Superheating, melting and vitrification through decompression of high-pressure minerals

Abstract

A noteworthy feature of some high-pressure silicate minerals is their ready vitrification, either through moderate heating at 1 bar^1–5, as for jadeite (NaAlSi₂O₆) or stishovite (SiO₂), or through room-temperature decompression6, as for calcium silicate perovskite (CaSiO₃). Little attention seems to have been paid to the actual significance of such transitions, and here I argue that these simply represent crystal fusion. The unusual aspect is that the temperature of fusion at low pressures is below the temperature range of the glass–liquid transition. Through a different, thermochemical line of evidence, this extends an overlooked argument outlined by Jeanloz⁷ following the report of the glass/ice I transition by Mishima et al.⁸. The similarities and differences with this transition will be pointed out, as will some theoretical and geophysical implications.