Overview
The Mars mine represents a vital component of the broader Higginsville Gold Operation (HGO), situated in the prolific Kalgoorlie Terrane of Western Australia. Historically significant and strategically located between the world-class gold mining centers of Norseman and St Ives, the Mars deposit is part of the highly prospective Challenger-Swordsman Paleochannel system. This system includes a cluster of notable deposits such as Neptune, Saturn, Jupiter, Mars, and Pluto, all of which contribute to the mill feed at the central Higginsville processing facility. Following the landmark merger in August 2024 between Westgold Resources Limited and Karora Resources, the Mars asset and the associated HGO infrastructure have been consolidated under the Westgold banner, creating a powerhouse in the Australian gold sector.
The Mars deposit itself is characterized as a sediment-hosted paleochannel gold deposit, a geological setting common in the Eastern Goldfields. Mining at Mars utilizes both historical data and modern geological modeling to extract high-grade material that is subsequently transported to the central HGO processing plant. The significance of the Mars mine lies not only in its individual contribution to the gold production profile but also in its integration within a regional “hub-and-spoke” processing model. By leveraging the existing 1.6 million tonnes per annum (Mtpa) capacity of the Higginsville plant, Westgold can efficiently process ore from multiple sources, including the high-grade underground material from the nearby Beta Hunt mine and various open-pit and paleochannel sources like Mars.
The project’s location within the Archean Kalgoorlie Terrane ensures a complex yet rewarding metallurgical profile. The stratigraphy generally trends northward, comprising deformed ultramafic gabbro-basalt successions adjoined by sedimentary units. This geological complexity necessitates a robust and versatile mineral processing circuit, which has been refined over nearly two decades of operation. As the industry moves toward the Higginsville Expansion Project (HXP), which contemplates increasing plant capacity to 2.6 Mtpa, the Mars mine remains a critical pillar in the operational strategy for Western Australian gold production.
Key Process Stages
The Higginsville mineral processing circuit, which handles ore from the Mars mine, is a sophisticated facility designed for high-availability and maximum gold recovery. Originally commissioned in 2008 and upgraded multiple times, the plant employs a combination of gravity concentration and conventional Carbon-in-Leach (CIL) technology. The primary stages of the processing circuit are outlined below:
- Multi-Stage Crushing: The circuit utilizes a four-stage (quaternary) crushing process. This includes an open-circuit primary jaw crusher, followed by a closed-circuit secondary cone crusher, a tertiary crusher, and a quaternary cone crusher incorporated in 2010 to optimize the feed size for the grinding circuit.
- Fine Ore Storage and Reclaim: Crushed material is stored in a fine ore bin to ensure a consistent feed rate to the mill, allowing for maintenance on the crushing circuit without interrupting the downstream processes.
- Grinding and Classification: The heart of the plant is an 8 MW ball mill operating in a single-stage grinding configuration. This mill works in a closed circuit with a hydrocyclone cluster to achieve the desired P80 grind size (typically 75 to 106 micrometers).
- Gravity Concentration: A portion of the cyclone underflow is diverted to a gravity separation circuit, featuring centrifugal concentrators and intensive leaching (e.g., Acacia reactor). This stage is critical for recovering “free” gold early in the process, which can account for up to 40-50% of the total gold recovered.
- Leaching and Carbon-in-Leach (CIL): The cyclone overflow (slurry) reports to the CIL circuit, which consists of one primary leach tank and six carbon adsorption tanks. Here, gold is dissolved using cyanide and adsorbed onto activated carbon.
- Refining and Gold Room: Loaded carbon undergoes stripping (elution), followed by electrowinning and smelting to produce gold doré bars.
- Tailings Management: The final tails are thickened and deposited in a purpose-built Tailings Storage Facility (TSF), with water reclaimed for reuse in the plant.
Critical Data
The following table summarizes the key technical and performance parameters of the Higginsville processing plant, which serves the Mars mine and associated deposits.
| Parameter | Value | Unit |
|---|---|---|
| Nominal Throughput Capacity | 1.6 | Mtpa |
| Planned Expansion Capacity (HXP) | 2.6 | Mtpa |
| Primary Mill Power | 8.0 | MW |
| Crushing Stages | 4 | Stages |
| Gold Recovery (Average) | 93.0 – 95.5 | % |
| Grinding Product Size (P80) | 75 – 106 | µm |
| Plant Availability (Grinding) | 92.0 | % |
| Crushing Availability | 65.0 – 72.0 | % |
| Operating Schedule | 24 / 7 | hr/day |
Technical Details and Sustainability
The technical sophistication of the Mars mining operations and the Higginsville processing circuit is exemplified by the 2010 addition of a quaternary crushing stage. In the hard-rock environment of the Western Australian goldfields, achieving a fine, consistent mill feed is paramount for maximizing throughput and reducing the energy intensity of the grinding stage. The integration of the 8 MW ball mill allows the HGO facility to handle competent ore types while maintaining a high availability of 92%. This grinding power is essential when processing the diverse mineralogy found in the Challenger-Swordsman paleochannels, where gold is often associated with silica-rich sedimentary host rocks.
Metallurgically, the Mars mine benefits from the high efficiency of the gravity concentration circuit. Recovering a significant percentage of gold through gravity before the CIL stage reduces the residence time required in the leach tanks and lowers reagent consumption, particularly cyanide and lime. The subsequent CIL circuit is optimized for high recovery, with the six adsorption tanks providing ample contact time between the gold-bearing solution and the activated carbon. The high average recovery rates, often exceeding 95%, demonstrate the effectiveness of this conventional yet refined flowsheet for the region’s orogenic and paleochannel gold systems.
From a sustainability and future-proofing perspective, the consolidation of the Mars mine under Westgold Resources has accelerated plans for the Higginsville Expansion Project (HXP). The HXP is not merely a capacity increase; it represents a move toward greater operational efficiency and environmental stewardship. By expanding the central processing hub, the company can reduce the carbon footprint associated with hauling ore from disparate sites to multiple smaller mills. Furthermore, the use of automated control systems in the grinding and leaching circuits helps optimize reagent addition and energy use, aligning with modern ESG (Environmental, Social, and Governance) standards.
Water management is another critical sustainability focus at the Mars operations. In the arid climate of Western Australia, reclaiming process water from the tailings thickeners and TSF is essential. The Higginsville plant is designed to maximize water reuse, reducing the reliance on local hypersaline groundwater sources. As the Mars mine continues to produce, the focus remains on extending the life of the operation through brownfields exploration and technical debottlenecking, ensuring that the HGO complex remains a centerpiece of the Australian gold industry for decades to come.
Source: Mars | Westgold Resources | Higginsville Gold Operation Technical Reports 2024-2025
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
