Cooling Rate Dependency of the Formation of Smectite Crystals from a High-Pressure and High-Temperature Hydrous Melt

Hirohisa Yamada1, Hiromoto Nakazawa1 and Eiji Ito2
1 National Institute for Research in Inorganic Materials Namiki 1, Tsukuba, Ibaraki 305, JAPAN
2 Institute for Study of the Earth's Interior, Okayama University Misasa, Tottori 682-02, JAPAN

Abstract: The effect of cooling rate on the formation of smectite crystals with high crystallinity was investigated using two different types of high-pressure and high-temperature apparatus, a modified belt type and a uniaxial split-sphere type. The cooling rate was changed after a treatment of the sample at 5.5 GPa and 1500°C. Smectite crystals were obtained at faster cooling rate, coexisting with coesite, kyanite, jadeite, corundum and/or glass. In the slowly cooled process, no smectite crystals were obtained but coesite, kyanite, jadeite and clinoenstatite were formed. These results indicate that smectite crystals are formed metastably during the quenching of the high-pressure and high-temperature hydrous silicate melt.

Key Words: High pressure experiment • Quenching rate • Smectite crystals

Clays and Clay Minerals; December 1995 v. 43; no. 6; p. 693-696; DOI: 10.1346/CCMN.1995.0430605
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)