Geochemistry and U-Pb zircon geochronology of the Nkout banded iron formations and associated metasiliciclastic rocks, NW Congo craton, southern Cameroon

ABSTRACT

The Nkout banded iron formations (BIFs)-hosted iron deposit is located in the Ntem Complex at the northwestern part of the Congo craton, southern Cameroon. We report geochronological and geochemical data of magnetite BIFs and interlayered mica schists from the Nkout iron ore deposit. The BIFs show typical features of chemical precipitates characterized by seawater-like shale-normalized rare earth elements plus yttrium spectra. Weak positive Eu anomalies indicate the contribution of high-temperature hydrothermal fluids to the BIFs, with low detrital input. The absence of true Ce anomalies indicates that the BIFs were likely to be deposited in anoxic seawater. LA-ICP-MS U-Pb detrital zircon data for the BIFs and associated metasiliciclasltic rocks constrained the maximum depositional age at ca. 2.8 Ga, suggesting that the Nkout BIFs are likely the oldest iron formations in the Ntem Complex. Our zircon U-Pb isotope data indicate that the Nkout succession experienced lower-amphibolite facies metamorphism at ca. 2.0 Ga, which correlates with the regional tectono-thermal event linked to the convergence and assembly of terranes between the Congo and São Francisco cratons during the Eburnean-Transamazonian orogeny.

KEYWORDS:

• Banded iron formations
• metasiliciclastic rocks
• geochemistry
• LA-ICP-MS zircon U-Pb dating
• maximum depositional age
• Congo craton

Acknowledgments

This paper is part of the Ph.D. thesis of the first author at the University of Yaounde I. The authors are grateful to the staff of the Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences in Beijing (China), for their support during EPMA and whole-rock geochemical analyses. We are grateful to Dr Pradip Kumar Singh and three anonymous reviewers for their constructive comments and Editor-in-Chief Dr Robert J. Stern for the efficient handling of the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2024.2326971

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Funding

The author(s) reported that there is no funding associated with the work featured in this article.