The equilibrium diaspore-corundum at high pressures
Fockenberg, Thomas; Wunder, Bernd; Grevel, Klaus-Dieter; Burchard, Michael
European Journal of Mineralogy Volume 8 Number 6 (1997), p. 1293 - 1300
published: Jan 8, 1997
manuscript accepted: Jun 26, 1996
manuscript received: May 22, 1996
ArtNo. ESP147050806008, Price: 29.00 €
Abstract The equilibrium curve 2 diaspore = corundum + H2O was experimentally investigated by reversal runs in a piston-cylinder apparatus in the pressure range 15 kbar-50 kbar. Its position is determined by reversal brackets at 15 kbar (488-519°C), 25 kbar (581-600°C), 30 kbar (629-648°C), 40 kbar (675-696°C), and 50 kbar (695-719°C), thus lying between the curves reported by Kennedy (1959) and Matsushima et al (1967). In addition, the behaviour of diaspore during heating at one atmosphere was determined using a Guinier camera with heating device. The resulting regression function for the volume has a higher slope in temperature than the function estimated by Berman (1988). Using this newly determined function to describe the thermal expansion of diaspore, the measurements of the isothermal compressibility of this phase performed by Xu et al (1994), and the other thermodynamic data provided by Berman (1988), the calculated curve fits the reversals presented in this paper rather well.