Sulfide and Fluoride Mineralization of the NNE Region of Achemmach (Central Morocco): Paragenetic Sequences and Pyrrhotite-Sphalerite Geothermometry Constraints

Abstract

Sulfide and fluoride mineralization in the NNE Achemmach (NNE-A) area is located in the NE of Central Hercynian Morocco. In veins or when disseminated, it is hosted either in Visean sedimentary formations or in the magmatic bodies, described for the first time in this article and corresponding to pillow-lavas, dolerites and olivine-bearing gabbros. The mineralization is multiphase and results from the succession of the following three events: (i) an early high-temperature hydrothermal event (T ≈ 350–420 °C) associated with a simple primary sulfide paragenesis composed of pyrrhotite, pyrite, chalcopyrite, sphalerite and galena with gangue of quartz.(ii) The second event corresponds witha low temperature fluorite hydrothermal one (T≈ 120–160 °C), whereas the (iii) third is marked by, the deposition of a late sulfide paragenesis in a carbonate gangue within a moderate temperature (T≈ 200–250 °C). The temperatures of the paragenetic stages (350–400 °C) are estimated on the basis of the geothermometry constraints of the mineralogical assemblages, particularly the pyrrhotite-sphalerite equilibrium, in which the FeO content varies from 9.23 to 14.42 Wt%, and in the full study of their corresponding fluid phases. They are in perfect agreement with the fluid inclusion data of the first event.