A NEW-TYPE OF HIGH-TEMPERATURE, HIGH-PRESSURE-CELL FOR SPECTROSCOPIC STUDIES OF HYDROUS SILICATE MELTS

A novel type of high-temperature, high-pressure cell has been designed for near-infrared and optical spectroscopy of hydrous silicate melts at pressures up to 3 kbar and temperatures up to 800 degrees C. It con sists of an externally heated cell with a disk-shaped sample chamber ( 4 mm in diameter and 0.2 mm in height) that is compressed between a tu ngsten carbide piston and a cylindrical sapphire window. A platinum ri ng surrounding the sample prevents loss of melt or water during the ex periment. The new spectroscopic cell was used for direct measurement o f H2O species in aluminosilicate melts by near-infrared spectroscopy. Other possible applications of the cell include the study of silicate melts doped with transition metal ions in the UV-VIS-NIR and the obser vation of the crystallization and dissolution of minerals in hydrous s ilicate melts under in situ conditions.