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Polymetamorphic Al, Mg‐rich granulites with orthopyroxene–sillimanite and sapphirine parageneses in Archaean rocks from the Hoggar, Algeria
Author(s) -
Kienast J. R.,
Ouzegane K.
Publication year - 1987
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350220607
Subject(s) - granulite , geology , sillimanite , geochemistry , metamorphic rock , archean , cordierite , mineral , petrology , geomorphology , paleontology , facies , quartz , chemistry , structural basin , biotite , catalysis , biochemistry , organic chemistry
An orthopyroxene–sillimanite association occurs in Al–Mg rich granulites within Archaean aluminous metapelites at In Hibaou (NW Hoggar). Sapphirine is characteristically present in those rocks as a reaction product of a high pressure mineral association. Other reaction products include cordierite and a second generation of orthopyroxene, confirming the presence of two superimposed metamorphic events (M1 and M2). The application of mineral geothermometers and geobarometers to the observed parageneses in the two metamorphic events gives the following P–T ranges M1, 10 ± 1.5 Kb — 800–900°C: M2, 5 ± 1.5 Kb — 800–700°C. These values are in general agreement with those deduced from associated pyrigarnites.