Summary:
The mineralization at Rajapalot is a stratabound, disseminated, hydrothermal, usually sulphide-associated, and structurally controlled gold-cobalt type. These are generally stratabound pyrrhotite-bearing iron-potassic (K-Fe) or iron+/-magnesium (Fe-Mg) systems with a Cu, Mo, W, B, Bi-Te (Se) association. There are no reasons to assume across the broader prospect area a lack of low-S “simple” Au-W-As gold systems.
The Rajapalot mineralization shows many of the characteristics of larger Proterozoic gold deposits, having a predominance of structurally controlled, stratabound occurrences commonly with best grade intercepts associated with fold hinges. Evidence is also emerging suggesting that organic matter also plays an important role in precipitating the high-grade potassic sulphidic gold-cobalt mineralization at Raja.
Mineralization
Prospects with high-grade gold and cobalt at Rajapalot occur across 3 km (east-west) by 2 km (north-south) area within the larger Rajapalot project exploration area measuring 4 km by 4 km with multiple mineralized boulders, base-of-till (BOT) and rare outcrops. High-grade Au-Co mineralization at Rajapalot has been drilled to 540 m deep at Raja and South Palokas prospects, but is not closed out at depth in any prospect. The only surface exposure of mineralization is at Palokas; however, with the exception of East Joki, all mineralization comes to the top of the bedrock below the till, less than 6 m below the surface. East Joki is 110 m from the surface at its shallowest, but is not drilled yet in the up-dip direction.
The Au-Co mineralization at Rajapalot differs markedly from the nuggety Au-U style originally discovered at Rompas. Grade continuity, negligible carbonate and a stratabound potassic or Fe-Mg host to the Au-Co mineralization predominates at Rajapalot, whereas Rompas gold was hosted in and associated with uraninite in dolomite-calcsilicate veins cutting mafic volcanics.
The main prospect areas defined by drilling are, from northwest in an anticlockwise direction, Palokas, South Palokas, The Hut, Terry’s Hammer, Rumajärvi (also herein referred to as Rumaj), Raja and East Joki (also herein referred to as Joki). Geochemically and spatially associated metals with the gold are As, W, Bi, and Te and with cobalt, Cu, FeO, S, and U.
Two distinct styles of gold mineralization dominate the Rajapalot area. The first, is a variably sulphidic magnesian-iron host, previously referred to internally as “Palokas” style. The magnesian-iron host is most likely an ultramafic volcanic (komatiitic) and occurs within approximately 100 vertical metres of the inferred Kivalo-Paakkola boundary (that is, near the incoming of pelites, calc-pelites and quartz muscovite rocks). A largely retrograde mineral alteration assemblage includes chlorite, Fe-Mg amphiboles (anthophyllite and cummingtonite series), tourmaline and pyrrhotite commonly associated with quartz-veining. Subordinate almandine garnet, magnetite and pyrite occur with bismuth tellurides, scheelite, ilmenite and gold, cobalt pentlandite and cobaltite.
The second style of gold-cobalt mineralization at Rajapalot, a potassic-iron (K-Fe) style (formerly referred to internally as “Rumajärvi” type) is characteristically associated with muscovite and / or biotite and chlorite in a diverse range of fabrics. Gold grades of more than 1 g/t Au are associated with pyrrhotite and contained within muscovite-biotite schists, muscovite and biotite-bearing albitic granofels and brecciated, variably micaceous albitic rocks. Magnetite is a common mineral, but not a necessity for anomalous gold grades. The host rocks are grey to white owing to their reduced nature and may be enclosed by light pink to red calcsilicate-bearing albitites.
Gold mineralization uncovered in boulders and drilling at the Boardwalk prospect (220 m SSE of South Palokas) is a variant on the Palokas style; drilling has not yet revealed the main source of the boulders; however, zones up to 20 m thick of above-detection Au in magnetite-altered mafic rocks (“iron formation”) has been intersected. Throughout the entire 10 x 10 km Rajapalot project area, variants of the iron-rich ultramafic rocks (host to Palokas prospect) have been recorded, included in a drill section at South Rompas (some 8 km west of Palokas).