Towards a holistic sulfate-water-O2 triple oxygen isotope systematics

Chemical Geology
By: , and 



Triple oxygen isotope (∆17O with δ18O) signals of H2O and O2 found in sulfate of oxidative weathering origin offer promising constraints on modern and ancient weathering, hydrology, atmospheric gas concentrations, and bioproductivity. However, interpretations of the sulfate-water-O2 system rely on assuming fixed oxygen-isotope fractionations between sulfate and water, which, contrastingly, are shown to vary widely in sign and amplitude. Instead, here we anchor sulfate-water-O2 triple oxygen isotope systematics on the homogeneous composition of atmospheric O2 with empirical constraints and modeling. Our resulting framework does not require a priori assumptions of the O2- versus H2O‑oxygen ratio in sulfate and accounts for the signals of mass-dependent and mass-independent fractionation in the ∆17O and δ18O of sulfate's O2‑oxygen source. Within this framework, new ∆17O measurements of sulfate constrain ~2.3 Ga Paleoproterozoic gross primary productivity to between 6 and 160 times present-day levels, with important implications for the biological carbon cycle response to high CO2 concentrations prevalent on the early Earth.

Publication type Article
Publication Subtype Journal Article
Title Towards a holistic sulfate-water-O2 triple oxygen isotope systematics
Series title Chemical Geology
DOI 10.1016/j.chemgeo.2021.120678
Volume 588
Year Published 2022
Language English
Publisher Elsevier
Contributing office(s) Geology, Energy & Minerals Science Center
Description 120678, 13 p.
Google Analytic Metrics Metrics page
Additional publication details