Lithogeochemical, mineralogical analyses and oxygen-hydrogen isotopes of the Hercynian Koudiat Aïcha massive sulphide deposit, Morocco

Chemical trends in altered footwall rocks are shown by absolute mass gains for Fe2O3total, MnO and MgO, by absolute mass losses for CaO, K2O and Na2O, and by a moderate loss in SiO2. Oxygen and hydrogen isotope compositions of Koudiat Aïcha lithofacies (6.2-12.4‰ for oxygen and −51‰ to −36‰ for hydrogen) have also been used to determine the temperature and origin of metalliferous fluids. The couple plagioclase-amphibole of gabbros provides equilibrium temperatures between 310 and 380 °C and suggests that the heat source for the ore-forming fluid system may have been igneous. On the other hand, oxygen and hydrogen isotope ratios cluster between normal values for sedimentary and magmatic rocks, suggesting a magmatic-metamorphic origin for the ore fluid.