The Iron Knob mining area (IKMA) lies at the northern end of the Middleback Ranges (MBR).

• Hosted within the Palaeoproterozoic Hutchison Group metasediments.
• Mineralization is within the Lower Middleback Iron Formation grades upwards from Carbonate Haematite to Jaspilite Haematite facies.
• Ore Formation is considered through passive supergene enrichment of Magnetite Banded Iron Formations.
• Strongest Enrichment within the LMIF Carbonate Facies – leading to complete replacement of carbonates in highest grade zones.
• The Metasediments have a history of complex deformation dominated by East – West compression.
• Mineralised zones are bounded to the East and West regional scale North – South Shear Zones.
• Multiple Stages of Archean amphibolite dykes cross cut both deposits and are influence on mineralisation and Geotechnical Parameters.

Middleback Ranges Hematite
Hematite in the MBR occurs as stratabound Palaeoproterozoic deposits of the Lower Middleback Iron Formation (LMIF), part of the Hutchison Group. The Hutchison Group forms part of the Cleve Subdomain of the Gawler Craton, and lies on its western edge. The Cleve Subdomain comprises tightly folded high-grade metamorphic rocks that are mainly derived from marine shelf sediments and mafic and acidic volcanics (Parker, 2012b).

Middleback Ranges Framework In the MBR, the Hutchison Group is composed of the Warrow Quartzite and the Middleback Subgroup. However, the Warrow Quartzite is not identified at all locations. The Middleback Subgroup comprises the Katunga Dolomite, the LMIF, the Cook Gap Schist and the Upper Middleback Iron Formation (UMIF). The LMIF hosts the Middleback Ranges hematite deposits.

Ore Genesis
MBR iron ores formed through supergene enrichment; the process selectively dissolved waste minerals and replaced them with iron ore mineralisation. Preferential enrichment occurred in carbonate facies iron formation, dolomitic marble and to a lesser degree silicate facies iron formation. The silicates were much less soluble than the carbonates, and resulted in patchy mineralisation in the silicate iron facies (Yeates 1990).

Magnetite was recrystallised and remobilised during a period of metamorphism and deformation. Multiple periods of uplift, erosion and weathering resulted in the oxidation of magnetite to hematite and martite through supergene processes. Iron ore formation requires the movement of fluids through the rock. Most deposits (apart from Iron Queen and Iron Chieftain) lie on the western side of the range, adjacent to a major fault or mylonite zone along the western edge of the range, which may have provided this pathway. The process was most intense where the dolomite and carbonate facies were thickened and then subsequently exposed during the supergene process (Yeates 1990). Iron Queen and Iron Chieftain lie on the east side of the range in similar geology; their geneses are thought to be similar.

Iron Monarch deposite Local Geology
• Ore is contained within a synformal keel.
• Hematisation is pervasive and typically massive, extending to +400m depth.
• Mineralisation is bounded to the West by the West Wall Shear zone and Sleaford Granit.
• Bounded to the East by the East Wall Shear and Hiltaba Granite and volcanics at depth.
• Key influences and controls on Slope stability of the North Wall and Mineralisation are the “Older” amphibolite dyke and “Younger” dolerite dykes.

Iron Princess deposite Local Geology
• Consists of 2 ore bodies – Eastern Orebody and Western Orebody.
• Eastern Orebody – 2 Lenses that vary in thickness from 6 to 30m, typically brecciated and powdery in nature consisting dominantly of haematite and goethite.
• Western Orebody – Moderate to steeply dipping multiple lenses, between 5 and 20m in thickness.
Ore is dominantly heamatite.
• Un conformably overlain by the unconsolidated “Princess Beds” in which small detrital channel ores exists.
• Bounded to the West by the Western Shear Zone and to the East by the Iron Knob Mylonite zone.

Scree Deposits
Hematite in the MBR occurs as stratabound Palaeoproterozoic deposits of the Lower Middleback Iron Formation (LMIF), part of the Hutchison Group. The Hutchison Group forms part of the Cleve Subdomain of the Gawler Craton, and lies on its western edge (Figure 3). The Cleve Subdomain comprises tightly folded high-grade metamorphic rocks, mainly derived from marine shelf sediments and mafic and felsic volcanics.

As in the IBMA, substantial economically minable scree ore deposits have been identified around the flanks of the iron ore pit. These breccias and scree have partially weathered to clay however, cementation of the breccias has produced relatively geotechnically competent units.

Exploration at the proposed scree deposits is yet to be completed. Based on previous investigations of scree deposits within the MBR, the scree at Iron Monarch is likely to consist of the following geological materials  Jaspilite,  Ferruginous scree,  Maghemite,  BIF,  Clays,  Calcrete.

Limonite and goethite have also been noted in highly oxidised scree units within the MBR. Scree can be cemented (with carbonates) and can also contain pisolites; these are rounded gravels where each pisolite displays concentric layers of iron rich minerals, commonly hematite.

Operations throughout the reporting period (FY 2020) continued the recovery and processing of low-grade stockpiles through the Integrated Processing Facility (IPF) and deposition of tailings into the Monarch void as approved under PEPR 2017/004.

SIMEC Mining placed the IKMA operations into care and maintenance on 1 July 2018. The decision to suspend operations at IKMA was a result of high production costs and ongoing low iron ore prices and part of SIMEC’s overall business response to this business environment. It was envisaged that mining operations would re-commence at some point following a sustained increase in the price of iron ore to a point at which the mine again becomes economically advantageous to operate.

While other areas of the IKMA are in a care and maintenance phase, SIMEC Mining are proposing to undertake scree mining operations.

Mining of scree ore will supply feed to SIMEC’s Integrated Processing Facility (IPF). Current (2020) IPF feed is from reclamation of historic low-grade dumps. The scree ore will supplement the low-grade feed and on depletion of stocks, will replace the low-grade feed altogether. During Monarch Scree mining operations, feed to the IPF is expected to be approximately 135 wet mass kilotonnes per month. A significant stockpile of IPF feed (approximately 100 kilotonnes) will be maintained, in order to feed the processing facility during times of mining cessation, due to detrimental weather conditions or other causes.

The proposed mining plan is to develop four (4) separate scree ore pits on the south-eastern slopes of the Monarch pit, with the two western scree pits located at the toe of existing waste dumps and embankments of disused haul roads.

The proposed scree ore pit designs are relatively shallow and have varying geometry as follows:
- A1 pit (NW pit – mns_a1) dimensions ~ 430m long × 155m wide × 20m deep;
- A2 pit (NE pit mns_a2) dimensions ~ 220m long × 35m wide × 20m deep;
- A3 pit (NE pit mns_a3) dimensions ~ 115m long × 50m wide × 7m deep;
- A4 pit (SW pit - mns_a4) dimensions ~ 390m long × 180m wide × 15m deep.

Pit ramps will be 10 m in width, with a ramp gradient of 1:10.

It is estimated that approximately 45 on site personnel, including both SIMEC mining personnel and contractors, will be required during Monarch Scree operations.

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Operations throughout the reporting period (FY 2020) continued the recovery and processing of low-grade stockpiles through the Integrated Processing Facility (IPF) and deposition of tailings into the Monarch void as approved under PEPR 2017/004.

Integrated Processing Facility (IPF was commissioned in April 2017)
A wash plant to upgrade approximately 750 Ktpa of low-grade ore (or scree ore) to a target Fe grade of around 59% was incorporated into pre-existing crushing and screening facilities to form a new Integrated Processing Facility. Production is based on a nominal yield of around 50%.

IPF feed source will come from a combination of existing LGO stockpiles and LGO product from ongoing Princess and Monarch mining operations (Princess and Monarch pits now on care and maintenance) before being replaced by scree ore feed as the low-grade ore resources are depleted.

The wash plant will be located to the south-west of the Iron Monarch pit. It will ........