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 CO ₂ for geothermometry, but theoretical calculations and recent experiments indicate paired analysis of the m/z 47 ( ¹³ C ¹⁸ O ¹⁶ O) and m/z 48 ( ¹² C ¹⁸ O ¹⁸ O) isotopologues (referred to as Δ 47 and Δ 48 ) can be used to study non-equilibrium isotope fractionations and refine temperature estimates. We utilize 5,448 Δ 47 and 3,400 Δ 48 replicate measurements of carbonate samples and standards, and 183 Δ 47 and 195 Δ 48 replicate measurements of gas standards from 2015 to 2021 from a multi-year and multi-instrument data set to constrain Δ 47 and Δ 48 values for 27 samples and standards, including Devils Hole cave calcite, and study equilibrium Δ 47 - Δ 48 , Δ 47 -temperature, and Δ 48 -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, Δ * 63 - 47 and Δ * 64 - 48 , and account for their dependence on the initial clumped isotope values of the mineral.