Length Scale Dependence of High-Pressure Amorphization: The Static Amorphization of Anorthite

Simon A. T. Redfern
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK

Abstract: High-pressure amorphization of anorthite has been observed by energy-dispersive X-ray diffraction of powdered samples held under static pressure in a diamond anvil cell. The onset of amorphization is accompanied by a significant reduction in the intensity of Bragg reflections at pressures between 10 and 14 GPa, and anorthite becomes completely X-ray amorphous between 14 and 20 GPa. These pressures are significantly lower than those suggested by earlier birefringence studies. The discrepancy can be reconciled in terms of a model of high-pressure amorphization in which partially amorphized anorthite can be regarded as a spatially heterogeneous anti-glass, with long-range order maintained but translational disorder dominating at shorter correlation lengths.

Keywords: high-pressure amorphization • anorthite • anti-glass • metamictisation

Mineralogical Magazine; June 1996 v. 60; no. 400; p. 493-498; DOI: 10.1180/minmag.1996.060.400.10
© 1996, The Mineralogical Society
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