Local
Kevitsa igneous complex layered ultramafic-mafic intrusive rocks dated at 2058 ± 4 Ma (Mutanen & Huhma, 2001). The body of the intrusion extents to 2 km. The Kevitsa intrusions ultramafic units are on lower parts of the intrusion, which is overlain by the gabbroic rocks that are located on the South-West side of the ultramafics. There is a dunite unit in the middle of the deposit, which is disconcordant to magmatic layering as well in the bottom of the intrusion. Xenoliths are common in the ultramafics and within the ore body. They are variable in sizes and by composition; they typically are sedimentary, mafic or ultramafic. There are also several mafic dykes, in the intrusion, ranging in different ages but they are not very voluminous.

The Kevitsa area has undergone several tectonic and metamorphic events which are evident in the intrusion and in the country rocks (Hölttä et al. 2007). The NNE-SSW trending Satovaara fault, and other structures which are associated with it, are a structurally significant feature of the area. The Satovaara fault has deformed the eastern margin of the Kevitsa intrusion and within the deposit, there are smaller scale structures in similar trend.

Property
The Ni-Cu-(PGE) mineralization is located in the centre of the intrusions ultramafic rocks, and it is hosted typically by olivine websterite and its variants. In the broad sense, they can be described as clinopyroxene-dominated rocks with 0-30 % orthopyroxene, 5-25 % olivine and 0-10 % plagioclase. These rocks have very subtle visual and geochemical differences. The distribution and form of observed mineralogical and geochemical patterns are interpreted to represent multiple magmatic phases. There are no internal contacts to these pulses, but in many instances the base of one pulse (olivine websterite) will grade relatively sharply into the upper part of another pulse (plagioclase bearing olivine websterite). These layers are irregular in shape. Geochemically, differentiation within these pulses is most clearly demonstrated by Al2O3. It is proposed by Luolavirta et al. (2017), that the Kevitsa magma chamber was initially filled by stable continuous flow (“single” input) of basaltic magma followed by differentiation in an at least nearly closed system. In the following stage, new magma pulses were repeatedly emplaced into the interior of the intrusion in a dynamic (open) system forming the sulfide ore bodies. This model would explain the contrasting intrusive stratigraphy in the different parts of the intrusion, which likely is reflecting different emplacement histories.

The most widespread alteration in Kevitsa resource area is amphibole alteration of ferromagnesian minerals. The alteration is typically pervasive in style and has generally ‘”sharp boundaries” i.e. it does not grade out. Pervasively amphibole altered rocks are often accompanied by carbonate alteration: there can be millimetre- to metre-scale carbonate or carbonate-quartz veining. The first alteration phenomenon in Kevitsa, being also common, is the serpentine alteration where the olivine is replaced by dark serpentine. Magnetite was initially primary mineral but it is also associated with other alteration styles as veins like serpentine and carbonate alteration. Epidote alteration is associated with the rodingite dykes. Actinolite-chlorite alteration seem to be associated with the structures. Narrow actinolitic selvedges are also common on carbonate ± quartz vein margins, but these wider, green actinolite features are a distinctive vein set. Talc-carbonate alteration is strongly associated with the shear zones, late fractures and veins representing CO2 bearing fluids. The style can range from selective replacement of ferromagnesian species to pervasive alteration of the rock.

Mineralization
The known economic Ni-Cu-PGE mineralization is disseminated in style. While having some minor semi massive sulphide veins. Overall mineralization volume is irregular in shape, and it is cut by several faults which locally are offsetting the mineralization. The predominant mineralization type is Ni-Cu, comprising 95 % of the deposit. Within it, are mineralization domains, which can be separated by the distribution of Cu and NiS grades, and as well with the amount of PGE’s. The so-called Ni-PGE mineralization is in relatively small in volume.

The main economical minerals are chalcopyrite and pentlandite, but mineralogically speaking pyrrhotite is the most common sulphide. Typically, the sulphide grain size varies from fine to medium, and the grain aggregates are in the interstitial spaces of the silicates. In unaltered rocks the sulphide silicate grains are smooth and plain but in amphibole altered rocks the boundaries are irregular and serrated. Chalcopyrite generally occur as large anhedral grains, sometimes with cubanite and talnakhite, and as fine intergrowths within the gangue silicates. Pentlandite can be coarse-grained sub-euhedral, smaller intergranular grain bands between silicates and pyrrhotite, and “exolution flame” inclusions within pyrrhotite or pyrite of very fine grain size. In addition to pentlandite the nickel occurs in crystal lattice of some silicate minerals such as olivine, clinopyroxene and tremolite. The nickel in silicates is not recoverable in metallurgical process and therefore sulphide nickel is analysed by selective leach method. Pd and Pt typically occur as sulfosalts, such as arsenides and tellurides. According to Kojonen et al. (2008), over half of the PGE carrying minerals are as inclusions in amphibole, serpentine and chlorite. PGE carrying minerals which are related to sulphides occur mostly on sulphide grain boundaries, inclusions in sulphides or in late fracture fillings in pentlandite.

The Kevitsa Mine is a Ni-Cu-PGE open pit mine located at Sodankylä, Finland.
Cu is the most valuable commodity in the Kevitsa Mine, even though the Kevitsa Mine produces more Ni concentrate.

Completed pits and current designs use the original slope design parameters of 80° batters mined in 12 metre high benches with a 10 metre wide berm every two benches (24 m). Ramps are all designed at 10% gradient for all Stage designs and the final pit. The ramps have different design widths depending on usage: trolley assist 55m width; Non Trolley Assist - Haulage 40 m width; Service 25 m width. [ TR 2016 p. 95-96.]

Conventional truck and shovel mining method with preliminary drilling and blasting operations are utilized at the Kevitsa Mine. BKMOY owns a mining fleet and uses contractor to assist ore re-handling on the ROM pad for primary crusher feed. The onsite technical group supervises the contractor. Since April 2020, ore and waste mining is not assisted anymore by contractor services.

The waste dump is located to the north-east of the pit. The stages are designed such that they generally comprise wide benches of between 50 m and 200 m in width, providing several mining horizons to satisfy the feed requirements for blending. In general, ore is hauled to a ROM Pad located immediately south of the pit, whereas waste is hauled to the waste dump located to the north and east of the ultimate pit.

KMO has a mixed fleet comprising of large efficient owner operated equipment to undertake the base movement load and mining contractors with smaller more flexible mining equipment to mine areas and materials that don’t allow the KMO equipment to operate efficiently.

The Kevitsa Mine commenced mining operations in autumn 2011, Hartikainen was then contracted to mine waste from stage 1. Mining has proceeded from initial excavation: stage 1 and stage 2 have been mined out and stage 4 mining has started in 2019. A strategic project will be held during 2021 in order to revise the life of mine with the feasibility of a possible expansion to an additional pushback, stage 5. The mining sequence broadly follows the sequence of events as follows:
- Grade control RC holes delineate the ore zones
- Blast patterns designed to reduce material throw and ore dilution - and a Blast Master planning process controls sequence of operation
- When possible, ore and waste blasted and mined separately as fragmentation requirements vary significantly. Blast movement monitoring is in place to minimize dilution and ore loss for mixed blasts
- Waste removed on each 12 m bench prior to the mining of ore, removal of waste in the successive cut-backs utilizes planned bulk systems of operation
- Trim blasts and perimeter blasting utilized to ensure pit wall profiles are cut to the correct angle and wall damage minimized
- Face shovels load rock into 225 t class trucks and ore hauled from the pit to the finger stockpiles which are integral part of the feed sequence to ensure ore blending can be achieved, haulage efficiencies can be maximized and operational flexibility enhanced at all times.

The primary crusher is a Sandvik CG820 gyratory crusher with 28 millimetre eccentric throw. This crusher is sized to handle a maximum rock size of about 1,200 millimetres and is equipped with a 535 kW drive.

The gyratory crusher product discharges directly into a surge pocket immediately below the crusher. Crushed ore is withdrawn from the surge pocket by a variable speed feeder onto a 1,200mm wide crusher discharge conveyor, which conveys the primary crushed ore to the screening plant.

The primary screen is 2.8 m wide by 5.5 m long, and is fed directly by the crushed ore conveyor. The screen is a double deck screen and has two functions – production of a coarse lump for grinding media in the AG mills, a mid-size pebble for grinding media in the pebble mill. The bottom deck undersize is conveyed to the AG mill stockpile with the coarse lumps, and the mid-size material –
typically being between 25 and 130 mm in size is conveyed to a pebble bin.

Mid-size pebbles discharge onto the secondary crushing feed conveyor, which delivers the pebbles to a combined pebble surge and secondary crusher feed bin. This 1200 m wide conveyor discharges material onto a vibrating screen located above the bin, which is equipped with a 60mm aperture deck, to provide segregated feed to the secondary and tertiary crushers.

The milling circuit comprises 2 primary AG mills and a single pebble mill. Each mill is 8.5 m in diameter (inside shell) and 8.5 m long (EGL). The primary mills are equipped with single pinion 7 MW drives; one of the AG mills is variable speed, and the other mill is fixed speed. The fixed speed mill runs at 75% critical, and the variable speed mill has a range of 65 to 80% critical. The pebble mill is equipped with two 7 MW drives.

The mineral processing facilities at Kevitsa have undergone several modifications and an expansion since commissioning in 2012. In 2020, 9.5 Mtpa expansion project was commissioned, with a design capacity of 9.9 Mtpa.

The following unit processes comprise the Kevitsa Metallurgical facility:

- Sequential flotation of copper and nickel concentrates.
- Copper flotation cleaning in four stages with regrind of scavenger concentrates product.
- Nickel flotation cleaning in five stages with regrind of the 2nd cleaner concentrate product.
- Flotation of sulphide rich concentrate from the nickel scavenger flotation tails to produce a low Sulphur content tailings with low acid forming capacity.
- Dewatering of Cu and Ni concentrates by thickening and filtration.
- Deposition of primary tailings into conventional (unlined) TSF.
- Deposition of sulphide rich concentrate into a dedicated lined tailings storage facility.