Apports des phyllosilicates dans la différenciation entre altération hypogène et altération supergène dans le basalte triasique du Moyen Atlas (Maroc)Contribution of phyllosilicates to distinguish between hypogene alteration and weathering in Triassic basalt from Middle Atlas (Morocco) |
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Authors: | Abdelilah Dekayir Michel Danot Nabil Allali |
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Institution: | 1. Département de géologie, faculté des sciences, BP 4010, Beni M''hamed, Meknès, Maroc;2. Laboratoire de chimie des solides, institut des matériaux Jean-Rouxel, 2, rue la Houssinière, BP 32299, 44322 Nantes cedex 03, France;3. Laboratoire de chimie minérale appliquée, faculté des sciences, BP 4010, Beni M''hamed, Meknès, Maroc |
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Abstract: | Triassic basalt of the Middle Atlas has been subject to metamorphic transformation then weathering. Occurrence in both metabasalt and saprolite of ubiquitous clay minerals, such as smectite and mixed layers chlorite–smectite, makes it difficult to distinguish between the two alteration facies and explains the interest of complementary sources of information. In the Bhallil weathering profile, petrographical and mineralogical analyses of primary igneous minerals and their alteration products coupled with Fe oxidation state determination in clay fractions allow to identify three alteration facies: (i) metamorphic basalt, where iron occurs mainly as the ferrous form; (ii) the lower part of saprolite, where iron is partially oxidized to its ferric form; (iii) the upper part of saprolite, where iron is completely oxidized. To cite this article: A. Dekayir et al., C. R. Geoscience 334 (2002) 877–884. |
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Keywords: | basalt Trias metamorphic alteration weathering Mössbauer spectroscopy phyllosilicate basalte Trias altération métamorphique altération supergène spectrométrie Mössbauer phyllosilicate Géomatériaux Minéralogie Geomaterials Mineralogy |
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