Summary:
The Kiena Mine lies within the Abitibi Subprovince of the Archean Superior Craton, located in the Val-d'Or mining district, in northwestern Quebec. The southern Abitibi Greenstone Belt in the area of the Kiena Mine Complex consists of 2714–2700 Ma volcano-plutonic assemblages, including the Malartic and Louvicourt groups, intruded by calc-alkaline plutonic rocks.
Auriferous mineralization observed on the Kiena Mine can be associated to Archean greenstone-hosted orogenic lode gold deposit type. The region has several large-scale strike faults and/or shear zones, trending W to WNW and dipping steeply to the north.
A total of seven zones were mined at Kiena. Five are aligned in an N-S corridor (from south to north): South, S50, VC, Kiena Deep A, North and 388. Those zones are situated in a sector were the Marbenite and Norbenite faults are changing direction. Regionally, those faults are N290º but change direction to N320º near those five zones. The sixth zone, Martin, is about 1.2 km east of the Kiena shaft.
The South Zone is hosted within the Marbenite Fault approximately one-hundred meters south of the S50 Zone. Mineralized breccia lenses and quartz-carbonate veining run parallel to hosting basalt, komatiite, and diorite dyke units. Pyrite alteration up to 5% vol. defines an alteration halo around the mineralization. that observed in the S50 Zone. The South Zone is generally strongly fractured by the fault zone. Wesdome tried to mine this zone in 2012 and 2013, but after producing 37,076 tonnes with an average grade of 1.74 g/t Au, production was abandoned due to dilution problems.
The gold mineralization in the S50 Zone, S50 (Deep) Extension, and Deep B Zone (the bulk of the mineralization at the Kiena Mine) are hosted within the Jacola Formation and proximal to the Marbenite Fault. The mineralization occurs along the contacts of basalt and sheared schist with local crosscutting intermediate to felsic dykes and consists of multiple generations of carbonate-albite-pyrite stockworks, breccias, and veins. Mineralization in the S50 Zone can be subdivided into three styles: stockwork veins, breccia 1, and breccia 2. Stockwork veins consist of carbonate-quartz-pyrite-pyrrhotite ± albite ± gold and display an alteration halo of albite and disseminated pyrite ± pyrrhotite. Breccia 1 is younger than the stockwork veins and consists of carbonate-pyrite-gold veins. Breccia 2 locally overprints breccia 1 and is made up of albite-pyrite-chalcopyrite-scheelite ± gold veins. The breccia 1 and breccia 2 styles of mineralization are more common in the upper levels of the Kiena mine, and with increasing depth there is a transition to stockwork veins being the dominant style of mineralization. The dominant sulphide present in the mineralization is also zoned. Pyrite is more dominant in the upper levels and pyrrhotite is more dominant in the lower levels. Mineralization is hosted within albite altered intermediate dykes, and locally within sheared basalt. The felsic porphyry dykes are younger than the albite dykes, considered to be synmineralization. Locally the albite dykes are mineralized by carbonate-quartz-pyrite ± pyrrhotite ± gold stockwork.
The Kiena Deep A Zone is localized adjacent Norbenite Fault deformation corridor. Contrary to previous beliefs, the Kiena Deep A Zone is not the extension of the S50 Zone. The structures, mineralization type, host rocks and grades are completely different. The Norbenite Fault plane at that depth (1,350 m below surface) strikes NNW and dips shallower (55°) to the east compared to the WNW direction near the surface and the dip of 70°. The Kiena Deep A Zone is divided into three main lenses: ZA, ZA1 and ZA2. A fourth smaller lens (H1ZA) is located in the hanging wall of the ZA at the contact between the basalt and the flow breccia units. The lenses occur along an isoclinal fold associated with the Norbenite Fault and a subsidiary fault. All lenses in the Kiena Deep A Zone are variably altered to chlorite, albite, carbonate and amphibole. Pyrite content is less than 2% with traces of pyrrhotite and chalcopyrite. Gold mineralization occur in folded laminated veins (shear veins) hosted within sheared ultramafic rocks. Folding is observed in shear zones. Veins are composed of vitreous to milky to grey quartz with carbonates and visible gold. There is more than one gold bearing vein generation. Sulphides range from traces to 1% locally (pyrite, pyrrhotite, chalcopyrite, sphalerite and galena).
The VC Zone follows the south side of the Norbenite Fault and was mined between 2006 and 2013. It consists of four lenses of steeply plunging gold-bearing carbonate-quartz-pyrite veins in albitized basalt wallrock. The VC Zone mineralization is similar to the S50 Zone mineralization. The VC1 Zone and VC6 Zone are roughly parallel to the VC Zone and are situated below the VC Zone. The VC1 mineralization is associated with pyrite in diorite dykes within talc schist. Fine quartz-chlorite-pyrite veins host gold within the dykes. The VC6 Zone is roughly one-hundred fifty meters southeast of the VC1 lenses. Hosted within sheared basalt and minor diorite dykes, the VC6 gold mineralization is within quartz-carbonate veinlets. Alteration around mineralization consists of carbonate, chlorite, with minor albite, silica, and amphibole.
The North Zone is 900 m north of the S50 Zone and 200 m north of the Norbenite Fault. It consists of two parallel lenses shaped like flattened tubes, each measuring 10 m by 60 m to 90 m in plan view and plunging 70° north, which can be traced over a length of at least 520 m. From 2007 to 2013, Wesdome extracted 458,860 tonnes of material from the North Zone with an average grade of 2.44 g/t Au. The main structural control for the gold mineralization is a sodium-rich diorite intrusion in basalt host rock. Mineralization occurs as a quartz-carbonate-sulphide matrix-filling in brecciated and albite-altered diorite, and as quartz-carbonate-pyrite veins and veinlets in basalt wall rock. These veins and veinlets are predominantly developed in a steeply dipping orientation that is suggestive of a sheeted or ribbon-vein system. There are subsidiary veinlets at oblique and sub-random orientations, which may be described as a pseudo-stockwork. Well-developed albitized envelopes with disseminated pyrite encompass the quartz-carbonate veins, and it is common to observe 5-10% disseminated pyrite where intense and closely spaced veining is developed.
The 388 Zone has been defined as a small deposit parallel to the North Zone at a distance of 300 m to the north. It was mined by Wesdome from 2007 to 2013. A total of 146,268 tonnes of material was mined from the zone at an average grade of 3.01 g/t Au. The 388 Zone has a vertical extend of 100 m. Gold mineralization is associated primarily with a single major quartz vein 2 m wide that developed in albitized basalt alongside a diorite dyke. The vein is rather erratic and structurally meanders within an irregular zone of altered basalt 3 m to 6 m wide. Small scattered quartz-carbonate veinlets with minor pyrite occur in the wall rock.
The Martin Zone lies 300 m northeast of the Norbenite Fault and is approximately 900 m to the east of the S50 Zone. The zone strikes approximately N340°. This zone is hosted by silicified, brecciated, pyritized and albitized basalts.