This continuing research project will examine the solution characteristics of highly charged cations in peralkaline, metaluminous and peraluminous SiO2-rich melts. Phase equilibria, kinetic, and spectroscopic techniques will be applied to the study of Nb, Ta, Ti and Sn in the haplogranite system K2O-Na2O-Al2O3-SiO2-H2O. High- temperature micro-Raman spectroscopy will be used for the study of melt microstructure. The objectives of the research are to establish a hierarchy of interactions of these highly charged cations with network-forming, network-modifying, and other highly charged cations and to examine the phase equilibria of highly evolved magmas such as high silica rhyolites and pegmatites.
