Corundum–quartz-bearing assemblage in the Ihouhaouene area (In Ouzzal, Algeria) |
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| Authors: | M GUIRAUD J-R KIENAST K OUZEGANE |
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| Institution: | Laboratoire de Minéralogie, URA CNRS No. 736, Muséum National d'Histoire Naturelle, 61, rue Buffon, 75005 Paris, France (email: );Laboratoire de Pétrologie, URA CNRS No. 736, Universitéde Paris VI-VII, Tour 26-0, 4 Place Jussieu, 75252, Paris, France;Institut des Sciences de la Terre, U.S.T.H.B., BP 9 Dar El Beïda, Algiers, Algeria |
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| Abstract: | Granulite facies quartzites from the Ihouhaouene region, in the northern part of In Ouzzal, contain the assemblage corundum+quartz+magnetite together with hercynitic spinel+quartz+magnetite, sillimanite+quartz+magnetite and almandine-rich garnet+quartz+magnetite. Two types of corundum have been recognized: the first is primary and is found with quartz and magnetite only; the second type is found together with magnetite and chlorite rimming spinel as a fine-grained corona. The textures show that spinel-rich magnetite probably exsolved primary corundum, sillimanite, spinel and garnet during the cooling history. The secondary corundum formed later from the spinel already exsolved from magnetite. The secondary corundum is certainly metastable with respect to quartz. This may also apply for the primary corundum. However, given the high-temperature setting of this rock, it cannot be excluded that the stable contacts observed between primary corundum and quartz indicate equilibrium between the two phases. Taking into account the uncertainties in the thermodynamic data, the stability of this assemblage would imply that this part of In Ouzzal has recorded very high P–T conditions, above 1100°C at 12 kbar. |
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| Keywords: | corundum+quartz high-temperature high-pressure granulite In Ouzzal Hoggar magnetite-bearing quartzite |
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