Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

Marine Fe cycling linked to dynamic redox variability, biological activity and post-depositional mineralization in the 1.1 Ga Mesoproterozoic Taoudeni Basin, Mauritania

Ghnahalla, Mohamed, Rouxel, Olivier, Chi Fru, Ernest ORCID: https://orcid.org/0000-0003-2673-0565, Bankole, Olabode M., Salem Sabar, Mohamed, Abd Elmola, Ahmed, Chraiki, Ibtissam, Abdelfadel, Fatima, Fontaine, Claude, Trentesaux, Alain, El Ghastalany, Rayane, Abdeina, El Houssein and El Albani, Abderrazak 2024. Marine Fe cycling linked to dynamic redox variability, biological activity and post-depositional mineralization in the 1.1 Ga Mesoproterozoic Taoudeni Basin, Mauritania. Gondwana Research 136 , pp. 33-52. 10.1016/j.gr.2024.08.012
Item availability restricted.

[thumbnail of GWR-D-24-00360_R4.pdf] PDF - Accepted Post-Print Version
Restricted to Repository staff only until 30 August 2025 due to copyright restrictions.
Available under License Creative Commons Attribution Non-commercial No Derivatives.

Download (3MB)

Abstract

The concentration of redox sensitive trace metals (RSTEs) and their isotopic composition preserved in Precambrian marine sediments, are critical for the reconstruction of ocean–atmosphere oxygenation history. Particularly, the concentration of Fe, its redox speciation, and isotopic distribution, have gained widespread use for inferring the biogeochemical processes that controlled Fe cycling in Precambrian oceans linked to the reconstruction of Earth surface redox budget. However, questions remain about the biotic and abiotic processes involved in Fe cycling in these ancient oceans, including the impact of post-depositional alterative processes on the reliability of the Fe redox proxy. Here we present a multi-proxy mineralogical and geochemical study of the ∼1.1 Ga Atar and El Mreiti strata of the Taoudeni Basin in Mauritania, to better constrain pathways involved in Fe cycling, linked to Fe mineralogy, redox speciation, isotopic ratios during this time and metamorphism. We compare unmetamorphosed sedimentary deposits with facies metamorphosed by dolerite sill intrusion. The results reveal the occurrence of diagenetic Fe minerals in the basal unmetamorphosed samples associated with light δ56Fe signatures, reflecting dominant anoxic conditions that promoted microbial dissimilatory Fe reduction. Notably, δ56Fe composition of these rocks reveal several fluctuations in evolving seawater redox state from oxic to anoxic/sulfidic conditions associated with changes in sea level stand and periods of full bottom water oxygenation and redox stratification. Overall, Ce anomalies suggest a general up sequence increase in seawater oxygen content. Metamorphosed rocks display heterogeneous δ56Fe distribution, consisting of light and heavy signatures associated with secondary Fe-bearing minerals produced by metamorphic and metasomatic overprinting of carbonated rocks by hot circulating fluids. The results thus indicate metamorphic overprinting of primary seawater δ56Fe promoted by increased mobility of reactive Fe during post-depositional metamorphic transformation. They show that post-depositional metamorphic/metasomatic overprinting complicates direct reconstruction of seawater biogeochemical Fe cycling and redox state using δ56Fe systematics.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Environmental Sciences
Publisher: Elsevier
ISSN: 1342-937X
Date of First Compliant Deposit: 7 October 2024
Date of Acceptance: 28 August 2024
Last Modified: 09 Oct 2024 02:01
URI: https://orca.cardiff.ac.uk/id/eprint/172649

Actions (repository staff only)

Edit Item Edit Item

Downloads

Downloads per month over past year

View more statistics