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Anoxic photochemical weathering of pyrite on Archean continents

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posted on 2023-05-21, 13:19 authored by Hao, J, Liu, W, Goff, JL, Jeffrey SteadmanJeffrey Steadman, Ross LargeRoss Large, Falkowski, PG, Yee, N
Sulfur 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 Advances

Volume

8

Issue

26

Article number

eabn2226

Number

eabn2226

Pagination

1-7

ISSN

2375-2548

Department/School

School of Natural Sciences

Publisher

American Association for the Advancement of Science (AAAS)

Place of publication

United States

Rights 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/)

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  • Open

Socio-economic Objectives

Expanding knowledge in the earth sciences

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