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Hydration of orthopyroxene–cordierite‐bearing assemblages at Laouni, Central Hoggar, Algeria
Author(s) -
GUIRAUD M.,
POWELL R.,
COTTIN J.Y.
Publication year - 1996
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 - 10.1046/j.1525-1314.1996.06016.x
Subject(s) - cordierite , geology , geochemistry , chlorite , mafic , paragenesis , crystallization , metamorphism , skarn , petrology , metamorphic rock , hydrothermal circulation , paleontology , fluid inclusions , biochemistry , chemistry , quartz , organic chemistry , catalysis
In the Laouni region (Central Hoggar, Algeria), retrogression of high‐grade orthopyroxene–cordierite‐bearing rocks led to the crystallization of orthoamphibole and garnet, and at a later stage of chlorite, from the original paragenesis. Calculated phase diagrams show that this retrogression occurred at about 3 kbar with the simplest model involving hydration at 650–700° C and at around 500° C, with the rocks experiencing a H 2 O less than 1, except possibly in the last stages of chlorite crystallization. As the other rock types occurring in the same area as the orthopyroxene–cordierite rocks display similar features, it is concluded that regional hydration occurred, presumably related to the release of fluids during the crystallization of the Pan‐African granitic and mafic magmas that are widespread in the Laouni area.