Structure/property Relations in Silicate-C-O-H-N Melts Melts and Fluids Characterized Experimentally, In-situ, at Mantle Redox Conditions, Pressure, and Temperature

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Intellectual merits. An experimental study is proposed to advance our understanding the processes that govern the budget and recycling of volatile components in the system C-O-H-N in the Earth?s interior. Relationships between structure and transport, volume, and thermodynamic properties of silicate melts and C-O-H-N fluid and fluid/melt element and stable isotope fractionation will be examined while samples are at temperature, pressure, and redox conditions primarily using a hydrothermal diamond anvil cell (HDAC). Major objectives are to: [1] Use vibrational spectroscopy to characterize structure and properties in silicate-C-O-H-N melt, mineral, and fluid systems as proxies to model the behavior of fluids and melts in natural magmatic systems. [2] Determine fractionation of structural species, and of isotopes between minerals, melts, and fluids in silicate-COHN systems using vibrational spectroscopy and microbeam analyses of quenched materials. [3] Develop structure-property models to explain the behavior of natural magmatic systems at P-T conditions corresponding to the upper mantle of the Earth. Current knowledge of structure of solubility and solution mechanisms of C-O-H-N volatile components in silicate melts is based largely on analytical and structural examination of quenched melts (glasses). However, this information does not precisely reflect properties of actual melts. Conversely, the proposed experiments will enable measurements of samples while they are being held at temperature, pressure and redox conditions representative of the Earth?s upper mantle. Characterization how melt structure affects mineral/melt element partitioning will be addressed by combining melt structural data with trace element partitioning experiments (relying on electron microprobe and ion probe analysis of run products). Partitioning of structural species between melts and fluids will be accomplished with vibrational spectroscopic techniques and will be compared with elemental analyses as a means to calibrate the partitioning of the structural species determined by vibrational spectroscopy. Protocols will also be developed for use of vibrational spectroscopy to determine D/H fractionation between fluid and melt while at desired pressure, temperature, and redox conditions. The proposed work will also provide new information on rheology, compressibility, and thermodynamics of component mixing for magmatic systems (melts and fluids) at deep crust and upper mantle conditions. Broader Impacts. The PI typically has one high school student and one undergraduate student (funded by the Geophysical Laboratory) working in his laboratory. This will continue as a part of the proposed research. These programs have been very successful resulting, for example, in seven articles in the peer reviewed literature from the work done in the PIs laboratories during the last several years with undergraduate and high school students as co-authors. In this regard, the PI contributes time to judge and supervise projects by middle and high school students. Winners of this fair proceed to national science competitions such as the International Science Fair and the Siemens Foundation's competition in Math-Science-Technology.