A Unified Clumped Isotope Thermometer Calibration (0.5–1,100°C) Using Carbonate‐Based Standardization

The potential for carbonate clumped isotope thermometry to independently constrain both the formation temperature of carbonate minerals and fluid oxygen isotope composition allows insight into long‐standing questions in the Earth sciences, but remaining discrepancies between calibration schemes hamper interpretation of temperature measurements. To address discrepancies between calibrations, we designed and analyzed a sample suite (41 total samples) with broad applicability across the geosciences, with an exceptionally wide range of formation temperatures, precipitation methods, and mineralogies. We see no statistically significant offset between sample types, although the comparison of calcite and dolomite remains inconclusive. When data are reduced identically, the regression defined by this study is nearly identical to that defined by four previous calibration studies that used carbonate‐based standardization; we combine these data to present a composite carbonate‐standardized regression equation. Agreement across a wide range of temperature and sample types demonstrates a unified, broadly applicable clumped isotope thermometer calibration. Plain Language Summary Carbonate clumped isotope thermometry is a geochemical tool used to determine the formation temperature of carbonate minerals. In contrast to previous carbonate thermometers, clumped isotope thermometry requires no assumptions about the isotopic composition of the fluid from which the carbonate precipitated. By measuring the clumped isotope composition (Δ47) of carbonate minerals with a known formation temperature, we can construct an empirical calibration for the clumped isotope thermometer that is necessary to convert from a Δ47 value to formation temperature. Many previous studies have created Δ47 temperature calibrations, but differences between calibrations have led to large uncertainty in final Δ47 temperatures. This study measures a large number of samples that span a wide range of temperatures (0.5–1,100°C) and include many different types of carbonates. These data show that a single calibration equation can describe many sample types and that when data are carefully standardized to a common set of carbonate materials, calibrations performed at different laboratories agree almost identically. We combine these data to present a carbonate clumped isotope thermometer calibration with broad applicability across the geosciences. Key Points Reanalysis of previous Δ47 calibration samples reconc