Technical Note: Developments and Applications in Triple Oxygen Isotope Analysis of Carbonates

Fosu, BR and Subba, R and Peethambaran, R and Bhattacharya, SK and Ghosh, P (2020) Technical Note: Developments and Applications in Triple Oxygen Isotope Analysis of Carbonates. In: ACS Earth and Space Chemistry, 4 (5). pp. 702-710.

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Abstract

Triple oxygen isotope systematics has evolved as a powerful tool in understanding various earth system processes. It has proven reliable in assessing paleoenvironmental conditions from natural archives (e.g., waters, ice cores, biota, sediments, etc.) owing to recent advances in high-precision mass spectrometric analysis. Toward the standardization of triple oxygen isotope analyses in carbonates, we describe a procedure of high-precision ��17O analysis of carbonates by a two-step protocol: acid digestion of carbonates to evolve CO2 followed by the catalytic CO2-O2 exchange method. The ��17O values of a suite of carbonate reference materials and several carbonates of different origins have been determined with good precision (�0.007�). The accuracy of sample ��17O values is dependent on the accuracy of ��17O composition of the reference CO2 used in determining the effective fractionation (θs) in the experimental setup. The obtained ��17O values (λ = 0.528, versus VSMOW) for NBS18-CO2 (-0.119�) and NBS19-CO2 (-0.169�) show a difference of 0.050�, similar to that obtained elsewhere via complete fluorination. The analyzed carbonates mostly conform to equilibrium mass-dependent fractionation laws, but we encountered a suite of samples from cold seeps, caves, and metasomatic environments that have ��17O values indicative of disequilibrium fractionation. We show that a combination of clumped isotope composition (�47) that provides estimates of formation temperature and triple oxygen isotope ratios in carbonates can help in reconstructing past environments, where paired carbonate data (δ13C-δ18O-�47-��17O) and parent water data (δ17O-δ18O-��17O) are particularly useful. Copyright © 2020 American Chemical Society.

Item Type:	Journal Article
Publication:	ACS Earth and Space Chemistry
Publisher:	American Chemical Society
Additional Information:	Copy right for this article belongs to American Chemical Society
Keywords:	triple oxygen isotopes, isotopic homogenization, fractionation exponent, clumped isotopes, carbonates
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited:	13 Mar 2021 06:29
Last Modified:	13 Mar 2021 06:29
URI:	http://eprints.iisc.ac.in/id/eprint/66108

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