Cordierite breakdown under high-pressure, hydrous conditions

✍ Scribed by Trevor H. Green; R. H. Vernon

• Book ID: 104785747
• Publisher: Springer
• Year: 1974
• Tongue: English
• Weight: 661 KB
• Volume: 46
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00487557

✦ Synopsis

Clear evidence exists for a cordierite breakdown reaction to amphibole-kyanitequartz 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 4-4 bars/~ occurring between 8 and 10.4 kb at 750~ and between 9.5 and 11.3 kb at 850~ The reaction is cut off at low temperature by the appearance of tale 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~ for high water fugaeities. Other experimental data on the hydration of hypersthene and cordierite-hypersthene stability, point to a temperature below 820~ and an upper pressure limit of 9.5 kb at 750-820~

Experiments at P~[~o <PtotaI indicate that the breakdown of cordierRe to amphibolekyanite-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~