Search

More than three million tons of sulphide tailings were discarded without any protection over the 36 year life of the now-abandoned Kettara pyrrhotite ore mine in Morocco. The impact of these tailings as well as the coarse wastes dumped on the surface site is highlighted by the elevated sulphate levels in the wells downstream of the wastes. Kinetic tests carried out on the sulphide tailings over 10 years ago, showed similar trends in metal dissolution despite large difference in test duration (21 and 53 weeks for the weathering and humidity cell tests, respectively). 40% of the sulphate release occurred in the first 3 weeks of the humidity test. The study showed that the elevated sulphate levels in the groundwater were not linked to the tailings where the original sulphide material is still present under an oxidised layer of 10 cm-1.2 m. Kinetic test results should therefore not be extrapolated to field scale without accounting for site-specific factors, especially particle size and climate., More than three million tons of sulphide tailings were discarded without any protection over the 36 year life of the now-abandoned Kettara pyrrhotite ore mine in Morocco. The impact of these tailings as well as the coarse wastes dumped on the surface site is highlighted by the elevated sulphate levels in the wells downstream of the wastes. Kinetic tests carried out on the sulphide tailings over 10 years ago, showed similar trends in metal dissolution despite large difference in test duration (21 and 53 weeks for the weathering and humidity cell tests, respectively). 40% of the sulphate release occurred in the first 3 weeks of the humidity test. The study showed that the elevated sulphate levels in the groundwater were not linked to the tailings where the original sulphide material is still present under an oxidised layer of 10 cm-1.2 m. Kinetic test results should therefore not be extrapolated to field scale without accounting for site-specific factors, especially particle size and climate.

The two deposits are typical examples of metamorphosed massive sulphide lenses hosted by Visean volcano-sedimentary formations. They consist essentially of pyrrhotite with associated sphalerite, galena, chalcopyrite, pyrite, arsenopyrite and glaucodot. Hajar has 15 000 000 t grading 10% Zn, 3% Pb and 0.7% Cu, while Kettara has been mined mainly for Fe. The effects of metamorphism and deformation differ at formation and crystal scales: at a formation scale, disharmonies in the contacts between orebodies and host rocks are most evident, whereas at a smaller scale the main features are banded ore texture, recrystallised interstitial sulphides and an increase in the size of sulphide crystals., The two deposits are typical examples of metamorphosed massive sulphide lenses hosted by Visean volcano-sedimentary formations. They consist essentially of pyrrhotite with associated sphalerite, galena, chalcopyrite, pyrite, arsenopyrite and glaucodot. Hajar has 15 000 000 t grading 10% Zn, 3% Pb and 0.7% Cu, while Kettara has been mined mainly for Fe. The effects of metamorphism and deformation differ at formation and crystal scales: at a formation scale, disharmonies in the contacts between orebodies and host rocks are most evident, whereas at a smaller scale the main features are banded ore texture, recrystallised interstitial sulphides and an increase in the size of sulphide crystals.

Large amounts of pyrrhotite-rich tailings at the abandoned Kettara mine are stockpiled on around 37 ha of fractured schist, with fine-grained jig processing tails stored in a pond and coarse tailings piles dispersed over the rest of the site. Hydrogeological and geochemical studies of the mine watershed were carried out, focusing on the spatial and temporal aspects of the effects of acid mine drainage, salinity variations, evolution related to the lithology, and evaporation. High levels of dissolved ions, including sulphate, in groundwater collected down-gradient of the tailings are evidence of acid mine drainage. However, the groundwater is low in metals and generally complies with Morocco's drinking water standards; only water in wells down-gradient of the mine waste are not of good quality. Most of the groundwater is acceptable for irrigation and all of it can be used for livestock., Large amounts of pyrrhotite-rich tailings at the abandoned Kettara mine are stockpiled on around 37 ha of fractured schist, with fine-grained jig processing tails stored in a pond and coarse tailings piles dispersed over the rest of the site. Hydrogeological and geochemical studies of the mine watershed were carried out, focusing on the spatial and temporal aspects of the effects of acid mine drainage, salinity variations, evolution related to the lithology, and evaporation. High levels of dissolved ions, including sulphate, in groundwater collected down-gradient of the tailings are evidence of acid mine drainage. However, the groundwater is low in metals and generally complies with Morocco's drinking water standards; only water in wells down-gradient of the mine waste are not of good quality. Most of the groundwater is acceptable for irrigation and all of it can be used for livestock.