Frontiers of Carbonate Clumped Isotope Thermometry

Carbonate minerals contain stable isotopes of carbon and oxygen with different masses whose abundances and bond arrangement are governed by thermodynamics. The clumped isotopic value Delta(i) is a measure of the temperature-dependent preference of heavy C and O isotopes to clump, or bond with or near each other, rather than with light isotopes in the carbonate phase. Carbonate clumped isotope thermometry uses Delta(i) values measured by mass spectrometry (Delta(47), Delta(48)) or laser spectroscopy (Delta 638) to reconstruct mineral growth temperature in surface and subsurface environments independent of parent water isotopic composition.Two decades of analytical and theoretical development have produced a mature temperature proxy that can estimate carbonate formation temperatures from 0.5 to 1,100 degrees C, with up to 1-2 degrees C external precision (2 standard error of the mean). Alteration of primary environmental temperatures by fluid-mediated and solid-state reactions and/or 1i values that reflect nonequilibrium isotopic fractionations reveal diagenetic history and/or mineralization processes. Carbonate clumped isotope thermometry has contributed significantly to geological and biological sciences, and it is poised to advance understanding of Earth's climate system, crustal processes, and growth environments of carbonate minerals.

Automated summary

Carbonate minerals have stable isotopes of carbon and oxygen that exhibit thermodynamic control over their abundances and bond arrangements. The clumped isotopic value Delta(i) measures the temperature-dependent preference of heavy isotopes to clump together in the carbonate phase. Carbonate clumped isotope thermometry uses Delta(i) values to determine mineral growth temperature independent of water isotopic composition. Its development has provided a mature temperature proxy with a wide applicability and high precision, contributing significantly to geological and biological sciences.