Multi-isotopic tracing (Mo, S, Pb, Re Os) and genesis of the Mo W Azegour skarn deposit (High-Atlas, Morocco)

Marcoux, Éric; Breillat, Noémie; Guerrot, Catherine; Négrel, Philippe; Hmima, Samia Berrada; Selby, David

Abstract

The MoCuW Azegour skarn, located in the High-Atlas in Morocco, is associated with a Late Hercynian alkaline granitic intrusion. Here the origin of the mineralisation via ReOs geochronology and using Mo, S and Pb isotopes is discussed. The age of mineralisation defined by ReOs molybdenite geochronology is 276 ± 1.2 Ma for the Azegour mine, and 267 ± 1.2 for the Tizgui deposit suggesting for multiple mineralisation events associated with the Hercynian alkaline granitic intrusion. The δ98MoNIST of molybdenite range from −0.60‰ to 0.42‰ (n = 26) for the Azegour mine and from 0.08‰ to 0.40‰ (n = 2) for the Tizgui mine. Variations of the δ98MoNIST occur either at the deposit scale with a difference of about 0.72‰, and at the sample scale (few cm), which exhibits a difference of up to 0.40‰. A multi-phased mineralisation is proposed as the main processes explaining the variation in the δ98MoNIST values although the influence of a Rayleigh fractionation process cannot be precluded. The high δ34S values determined from molybdenite, pyrrhotite, and chalcopyrite (8–14.7‰) suggest a sedimentary origin for sulphur from the Cambrian sedimentary country rocks. Whereas, the initial 206Pb/204Pb compositions of common lead (18.08–18.30) for chalcopyrite and pyrrhotite imply a strong contribution of lead from the host volcano-sedimentary units.

Citation

Marcoux, É., Breillat, N., Guerrot, C., Négrel, P., Hmima, S. B., & Selby, D. (2019). Multi-isotopic tracing (Mo, S, Pb, Re Os) and genesis of the Mo W Azegour skarn deposit (High-Atlas, Morocco). Journal of African Earth Sciences, 155, 109-117. https://doi.org/10.1016/j.jafrearsci.2019.04.007

• Journal Article Type: Article
• Acceptance Date: Apr 8, 2019
• Online Publication Date: Apr 11, 2019
• Publication Date: Jul 31, 2019
• Deposit Date: Apr 12, 2019
• Publicly Available Date: Apr 11, 2020
• Journal: Journal of African Earth Sciences
• Print ISSN: 1464-343X
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 155
• Pages: 109-117
• DOI: https://doi.org/10.1016/j.jafrearsci.2019.04.007
• Public URL: https://durham-repository.worktribe.com/output/1298782