Diagenetic Evolution of Upper Jurassic-Lower Cretaceous Berdiga Formation, NE Turkey: Petrographic and Geochemical Evidence

Upper Jurassic-lower Cretaceous Berdiga Formation crops out extensively in NE Turkey. The host carbonates at Eski Gumushane section are pervasively dolomitized by fabric-destructive and fabric-preserving replacive dolomites (RD). These dolomites are Ca-rich and non-stoichiometric (Ca56-58Mg42-44). They have highly variable but low delta O-18 (-11.38 to -4.05 parts per thousand V-PDB) and delta C-13 (0.69 to 3.13 parts per thousand V-PDB) values, radiogenic Sr-87/Sr-86 ratios (0.70753 to 0.70884), extremely high Fe (2727-21053 ppm) and Mn (1548-27726 ppm) contents. Micro-crystalline quartz cement, dolomite cement and the scattered euhedral pyrite minerals (average 5 mu m) are also observed in the dissolution porosity of replacive dolomites. This study demonstrates that these carbonates have undergone a complex diagenetic history from shallow to deep burial associated with syn-sedimentary extensional tectonic activity during the Albian-Aptian and later with the hydrothermal emplacement of the polymetallic mineralization during the Eocene.