Isotopic and geochemical constraints on lead and fluid sources of the Pb-Zn-Ag mineralization in the polymetallic Tighza-Jbel Aouam district (central Morocco), and relationships with the geodynamic context

International audienceThe Wsingle bondAu, Pbsingle bondZnsingle bondAg, and Sbsingle bondBa mineralizations of the polymetallic Tighza-Jbel Aouam district (central Meseta, Morocco), are hosted in Paleozoic rocks surrounding late-Carboniferous granitic stocks. The Pbsingle bondZnsingle bondAg Tighza deposit formed at 254 ± 16 Ma, and is clearly disconnected from the late-Variscan Wsingle bondAu deposit (295-280 Ma). The Pbsingle bondZnsingle bondAg mineralization precipitated from a complex hydrothermal fluid. It displays air-normalized 3He/4He ratio (0.018–0.103) typical of the upper crust. This crustal component is confirmed by the oxygen and carbon isotope compositions (δ18O = +19 to +25‰; δ13C = −3.6 to −11.2‰) and the ɛNd values (−4.84 to −9.01) of gangue carbonates, which show mixing of (i) fluids that have interacted with late-Carboniferous magmatic rocks, and (ii) fluids in equilibrium with the Paleozoic metasediments. In addition, the Pbsingle bondZnsingle bondAg mineralization has 40Ar/36Ar values in the range 284–315 typical of a meteoric fluid. The radiogenic Pb isotopic compositions (207Pb/204Pb = 15.70–15.80 and 206Pb/204Pb = 18.30–18.50) suggest leaching of Pb from the surrounding Paleozoic metasediments and late-Variscan granites, whereas the low radiogenic signatures (207Pb/204Pb = 15.40 and 206Pb/204Pb = 18.05) provide evidence of a deeper source attributed to the lower crust.Crustal thinning related to extensional tectonics in late-Permian and Early-Triassic lead to high-K calc-alkaline to alkaline magmatic activity, which is evidenced by a dense SW-NE-trending dike network that pre-dated the Atlantic Ocean opening (early Liassic times). This magmatic event induced a regional heat flux increase that triggered the circulation of a complex hydrothermal fluid, which has a strong crustal component, but also a meteoric and a lower crustal components. The polymetallic district of Tighza-Jbel Aouam thus results from superposition of an intrusion related porphyry-gold mineralization (Wsingle bondAu, 286 Ma) followed by a Pbsingle bondZnsingle bondAg epithermal mineralization (254 Ma), during two distinct magmatic-hydrothermal events.The proposed metallogenic model for the Pbsingle bondZnsingle bondAg Tighza-Jbel Aouam deposit provides new constraints for the Pbsingle bondZnsingle bondAg exploration in the Moroccan Meseta. Exploration targets must take into account the following geological features: (i) Permo-triassic high-K calk-alkaline to alkaline dikes, (ii) extensional tectonics and reactivation of ancient crust-scale faults and shear zones, and (iii) Paleozoic series containing organic matter (e.g., black shales) subjected to low grade metamorphism (e.g., greenschist facies)

The origin of fluorite deposits in the Bou-Izourane district (Central High Atlas of Morocco) and its relationships with the Tamazeght magmatic complex

International audienc

Virtues of fluorite-case of Bou-Izourane fluorite

International audienceFluorite minerals are among the non-metallic natural substances that have played an important role in the industry for decades. The economic importance of each of the grades of fluorite marketed meets precise chemical specifications such as its melting quality and fluor content. They also provide specific and very diverse outlets: iron and steel industry, aluminum metallurgy, plastics manufacturing, solvents, refrigerants, welding, glassmaking, cement industry, etc. In Morocco, fluorite is a very important resource because of its multiple high-grade deposits, which currently make it the 8th largest producer of metallurgical fluorite concentrate in the world with 70 kt produced per year. In the Moroccan High Atlas, the fluorite district of Bou-Izourane, located 40 km south of the city of Midelt, is estimated to be one of the most important fluorite deposits in Morocco. There are at least four violet fluorite sites in this district, the two deposits of Bou-Izourane and Bou-kharouba in the eastern part of the study area. The western part of the Bou-Izourane region hosts the two other deposits (Tabja and Bou-Imtessene). Although the Bou-Izourane fluorite is more or less colored (Violet-Lilac) with remarkable quality and perfect transparency, its uranium content, especially at the Tabja and Bou-Imtessene sites, is quite high (97.4–188.5 ppm). This property of uranium richness is an axis of research in addition to the determination of its physico-chemical characteristics, which will define the virtues and the fields of use of this fluorite. This document has been written in the hope that it will be of some use in highlighting the potential of the fluorite of the Moroccan Bou-Izourane deposit

Age des évènements magmatiques et hydrothermaux du district polymétallique de Tighza-Jbel Aouam (Maroc Central)

International audienc

Sources du Plomb et des fluides de la minéralisation Pb-Zn-Ag du district polymétallique Tighza-Jbel Aouam (Maroc central) et contexte géodynamique

International audienc