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The occurrence of deerite in highly oxidizing conditions within the ‘schistes lustrés’of eastern Corsica
Author(s) -
VERNIÉ P.,
KIENAST J. R.,
MÉVEL C.
Publication year - 1986
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1986.tb00359.x
Subject(s) - pyroxene , amphibole , geology , hematite , magnetite , mineral redox buffer , paragenesis , mineralogy , metamorphism , geochemistry , electron microprobe , pyrrhotite , pileus , analytical chemistry (journal) , chemistry , metamorphic rock , pyrite , olivine , quartz , paleontology , chromatography , mantle (geology) , mushroom
A deerite‐bearing rock occurs at the boundary between quartzite and metabasites within the ‘schistes lustrés’of eastern Corsica. It contains the typomorphic assemblage pyroxene, blue amphibole, hematite and magnetite. Pyroxene shows homogeneous composition close to the aegirine end‐member and blue amphibole is zoned from crossite core to riebeckite rim. The bulk chemical analysis of the rock is remarkable by its very high iron content and the presence of an unusually large amount of Zn which is concentrated in both deerite and amphibole. Electron microprobe analyses of the Corsican deerite are compared with those published in the literature; as shown by deerite from the Fransciscan iron formation, the principal substitution for Fe 2+ is Mn whereas the amount of substitution for Fe 3+ is low. In the system SiO 2 ‐FeO‐Fe 2 O 3 ‐Al 2 O 3 ‐Na 2 O‐MgO‐H 2 O the typomorphic paragenesis can be described by an univariant reaction interpreted as the result of a pressure decrease. P‐T conditions of metamorphism, previously estimated to be 8 kbar and 300°C, are in good agreement with present knowledge of the deerite stability field. The occurrence of hematite and magnetite in equilibrium permits an estimation of the oxygen fugacity (log f o 2 = ‐29.41 bar). Oxidation conditions are higher than those previously mentioned in the literature for similar assemblages.