Evolution of seawater continentally-sourced Nd isotopic composition prior to and during the Great Oxidation Event

• Published in: Precambrian research 2021-08, Vol.362, p.106292, Article 106292
• Main Authors: Narduzzi, Francesco, Bosch, Delphine, Philippot, Pascal
• Format: Article
• Language: English
• Subjects: Earth Sciences; Geochemistry; Great Oxidation Event; Hamersley Basin; Nd isotopes; Paleoproterozoic Glaciations; Sciences of the Universe; Subaerial Large Igneous Provinces; Weathering of exposed continental landmasses
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2021.106292

•Nd-isotope systematics of Fortescue, Hamersley and Turee Creek sediments and volcanics.•Role of LIPs weathering to riverine fluxes during the Archean-Proterozoic transition.•Major change of continentally-sourced material at the onset of the GOE.•Elevated rates of weathering stimulated the GOE and first global glaciation. An ongoing debate concerns what initiated the Great Oxidation Event (GOE) and associated glaciation between ~ 2.45 and 2.2 Ga. One possibility is the emergence of continental landmasses and the increase of subaerial igneous province weathering during the Late Archean. We test this hypothesis in the Hamersley Basin by reporting Nd-isotope data from a succession of iron formations (IFs), mudstone/siltstones and glacial diamictites from the Boolgeeda Iron Formation and overlying Turee Creek Group deposited during the GOE. In a 147Sm/144Nd - ɛNd(t) diagram, the data define a negative trend indicating the contribution of a high ɛNd(t) ~ +3 hydrothermal component and a strongly negative ɛNd(t) ~ -9 crustal component, which is compatible with the Nd-isotope composition of the upper continental crust but also of the underlying felsic volcanics of the Woongarra Rhyolite and crustally-contaminated mafic volcanics of the Fortescue Group. A less pronounced negative trend originating from the same hydrothermal source but correlated with non-contaminated ultramafic Fortescue volcanics (ɛNd(t) ~ -2) is observed for the older Joffre, Dales Gorge and Marra Mamba IFs. As Nd-isotopes are not sensitive to redox conditions, the major shift of Nd-isotopic compositions at ~ 2.45 Ga cannot be linked to a change in the weathering regime, rather to a change in the nature of the continental surface exposed to weathering. One explanation is that the Sm-Nd sources for sediments deposited before and during the GOE were locally derived from the underlying subaerial LIPs, reflecting a change in the geodynamic context of deposition and/or hydrographic network and catchment areas. Another explanation could be a significant change in the nature of fluid–rock interactions due to the increase role of weathering processes associated with the emergence of continental landmasses. Additional Nd isotope data from different cratons worldwide are needed, however, to infer as to whether or not the marked shift in Nd isotope compositions recorded in the Turee Creek Group reflect a change in the global hydrological cycle. Our data support the role of large subaerial magmatic provinces