The Ait Dawd Cu-Ni vein deposit: new mineralogical insights to understand the mineralizing criteria of the western High Atlas district (Morocco)

The Ait Dawd Cu-Ni-Au vein deposit is hosted within the Cambrian-Ordovician formations of the Erdouz terranes from the western High Atlas (Morocco). These formations are folded during the Variscan orogeny and the schistosity is striking NNE to NE and strongly dipping to the east (40° to 70). Significant ore deposits in the region occur only within relatively small well-endowed mineral occurrences, likely to be controlled by the Permian Azegour granite and its rhyolitic to microdioritic dyke swarm. However, four distinct styles of mineralization are present in this area: the world-class Azegour Mo skarn deposit, the Amensif polymetallic carbonate-replacement deposit, the Talat n’Imjjad Cu-Au shear zone, and the Ait Dawd Cu-Ni-Au vein deposit. This latter was the subject of this study to explore its mineral paragenesis using petrographic observations, SEM, and EPMA investigations. The primary mineral assemblage is composed of chalcopyrite, pyrite, arsenopyrite, galena and sphalerite, tetrahedrite, freibergite, native gold, and native bismuth. Argento-pentlandite and cobaltite-gersdorffite series are intimately associated or enclosed within chalcopyrite. Native gold is free in a quartz gangue or associated with chalcopyrite. The secondary minerals are composed of malachite, azurite, covellite, anglesite, and iron oxides. The gangue minerals are consisting of quartz, calcite, dolomite, ankerite, and chlorite. The recognized hydrothermal alterations in the studied area are formed mainly by silicification, chloritization, sericitization, and carbonatation. The presence of disseminated cobaltite-gersdorffite and argento-pentlandite in this area is in favor of the magmatic source of the ore fluids responsible of the deposition of several mineralizations. Several pending questions should be emphasized on the genetic model and the role played by the Permian magmatism in the genesis and the mineral exploration of the entire mineralization within the western High Atlas mining district.