Deposit Types
Two main PGE deposit types occur within the Bushveld Complex:
• Relatively narrow (maximum 1 m wide) stratiform layers (reefs) that occur towards the top of the Upper Critical Zone typically 2 km above the base of the intrusion (Merensky reef-style), mainly found in the Western and Eastern Limbs. These narrow zones have been the principal targets for mining in the past; however, more recently wider zones with more irregular footwall contacts have been mined (termed potholes).
• Contact-style mineralisation at the base of the intrusion (Platreef-type) occurs mainly in the Northern Limb.

In general, within the Northern Limb, the Platreef comprises a variably layered, composite norite–pyroxenite–harzburgite intrusion that lies at the base of the Bushveld Complex, in contact with metasedimentary and granitic floor rocks. McDonald and Holwell (2011) reviewed the major literature on the Platreef and Northern Limb, and have concluded:
• The Platreef remains a complex and enigmatic deposit.
• Stratigraphic relationships with other stratiform deposits such as the Merensky and UG2 reefs have been suggested.
• The extent to which the Northern Limb was connected to the rest of the complex across the Thabazimbi–Murchison Lineament remains to be established.
• The Platreef represents a complex of sills intruded into basement granite-gneiss, Transvaal Supergroup sediments or pre-Platreef Lower Zone intrusions.
• Intrusive relationships of the Main Zone gabbronorites, into solidified and deformed Platreef, removes the Main Zone as a source of metals for the Platreef.
• Mineral chemistry, bulk geochemistry, and Sr, Nd, and Os isotope geochemistry of the Platreef are most consistent with an ultramafic (Critical or Lower zone) component.
• Platreef Nd values and 187Os/188Os initial isotope ratios overlap clearly with the Merensky Reef but not the UCZ.
• Conventional and mass-independent S isotopes suggest a primary mantle source of S that was overprinted by the addition of local crustal S where Platreef intruded pyrite-rich shales. Assimilation of S is viewed as a modifying process, not as the primary trigger for mineralisation.

Mineralisation
The Platreef Project is hosted within the Palaeoproterozoic (2.06 Ga) Bushveld Igneous Complex (BIC), which is the largest of the known layered igneous intrusions, covering an area > 65,000 km². The BIC hosts up to 75% of the world’s platinum resources (Naldrett et al, 2009).

The BIC includes an early bimodal volcanic sequence (the Rooiberg Group) that is followed by an intrusive layered series of ultramafic and mafic units known as the Rustenburg Layered Suite (RLS) and the Lebowa Granite and Rashoop Granophyre Suites. The RLS is 7 to 8 km thick and ranges in composition from dunite to diorite.

Hall (1932) divided the RLS into 5 zones in descending order:
• Upper Zone (UZ) — Gabbroic succession.
• Main Zone (MZ) — A succession of gabbronorites with occasional anorthosite and pyroxenite bands.
• Critical Zone (CZ) — The Lower Critical Zone (LCZ) consists of orthopyroxenitic cumulates, and the Upper Critical Zone (UCZ) comprises packages of chromitite, harzburgite, pyroxenite, norite, and anorthosite. The CZ hosts PGE–Au–Ni–Cu and chromite deposits in several different chromitite layers known as reefs. The most significant are the Merensky Reef and the Upper Group 2 (UG2) Reef of the Eastern and Western Limbs. These range on average from 0.4–1.5 m in thickness and the contained PGE (Pt, Pd, Rh, Au) content typically ranges from 4–10 g/t (Cawthorn, 2005).
• Lower Zone (LZ) — Upper and lower peridotites separated by a central harzburgite.
• Marginal Zone (MZN) — Norites with variable proportions of accessory clinopyroxene, quartz, biotite and hornblende, indicating magma contamination from the underlying metasediments. This unit is not always present.

In the East and West Limbs of the BIC, the RLS was intruded into the Magaliesberg Formation of the Proterozoic Transvaal Supergroup. In the North Limb, the RLS intrudes progressively older country rocks northward (Magaliesberg Formation, Malmani Subgroup and Duitschland Formation). In the East and West Limbs of the BIC, the CZ includes the Merensky Reef and UG2 chromitite that are exploited for PGE mineralisation. In the North Limb of the BIC, the mineralised horizons have been referred to as the Platreef. The North Limb hosts the Platreef Project.

Structure
Structurally, the Northern Limb is separated from the rest of the Bushveld Complex by the Thabazimbi-Murchison Lineament (TML). The TML is a pre-Bushveld, major, compressional tectonic boundary (suture zone) that formed as a result of the collision of the Pietersburg terrane and Kaapvaal shield around 2.97 Ga during the Murchison Orogeny (Friese, 2003, 2004). The Ysterberg-Planknek and Zebediela Faults play a significant role in the regional geology of the Northern Limb.

The tectono-thermal evolution can broadly be subdivided into pre- and syn-emplacement folding and multiple faulting events. Folding in the Northern Limb has been controlled by two principal transpressional events caused by movements along the TML in the south and the Palala Shear Zone.

According to Nex, (2005), this led to the formation of two main open-fold geometries within the Transvaal sediments. The first and most dominant folding event was caused by NE-SW sinistral transpression. This resulted in regional NNW trending low amplitude, sub horizontal open folding. These F1 folds developed within Archaean basement and Transvaal Supergroup and represent the earliest developed structures which formed contemporaneously as a result of mild ENE-WSW compression during the Limpopo-Murchison Orogeny at 2.78–2.64 Ga. Subsequent NW-SW transpressive inversion refolded the earlier F1 fold axis resulting in basin and dome fold interference patterns (Friese, 2012).

Significant brittle faults and ductile shear zones are known throughout the Northern Limb, and the major, widely-spaced, ENE-trending shear zones dominate the regional map pattern. These combine to form large strike-slip duplex systems, which host a complex array of riedel shears, normal faults, thrusts and dilational tension fractures that have been invaded in part by igneous dykes and quartz-feldspar veins. These faults are reactivated during a major E-W crustal extension event associated with major brittle fracturing.

The Platreef Project is designed based on highly mechanised Longhole Stoping and Drift-andFill mining methods.

Primary access to the mine will be by a 1,100 m deep, 10 m diameter production shaft (Shaft 2). Secondary access to the mine will be via a 996 m deep, 7.25 m diameter ventilation shaft (Shaft 1). During mine production, both shafts will also serve as ventilation intakes. Three additional ventilation exhaust raises (Ventilation Raise 1, 2, and 3) are planned. Ventilation Raise 1 will be a 950 m deep, 6 m diameter raise located near the centre of the mining area and adjacent to the two intake shafts. Ventilation Raise 2 will be an 800 m deep, 6 m diameter raise located near the northern edge of the mining area. Ventilation Raise 3 will be a 725 m deep, 6 m diameter raise located near the southern edge of the mining area.

Three main access levels will be established as primary haulage levels. These are the 750 m, 850 m, and 950 m Haulage Levels. Mining access ramps will connect the haulage levels with the mining sublevels and other infrastructure. The mining sublevels will be developed from the ramps at regular vertical intervals in the production areas. Drilling and extraction levels for stopes will be driven from the sublevels. Ventilation raises and ore passes will also connect the sublevels with the main haulage levels.

The main mining methods will be Longhole Stoping and Drift-and-Fill mining. These methods provide a safe, mechanised, and productive mining plan. The Longhole Stopes were designed at a 20 m height. This modification allowed for an improvement in the overall grade of the mine plan. All Longhole Stoping will be a transverse mining method using 6 m wide top cuts. This change allows for development to be taken off the critical path, as the secondary top cuts can be driven prior to the primary top cuts being mined and filled.

Mine planning
Lateral Development:
- Maximum grade will be 15%.
- Ramps will level off at sublevels to reduce risk of rollovers.
- Ore passes will be spaced 400 m apart on the levels.
- Electrical bays will be spaced 400 m apart.
- Level development will be inclined slightly to have water drain to the sumps (actual incline to be designed during detail design).
• Vertical Development:
- All raises except Shaft 1 and Shaft 2 will be raisebored.
- Maximum raisebore diameter is 6 m.
• Longhole Stoping:
- Bottom-up Longhole Stoping will be used.
- Minimum inclination of stopes on the footwall side will be 55°.
- The unfilled stope length for the 20 m high Longhole Stopes should not exceed 60 m.
- As much as possible, stopes should be aligned to minimise the risk of failure.
- A primary-secondary stoping sequence is recommended.
- Adjacent secondary stopes are not mined simultaneously.
- Secondary stope development can be carried out at any stage, regardless of whether nearby stopes have been backfilled.
- Over break thickness for top sides, hanging wall, footwall, end sides, and secondary stope sides is 0.5 m.
- Over break thickness for the floor is 0.3 m.
• Drift-and-Fill:
- Overhand Drift-and-Fill will be used.
- Each horizontal slice is mined completely before mining of the slice above begins.
- Drifts will be driven with flat backs for recovery purposes.
- Mining widths should be limited to 5.5 m to reduce the length of ground support in the back and walls to 2.4 m. If mining widths exceed 5.5 m, additional support will be required.
- Assuming a mining width of no more than 5.5 m, the mining sequence should be primary-secondary-tertiary to ensure that slender backfill ribs are not formed. For this method a 5.0 m width was utilised.
- An average of 0.15 m of over break will be used to estimate the overall dilution from each paste fill rib.

Mining Method
Sublevel Blasthole (Longhole) Stoping with cemented paste fill / rock fill, supplemented with development waste rock, where possible, to fill open stopes in the thicker ore zones. This method will minimise mining costs and achieve the highest productivity. The remainder of production may come from thinner high-grade zones. Drift-and-Fill methods will be used in these zones.

Two longhole mining scenarios were studied and evaluated for the Platreef 2022 FS:
• Transverse Longhole Stoping
• Longitudinal Longhole Stoping.

Longitudinal Longhole Stoping was considered specifically where deposit thickness could not support stope lengths of 15 m or more, normal to the strike, where Transverse Longhole Stoping would not be a suitable option. From the Vertical Miner software results, three major areas (Zone 1 north section, Zone 4, and Zone 2 central locations), were identified as the ideal candidate for this mining method. Stope shapes were created accordingly. After reviewing the longitudinal stope shapes created by MSO, the entire methodology had to be dismissed due to geotechnical considerations, such as hydraulic radius and mining direction. The ribs of the stope were parallel to the fault planes and the hydraulic radius provided would not support such stope shapes with meaningful sizes.

For the thinner and high-grade areas, two mining methods were evaluated:
• Cut-and-Fill
• Drift-and-Fill.
After reviewing the mining shapes (pancakes), it was concluded that Drift-and-Fill mining would be possible and is the most suitable solution due to higher productivities and performance rate.

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The process plant for the Platreef 2022 FS is designed to treat 0.77 Mtpa and 4.4 Mtpa Platreef ore in Phase 1 and 2 respectively. The plants include all processing requirements from the runof-mine (ROM) storage through to final concentrate plant load out and tailings disposal.

The process design for the respective 0.77 Mtpa and 4.4 Mtpa concentrator plants have been developed based on the testwork findings and assessments, various desktop level trade-off studies and relevant DRA design information. The Platreef concentrator flow sheet is based on a conventional three-stage crushing and ball milling circuit followed by flotation. This single-stage milling and flotation process flow sheet is well known in industry, and has historically been proven as a suitable processing route for various platinum ores.

The phased approach to the construction will see the construction of a 0.77 Mtpa concentrator plant in the Phase 1 of the project. This will be followed by the co ........