Comparison of dolomitization models of Triassic-Neocomian carbonates in the easthern High Zagros

The Mesozoic sequence in the Zagros Region (SW Iran) consists dominantly of carbonates especially dolomite that play the role of reservoir in many oil and gas fields of the region. To investigate the function of sedimentary and diagenetic processes in the formation of Triassic-Neocomian dolomites of the easthern High Zagros, this study focuses on petrography and geochemistry of the carbonates crop out in the Khaneh Kat anticline. Field and laboratory data led to the recognition of four different dolomitization models within the studied carbonates. The Lower-Middle Triassic and Upper Jurassic dolomites are medium to thick-bedded and composed of fine to medium-grained relatively ordered dolomite. The stoichiometric chemistries and heavier oxygen isotope ratios of these dolomites as well as the considerable presence of evaporites indicate the favorable conditions for the formation of early dolomite due to downward-percolating of concentrated evaporate brines (reflux model). The Upper Triassic dolomitic portion of the Zagros consists of medium to coarse-crystalline, massive-bedded dolomites with relatively light isotopic composition. Mineralogy and geochemistry of these dolomites indicate a high temperature origin as well as their relationship to diagenetic processes, including recrystallization in a deep-subsurface environment (burial model). In the Upper Jurassic portion of the succession, dolomites are ...