153042 - Anoxic photochemical weathering.pdf (218.74 kB)
Anoxic photochemical weathering of pyrite on Archean continents
journal contribution
posted on 2023-05-21, 13:19 authored by Hao, J, Liu, W, Goff, JL, Jeffrey SteadmanJeffrey Steadman, Ross LargeRoss Large, Falkowski, PG, Yee, NSulfur is an essential element of life that is assimilated by Earth's biosphere through the chemical breakdown of pyrite. On the early Earth, pyrite weathering by atmospheric oxygen was severely limited, and low marine sulfate concentrations persisted for much of the Archean eon. Here, we show an anoxic photochemical mechanism of pyrite weathering that could have provided substantial amounts of sulfate to the oceans as continents formed in the late Archean. Pyrite grains suspended in anoxic ferrous iron solutions produced millimolar sulfate concentrations when irradiated with ultraviolet light. The Fe2+(aq) was photooxidized, which, in turn, led to the chemical oxidation of pyritic sulfur. Additional experiments conducted with 2.68 Ga shale demonstrated that photochemically derived ferric iron oxidizes and dissolves sedimentary pyrite during chemical weathering. The results suggest that before the rise of atmospheric oxygen, oxidative pyrite weathering on Archean continents was controlled by the exposure of land to sunlight.
History
Publication title
Science AdvancesVolume
8Issue
26Article number
eabn2226Number
eabn2226Pagination
1-7ISSN
2375-2548Department/School
School of Natural SciencesPublisher
American Association for the Advancement of Science (AAAS)Place of publication
United StatesRights statement
© 2022 The Authors. some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under the terms of of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, (https://creativecommons.org/licenses/by/4.0/)Repository Status
- Open