Dolomite recrystallization revealed by Δ₄₇/U-Pb thermochronometry in the Upper Jurassic Arab Formation, United Arab Emirates

The process of recrystallization affecting dolomitic successions remains a longstanding enigma in carbonate research. Recrystallization influences the accuracy of genetic dolomitization models as well as the prediction of porosity and permeability distribution within dolomitic reservoirs. We investigate early-formed dolomites of the Upper Jurassic Arab Formation reservoir (Arabian Platform, United Arab Emirates), where recrystallization is not easily ascertained based on petrographic and O-C-Sr isotope analyses. Conversely, the application of Δ₄₇/U-Pb thermochronometry revealed the occurrence of burial recrystallization over a temperature-time interval of ~45 °C/45 m.y. during the Early and Late Cretaceous. The process was initially driven by Late Jurassic mixed marine-meteoric fluids, which evolved during burial in a closed hydrologic system and remained in thermal equilibrium with the host rocks. Recrystallization was a stepwise process affecting the succession heterogeneously, so that samples only few meters apart presently record different temperature-time stages of the process that stopped when hydrocarbons migrated into the reservoir. Our results illustrate how Δ₄₇/U-Pb thermochronometry may provide a novel approach to unravel dolomite recrystallization and to precisely determine the timing and physicochemical conditions (temperature and δ¹⁸O_w) that characterized the process. Therefore, this study paves the way for better appraisal of recrystallization in dolomitic reservoirs.