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Evidence against the stability of orthoenstatite above ∼1005°C at atmospheric pressure in CaO‐MgO‐SiO 2
Author(s) -
Carlson William D.
Publication year - 1985
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl012i007p00409
Subject(s) - pyroxene , enstatite , diopside , orthorhombic crystal system , atmospheric pressure , atmosphere (unit) , phase (matter) , geology , mineralogy , chondrite , thermodynamics , astrobiology , olivine , physics , optics , meteorite , quantum mechanics , diffraction , oceanography
Reversals locating the equilibrium orthoenstatite = protoenstatite + diopside in CaO‐MgO‐SiO 2 demonstrate that orthoenstatite cannot exist stably above 1005±10°C at one atmosphere pressure. This in turn suggests that the orthorhombic low‐Ca phase found near 1400°C at atmospheric pressure in this system (formerly identified as orthoenstatite) is in fact a previously unrecognized pyroxene polymorph.