Nature of Silicate Melts: Role of Highly Charged Cations

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This is a continuation of the research supported by NSF grant EAR-8416796 to determine the solution behavior of highly charged cations in peralkaline, metaluminous and peraluminous "granitic" melts. The proposed research involves the determination of (1) the redox equilibria of Fe+2 -Fe+3 in K2O-Al2O3-SiO2 melts doped with TiO2, P2O5, Group 1A and Group 2A elements, (2) the coordination of Fe+3 in these melts using Mossbauer spectroscopy, (3) the saturation of unary oxide phases such as rutile, cassiterite among others as functions of Group 1 and, Group 2 elements, P2O5, TiO2 and B2O3 contents, (4) the saturation of unary oxide phases as functions of H2O content in peralkaline melts, (5) vibration and NMR spectra K2O.5SiO2 glasses containing Period 5 elements, (6) two liquid partitioning experiments in flourine and chlorine-doped melts. These studies combined with thermodynamic modeling of the equilibria will increase our understanding of the complex interactions that occur in these important end-member types of granitic magmas.