Equilibrated Gas and Carbonate Standard-Derived Dual (Δ47 and Δ48) Clumped Isotope Values

Carbonate clumped isotope geochemistry has primarily focused on mass spectrometric determination of m/z 47 CO₂ for geothermometry, but theoretical calculations and recent experiments indicate paired analysis of the m/z 47 (¹³C¹⁸O¹⁶O) and m/z 48 (¹²C¹⁸O¹⁸O) isotopologues (referred to as $$ and $$) can be used to study non-equilibrium isotope fractionations and refine temperature estimates. We utilize 5,448 $$ and 3,400 $$ replicate measurements of carbonate samples and standards, and 183 $$ and 195 $$ replicate measurements of gas standards from 2015 to 2021 from a multi-year and multi-instrument data set to constrain $$ and $$ values for 27 samples and standards, including Devils Hole cave calcite, and study equilibrium $$-$$, $$-temperature, and $$-temperature relationships. We compare results to previously published findings and calculate equilibrium regressions based on data from multiple laboratories. We report acid digestion fractionation factors, $$ and $$, and account for their dependence on the initial clumped isotope values of the mineral.