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On some sources of errors in phase‐equilibria investigations at ultra‐high pressure; phase diagram of silica
Author(s) -
Ostrovsky I. A.
Publication year - 1967
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350050207
Subject(s) - stishovite , coesite , pyrophyllite , phase diagram , quartz , geology , mineralogy , brine , thermodynamics , phase (matter) , mantle (geology) , analytical chemistry (journal) , chemistry , geochemistry , environmental chemistry , physics , organic chemistry , paleontology , eclogite , subduction , tectonics
Large pressure gradients and unrecognizable variations of pressure occur when solid substances are compressee by cold anvils (pistons) and heated by internal heaters. To improve the reliability of the results the miniaturization of samples and preliminary firing of pyrophyllite (which transmits pressure) are suggested. The equilibrium coesite—stishovite may be empirically expressed as: P kb = 85 + 0·364 T (°C) Stishovite must be playing an important role in the mantle at depths greater than 500 km. Quartz and stishovite do not coexist in nature whatever PT‐conditions are.