Boumadine Polymetallic Deposit

Technical report

Mining Installations

Remains of the mining installations are still visible at the mine site. They were probably dismantled shortly after the mine closure in 1992. Two dry stacked tailings are exposed on the site totaling approximately 240,000 t of material. These residues were generated upon the underground exploitation of the Boumadine deposit from 1988 to 1992. There are existing surface and underground mine workings which include at least 6 excavated shafts (638 m) and 6,036 m of underground adits, raises and stopes distributed in 5 main areas: Central Zone, Northern Zone, Southern Zone, Tizi Zone and Imariren Zone. Numerous pits and trenches are visible throughout the property. These can be small, a few square meters in area, but others extend for over 1,000m2.

Mineralization

The polymetallic mineralization at Boumadine extends at least for 4 km on the surface. The mineralized zones consist of 1 to 4 m-wide N160°E-oriented lenses/veins dipping sharply (> 70°) to depths of 350 m and spatially associated with the TTF.The veins contain massive pyrite, sphalerite, arsenopyrite, and galena with subordinate amounts of chalcopyrite, cassiterite, silver-rich sulfosalts, stannite, enargite, bismuthinite, native silver, tin, copper and bismuth. The upper 40 m are affected by supergene alteration (Fe-hydroxyde-rich ‘‘mantos’’), that were near completely mined by artisanal workers.The felsic volcanic hosts display a silicic-argillic alteration halo, 40-100 m wide, which overprints the pervasive propylitised rocks and confers a bleached aspect to the halo. This alteration zone contains an assemblage of quartz-sericite-pyrite with pyrite decreasing away from the veins. The Boumadine deposit is interpreted as low-intermediate sulphidation epithermal silver-gold base metal deposit, with the potential of discovering Cu±Au porphyry-type mineralization at depth.

There are two principal mineralizing stages controlled by the strain applied to the TTF volcanosedimentary assemblage. The first mineralizing event involved the deposition of massive pyrite, occasionally banded, succeeded by the injection of parallel veinlets of arsenopyrite in the first stage pyrite. These veins were formed under a N160°E shortening strain. The second stage of mineralization first involved crystallization of sphalerite and galena cementing the first stage sulphides or occurring as vein filling material forming banded ore. The latest mineralization stage started with the deposition of quartz in dissolution cavities and as crosscutting veinlets, followed by crystallization in decreasing abundance of: grey copper, argentopyrite, schapbachite, pyrargyrite, polybasite and native antimony-silver-bismuth. Emplacement of polymetallic and precious metal veins is consistent with a N30°E shortening direction.