Hydrous Magmatic Processes: An Experimental Study of Structure and Properties of Hydrous Silicate Melts, In-Situ, at High Pressure and Temperature

Carnegie Institution Of Washington, Washington DC

Investigators

Abstract

Intellectual merit. Mass and energy transfer processes in the Earth and terrestrial planets involve melting and crystallization at high temperature and pressure. As an important contribution to our understanding of such magmatic processes, a research program is proposed (1) to conduct an experimental study, in-situ, at high pressures and temperatures of the structure of hydrous silicate melts, and (2) to determine of how melt structure governs physicochemical properties of hydrous melts. The research is motivated by the fact nearly all magmatic processes are strongly affected by their H2O content. Experimental characterization of solution mechanisms of H2O in silicate melts commonly relies on data obtained from hydrous glasses serving as proxies for silicate melts. However, transformation of hydrous melts to hydrous glasses causes structural changes. The glass data cannot be used for quantitative modeling of physicochemical properties of hydrous melts. In this study, we will, therefore, determine hydrous melt structure of binary metal oxide-silica and ternary metal oxide-alumina-silica systems while the materials are at high pressure and temperature. These simple model systems will be used in order to identify and isolate individual chemical components governing structure and structure-property relationships. Structural studies will be conducted via Raman and FTIR spectroscopy of hydrous melts in a hydrothermal diamond anvil cell operating in the 25-1000C and 0.1MP-1.5 GPa temperature, and pressure ranges, respectively. The melt data will be augmented by determination of hydrous glass structure using Raman, FTIR, and NMR spectroscopic methods. Structure analysis of melts and their glasses will also contribute to our understanding of glass-forming processes and provide information to assess the extent to which silicate glass structure can be used as a proxy for melt structure. Broader impacts. The research program will involve, on average, 1-2 post-doctoral researchers and 2 undergraduate and high school students throughout 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. In addition, continuing and expanding 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.