Comparison of clumped isotope signatures of dolomite cements to fluid inclusion thermometry in the temperature range of 73–176 °C

Abstract

Widespread application of the novel clumped isotope paleothermometer (Δ47) using dolomite samples from shallow crustal settings has been hindered by a lack of adequate constraints on clumped isotope systematics in dolomites that formed at temperatures greater than 50°C. Consequently, many high-temperature applications involving diagenetic dolomites have required an assumption that the relationship between temperature and Δ47 in diagenetic dolomite resembles the theoretical temperature dependence for calcite. Here we present Δ47 results from dolomite cements for which precipitation temperatures were determined independently using fluid inclusion microthermometry. We compare a rock-based “calibration” for samples from the temperature range of ∼73 to 176°C to previously published laboratory-derived calibrations for synthetic calcites. This novel combination of approaches yields results that are broadly consistent with results reported from controlled laboratory experiments, providing an important confirmation of the utility of clumped isotopes in real-world systems. Our results suggest that the Δ47 of dolomite cements may provide key information in the reconstruction of burial and thermal histories and also in the recognition of potential petroleum reservoirs.