IMMISCIBILITY PRODUCED BY MELTING OF EXTRUSIVE ROCKS

Abstract

A series of melting tests were conducted on samples of various compositions collected from volcanic rocks of the Rudnyy Altai ore-bearing complexes, as well as from obsidian formed in most recent volcanic eruptions in Armenia. The tests were run in a high-pressure vessel with a 3.5-cm3 reaction zone by heating sealed metal ampoules with the material to between 110° and 1350° ±50°C at a constant pressure of 10 kb. It is found that at about 1100°C the rock does not melt and is converted merely to compact sinter. At higher temperatures, too, there is only partial melting. Homogeneous glass was obtained at 1350°C, as well as between 1100° and 1300°C in the presence of volatiles. The results clearly confirm the view that volatiles and phosphorus sharply lower the melting point and actively stimulate layering of melts.