St Ives lies within the Kambalda domain, a subset of the Norseman-Wiluna Belt. The Kambalda domain is bound by the north-northwest trending Boulder-Lefroy fault (BLF) and Zuleika shear. The region has undergone four compressional events predated by early extension, and has been metamorphosed to upper greenschist or lower amphibolite facies.

The main structural feature of the St Ives area is the gently south-plunging Kambalda anticline, which extends 35km from the south end of the Kambalda dome to the Junction mine. The majority of known gold deposits are proximal to the trace of the anticlinal axis. A major second order structure known as the Playa shear splays off the BLF shear zone and can be traced through the St Ives field for a distance in excess of 10km.

There are several styles of gold mineralisation at St Ives. Individual deposits may contain more than one of these styles:

• Lode mineralisation: Archaean lode mineralisation typically consisting of 0.5m to 20m wide mesothermal vein complexes that may also have hydraulic breccias and/or mylonites. Mineralisation is typically discontinuous with short range predictability
• Supergene mineralisation: Broad zones of flat-lying gold mineralisation in weathered Archaean and overlying tertiary sediments
• Palaeoplacer mineralisation: Placer deposits hosted by palaeochannels in the unconsolidated tertiary sediments that overlie the Archaean basement.

St Ives has four underground mine areas and seven open pits contributing to the Mineral Reserve. There are seven underground mines and 16 open pits contributing to the Mineral Resource.

St Ives operated two underground mines and two open pits in 2021.

The underground mines are accessed via a decline. Mining contractors (Invincible and Hamlet) and owner operator fleet (Hamlet) deploy long-hole stoping and paste/rock fill. Current underground mines are relatively shallow and configured to mitigate geotechnical seismic risk through mine design, scheduling and defined ground support regimes.

Open pits are mined using conventional drill and blast with truck and shovel. Surface mining operations are conducted using an owner-operator mining fleet.

Ore from both open pit and underground operations is transported with road trains from individual mining operations to the central St Ives processing RoM pad.

The current active Leviathan in-pit TSF (with a Low ANCOLD consequence rating) has enough capacity to store the remaining LoM volumes.

Emphasis has been on the continued expansion of the Invincible underground operations with full production now established. Ore production from the Invincible Complex now exceeds 2Mtpa. Highly prospective targets continue to be explored along the strike of Invincible South in the Greater Invincible area.

Open-pit production continued at Neptune with mining completed in stages 5 and 6. Pre-stripping of the Neptune, stage 7 open pit commenced with ore delivery expected in Q1 2022.

The site-wide underground paste strategy was implemented in 2021, enabling a greater proportion of the ore body to be extracted by reducing the number and size of pillars between underground stope panels. In 2021, the new upgraded paste fill plant was commissioned at Invincible and the work is continuing in 2022 to include Invincible South and Invincible Deep.

The LoM mining mix has been transitioning from open pit to predominantly underground operations over the last few years and discovering new, sizeable open-pit opportunities will continue to be prioritised to rebalance the overall mix.

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St Ives operates a 4.7Mtpa processing plant that consists of primary crushing, SAG/ball milling, gravity and leach/CIP circuits.

Gravity Circuit:
- 2 Falcon concentrators, 2 Jigs, regrind mill and ILR reactor;
Leach:
- 5 conventional leach tanks;
CIP Circuit:
- 6 Stage Carousel Pump Cell arrangement;
AARL Elution Circuit:
- Capacity of elution circuit 5 tons of carbon per day;
Electro winning:
- 5 electro- winning cells (1x dedicated to gravity).

A gravity circuit recovers the gravity-recoverable gold from the milling circuit and the concentrate is treated separately through to bullion form. The mill cyclone overflow product flows to a five-stage leach circuit consisting of mechanical agitators, reagent addition and oxygen sparging. Leached slurry passes through the six-stage carousel pump cell adsorption plant and subsequent five-tonne-capacity acid wash, elution and electrowinning circuits which produce calcin ........