Early dolomitization and partial burial recrystallization: a case study of Middle Triassic peritidal dolomites in the Villány Hills (SW Hungary) using petrography, carbon, oxygen, strontium and clumped isotope data

Abstract

Peritidal carbonates of the Csukma Formation (Csukma Dolomite Member) in the Villany Hills, SW Hungary, were investigated to determine the nature of the dolomitization and recrystallization processes that affected these rocks during their complex tectonic evolution, and to evaluate if clumped isotope data preserved signals from the original dolomitization event or are indicative of the later recrystallization processes. Sedimentary and petrographic features, as well as geochemical characteristics integrated with the tectonic evolution of the area indicate that dolomitization likely occurred penecontemporaneously via geothermal convection of normal-to-slightly modified seawater in a near-surface to shallow burial setting. This was followed by partial recrystallization of the dolomites in an intermediate burial setting with low water-to-rock ratios. Results of this study suggest that the clumped isotope temperatures of dolomites, partially recrystallized via dissolution–re-precipitation, may provide a minimum estimate of the temperature of recrystallization. However, caution has to be taken when interpreting the thermal history and fluid evolution of successions that were affected by significant recrystallization, because the clumped isotope temperatures and the calculated fluid compositions might inaccurately represent the diagenetic conditions.