Calcitization/dedolomitization of Jurassic dolostones (Lebanon): results from petrographic and sequential geochemical analyses |
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| Authors: | FADI H NADER RUDY SWENNEN EDDY KEPPENS |
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| Institution: | 1. Department of Geology, American University of Beirut, PO Box 11‐0236/26, Beirut, Lebanon (E‐mail: fadi‐henri.nader@ifp.fr);2. Present address: Department of Sedimentology–Stratigraphy, Institut Fran?ais du Pétrole, 1 & 4 Av. de Bois‐Préau, 92852 Rueil‐Malmaison Cedex, France.;3. Geologie, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B‐3001 Heverlee, Belgium;4. Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium |
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| Abstract: | Calcitized Jurassic dolostones from central Mount Lebanon (Kesrouane Formation) are discussed utilizing petrographic, mineralogical and geochemical data. In particular, two sequential extraction methods for both major/trace elements and stable isotope analyses provide results that support and refine conventional bulk analyses data. The new data demonstrate that the major dedolomitization phase of the investigated Jurassic carbonates occurred as a result of the migration of karst‐related meteoric waters (characterized by soil‐derived carbon, and estimated δ18OV‐SMOW composition between ?7·2‰ and ?3·4‰) into previously dolomitized horizons within the limestone rock, during the final uplift and emergence of Mount Lebanon, after Palaeogene time. The study demonstrates that, in this case, the mechanisms of dedolomitization and their resulting fabrics are controlled primarily by the texture of the original dolomite rock. Pervasively dolomitized rocks, where the micritic matrix is entirely dolomitized, show calcitization mainly through dissolution/precipitation. By contrast, the rock textures that still include a considerable amount of limey micritic matrix – spared from dolomitization – are more prone to mole per mole and mimic replacement of the dolomite crystals by calcite. |
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| Keywords: | Dedolomite sequential extraction oxygen isotope stoichiometry |
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