Petrographic, chemical and stable isotope investigations have been made on calcite, dolomite, and Fe-dolomite/ankerite from Permian-Triassic clastic sequences from the Iberian Range (Spain). Calcite and dolomite cements have precipitated before the Fe-dolomite/ankerite. Calcite, however, has also formed by calcitization of dolomite due to uplift. The negative δ13CPDB values (-9.51 to -2.13%) in these carbonates suggest derivation of carbon from oxidation of organic matter in the early carbonates and from decarboxylation of organic matter in the late Fe-dolomite/ankerite. Early diagenetic dolomitic cements have heavier δ13C(> -3.54%), higher Mn/(Mn + Fe) and Mn/(Mn + Mg) and lower Fe/(Fe + Mg) ratios than later diagenetic dolomitic cements. The latters are also characterized by lighter δ18OPDB (> -10.64%) than the early cements due to increase in temperature and to pore water-mineral reactions.
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