Composition of silicate melt of fluorite-containing ongonites at 700–800 °C, 1 kbar and different oxygen fugacity

Abstract

Experiments on the melting of samples of fluorite-containing ongonites from the Ary-Bulak massif at 700–800 °C at a pressure of 100 MPa and oxygen fugacity corresponding to the Ni–NiO and Mt–Hem buffers were carried out. In all experiments, the limit of fluorine content in the aluminosilicate melt and saturation with respect to fluorite and topaz were reached. The change in oxygen fugacity does not qualitatively affect the phase relations in the studied samples, but leads to a slight increase in the solubility of topaz and a decrease in the solubility of fluorite in the silicate melt. In the composition of the silicate melt, there is a corresponding change in the value of the agpaite coefficient Ka and the content of CaO.