T204 Ultrahigh-Pressure Metamorphism: Observations from Nano through Outcrop to Plate-Tectonic Scales II: In Honor of J.G. Liou, 2011 MSA Roebling Medalist (Note: This session has moved to Wednesday, 8 a.m.–noon, Room 101FG)
Tuesday, 11 October 2011
1:30 PM - 5:30 PM
Room M101AB
KYANITE-SILLIMANITE EQUILIBRIUM AT 900 C BY CRYSTAL WEIGHT CHANGE
Paper number: T204-13
Program: Technical Sessions
Time: 4:30 PM – 4:45 PM
Authors
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Craig E. ManningUniversity of California, Los Angeles, CA
Abstract
The sillimanite to kyanite transition was redetermined at 900 C in piston cylinder apparatus with NaCl pressure medium using a hydrothermal weight change method and very pure natural sillimanite and kyanite single crystals. Weight changes of the kyanite crystals in experiments of 24 hr. duration traversed the sillimanite-to-kyanite equilibrium boundary in 0.5 kbar increments from 10.0 to 15.0 kbar. Kyanite crystals were weighed before and after the experiments on an ultramicrobalance to a precision of 0.2 microg and water was weighed to a precision of 2 microg by difference after sealing without weight loss. The weight change data yield a null point of 11.7+-0.2 kbar. We thus confirm that the equilibrium transition lies in the upper one-half of the approximately one-kbar-wide interval of uncertainty found by previous investigators at that temperature.