Kuhmo - Arola

The Arola prospect is located immediately west of the town site of Harmankyla and is located within a north-south trending greenstone belt dominated by mafic volcanic rocks and ultramafic units. The belt is less than two kilometres wide in this area; however it widens to five to eight kilometres in the north and south. The local geology comprises a sequence of amphibolite, schistose sedimentary rocks including graphitic schist, serpentinite and talc-carbonate altered ultramafic rocks. Bedding and schistosity are almost vertical and the stratigraphic bottom within the mineralised area is interpreted to be towards the east. The deposit is hosted by sheared and quartz-carbonate-chlorite altered Cr-basalt units juxtaposed against metasedimentary rocks, including greywacke and phyllite, along the eastern contact (Figure 1). These sediments are the source of the electromagnetic anomaly in the area that can be followed approximately one kilometre north and south from the deposit. Unaltered Cr-basalts, which are considered as part of the Archean komatiitic sequence are located on the western side of the mineralised chlorite schist. The deposit is interpreted as mobilised but the origin is probably komatiitic.

The Arola deposit can be divided into three distinct zones comprising discontinuous lenses over 400 metres of strike length and 400 metres below surface. Two of the zones are almost parallel to the orientation and shearing of the host rock and they are about 40 metres apart from each other. The third mineralised zone cross cuts the schistosity at an angle of approximately 35º. All mineralised zones are composed of several discontinuous lenses. The more coherent lenses are interpreted to plunge approximately 40° to the north (SMOY, 1968, reference 15).

The main sulphide minerals are pyrrhotite, pyrite and pentlandite. Nickel content is commonly less than 1%; the highest grade assayed is 5.72% nickel. Copper grade is low, usually less than 0.1% and the highest value is 0.4% copper. The content of platinum group elements is very low, <0.04ppm. Nickel tenor varies quite a lot from 2% up to 25%, the average being 10-15%.

Outokumpu completed a polygonal resource estimate on vertical cross sections which quotes 1.5 million tonnes at 0.46% nickel.

Figure 1. Geology of the Arola prospect by the GTK. Magnetic anomalies are shown in green and conductors in blue. Drill hole collars are shown as white dots and the Arola deposit in red. Map grid is 1x1km.