HYDROTHERMAL DIAMOND-ANVIL CELL STUDY OF MELTS - EUTECTIC MELTING OF THE ASSEMBLAGE CA(OH)(2)-II PHASE(CACO3 WITH EXCESS H2O AND LACK OF EVIDENCE FOR PORTLANDITE)
Im. Chou et al., HYDROTHERMAL DIAMOND-ANVIL CELL STUDY OF MELTS - EUTECTIC MELTING OF THE ASSEMBLAGE CA(OH)(2)-II PHASE(CACO3 WITH EXCESS H2O AND LACK OF EVIDENCE FOR PORTLANDITE), The American mineralogist, 80(7-8), 1995, pp. 865-868
Eutectic melting temperatures for the assemblage Ca(OH)(2) + CaCO3 in
the presence of excess H2O were determined along six isochores of H2O
in a hydrothermal diamond-anvil cell. These temperatures range from 61
0 degrees C at 1204 bar to 583 degrees C at 7203 bar; they agree very
well (within 3 degrees C) with data obtained from high-pressure differ
ential thermal analysis (HP-DTA) and are about 20 degrees C lower than
those obtained from quench experiments. The additional DTA peaks near
630 degrees C for the melting experiments of pure portlandite reporte
d by Harker (1964) and Bai et al. (1994) may be the result of a small
amount of melting, caused by CaCO3 contamination, and not the result o
f a solid phase transition between portlandite and ''portlandite II.''