Petrographic and Geochemicial Characteristics of the Kızıloren Formation (Upper Triassic‐Lower Jurassic) in the Akpınar (Konya, Turkey) Area

Abstract

Abstract:This paper describes the occurrence of dolomite and the mechanism of dolomitization of the Upper Triassic‐Lower Jurassic Kızıloren Formation in the autochthonous Bolkardagı unit of the middle Taurus Mountains in south western Turkey. Dolomites were analyzed for geochemical, isotopic and crystallographic variation. Dolomites occur as a replacement of precursor carbonate and cement. The dolomite crystals range from <10 to ∼1000 μm existing as both replacements and cements. Sr concentrations range between 84 and 156 ppm, and the molar Sr/Ca ratios of dolomitizing fluids are estimated to range between 0.0066 to 0.013 ratios. Dolomites are Ca‐rich (with average CaCO3 and MgCO3 equal to 56.43 and 43.57 mol%, respectively) and they are non‐stoichiometric, with an average Sr=116 ppm, Na=286 ppm, Mn=81 ppm, Fe=1329 ppm, and δ18O and δ13C ranges from −0.6‰ to −6.1‰ Pee Dee Belemnite [PDB], and +1.2 to +3.9‰ PDB. The North American Shale Composition [NASC]‐normalized rare earth element (REE) values of the both limestone and dolomite sample groups show very similar REE patterns characterized by small positive Eu (mean=1.32 and mean=1.42, respectively) and slightly or considerably negative Ce (mean=0.61 and mean=0.72, respectively) anomalies and a clear depletion in all REE species. The Kızıloren Formation dolomites have been formed as early diagenetic from mixing zone fluids at the tidal‐subtidal environment and at the late diagenetic from basinal brines at the shallow‐deep burial depths.