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

Area of Science:

• Geochemistry
• Isotope Geochemistry
• Paleoclimatology

Background:

• Carbonate clumped isotope geochemistry traditionally uses mass spectrometry of m/z 47 CO2 for geothermometry.
• Recent studies suggest paired analysis of m/z 47 (Δ⁴⁷) and m/z 48 (Δ⁴⁸) isotopologues offers insights into non-equilibrium fractionations and refined temperature estimates.

Purpose of the Study:

• To constrain Δ⁴⁷ and Δ⁴⁸ values for carbonate samples and standards using extensive multi-year, multi-instrument data.
• To investigate equilibrium relationships between Δ⁴⁷-Δ⁴⁸, Δ⁴⁷-temperature, and Δ⁴⁸-temperature.
• To compare results with previous findings and calculate equilibrium regressions from multiple laboratories.

Main Methods:

• Utilized 5,448 Δ⁴⁷ and 3,400 Δ⁴⁸ replicate measurements of carbonate samples/standards.
• Analyzed 183 Δ⁴⁷ and 195 Δ⁴⁸ replicate measurements of gas standards (2015-2021).
• Calculated acid digestion fractionation factors (ε⁴⁷ and ε⁴⁸) and their dependence on initial clumped isotope values.

Main Results:

• Constrained Δ⁴⁷ and Δ⁴⁸ values for 27 samples, including Devils Hole cave calcite.
• Established equilibrium regressions for Δ⁴⁷-Δ⁴⁸, Δ⁴⁷-temperature, and Δ⁴⁸-temperature relationships.
• Reported acid digestion fractionation factors accounting for initial clumped isotope values.

Conclusions:

• Paired analysis of Δ⁴⁷ and Δ⁴⁸ isotopologues enhances the application of carbonate clumped isotope geochemistry.
• The study provides refined temperature estimates and insights into non-equilibrium isotope fractionations.
• Accurate determination of fractionation factors is crucial for reliable geothermometry.