Oko Gold Project: 10,000 tpd CIL Gold Recovery Process

Source: Unnamed_Company_72 (2026)
Website: https://g2goldfields.com/projects/oko-aremu-trend/

Critical Data

Overview

G2 Goldfields Inc. is advancing the Oko Gold Project with a state-of-the-art processing facility designed to treat 10,000 tonnes per day (tpd) of mineralized material over an estimated 12.1-year mine life. Located in a region with both oxide/saprolite and fresh mineralization, the facility employs a proven flowsheet combining primary crushing, semi-autogenous grinding (SAG) and ball milling with pebble crushing, gravity concentration, cyanide leaching in a carbon-in-leach (CIL) circuit, carbon elution and regeneration, electrowinning, and smelting to produce gold doré bars. The process achieves a weighted average gold recovery of 94%, recovering approximately 3,192 thousand ounces (koz) of gold over the life of mine from a total mined inventory of 3,399 koz at an average head grade of 2.39 g/t Au. The plant operates 24 hours per day, 365 days per year, with a nominal throughput of 10,000 t/d and a grinding circuit designed to produce a cyclone overflow P80 of 80 microns. A separate material handling system for saprolite ore uses a mineral sizer to address the challenging handling properties of the fine, moist material. Tailings are treated via the SO2/air cyanide destruction process to reduce weak acid dissociable (WAD) cyanide to below 5 mg/L before disposal in a tailings storage facility, ensuring environmental compliance. This comprehensive gold recovery methods approach underscores the project’s technical robustness and economic viability.

Key Process Stages

• Stage 1: Primary Crushing – Fresh mineralization is crushed using a jaw crusher at a nominal rate of 595 t/h (70% utilization) to 100% passing 100 mm. Saprolite ore is handled separately with a mineral sizer. The crushed product is stacked on a stockpile with 10,000 tonnes live capacity.
• Stage 2: Grinding Circuit – A single SAG mill (7.1 m diameter × 4.3 m long, 4,500 kW motor) and ball mill (6.1 m diameter × 9.2 m long, 6,500 kW motor) operate in closed circuit with cyclones and a pebble crusher. The target product size (P80) is 80 microns. The SAG mill operates with a 12% ball charge, and the ball mill circulating load is 300%.
• Stage 3: Gravity Concentration – Approximately 25-30% of cyclone feed is diverted to centrifugal concentrators for coarse gold recovery. The gravity concentrate (0.03% weight recovery) is treated in an intensive cyanide leach reactor (batch process) with high cyanide concentration, achieving 21.4% gold recovery from plant feed. Gold solution from the ILR is sent to a dedicated electrowinning cell.
• Stage 4: Carbon-in-Leach (CIL) Circuit – Thickened slurry (42% solids for fresh, 35% for saprolite) enters six 4,027 m³ mechanically agitated tanks in series, providing 24 hours retention time. Cyanide and lime are added to maintain leaching conditions. Activated carbon (density 10 g/L) adsorbs dissolved gold; loaded carbon reaches 2,000 g/t Au. Gold extraction from leach feed averages 92.9%.
• Stage 5: Carbon Elution & Regeneration – Loaded carbon (10 t/d capacity) undergoes acid washing (3% HCl) followed by ZADRA elution at ~150°C and 500 kPa using 2% NaOH and 0.2% cyanide. Pregnant solution feeds electrowinning cells; gold sludge is smelted into doré bars (90% Au+Ag). Two strip cycles per day produce about 720 oz of gold daily. Stripped carbon is thermally regenerated in a kiln and returned to the CIL circuit.

Additional Interesting Data and Summary

The Oko Gold Project’s recovery methods are underpinned by extensive metallurgical test work (Section 13 of the report) that informed the process design criteria. The processing facility is designed to handle variable ore types—saprolite (5,287 kt at 0.93 g/t) and fresh (38,874 kt at 2.59 g/t)—with distinct comminution and leaching requirements. The Bond ball work index for fresh ore is 17.76 kWh/t, indicating competent material requiring higher grinding energy, while saprolite is softer at 12.44 kWh/t. The primary crusher for fresh material uses a jaw crusher with a work index of 15.00 kWh/t; saprolite uses a mineral sizer to circumvent handling difficulties. The grinding circuit includes a pebble crusher handling 2,500 t/d of SAG mill oversize, reducing it from F80 60 mm to P80 13 mm before recirculation. The pre-leach thickener (35 m diameter) adjusts feed density to 42% solids (fresh) or 35% (saprolite) for optimal CIL performance. The CIL circuit requires 24,161 m³ total leach volume across six tanks, with a carbon loading of 2,000 g/t Au and eluted carbon at 80 g/t. The ZADRA elution system operates two strips per day at 10 t/d capacity, using one 5-t vessel. Electrowinning recovers gold onto cathodes, with soluble and refining losses capped at 1.0%. Gold production averages 263,816 oz/y, with LOM recovery of 3,192 koz from a mined inventory of 3,399 koz. The cyanide destruction circuit employs the SO2/air process (using sodium metabisulphite as SO2 source) in two 504 m³ tanks with 60 minutes retention, reducing WAD cyanide to <5 mg/L. Tailings are further degraded naturally in the storage facility. Reclaim water is pumped back for reuse, supporting sustainability. Economic impact is significant: at an average price of $1,900/oz, the LOM gold production (3,192 koz) represents approximately $6.1 billion in gross revenue, with the facility creating long-term employment and regional development. Environmental stewardship is emphasized through the cyanide destruction system and a comprehensive reagent management plan, including containment and safety stations. The facility’s 12.1-year mine life and 94% recovery rate position the Oko Gold Project as a technically sound and economically attractive gold development, with forward-looking potential for expansion if additional resources are defined.

Key Processes: CIP/CIL, Cyanidation, Gravity Separation, SAG Mill, Ball Mill, Crushing

Target Commodities: Gold, Silver, Copper