Overview
The Loulo-Gounkoto Complex, often abbreviated as LGC, represents one of the most significant gold mining operations on the African continent. Located in the Kenieba district of western Mali, near the border with Senegal, this sprawling complex is a flagship asset for Barrick Gold Corporation, which operates the site through a joint venture with the Malian government (80% Barrick, 20% State of Mali). The “LGC 2” designation frequently refers to the second major phase of the complex’s evolution, specifically the expansion and modernization of its processing capabilities to handle a diverse blend of ores from multiple open-pit and underground sources, including the Yalea, Gara, and Gounkoto deposits.
The significance of LGC 2 lies in its role as a central hub for mineral processing in the region. By consolidating the output of two distinct mining permits—Loulo and Gounkoto—into a unified, high-efficiency processing stream, the project has achieved remarkable economies of scale. The complex has transitioned from a series of independent pits to an integrated powerhouse that utilizes advanced metallurgical techniques to treat both free-milling and moderately refractory ores. This technical evolution has been essential in maintaining the complex’s status as a Tier One gold asset, capable of producing over 500,000 ounces of gold annually. The integration of the Gounkoto “Super Pit” and the continued development of underground operations at Yalea and Gara have necessitated a robust, flexible processing circuit capable of adapting to varying head grades, mineralogical complexities, and hardness profiles.
The LGC 2 mineral processing infrastructure is not merely a collection of machinery but a meticulously engineered system designed for maximum availability and gold recovery. With a nameplate capacity that has evolved to exceed 5 million tonnes per annum (Mtpa), the circuit incorporates industry-standard technology including three-stage crushing, multi-stage milling, and Carbon-in-Leach (CIL) recovery. As the operation looks toward the future, the LGC 2 framework includes planned expansions to incorporate independent secondary and tertiary crushing circuits and additional milling capacity to sustain production through 2029 and beyond. This strategic growth ensures that the Loulo-Gounkoto Complex remains at the forefront of global gold production, balancing high-throughput demands with rigorous environmental and social standards.
Key Process Stages
The LGC 2 mineral processing circuit is designed as a conventional gold recovery plant, optimized for the specific challenges of the Birimian greenstone belt ores found in Mali. The process flow is characterized by its adaptability, allowing for the treatment of both “hard” primary sulfide ores and “soft” weathered oxide ores. The key stages of the processing circuit are outlined below:
- Primary Crushing: Hard rock ore is delivered to a primary gyratory crusher (FFE Minerals 1,300 mm by 1,750 mm) powered by a 450 kW motor. This stage reduces the Run-of-Mine (ROM) material to a manageable size for subsequent grinding. A tramp iron magnet and metal detectors are utilized to prevent damage from steel contaminants.
- Secondary and Tertiary Crushing: The primary product feeds into two Sandvik CS660 Hydrocone secondary crushers operating in open circuit. This is followed by a tertiary circuit consisting of four CH660 Hydrocone units operating in closed circuit to produce a final crushed product size suitable for the milling circuit.
- Primary Grinding: The comminution circuit features a large 8 MW primary mill (SAG/Primary) that handles the initial size reduction of the crushed ore. This mill is the cornerstone of the grinding circuit, ensuring that the material is prepared for finer grinding stages.
- Secondary Ball Milling: Two identical 4.5 MW single-stage ball mills operate in parallel to further reduce the ore to the target P80 grind size. A scat conveyor system returns any oversized material back to the primary mill via a cone crusher, maximizing grinding efficiency and protecting the downstream circuits.
- Gravity Recovery: A portion of the milling circuit output is diverted to centrifugal concentrators to recover coarse gold before it enters the chemical leaching process. This reduces the load on the CIL circuit and improves overall recovery efficiency.
- Carbon-in-Leach (CIL): The ground slurry is processed through a series of CIL tanks. Here, gold is dissolved using a dilute sodium cyanide solution and simultaneously adsorbed onto activated carbon. The circuit is designed to handle varying levels of arsenic and copper, which can impact adsorption kinetics.
- Elution and Electrowinning: Loaded carbon is stripped of gold using a Twin Zadra elution process. The resulting pregnant solution is subjected to electrowinning, where gold is deposited onto cathodes, which are then processed into doré bars.
- Tailings Management: Process tailings are split between a traditional slime dam and a paste plant for backfilling underground workings, assisting in ground stability and reducing the surface environmental footprint.
Critical Data
The following table summarizes the key technical parameters and performance metrics for the LGC 2 processing circuit, based on recent operational data and design criteria.
| Parameter | Value | Unit |
|---|---|---|
| Annual Plant Throughput | 5,087,000 (2022 Actual) | tonnes (kt) |
| Average Throughput Rate | 605 | tonnes per hour (tph) |
| Design Gold Recovery | 91.2 – 93.1 | percent (%) |
| Primary Mill Power | 8.0 | Megawatts (MW) |
| Secondary Ball Mill Power (per unit) | 4.5 | Megawatts (MW) |
| Total Installed Grinding Power | 17.0 | Megawatts (MW) |
| Target Grind Size (P80) | 75 – 150 (varies) | micrometres (µm) |
| Primary Crusher Motor | 450 | Kilowatts (kW) |
| Secondary/Tertiary Crusher Motors | 315 | Kilowatts (kW) |
| Expansion Target Throughput (2029) | 4,200 | tonnes per day (tpd) |
Technical Details and Sustainability
The LGC 2 circuit is more than just a mechanical process; it is a testament to the integration of metallurgical science and operational resilience. One of the most critical technical challenges managed by the processing team is the presence of deleterious elements like arsenic and copper, particularly in the Yalea deposit. These elements can interfere with the adsorption of gold onto activated carbon and increase the consumption of cyanide and oxygen. To mitigate this, the LGC 2 circuit employs sophisticated reagent management and oxygen plant facilities to maintain high dissolved oxygen levels, ensuring efficient leaching kinetics even when treating complex mineralisation. The use of a Twin Zadra elution system further enhances the recovery process, providing a robust method for stripping gold from carbon in a high-temperature, high-pressure environment.
From a sustainability perspective, the Loulo-Gounkoto Complex has set a benchmark for responsible mining in West Africa. The processing facility is supported by a large-scale solar power plant, which significantly reduces the operation’s reliance on thermal power generation and lowers its carbon footprint. This transition to renewable energy is part of a broader commitment to environmental stewardship. Water management is another critical area; the LGC 2 circuit utilizes a closed-loop system where thickener overflow and tailings decant water are recycled back into the milling process, minimizing raw water intake from the nearby Falémé River. Furthermore, the use of paste backfill technology for underground mining not only improves safety but also serves as an effective tailings sequestration method, reducing the risk and size of surface tailings storage facilities (TSFs).
The future outlook for LGC 2 is focused on the “Phase 2” expansion project scheduled for completion by 2029. This project is designed to sustain the 5 Mtpa throughput as the complex moves deeper into the Yalea and Gara underground mines and concludes the mining of the Gounkoto Super Pit. The expansion will introduce an independent secondary and tertiary crushing circuit feeding a new single-staged ball mill, providing the redundancy and capacity needed to process increasingly harder ore from depth. By continuously reinvesting in technology and infrastructure, the Loulo-Gounkoto Complex ensures that it can adapt to the changing nature of its ore bodies while remaining a cornerstone of Mali’s economy and a leader in sustainable mineral processing.
Source: LGC 2 (Loulo-Gounkoto Complex)
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
