Metasomatic zoning, mineralizations and genesis of Cu, Zn and Mo azegour skarns (Western High Atlas, Morocco)

International audienceThe Cu, Zn, Mo and W deposit of Azegour is located on the north side of the western High Atlas. Deposition of mineralizations is associated to the hydrothermal transformations that affected carbonated bars of the Palaeozoic series during the intrusion of the calc-alkaline hyperaluminous granite of Azegour. The type of the hydrothermal transformations recorded in the carbonated bars is controlled by the lithological nature of the protolith and is closely confined with the volcanic and volcanoclastic levels. At least five paragenetic stages of skarn formation and ore deposition have been recognized: Stage I: clinopyroxene; stage II: wollastonite ± vesuvianite; stage III: garnet; stage IV: quartz ± potassium feldspar ± calcite ± sulphides ± molybdenite ± cassiterite ± scheelite ± fluorite ± accessory minerals (apatite, zircon, sphene) and stage V: amphibole ± calcite ± chlorite ± muscovite ± epidote ± sulphides. Two mineralizations stages can be distinguished. The first stage essentially of sulphides and sulfoarsenides (Cu, Pb, Zn, As and Ag) was mainly observed in volcanic and volcanoclastic rocks in contact with the dolomitic marble. These mineralizations are previous to the metamorphic and structural events having affected the Azegour area. The second stage of mineralization (Mo, W and Sn) observed in the skarnified marble of granitic metamorphic aureole is associated to a hydrothermal metamorphism produced by an acidic fluid arising from the granitic pluton. The temperature deposition of mineralization during the ultimate prograde stage is lower than that required for the grenatites formation which approaches 640°C