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 Δ47 and Δ48) can be used to study non-equilibrium isotope
fractionations and refine temperature estimates. We utilize 5,465 Δ47
and 3,400 Δ48 replicate measurements of carbonate samples and standards,
and 183 Δ47 and 195 Δ48 replicate measurements of gas standards from
2015-2021 from a multi-year and multi-instrument dataset to constrain
Δ47 and Δ48 values for 27 samples and standards, including Devils Hole
cave calcite, and study equilibrium Δ47-Δ48, Δ47-temperature, and
Δ48-temperature relationships. We compare results to previously
published findings and calculate equilibrium regressions based on
inter-laboratory values. 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.