The characteristics of the gold deposits at Higginsville are consistent with the greenstone-hosted quartz-carbonate vein (mesothermal) gold deposit model.

Throughout the Higginsville Gold Operations, a significant proportion of gold deposits are hosted by sediments within Southern Palaeochannel networks. Mineralised zones comprise both placer gold, normally near the base of the channel-fill sequences, and chemically-precipitated secondary gold within the channel-fill materials and underlying saprolite. These gold concentrations commonly overlie, or are adjacent to, primary mineralised zones within Archaean bedrock. Outcrop is generally poor, due to extensive ferruginisation, calcareous soils, aeolian sands and extensive areas of remnant lacustrine and fluvial sediments. The result is a complex, layered regolith, with considerable chemical re-mobilisation and re-deposition (Lintern et. al., 2001).

Higginsville is located almost entirely within the well-mineralised Archean Kalgoorlie Terrane, between the gold mining centres of Norseman and Saint Ives. The Archaean stratigraphy has a general northward trend comprising multiply deformed ultramafic – gabbro – basalt successions adjoined by sediments to the west and east. Shearing and faulted contacts are common. The units have been structurally repeated by east over west thrust faulting.

The HGO can be sub-divided into six major geological domains:
- Trident line-of-lode;
- Chalice;

Currently, Karora is mining from the Spargos open pit mine in the Higginsville Greater area and the Aquarius and Two Boys underground operations in the Higginsville Central Area.

HGO mined 855,000 tonnes during 2021 at an average grade of 1.61 g/t containing 44,247 ounces of gold. Details of production by source is provided below:

HIDDEN SECRET
Hidden Secret continued to perform well during the fourth quarter, with mining of high-grade areas as per schedule. Mine production from Hidden Secret totalled 182,000 tonnes containing 8,155 gold ounces. Hidden Secret was the main ore source for processing throughout the quarter but will be replaced in the first quarter of 2022 with production from the Spargos open pit which commenced its production during the fourth quarter of 2021. Mine production from Hidden Secret is scheduled to be completed in the first quarter of 2022, with an extensional drilling program planned once mining ceases.

SPARGOS
The initial pre-strip development was completed at Spargos during the fourth quarter of 2021, with mine production and ore extraction commencing during the same quarter. Spargos infrastructure is in place to support mining of the Stage 1 open pit. Dewatering planning and approvals, in preparation for Stage 2 of the open pit mining (extension at depth), are in progress with completion of two dewatering bores and a management plan submitted for licence approval. The next stage of exploration drilli ........

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The processing plant consists of an open circuit jaw crusher followed by closed circuit secondary and tertiary crushers, a fine ore bin, ball mill, gravity separation circuit, one leach tank, and six carbon adsorption tanks.

The primary sections of the processing plant that are currently in use are:
- Crushing and conveying;
- Ore storage & reclaim and grinding;
- Leaching and carbon adsorption;
- Carbon stripping, electrowinning, refining and carbon re-generation;
- Tailings thickening;
- Tailings deposition and storage;
- Reagent mixing and handling; and
- Plant services.

Gravity and Intensive Cyanidation
A gravity separation circuit is included in the design to enhance the recovery of gold that concentrates in the hydro-cyclone underflow stream.

A 100 t/h bleed of the hydro-cyclone underflow stream is delivered to the gravity feed screen for classification. The gravity feed screen is a 1.2m wide b ........