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The Råna Intrusion is located approximately 20 km southwest of Narvik, in the municipality of Narvik, northern Norway. The Bruvann Ni-Cu-Co deposit belongs to the Råna Intrusion.
The Norwegian State holds the large mining claim of the closed Bruvann mine and Bruvann ApS, a fully owned subsidiary of Scandinavian Highlands Holding A/S) has subsequently rented the mining rights. The licence area covers 2.0 km2. According to the document made between the Norwegian State (Directorate of Mining) and Bruvann ApS, the company can examine the possibilities for further mining and ultimately obtain mining license.
Råna ApS, another subsidiary of Scandinavian Highlands Holding A/S holds a 15.5 km2 big exploration licence area, covering the majority of the ultramafic rocks exposed along the northern parts of the intrusion.
According to Foslie (1941) the mineralisation potential in the Råna Intrusion was discovered around 1912–14. The eastern part of the Bruvann ore body was discovered in 1912 and the Eiterdal deposit in 1913. The Germans made reconnaissance prospecting in the area during WWII (1940−1942) by the organisation/company Erzstudiengesellschaft. Norsk Bergverk continued exploration after the war (1954−1960) but ore volume was not indicated until Stavanger Staal A/S with the Norwegian Geological Survey (NGU) made an extensive drilling program (1970−1975). The first volume indications based on the assays of approximately 25,000 m drill core suggested the presence of 43 Mt (cut off equal to 0.15% Ni) with a grade of 0.33% Ni, 0.08% Cu and 0.015% Co. A calculation made by Falconbridge (1985) (now liquidated) on the same data gave 26.4 Mt (cut off equal to 0.3% Ni) with a grade of 0.42% Ni, 0.1% Cu and 0.02% Co. (alternatively cut off at 0.4%, 0.5% and 0.6% Ni gave a tonnage of 12.7 Mt, 7.8 Mt and 3.6 Mt respectively).
Together with the work around the Bruvann deposit some regional work was made. Especially the ultramafics exposed to the north of Bruvann (Arnes Block) and the lower part of the northern slopes of the Rånkeipen Block were targeted for pitting and trenching activities. Several smaller Ni-occurrences were found but Bruvann remained the main target.
Nikkel & Olivin A/S, a Norwegian registered company, was established as an operating mining company in 1989. The business base was the Falconbridge resource calculations and an assumption about simultaneous production of olivine and aggregates. Mining started less than one year later. Outokumpu (Finish registered company) bought the concentrate. Neither the olivine- nor the aggregate production had commercial success and after only three years of production Outokumpu bought the majority in Nikkel & Olivin A/S. Prior to the take over in 1993, a new calculation of remaining ore was made (Ekberg, 1992). The calculations gave a measured undiluted mineral resource of 8.1 Mt with a grade of 0.54% Ni with a cut off equal to 0.35% Ni - alternatively 4.8 Mt with a cut off equal to 0.45% Ni or 1.8 Mt with a cut off equal to 0.55% Ni.
In 1997 Outokumpu made a strategic decision that the company should redraw from mining. The mines that represented value were sold and Bruvann mine was closed as scheduled in 2001. As planed Bruvann mine closed in 2001 after twelve years of production. The Bruvann deposit was mined as an open pit and underground mine. The extraction process i.e. crushing, milling, and flotation, was located near the mine entrance (approximately 400 masl). The total mined tonnage from 1989 to 2001 was 8.2 Mt with a grade of 0.52% Ni and a cut off in the range 0.43−0.47 depending on the nickel price.
Outokumpu made a small exploration program from 1996 until 2001. The exploration had a strong focus on supply to the existing mine facilities and was therefore almost entirely limited to the surroundings of the existing mine. A regional helicopter borne electromagnetic (HEM) survey covering the northern part of the intrusion was made in 1996. It outlined an area with high conductivity five km east of the Bruvann mine, but the anomaly was not followed up. In 2001 few surface diamond drill holes were made approximately two km to the north of the Bruvann mine, but though the initial indications were promising, the exploration activities stopped together with the mining.
The nickel mineralisation in the Bruvann mine is hosted by peridotite close to the contact with surrounding gneisses. The mineralisation is mainly Type 2 disseminated sulphides. However, massive and semi-massive ore i.e. Type 1 exists near the southern contact to the gneisses. Type 1 mineralisation has been discovered on both sides of the main fault zone. The main nickel carrier is pentlandite, but other sulphide minerals such as pyrrhotite and chalcopyrite also occur. Olivine contains approximately 0.09% Ni in its lattice (Storhaug, 2000). Historical the Ni/Cu = 4:1 (NGU ore database).
The deposit consists of several lenses which are separated by faulting. The main fault zone, orientated roughly N−S, divides the nickel deposit into Ostmalmen (eastern ore body) and Vestmalmen (western ore body). The vertical distance between the two ore bodies is 75 to 200 m. Ostmalmen is subdivided into Sydost dagbrudd, Kronpillar and Dypmalmen. Vestmalmen is subdivided into Dinosaurmalmen, Sydmalmen and Nordmalmen (Storhaug, 2000). The mineralised zone extends approximately 900 meter in an east−west direction, and 700 m in a north−south direction where Vestmalmen is dipping towards west and Ostmalmen is dipping towards south (Storhaug, 2000).
A comprehensive database has been established based on knowledge of the mine design and the outcome of drilling during mining (1989−2001). The database contains approximately 100,000 m drill core data (more than 170,000 data points). Using Gemcom Surpac, Geology and Mine Planing software, the entire Bruvann Mine has been reconstructed in a 3D model. A block model using kriging reveals a remaining measured resource of 9.15 Mt with an average grade of 0.36% Ni (cut off = 0.30% Ni) or alternatively 5.5 Mt with a grade of 0.39% Ni (cut of = 0.35% Ni). The calculations are based on kriging methods.
Validation of the mine structures, i.e. drifts, stopes and ramps in Vestmalmen has been done analysing mine maps as well as consulting L. Storhaug, former geologist at the Bruvann Ni mine. Likewise, stopes in Ostmalmen have been compared with mine maps.
Storhaug, L., 2000, Ore Reserve Statement of Nikkel og Olivin a/s, p. 13.
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