Textures and phase relationships in ferrous granulites from Tidjenouine (Hoggar, Algeria): fayalite–ferrossilite–quartz secondary assemblage |
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Authors: | Abderrahmane Bendaoud Khadidja Ouzegane Jean-Robert Kienast |
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Affiliation: | a Faculté des Sciences de la Terre, de Géographie et d’Aménagement du Territoire, U.S.T.H.B., B.P.32, Dar el Beida, Algiers, Algeria;b Laboratoire de Pétrologie, CNRS UMR 7097 IPGP, Université de Paris 7, Tour 26-O, 4 place Jussieu, 75252, Paris, France |
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Abstract: | Ferrous granulites in the area of Tidjénouine (Central Hoggar) exhibit a remarkable mineralogical composition characterized by the association orthoferrossilite–fayalite–quartz. These granulites are metamorphosed mafic igneous rocks showing the juxtaposition of different metamorphic parageneses. Peak paragenesis with garnet–clinopyroxene–amphibole–plagioclase–quartz reach to assemblage with orthopyroxene–plagioclase2. Secondary orthopyroxene reacted with garnet to produce symplectites with fayalite + plagioclase + quartz. The latest stage corresponds to an orthopyroxene–fayalite–quartz–plagioclase assemblage. The metamorphic history of the ferrous granulites is inferred by combining the study of phase relations with the construction of a petrogenetic grid and pseudosection in the CFMASH and CFAS systems using the Thermocalc program of [J. Metamorph. Geol. 6 (1988) 173]. The evolution of paragenetic minerals indicates a metamorphic P–T path through the following conditions: 7.1 ± 1 kbar at 880 °C, 4.9 ± 1.6 kbar at 750 °C and 3–4 kbar at 700 °C, which is consistent with a clockwise P–T path recorded throughout the area. |
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Keywords: | Fayalite– orthoferrossilite– quartz Granulite Tidjenouine Central Hoggar |
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