fractionation of volatile components between condensed and gaseous phases are important components of this knowledge base and form the core of the proposed research. A research program is proposed to experimentally determine (i) the solubility and solution mechanisms in silicate melts of volatiles in the C-H-O-N system as a function of bulk composition, temperature, pressure, and redox conditions with particular emphasis on reduced species, and (ii) isotope fractionation between nitrogen and carbon dissolved in silicate melts and in coexisting gas at mantle pressures and temperatures as a function of speciation of the volatiles in melt and coexisting gas. Preliminary experimental data suggest that this work will have profound implications for core-formation, the Earth's evolution, volatile budget, and degassing processes. The proposed work will provide information on melt structure of simple silicate melt systems with expansions to more complex chemical systems (including Fe-bearing) as needed. These properties will be determined as a function of composition, pressure, temperature, and hydrogen fugacity. Structural studies will be conducted via Raman, Mossbauer, and FTIR spectroscopy. Chemical and isotopic analyses of melts and coexisting gas will be carried out with the electron microprobe, gas chromatography, and mass spectrometry.Broader impacts. In addition to the PI proposed research program will involve on the average 1-2 post-doctoral researchers and 2 undergraduate and high school interns during the 3-year period of the proposed research. The students and post-docs will be involved in execution of experimental projects and in the application of the experimental results to characterization of rock-forming processes. They will, therefore, aid in reaching the goals of the proposed research. In addition, continuing international collaboration between the PI and researchers from the Institute for the Study of the Earth's Interior (ISEI, Misasa, JAPAN) and Institut de Physique du Globe (Paris, FRANCE) will further aid the proposed research program. In particular, collaboration between researchers at the Geophysical Laboratory and at ISEI will be central to the successful completion of the proposed project.