| The deposit is situated inside the Rombak Basement Window (RBW) and near the Swedish border SSE of Narvik. Stream sediment gold anomalies are common throughout the RBW , especially in the central and northern part. However, the only significant gold mineralisation found so far occurs at Gautelisfjell in the south, where a small semi-massiv lens of arsenopyrite (2,5 m x 80 m) was tested in 1916-1920 (Bugge and Foslie, 1922). In 1983-86 Folldal Verk A/S investigated the deposit and surrounding areas (Korneliussen et al., 1986).
The bedrocks in the RBW comprise lower amphibolite facies turbidites, mafic to intermediate volcanites and subordinate units of arenites and marbles (Korneliussen, 1989) which form several separate rafts within younger granitic intrusions of Paleoproterozoic age. The Gautelisfjell mineralisation occurs inside one of these rafts, being dominated by a sequence of dolomitic and calcitic marbles and turbiditic metagreywackes resting with a basal sequence of meta-conglomerates and psammites on a basement of trondhjemitic orthogneisses (c.1940 Ma). These rocks are intruded by a granite pluton yielding an age of 1770 Ma (Romer et al., 1992). The gold mineralisation is according to Skyseth and Reitan (1995) and Romer (1994), found associated with Caledonian shear zones inside the supracrustal rocks and surrounding plutonic rocks. These include early NNE-SSW-striking and W-dipping structures and late steeply dipping NW-SE trending structures. The latter represents late-orogenic zones of extension. Along these structures three main types of gold mineralisation can be recognised including 1) stratabound massive to disseminated arsenopyrite with native gold in a matrix of quartz occurring along the calcitic marble/greywacke contact, 2) chalcopyrite-gold mineralisation with minor pyrrhotite and pyrite occurring along calc-silicate zones in the marbles and quartz veins in the greywackes and 3) low-sulphide ores of fine-grained disseminated gold (0,002-0,04 mm) in impure dolomitic marble together with magnetite and chlorite, as well as minor chalcopyrite and pyrite. The latter type is nearly invisible. Analyses of the gold mineralisation in the Gautelisfjell area range from 0.5-45 ppm Au (max. 300 ppm) with an average at about 4 ppm. Drillcores yield gold grades up to 6-7 ppm in 3 m sections.
The ore deposition is related to greenschist facies retrogression, thus postdating the Caledonian peak metamorphism under epidote-amphibolite facies conditions. The migrating fluids precipitating the gold and associated ore minerals, were hyper-saline (33-40 % NaCl equiv.) with temperatures in the range 215-320 C (Skyseth and Reitan, 1995). |