[SIT21-P04] Viscosity of potassium titanosilicate melt at high pressure
Keywords:magma, viscosity, high pressure
We performed in situ falling sphere viscometry in the pressure range from 1.3 to 7.4 GPa, by using the MAX-III high pressure apparatus at BL14C2 and NE7A beamlines at Photon Factory in KEK, Tsukuba, Japan. A falling platinum sphere in the melt was monitored by using an X-ray CCD camera with a YAG:Ce fluorescence screen. We observed that the viscosity of KTS4 melt decreased up to 3.3 GPa. In contrast, the pressure dependence in viscosity was not observed above 3.3 GPa. Based on XANES spectra of K2TiSi4O11 glasses quenched under high pressure, Paris et al. (1994) showed that the coordination number of titanium increased with increasing pressure. The present study suggests that the melt becomes depolymerized by the coordination change of titanium under high pressure.