PHASE EQUILIBRIA IN THE NEPHELINE-DIOPSIDE-SPHENE SYSTEM

Abstract

The mineralogy and geochemistry of titanium in rocks of the ultramafic-alkalic association are complex and varied. The reasons are, first, the high concentration of titanium in the primary magmas of this association, and, second, the complicated effect of the high activity of alkali on the behavior of titanium, which is amphoteric. Typical natural parageneses of titanium minerals and their chemical composition have been studied in great detail, but there are insufficient data on the phase equilibria of titanium compounds in silicate systems, which serve as models for ultramafic-alkalic magmas. The authors present their experimental data of phase equilibria in the nepheline-diopside-sphene system.