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

Abstract

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.