Precise kinetic parameters for thermal resetting of clumped isotope signatures in biogenic and abiogenic calcites

Carbonate clumped isotope (∆₄₇) thermometry is a powerful tool to reconstruct paleotemperatures. However, episodes of heating or cooling can alter original ∆₄₇ values through diffusive C-O bond reordering—i.e., isotopic exchange between neighboring carbonate groups within the mineral lattice—and/or oxygen-isotope exchange between carbonate groups and water (collectively termed “thermal resetting”). Nevertheless, if precise kinetic constraints are available, altered ∆₄₇ values can be utilized to reconstruct thermal histories of sedimentary basins or to restore primary ∆₄₇ values from carbonates which experienced thermal resetting in their geological history. Here, we present new high-resolution heating experiments on optical (abiogenic) and belemnite (biogenic) calcite. By capturing early signals and conducting experiments at lower temperatures than in previous studies, we derive new precise disordered kinetic parameters for both materials [optical calcite: µ _E = 216.47 ± 6.95 kJ mol^-1, σ _E = 14.51 ± 1.22 kJ mol^-1, and v₀ = 28.61 ± 1.12 ln(min)^-1; belemnite calcite: µ _E = 180.15 ± 7.94 kJ mol^-1, σ _E = 22.24 ± 2.62 kJ mol^-1, and v₀ = 27.76 ± 1.43 ln(min)^-1]. Additionally, we present new FTIR data on pristine and heated belemnite calcite that confirms the presence of intracrystalline water and organic matter that is suggested to facilitate its faster thermal resetting. Complementary “snapshot” experiments on a diverse suite of materials reveal a systematic difference in thermal resetting behavior between biogenic and abiogenic calcites, highlighting the importance of structural and compositional characteristics in controlling resetting kinetics. These snapshot experiments can complement petrographic and geochemical methods in assessing the pristine nature of calcite samples and provide guidance for selecting the appropriate kinetic parameters for thermal modeling of different calcites.