Cordierite breakdown under high-pressure, hydrous conditions

Trevor H. Green*, R. H. Vernon

*Corresponding author for this work

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Clear evidence exists for a cordierite breakdown reaction to amphibole-kyanite-quartz in high-grade metamorphic rocks of the Arunta Complex, Australia. Using the natural minerals this reaction has been duplicated experimentally. It proceeds over a divariant band with a slope of 12±4 bars/°C, occurring between 8 and 10.4 kb at 750° C and between 9.5 and 11.3 kb at 850°C. The reaction is cut off at low temperature by the appearance of talc and at high temperature by the appearance of orthopyroxene. The maximum pressure stability of the amphibole-kyanite-quartz assemblage is about 20 kb. These data suggest that the natural rock was subjected to pressures of at least 8 kb at 750-850° C for high water fugacities. Other experimental data on the hydration of hypersthene and cordierite-hypersthene stability, point to a temperature below 820° C and an upper pressure limit of 9.5 kb at 750-820°C. Experiments at {Mathematical expression}<Ptotal indicate that the breakdown of cordierite to amphibole-kyanite-quartz is a hydration reaction, and occurred in the natural rock as a result of an increase of water fugacity at constant total pressure (8-9.5 kb) and temperature (750-820°C).

Original languageEnglish
Pages (from-to)215-226
Number of pages12
JournalContributions to Mineralogy and Petrology
Volume46
Issue number3
DOIs
Publication statusPublished - Sep 1974

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