The primary goals of this proposal are to 1) resolve relatively poorly constrained aspects of volume mixing properties in reduced iron-bearing silicate melts, 2) resolve pressure and temperature dependence of iron speciation reactions in such melts, and 3) use spectroscopic evidence to investigate the structure of iron species in silicate melts. This work will improve our ability to predict iron redox state in silicate melts as a function of pressure, temperature and bulk composition. This team will perform the first measurements of the density of ferrous iron-dominated silicate melt compositions that are relevant to natural magmas. The expected results will enable improved predictions of partial molar volumes of ferrous and ferric iron in silicate melts, the compositional dependence of all iron speciation in silicate melts, and the pressure dependence of mineral-melt reactions in iron-bearing systems. Previously obtained Mossbauer and Raman spectroscopic data, combined with compositional data from this study and the literature will lead to better refinement of the structure of iron-bearing molecules present in silicate melts and lead to improvement of redox models for such melts. To more accurately predict iron redox state in natural silicate melts as a function of pressure, temperature and bulk composition. Achievement of these goals will lead to more realistic understanding of the behavior of igneous systems and their role in planetary evolution.
Broader Impacts The proposed laboratory experiments will provide an ideal opportunity for involving good undergraduate researchers in the scientic process and their active participation in cutting edge science. Most undergraduates who have worked in this laboratory have participated in at least one major national scientific meeting. This grant also will provide funding for a Ph.D. researcher The work itself has many applications beyond the immediate goals (e.g., in the fields of cosmochemistry, planetology, and material science).
