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Constraints on triple oxygen isotope kinetics

November 23, 2021

Isotopic disequilibrium is not as well constrained as equilibrium, hindering interpretation of isotopic variations. Kinetic isotope effects, a subset of disequilibrium, are common in nature and have been assumed to be distinct from equilibrium and mass independent isotope effects based on underdeveloped criteria. Using basic physical principles, we provide needed mechanistic constraints on mass-dependent kinetic isotope effects for the triple oxygen isotope system. We find some kinetic isotope effects yield large isotopic variations, exceeding equilibrium, which could be mistaken for mass independent relationships. Meanwhile, other kinetic isotope effects are found to have triple oxygen isotope relationships that could be mistaken for equilibrium isotope effects. Comparison against prior case studies of thermal decomposition of calcite (CaCO3) and brucite (Mg(OH)2) further tests our results. Although oxygen is the focus here, our approach applies to any system with more than two isotopes.

Publication Year 2022
Title Constraints on triple oxygen isotope kinetics
DOI 10.1016/j.chemgeo.2021.120646
Authors Justin A. Hayles, Bryan Alan Killingsworth
Publication Type Article
Publication Subtype Journal Article
Series Title Chemical Geology
Index ID 70227284
Record Source USGS Publications Warehouse
USGS Organization Geology, Energy & Minerals Science Center