Original paper

Boron-free kornerupine: its upper pressure stability limit in the system MgO-Al2O3-SiO2-H2O (MASH)

Wegge, Sabine; Schreyer, Werner

European Journal of Mineralogy Volume 6 Number 1 (1994), p. 67 - 76

27 references

published: Feb 4, 1994
manuscript accepted: Sep 7, 1993
manuscript received: Feb 5, 1993

DOI: 10.1127/ejm/6/1/0067

BibTeX file

ArtNo. ESP147050601007, Price: 29.00 €

Download preview PDF Buy as PDF

Abstract

Abstract Synthetic boron-free kornerupine obtained at 7 kbar water pressure and 830°C has the formula (Mg3.72Al5.21)[6](Al1.28Si3.72)[4]O19.76(OH)2.24. It thus lies exactly on the join enstatite-corundum, midway between the M:A:S ratios 4:3:4 and 1:1:1. By extending the work of Seifert (1975) towards higher water pressures, the upper pressure stability limit of this phase was determined to lie between about 11.5 and 13 kbar for T = 800-900°C. The high-pressure breakdown assemblage is enstatite + corundum, and the reaction curve has a flat positive slope. Thus dehydration of B-free kornerupine at this pressure proceeds toward lower temperatures. The lower temperature stability limit in the range 7-11 kbar is defined by breakdown to the more hydrated assemblage chlorite + talc + corundum between 735°C and 750°C, the reaction curve possessing a steep, probably positive slope

Keywords

system MgO-Al2O3-SiO2-H2Okornerupinecompositional datareaction relationsstability