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Effect of pressure on reversible solid-solid transitions in nepheline and carnegieite

Published online by Cambridge University Press:  05 July 2018

Lewis H. Cohen
Affiliation:
Department of Earth Sciences, University of California, Riverside 92502
William Klement Jr.
Affiliation:
School of Engineering and Applied Science, University of California, Los Angeles 90024. Now on leave at National Physical Research Laboratory, Pretoria, Republic of South Africa

Summary

Differential thermal analysis of a rapidly reversible transition in carnegieite to 7 kbar shows the transition temperature increases from ⪝ 707°C (on heating) at I bar with initial slope ≈ 8·0 deg kbar−1 and anomalous curvature (d2T/dp2 > o), with hysteresis between heating and cooling signals that decreases with pressure. DTA of rapidly reversible transitions in nepheline shows the very subtle transition near 185°C (on heating) at 1 bar decreases with pressure to ≈ 170°C near 2-3 kbar and hardly varies in temperature up to 6 kbar; and the higher temperature transition increases from ≈ 872°C (on heating) at 1 bar with slope ≈ 25 deg kbar−1, to 5 kbar, with the hysteretic interval remaining essentially unchanged in the investigated range.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1976

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