Björkdal Gold Mineralisation
The Björkdal gold deposit is a lode-style, sheeted vein deposit hosted within the upper portions of the Skellefte Group sediments. To date, the deposit measures roughly 2,000 m in length, 1,800 m in width and extends 600 m deep. Gold can be found within quartz veins that range in thickness from less than one centimetre to more than several decimetres. These veins are usually observed with vertical to sub-vertical dips and strike orientations between azimuth 000° and azimuth 090°. The majority of veins strike between azimuth 030° and 060°. Veining is locally structurally complex, with many cross-veining features observed and thin mineralised quartz veinlets in the wall rocks proximal to the main quartz veins.

Gold-rich quartz veins are most often associated with the presence of minor concentrations of sulphide minerals including pyrite, pyrrhotite, marcasite, and chalcopyrite. Associated non-sulphide minerals include actinolite, tourmaline, and biotite. Scheelite and bismuthtelluride compounds (i.e. tellurobismuthite and tsumoite) are also commonly found within the gold-rich quartz veins, which are typically excellent indicators of gold mineralisation.

Gold occurs dominantly as free gold, however, gold mineralisation can also be associated with bismuth-telluride minerals, electrum, and pyroxenes. Silver is observed as a minor by-product in the Björkdal processing plant, however very little is known about its deportment within the deposit, although it has been assumed to be associated with electrum in the mineralisation.

Björkdal Skarn Mineralisation
Skarnification occurs commonly within the Mine, especially in the limestone/marble unit where it occurs as discreet patches and lenses, these lenses typically measure 200-400 m along strike, 100-200 m down dip and are usually no more than 10 m thick. However, similar calc-silicate alteration has taken place in areas where local shearing has affected the volcanoclastic host rock. The altered rock texture appears sheared and mottled to a varying degree; locally the rock can have a folded appearance. In places where the skarnification is the strongest, the precursor rock texture has been completely overprinted. The skarnified rock has been divided to prograde and retrograde phases based on their dominant mineralogy. Prograde skarn is light green and is dominated by clinopyroxene patching with partial to complete breakdown of the pyroxene patches to amphiboles (actinolite/tremolite), chlorite, calcite, and to a minor degree serpentine and talc. The retrograde skarn is finer grained and darker green in colour than the prograde skarn and consists primarily of amphiboles, chlorite, and calcite. It is likely that the retrograde skarn represents patches of alteration where the calc-silicification did not progress as far as it did in the prograde skarn. The limestone can also be dolomitic and silicified as well as containing irregular quartz patches, quartz veins, and overprinting calcite veins.

Structural Development of the Mineralisation
The relationship between mineralised veins and the local structures appears complex with various cross-cutting relationships observe in the Mine suggesting multiple phases of deformation throughout the mineralisation emplacement. A total of 25 major, north to northeast (true) dipping, strike-slip shears have been identified within the Björkdal Deposit, with numerous, localised systems observed throughout. The majority of the significant gold grades observed within the deposit are hosted in a proximal position (approximately 30 m) to the shear zones.

Norrberget
The mineralisation at Norrberget is stratabound within an interbedded altered volcaniclastic package that sits unconformably below a 30 m to 40 m thick marble unit. Gold mineralisation has been observed up to 50 m below this contact. Gold mineralisation is principally hosted in an amphibole-albite banded alteration and is also common where volcaniclastics are interbedded with crystalline tuff units. Theses alteration bands vary between one centimetre and 50 cm in thickness, are typically fine to medium grained and appear to be sheared. Trace sulphides and minor quartz/carbonate are associated with the bands.

Gold is also associated with the amphibole veinlets with the mafic crystalline tuff associated with carbonate and minor sulphides. Lesser amounts of gold can also be found within the heavily silicified volcaniclastics where minor amphibole is observed. Where visible gold can be identified within alteration banding, it is observed to be between or on the contact of grains.

Although veining is common, gold mineralisation is rarely associated with the quartz veins. Visible gold has been identified in veins consisting of grey fractured quartz along with amphibole, carbonate, silver, minor chalcopyrite, pyrrhotite, and galena. Veins consisting of quartz, carbonate, and albite with euhedral amphibole crystals can also carry gold mineralisation, however, the gold grade is not consistent along them. These veins can be intermixed and individual veins can continue for up to 50 m.

Deposit Type
The predominant source of ore at Björkdal is contained in a package of anastomosing, sheeted quartz-veins. This epigenetic vein network appears to be structurally controlled and consists of more than one thousand sub-parallel quartz veins that typically strike 030° to 090° from true-north. Such strong structural-geological influences over geometry of any quartz vein hosted mineralisation clearly suggests a strong spatial and temporal relationship with orogenic/tectonic processes (i.e. mesothermal/greenstone gold systems). In contrast, the mineral associations with gold mineralisation, and the large alteration signature of the Björkdal area, could alternatively suggest that host depositional mechanisms are responsible for the mineralisation at Björkdal as there are some similarities with skarn and/or porphyry systems.

A much smaller, yet prolific source of ore at Björkdal is observed in strongly altered lenses of Skarn. Skarnification occurs commonly within the Mine, especially in the limestone/marble unit where it occurs as discreet patches and lenses, these lenses typically measure 200-400 m along strike, 100-200 m down dip and are usually no more than 10 m thick. However, similar calc-silicate alteration has taken place in areas where local shearing has affected the volcanoclastic host rock. The altered rock texture appears sheared and mottled to a varying degree; locally the rock can have a folded appearance. In places where the skarnification is the strongest, the precursor rock texture has been completely overprinted.

Norrberget
Primary mineralisation at the Norrberget deposit is observed to be associated with amphibole alteration bands and veinlets, and where mafic tuffs and volcaniclastic rocks are interbedded and in contrast to what is observed at Björkdal. The mineralisation is preferentially emplaced where there is a structural change to the rock such as at lithological contacts, altered bands and where shearing interacts with the interbedded sequences, due to the changing rheological characteristics of the unit. The abundance of pyrrhotite and pyrite appears to be controlled by specific lithology types within the volcaniclastic package which can indicate a differing redox based upon temperature change and fluid evolution.

The mineralisation at Norrberget is limited spatially to 50 m stratigraphically below the lower marble contact, which is believed to be a result of the cooling and redox changes of the fluid as it passes through the units.

The gold is very fine-grained and rarely visible. Where gold grains have been observed, they are found to lie on the boundary or in interstitial material between grains. Elevated gold grades are mostly found in areas with little to no pyrite.

The current environmental permit limits the total Björkdal production capacity to 1.70 Mtpa. In 2019, mining of the open pit was stopped for economic reasons and this production was replaced with ore from the low grade stockpile and an increase in underground production. The remaining open pit material remains economically viable, however, the low grade stockpile realises more value, so open pit mining has been deferred for several years until the stockpile is diminished and open pit production is needed to offset reducing underground production.

The current production strategy is to maximise the underground extraction and delivery to the processing plant with any additional feed requirements sourced from stockpiles.

As presently envisaged in the LOM plan, open pit pre-stripping and production will be restarted in 2025 to supplement the decrease in production from the underground mine.

Underground
The known Björkdal underground deposit lies within a footprint of approximately 1,600 m x 600 m and has a vertical extent of approximately 480 m.

The long-term LOM underground production rate is planned to average 1,135,000 tpa up until 2024, and 648,000 tpa thereafter until production tails off in 2029. On vein development (OVD) will be carried out over approximately four years and stope production will be carried out over approximately eight years. A decrease in production is planned after 2025, when the underground output reduces. The balance of tonnage required for the processing plant will comprise open pit and stockpile material.

Primary access to the underground operation is via ramp systems originating from two portals located in the wall of the existing open pit. Open pit mining and removal of the crown pillar in the north/east wall will disrupt this access as well as the supply of other services such as
emergency egress, electrical, ventilation, and mine drainage systems. Open pit ore mining will therefore commence at Nylunds initially until underground operations cease, with limited pre-stripping only above the underground access and infrastructure in the crown pillar area.

Studies are continuing to investigate the economic viability of constructing an additional portal access prior to open pit mining when the existing portals become inaccessible.

The underground mining method used at Björkdal is longhole stoping with a sub-level spacing of 15 m to 20 m, depending on the zone. Cross-cuts are established perpendicular to the vein system. Veins are then developed by drifting on each sub-level from the cross-cut. All preproduction vein, cross-cut, and ramp development is drilled and blasted using conventional trackless mining equipment.

Stoping blocks are drilled with approximately 15 m long and 70 or 76 mm diameter up-holes connecting to the bottom of the overlying stope using Epiroc Simba drill rigs. When production drilling has been completed, initial slot raises are developed and drill lines blasted in groups of three to five rings using a burden of 1.5 m and retreating towards the hangingwall. The material is removed between blasts, which allows a void for each successive blast. Remotely operated scoops are used to muck the stopes to nearby rehandle areas or directly into trucks.

The majority of waste mined underground from capital development is placed directly into voids as unconsolidated backfill. If insufficient voids are available underground, waste is occasionally hauled to surface for temporary storage and backhauled underground at a later date for placement as fill. Generally, more waste is required for fill placement than is produced from development underground and therefore, suitable additional material is sourced from surface and transported underground by trucks returning from hauling ore to surface.

All underground material is loaded by Volvo L180 front end loaders (FELs) or Sandvik 514 loadhaul- dumpers (LHDs) and hauled to surface by a contractor using 26 t Scania R520 XT highway tipper trucks. The objective of the current materials handling strategy is as follows:
• Development material from cross-cuts and ramps above a grade of 0.37 g/t Au is hauled to a B-ore stockpile at the mill.
• OVD material is hauled to the OVD production ROM stockpile where it is classified as waste or ore and sent to the appropriate location.
• All stope production, regardless of grade, is hauled to the stope production stockpile.

In consideration of the variable vein geometry and existing equipment configuration, 3.7 m has been measured as the average minimum mining width. This includes a base 2.5 m minimum width plus an allowance for 0.6 m for overbreak on both the hangingwall and footwall sides of the stope. An additional 10% dilution is added for planning purposes.

Most of the mined out stopes are left open without any backfill, however the relatively new Aurora Zone will have stopes that will be wider, longer, and higher than in other areas. In these areas, the stopes are planned to be mined and backfilled with unconsolidated fill. This will allow pillars to be reduced and will increase the extraction ratio.

Infrastructure
The underground mine workings are accessed by two ramps located in the wall of the existing open pit. The ramps cut through the ore body and connect to cross-cuts that run perpendicular to the vein structure. All material mined underground is hauled to the surface via these two ramps by a contractor using rigid trucks.

Ventilation
The underground ventilation system is simple and effective. Fresh air is introduced into the mine via two primary intake air shafts located adjacent to the open pit and is distributed to the working areas by means of 23 secondary fans installed throughout the mine. Fresh air is drawn through old stopes to avoid the need for heating during the winter months. The return air is exhausted via two main ramp systems into the open pit.

Open Pit
The open pit has currently been halted and is planned to be restarted in 2025, however this could be delayed further in the event of additional underground reserves being identified. The planned method is standard truck and shovel mining, as done historically. Details will be redefined closer to the restart date.

Norrberget
Norrberget is planned to supply approximately 162,000 tonnes of ore over 2029 and 2030. Given the volume is a relatively small proportion of the total and will be mined at a later stage than the rest of the operation, the details of the mine plan are summarised here.

Mining Method
At Norrberget, open pit mining will be carried out by a contractor, using trucks and excavators. This production will be part of an integrated mining contract for both Björkdal and Norrberget.

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The concentrator includes primary, secondary, and tertiary crushing, primary, and secondary grinding, a series of gravity concentration steps, regrinding, and flotation to produce three gravity concentrates and a flotation concentrate.

The cyclone underflow (P80 800 µm) is fed to rougher spiral concentrators. Tailings from the rougher and cleaner spirals are returned to the secondary ball mill number 3 with a discharge P80 475 µm. From the discharge of mill number 3, the slurry is pumped to combine with the discharge from ball mills 1 and 2. The discharge from the three mills is pumped to the classifying screen.

Concentrate from the rougher spirals is fed to the cleaner spiral classifiers. Tailings from the cleaner spirals are combined with the tailings from the rougher spirals and processed in the regrind secondary ball mill number 3 circuit. Concentrate from the cleaner spirals is cleaned on shaking tables. Tailings from the shaking tables are fed to a Knelson ........