Abstract

Mixtures consisting of 50 weight percent of 1921 Kilauea basalt, 16 percent H2O, and 34 percent CO2 were equilibrated at 800°, 900°, 1000° and 1100° C and 2, 5, and 8 kb. Oxygen fugacity was buffered by Ni + NiO. The fluid phase solute was analyzed for Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, Ba, and Sr.

Total solute content ranges from 0.5 to 2 weight percent of the fluid. It is mostly composed of SiO2, Al2O3 and MgO; total iron is depleted compared to the starting material. The high ratios of Mg/Fe and Mg/Ca and the low total solute content appear to rule out gas transfer as a differentiation mechanism under conditions similar to those of this study. The low solubility of iron may explain magnetite deposits formed at diabase-limestone contacts.

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