Anomalous δ¹⁵N values in the Neoarchean associated with an abundant supply of hydrothermal ammonium

authored by

Ashley N. Martin, Eva E. Stüeken, Michelle M. Gehringer, Monika Markowska, Hubert Vonhof, Stefan Weyer, Axel Hofmann

Abstract

Unusually high δ¹⁵N values in the Neoarchean sedimentary record in the time period from 2.8 to 2.6 Ga, termed the Nitrogen Isotope Event (NIE), might be explained by aerobic N cycling prior to the Great Oxidation Event (GOE). Here we report strongly positive δ¹⁵N values up to +42.5 ‰ in ~2.75 – 2.73 Ga shallow-marine carbonates from Zimbabwe. As the corresponding deeper-marine shales exhibit negative δ¹⁵N values that are explained by partial biological uptake from a large ammonium reservoir, we interpret our data to have resulted from hydrothermal upwelling of ¹⁵N-rich ammonium into shallow, partially oxic waters, consistent with uranium isotope variations. This work shows that anomalous N isotope signatures at the onset of the NIE temporally correlate with extensive volcanic and hydrothermal activity both locally and globally, which may have stimulated primary production and spurred biological innovation in the lead-up to the GOE.

Organisation(s)

Institute of Earth System Sciences
Mineralogy Section
Geochemistry

External Organisation(s)

Northumbria University
University of St. Andrews
University of Kaiserslautern-Landau (RPTU)
Max Planck Institute for Chemistry (Otto Hahn Institute)
University of Johannesburg

Type

Article

Journal

Nature Communications

Volume

16

ISSN

2041-1723

Publication date

22.02.2025

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Chemistry, General Biochemistry,Genetics and Molecular Biology, General Physics and Astronomy

Sustainable Development Goals

SDG 14 - Life Below Water

Electronic version(s)

https://doi.org/10.1038/s41467-025-57091-3 (Access: Open)