Multi-isotopic tracing (Mo, S, Pb, ReOs) and genesis of the MoW Azegour skarn deposit (High-Atlas, Morocco). (July 2019)

• Record Type: Journal Article
• Authors: Marcoux, Éric; Breillat, Noémie; Guerrot, Catherine; Négrel, Philippe; Hmima, Samia Berrada; Selby, David
• Is Part Of: Journal of African earth sciences. Volume 155(2019)
• Page Start: 109
• Page End: 117
• Publication Date: 2019-07
• Subjects: Azegour skarn -- Molybdenite -- Molybdenum -- Lead -- Sulphur -- Isotopes -- Re-Os geochronology -- Mineralisation; Earth sciences -- Africa -- Periodicals; Earth sciences -- Middle East -- Periodicals; Geology -- Africa -- Periodicals; Geology -- Middle East -- Periodicals; Sciences de la terre -- Afrique -- Périodiques; Sciences de la terre -- Moyen-Orient -- Périodiques; Géologie -- Afrique -- Périodiques; Géologie -- Moyen-Orient -- Périodiques; Earth sciences; Geology; Africa; Middle East; Periodicals; Electronic journals; 556.05
• DOI: 10.1016/j.jafrearsci.2019.04.007
• Languages: English
• ISSNs: 1464-343X

Abstract

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 δ 98 MoNIST 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 δ 98 MoNIST 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 δ 98 MoNIST values although the influence of a Rayleigh fractionation process cannot be precluded. The high δ 34 S 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 206 Pb/ 204 Pb compositions of common lead (18.08–18.30) for chalcopyrite and pyrrhotite imply a strong contribution of lead from the host volcano-sedimentary units. Highlights: The MoCuW Azegour skarn is Permian (276 ± 1.2 Ma, ReOs geochronology). Multiple Permian mineralisation events associated with the Azegour granite are likely. δ 34 S values determined from sulphides suggest a sedimentary origin for sulphur. Source of common lead has to be sought in the host Cambrian volcano-sedimentary units.