The Garpenberg mine is situated in the mineralized Palaeoproterozoic igneous province of Bergslagen, south central Sweden, which is host to a variety of ore deposits, and especially Fe-oxide and polymetallic sulphide deposits. Garpenberg, which is the largest sulphide deposit in the region, consists of several individual ore bodies distributed over a distance of 4 km within the Garpenberg supracrustal inlier, see Figure 3-3. The main host rock to the ore is calcitic marble (limestone) altered to dolomite and Mg +/- Mn-rich skarns. The footwall consists of rhyolitic pumiceous, graded massflow breccia and rhyolitic ash-siltstone and sandstone affected by strong phlogopite-biotitecordierite-sericite-quartz alteration. The hanging wall includes polymict conglomerates and rhyolitic pumiceous breccias. The stratigraphic succession is attributed to the volcanic cycle of a felsic caldera complex. The pumiceous breccias in the hanging-wall record a climactic eruption that formed a caldera over 500 m deep and over 9 km in diameter in the Garpenberg area. The limestone horizon is interpreted as a stromatolitic carbonate platform, formed in a shallow, marine environment during a hiatus in volcanism.

The Garpenberg inlier has been interpreted as a NE-SW trending, tight to isoclinal complex syncline with a sub-vertical axial plane (Allen et al., 2003). The structure is compressed at the southern end and opens to the north. The ore-host limestone shows a complex geometry due to large scale folding, shearing and faulting. These structural features have resulted in complex synforms and antiforms, and have a major influence on the position, geometry and metal grades of the ore bodies. The largest ore bodies are linked to antiforms, such as Lappberget and Huvudmalmen.

Mineralization in Garpenberg mainly consists of pyrite, sphalerite, galena and silver minerals. The ore bodies occur at the heavily skarn- and dolomite-altered contact zone between the limestone and underlying metavolcanic rocks, forming massive to semi-massive sulphides ore lenses. There is also significant mineralization in the footwall metavolcanic rocks (mica quartzites) that are stratigraphically underlying the marble horizon. The footwall mineralization is tectonically controlled and forms remobilized semi-compact thin veins that are often associated to mica-rich shear zones. Mineralization is mainly of replacement style and is likely to have taken place where metal-bearing fluids penetrated up along synvolcanic, extensional faults and came in contact with reactive limestone to form large, massive sulphide bodies. The initial main stage of mineralization and alteration at all the known Garpenberg ore bodies is interpreted to be essentially syn-volcanic in timing and to predate regional metamorphism and deformation (Jansson & Allen, 2011).

Garpenberg is a Zn-Pb-Ag-(Cu-Au) underground mine where the ore is mined from between 450 meters to more than 1 400 meters below surface. The mine encompasses several polymetallic ore bodies. Almost 80 % of the mined tonnage derives from the largest ore body, Lappberget. Almost 90% of the mined ore in Garpenberg is extracted by sublevel stoping (also called longhole stoping), where the ore is mined in layers between two drifts vertically 25 m apart. Most areas are mined with transversal longhole stoping, where the development and stope axis are perpendicular to the strike of the orebody. In some more narrow areas, longitudinal longhole stoping is used. The orientation of this method is along or parallel to the strike of the orebody. The ore body is split into primary and secondary stopes, which are mined in a predefined order and pyramid shape sequence. The standard stope dimensions are 24 - 25m high, 10 m wide for primary stopes and 15 m wide for secondary stopes. In general, the ore bodies are divided in mining blocks with 6 levels of stopes in each block. The last level of each mining block is the sill pillar, which separates the different mining blocks. This division allows the mine to have several production areas being scheduled and mined at the same time. Another consideration that was recently introduced concerning the mine design of Lappberget is the division into a main and a second pass sequence (2pass). The main sequence contains more of the high-grade areas and is scheduled prior to the second pass sequence, which in general contains lower grade ore. Other mining methods include cut and fill and avoca (rill). With the cut and fill method mining is carried out in slices along the steeply dipping, narrow ore body. The bottom slice is mined first. The excavated area is then backfilled, so mining can continue with the slice above. The rill method used in Garpenberg is in fact similar to longitudinal stopping, but the stopes are split in 20 m long slices. After being blasted and mucked, the stopes are backfilled before the next slice is blasted. This process repeats until the full size of the stope is done. Mining method Ore body Min width (m) Sublevel stoping Lapp, Kvarn, Kasp, Damm, 10 alt 15 Huvudmalmen Cut and fill Damm 7 Avoca (rill) Damm 7 Transport to the crushers is done by trucks from the active mining areas. The crushed ore is hoisted to surface in a shaft, unloaded into a bin in the headframe and then transported by conveyor belts to an intermediate ore storage, which can hold approximately a week of production. Waste rock, which is mined and separated in the mine, are used for back filling in the mine. The portion of the finely ground waste rock that is separated in the concentrator is known as tailings. Some of the tailings are mixed with a binding agent and pumped back into the mine for back filling. Surplus tailings are deposited in a pond at the Tailings Management Facility (TMF) from where processed water is recovered.

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After grinding, the ore is screened, with the coarse fraction being returned to the primary mill and the fine fraction undergoing gravimetric separation (Knelson) in order to separate coarse gold out at an early stage of the process. Knelson concentrate is collected in big bags. After gravity separation, material is classified using hydrocyclones. The overflow constitutes the main flotation feed, while the underflow undergoes flash flotation in the grinding circuit, from which the concentrate is sent directly to CuPb separation in the flotation plant and the tailings back to the mills.

Flotation is carried out in a three-stage process flotation circuits: CuPb flotation, CuPb separation and Zn flotation. Regrind mills are installed both in the CuPb and Zn circuits. The mineral concentrates are dewatered using thickeners and pressure filters. Three mineral concentrates are produced in flotation: zinc, lead and copper concentrates. The precious metals report primarily to the c ........