Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ohi, S. Articles by Kitamura, M. Search for Related Content GeoRef GeoRef Citation

An isosymmetric phase transition of orthopyroxene found by high-temperature X-ray diffraction

¹ Department of Geology and Mineralogy, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
² Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan

Correspondence: ^* E-mail: shugo-ohi{at}kueps.kyoto-u.ac.jp

High-temperature synchrotron X-ray powder diffraction experiments for the composition of (Ca_0.06Mg_1.94)Si₂O₆ have been carried out in the present study to clarify whether orthopyroxene has a transition between low- and high-temperature phases. Our results show that discontinuous changes of unit-cell dimensions and volume occur at 1170 °C during both heating and cooling processes and that the space group of Pbca does not change during this reversible phase transition. These facts indicate a first-order and isosymmetric phase transition. This high-temperature phase is thermodynamically distinct from the low-temperature phase, i.e., orthoenstatite in the Mg-rich portion of Mg₂Si₂O₆-CaMgSi₂O₆ phase diagram, although they have the same space group.

Key Words: Orthopyroxene • isosymmetric phase transition • in-situ X-ray experiments • enstatite-diopside system

This article has been cited by other articles:

				S. Jahn and R. Martonak Phase behavior of protoenstatite at high pressure studied by atomistic simulations American Mineralogist, July 1, 2009; 94(7): 950 - 956. [Abstract] [Full Text] [PDF]