Boreal Mineral’s Adak exploration license (8,647 hectares) is located in the highly prospective Skellefteå Mining District which contains the historical produces Boliden (Boliden), Rakkejaur (Boliden), and Petiknäs södra (Boliden), Storliden (Lundin) and the active Renström (Boliden), and Kristenberg (Boliden) mines which occur over 120 kilometers in the highly prospective Skellefteå Group rocks (Figure 1).
Boreal’s Adak project consists of the historical Adakfältet Mine Field which consists of the Adak, Lindsköld, and Brännmyarn mines which together account for 6.33 Mt @ 2.02% Cu, 0.6 g/t Au, 9 g/t Ag and the Rudtjebäcken Mine with 4.75Mt @ 0.9% Cu, 3% Zn, 0.3 g/t Au, 10 g/t Ag (historical, non-43-101compliant resources). These mines were contract mined by Boliden on behalf of the Swedish Government between 1932 and 1977, when the mining complex was destroyed by a fire. The facilities were not rebuilt or re-opened since. Boreal’s compilation of historic data includes surface, and subsurface geological data including over 700 drill holes and extensive underground development data. This database coupled with modern direct detection electromagnetic geophysical methods has identified high potential drill targets within and adjacent to the existing mining footprint.
Mineralization in the Adak Field consists of massive, vein and disseminated precious metal rich base metal sulphides (chalcopyrite, sphalerite, galena) with associated pyrite, pyrrhotite and arsenopyrite. Volcanogenic massive sulphide mineralization occurs in altered and metamorphosed mafic to felsic metavolcainc rocks of the Proterozoic Skellefte Group (Hallberg et al., 2012). These rocks consist of cummingtonite-cordierite-anthophyllite gneiss, cordierite-biotite-chlorite schist and calc-silicate assemblages within the core of the Adak Dome, a localized region of uplift, and are in turn overlain by less altered mafic metavolcanic rocks (Hallberg et al., 2012).
The Adak Area Mines
The mines at Adak can be divided into 2 groups based on ore mineralogy. The Adak, Lindsköld, Karlsson and Brannmyran mines, collectively called Adakfältet are copper rich and processed on the mine site. The Rudtjebacken mine produced a zinc-rich ore that was processed at the nearby Kristineberg zinc-copper mine (Amdahl, 1979).
The Adak Mine
The Adak Mine, located in the northwestern quadrant of the Adak Dome was developed by open cut & underground methods over an area of 500 square meters. Between 1930 and 1977 a total of 1.9 Mt @ 2.06% Cu was extracted from 3 shafts over 9 levels including 7,426m of development (Amdahl, 1979). Adak contains two styles of mineralisation. Stratiform volcanogentic massive sulphide (VMS) associated with altered schists. Sulphide mineralization is typically massive in the deeper portions of the system, transitioning to semi massive to disseminated in the upper portions of the mine. Breccia hosted mineralization occurs in the siliceous metavolcanic rocks (quartzite) and represents the second style of mineralization. A large number of elongated deposits plunge gently towards the southwest and contain higher grades joint intersections. The sulphide mineralogy at Adak consists of chalcopyrite, pyrrhotite, and minor sphalerite.
The Lindsköld Mine
The Lindsköld Mine is located just to the north of the Adak mine (see figure 5) and was also developed by open cut and underground methods with wall-stripping being the main method employed underground. The mine covers an area of 800 square meters and produced 3.38Mt @ 2.21% Cu (Amdahl, 1979). The western part of the orebody was very rich with a core of 150,000t @ 5.45% Cu (Amdahl, 1979). The ore consists of gently dipping lenses hosted by altered schists. Mineralogy is similar to that at Adak. Development consisted of a 281 meter shaft accessing 6 levels with 7,738m of tunnels. This mine was operational until 1977.
The Brännmyran Mine
The Brännmyran Mine located in the southeastern quadrant of the Adak Dome. Brännmyran was an underground development that covered an area of 1,300 square meters and consisted of two sheets of VMS style mineralization at slightly different horizons with a third zone situated eastward. Mine access was via a 282 meter shaft accessing 5 10 levels with 2,944 meters of tunnels. Mining was predominantly done by wall stripping. A total of 0.98Mt @ 1.7% Cu mined between 1960 and 1976 (Amdahl, 1979).
The Karlsson Mine
The Karlsson Mine was a satellite mine to the east of Adak. It was an open cut and underground operation with a 26 meter shaft accessing a single level with 80 meter of development. The mine covered 60 squre meters and produced 14,466t @ 4.3% Cu (Amdahl, 1979). Karlsson was operational from 1944-1946.
The Rudtjebäcken Mine
The Rudtjebäcken Mine located in the Eastern quadrant of the Adak Dome. It had a strike length of 1 kilometer and an average thickness ranging between 4-5 meters (dipping northeast). Rudtjebäcken contains a VMS lens above a disseminated zone, hosted by metamorphosed tuffaceous volcanic rocks. The southeast section of the lens averaged 2.5% Cu (Amdahl, 1979). Sulphide mineralogy consists of include pyrite, pyrrhotite, sphalerite and chalcopyrite. A total of 4.75Mt @ 0.9% Cu, 3% Zn, 0.3g/t Au & 10g/t Ag was mined between 1947 and 1975 (Amdahl, 1979). Ore was processed at Boliden’s plant at Kristineberg.
The project has excellent infrastructure including a 35 kilometers access road to a rail siding at Slangäs which is in turn situated 35km from Boliden’s Kristineberg mine. Adak is situated 120 kilometers from a central concentrator in Boliden which processes ore from many mines in the area including Kristineberg, Renström and Maurliden. In addition, the project is located 160 kilometers from a Boliden copper smelter at Rönnskär.
Amdahl K., 1979. Adakfältet 1920 - 1979. En dokumentation, bilaga till anslagsframställning för 1980/1981 (60336 kB). Swedish geologiska undersokning. http://resource.sgu.se/dokument/geodigitalia/rapporter/brap_200216.pdf
Hallberg, A., Bergman, T., Gonzalez, J., Larsson, D., Morris, G.A., Perdahl, J.A., Ripa, M., Niiranen, T., and Eilu, P. 2012. Metallogenic areas in Sweden. Geological Survey of Finland, Special Paper 53, pp. 139-206
Figure 1: The Location of the Adak Project, Skellefteå District, Northeastern Sweden
1 Grade-Tonnage information obtained from Mineral deposits and metallogeny of Fennoscandia, Geological Survey paper of Finland, Special Paper 53. Pasi Eilu Editor. 401 p. 2012.
Figure 2: Website Geology and Location of Historical Mines