Operations
Content Image

Essakane Gold Mine, Burkina Faso

Geology & Mineralization

Geology

The Essakane Project occurs in the Paleoproterozoic Gorouol greenstone belt in northern Burkina Faso. The local stratigraphy can be subdivided into a succession of lower-greenschist facies metasediments (argillites, arenites and volcaniclastics), conglomerates and subordinate felsic volcanics, and an overlying Tarkwaian-like succession comprising siliciclastic metasediments and conglomerate. Each succession contains intercalated mafic intrusive units that collectively comprise up to forty percent of the total stratigraphic section.

The region preserves evidence for at least two regional deformational events. D1 structural elements such as the Essakane host anticline are refolded by a series of NNE-trending F2 folds. Later localized deformation occurs near the margin of a calc-alkaline batholith in the south of the project area. The Markoye Fault trends NNE through the western portion of the project area and separates the Paleoproterozoic rocks from an older granite-gneiss terrane to the west.

 








Mineralization

Essakane is an orogenic gold deposit characterized by quartz-carbonate stockwork vein arrays and is hosted within the lower meta-sedimentary sequence. The deposit occurs in an upright asymmetric anticline that plunges shallowly to the northwest. The highest concentration of quartz veins and gold mineralization occurs in the 50-70m thick ‘main arenite unit’, and spatially in the hinge zone and eastern fold limb of the host anticline.

There are two distinct structural controls on gold mineralization: (i) gold associated with bedding parallel deformation; and (ii) gold associated with structures formed by the anticlinal folding event. The vein arrays are complex and consist of: (i) early bedding parallel laminated quartz veins; (ii) late steeply dipping extensional quartz veins; (iii) axial planar veins and pressure solution seams in the fold axial zone.

Alteration in the host arenite unit typically consists of a sericite > carbonate > silica ± albite ± arsenopyrite ± pyrite assemblage. Arsenopyrite and pyrite occurs within and adjacent to quartz veins are disseminated throughout areas of wallrock alteration. Traces of chalcopyrite, pyrrhotite, galena and hematite can occur with the arsenopyrite. Gold occurs as free particles within the veins and also as intergrowths in arsenopyrite on vein margins or in the host rocks. The regolith profile within the deposit area consists of one to three metres of laterite, a 30 to 50 metre thick upper saprolite zone and a 10 to 30 metre thick lower saprolite zone that is underlain by competent rock. The Essakane deposit has a strike length of 2,500 metres and is open to the north, although economic mineralization follows the fold plunge to become progressively deeper. Mineralization has been confirmed to 270 m vertically below surface but the full depth extent in the fold hinge and east limb has not been tested.