Kankberg Geology
The Kankberg Mine lies within the eastern part of the Skellefte mining field, one of the most important mining regions in Sweden, where Boliden has been active since the 1920s. It’s significance in relation to 52 other known deposits in the field is shown in Figure 11 from a paper by Allen et al (1996) that describes the marine volcanic arc setting of these Zn-Cu-AuAg polymetallic massive sulfide deposits, vein Au deposits and porphyry Cu-Au-Mo deposits.

The host rock in the Kankberg area is dominated by volcanic rocks of primarily dacitic and rhyolitic compositions forming quartz-feldspar porphyritic, rhyolitic and dacitic rock types. The felsic magmas forming these volcanics intruded as shallow (subvolcanic) dykes and sills and extruded as lavas at the surface where they mixed with sediments and mass flows derived from volcanic slopes. The volcanism initiated a convection of solutions through the rocks. These solutions dissolved and transported minerals and metals to sites of deposition.

After the major volcanic period had ended the area was subsequently deformed and folded. This resulted in a dominantly vertical trend of the rocks and structures. At a later stage, brittle deformation took place. Fractures and fissures were intruded by mafic magma forming basaltic and andesitic dykes, which are common in the Kankberg area.

Mineralization
Gold mineralization is hosted in a complex mix of volcanic rocks consis ........

Boliden Area Operation consist of Renström, Kristineberg and Kankberg underground mines.

Renström mine
The Renström mine is located 47 km northwest of Skellefteå in Västerbotten county, northern Sweden. A combination of underground methods are currently used, between depths of 600 and 1500 m. Access to the mine is via a central shaft and ramp-drive system from the historic Petiknäs mine to the northwest.

The dominating mining method at Renström is cut and fill, although since 2016, an increasing proportion of production is from long hole stoping methods. All stopes are backfilled with either hydraulic fill (tailings from mill), cemented rock fill or uncemented rock fill (Barren rock from developments).

Methods Proportions
Cut & fill - 72%;
Open stoping - 24%;
Retreat mining - 3%;
Bench - 1%.

Cut and fill mining is a selective open-stope mining method suitable for steeply dipping, high grade deposits. The overhand cut and fill technique is used at Renström, where mining begins at the bottom of the ore lens and progresses upward.

At Renström, cut and fill is selected where:
- Ore is hosted in long, thin lenses;
- Mineralisation is geometrically complex and difficult to follow; and
- Wall rock is too weak to support larger scale production methods.

Stopes are 5-6m high and typically 6-8m wide, subject to orebody thickness. Main levels are typically 65m high, including sill ........

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Ore is delivered by truck to the industrial area where each truck is weighed on a truck scale in order to determine the tonnage arriving to the industrial area. The ore arriving at the industrial area is either taken into the processing plant or stored in a stockpile. Separate stock piles are kept for each of the individual mines in the Boliden area. Ore from the different mines is processed in campaigns where fresh ore from the mine is combined with ore from stockpiles. The feed tonnage to the processing plant is determined using a weighing system with a stationary belt scale. Feed tonnage and weights from the trucks scale are used to determine current tonnage on the stockpiles. In the processing plant the ore is ground in two stages. The primary mill is a fully autogenous mill and the secondary mill is a pebble mill fed with pebbles extracted from the primary mill. The ground ore is classified using screens and hydrocyclones. A gravimetric concentrate containing coarse grained gold ........