The South Middleback Ranges (SMR) lies at the southern end of the Middleback Ranges (MBR). Hematite in the MBR occurs as stratabound Palaeoproterozoic deposits of the Lower Middleback Iron Formation (LMIF), which is 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 2012).

The Hutchison Group in the MBR is composed of the Warrow Quartzite and the Middleback Subgroup. 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.

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 oxidat ........

South Middleback Range (SMR) includes Iron Chieftain, Iron Knight, Iron Duchess, Iron Magnet and Iron Duke. SMR Ore mined includes both hematite DSO and magnetite mined. Iron Duchess region The Iron Duchess region includes the Duchess North and Duchess South pits. The Duchess South pit was mined via an open pit cut-back mining process using traditional drill, blast, load and haul methods. The mine sequencing showed a continuous supply of ore from this pit leading to depletion. Ore was stockpiled and then crushed and screened using mobile processing plants. Low-grade ore and waste materials are stockpiled. The Duchess North area was mined in earlier decades and is known to contain a significant resource. Current mine development commenced in July 2018. The Duchess North pit has been and can be used to store reclaimed water from the magnetite concentrator and OBP tailings operations. As described in SIMEC Mining’s June 2020 Program notification (WPC-198), reclaimed water from the Duchess North pit has recently (2021) either been used or relocated to the Duchess South pit, as to allow mining of the Duchess North resource to continue, under Stage B Part 2 of the mine plan. It is proposed that the Duchess North mining be extended to the North, with a new pit, Duchess North D, to be developed within the bounds of ML6431, ML2705, ML2707 and ML2708. New supporting infrastructure, including WRDs and access roads, will be constructed in order to support these new operation ........

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