Overview
The Fidus mine, primarily centered on the expansive Los Ricos North project, represents a benchmark in modern mineral processing, particularly within the silver-gold corridors of Jalisco and Nayarit, Mexico. Owned and operated under the strategic oversight of GoGold Resources Inc., the Fidus mine project is distinguished by its unique approach to resource exploitation, transitioning through distinct geological phases over its life-of-mine (LOM). The project site is strategically located in the municipalities of Hostotipaquillo (Jalisco) and La Yesca and Ixtlan del Rio (Nayarit), covering a significant concession area of over 13,799 hectares. This region, historically known for the Monte Del Favor Mine area, provides a rich geological backdrop for what is now a high-throughput, technologically advanced operation.
The significance of the Fidus mine lies in its flexible metallurgical flowsheet, designed to handle a complex variety of ores from multiple deposits, including El Orito, Mololoa, Casados, and El Favor. Unlike standard single-stream operations, the Fidus processing facility is engineered to initially process oxide deposits through conventional tank leaching and Merrill Crowe precipitation. Starting in year nine of the operation, the facility is slated for a strategic expansion and transition to treat sulphide material from the Orito Deposit via conventional flotation. This multi-phase strategy ensures that the project remains economically viable across changing mineralogical profiles while maximizing the recovery of precious metals. The project’s nominal throughput of 8,000 tonnes per day (tpd) positions it as a significant contributor to regional gold and silver production, leveraging a Preliminary Economic Assessment (PEA) that highlights high extraction efficiencies and robust environmental management. By integrating sophisticated comminution circuits with advanced precipitation and flotation stages, Fidus sets a technical standard for multi-metallic mineral processing in North America.
Key Process Stages
The Fidus processing circuit is a highly integrated system designed for high availability and maximum recovery. The following stages outline the flow of material from the Run of Mine (ROM) pad to the final doré production:
- Primary Crushing: ROM ore is delivered to a conventional jaw crusher, reducing the particle size to a manageable fraction for the secondary grinding circuit. This stage is critical for maintaining a consistent feed rate to the downstream mills.
- SABC Grinding Circuit: The heart of the comminution stage features a Semi-Autogenous Grinding (SAG) mill with variable frequency drive (VFD), operating in a closed circuit with a pebble crusher. This is followed by a closed-circuit ball mill with hydrocyclones to ensure a product size (P80) of approximately 74 µm.
- Pre-Leach Thickening (Oxide Phase): Classified material from the cyclones is thickened in a high-rate pre-leach thickener. This increases the slurry density, optimizing the subsequent leaching kinetics and reducing the overall volume of slurry to be treated.
- Cyanide Leaching: The thickened slurry undergoes conventional tank leaching where gold and silver are dissolved into solution. The retention time is carefully managed to maximize extraction rates, particularly for the silver-rich oxide ores.
- Merrill Crowe Precipitation: Instead of a traditional Carbon-in-Leach (CIL) circuit, the Fidus mine utilizes a Merrill Crowe plant. This process involves the clarification of the pregnant solution, de-oxygenation, and the addition of zinc dust to precipitate the gold and silver out of the solution as a high-grade sludge.
- Sulphide Flotation (Phase 2): Commencing in the later years of the mine life, a dedicated flotation circuit will treat the sulphide material from the Orito deposit. This involves the production of a copper-gold-silver concentrate through multiple cleaning stages, which is then thickened and filtered.
- Tailings Management: The final discharge is filtered using pressure filters to produce “dry” stackable tailings with approximately 14% moisture, facilitating safer storage and significantly reducing water consumption through recirculated overflow.
Critical Data
The following table summarizes the key technical parameters and metallurgical performance metrics for the Fidus mine processing circuit:
| Parameter | Value | Unit |
|---|---|---|
| Nominal Throughput | 8,000 | tpd |
| SAG Mill Installed Power | 3.7 | MW |
| Ball Mill Installed Power | 5.6 | MW |
| Pebble Crusher Power | 175 | kW |
| Grind Size (P80) | 74 | µm |
| Oxide Gold Recovery | ~93.6 | % |
| Oxide Silver Recovery | ~77.0 | % |
| Sulphide Gold Recovery | 76.0 | % |
| Sulphide Silver Recovery | 88.0 | % |
| Final Tailings Moisture | 14.0 | % |
| Merrill Crowe Induction Furnace | 600 | kW |
Technical Details and Sustainability
The Fidus mine’s technical superiority is perhaps most evident in its approach to metallurgical testing and environmental stewardship. Metallurgical testwork, conducted by SGS and analyzed by P&E Mining Consultants, has demonstrated that the oxide ores from the Favor, Trini, and Casados deposits respond exceptionally well to direct cyanidation under aggressive leach conditions. However, the project distinguishes itself by addressing the “partially refractory” nature of the Orito sulphide deposit through a specialized flotation expansion. By utilizing a Merrill Crowe plant for the oxide phase, the project achieves near-complete precipitation (98-100% for gold and silver) from the pregnant leach solution (PLS). This choice of Merrill Crowe over CIL is technically justified by the high silver-to-gold ratios found in the Fidus deposits, as the high mass of silver would otherwise require an excessively large carbon regeneration circuit.
Advanced testing has also explored the inclusion of a Sulfidization, Acidification, Recycling, and Thickening (SART) process. SART testing determined that cyanide free recovery could range from 99% to 161% when using sodium hydrosulphide (NaHS) stoichiometric additions at a pH of 4. This process is vital for managing copper-gold ores, as it allows for the recovery of copper as a byproduct while recycling the cyanide back into the leaching circuit, thereby reducing reagent costs and environmental footprint.
Sustainability is a core pillar of the Fidus mine design. The implementation of dry stack tailings is a major environmental breakthrough for the region. By utilizing three large pressure filters to produce tailings at 14% moisture, the mine avoids the risks associated with traditional wet tailings dams, such as seepage or structural failure. Furthermore, the thickener overflow and filtered solution are recirculated to the grinding circuit, creating a semi-closed water loop that minimizes the need for fresh water intake from the local environment. The project also accounts for the future integration of a copper-gold concentrate production line, ensuring that the mine can adapt to the lower-grade sulphide ores without compromising sustainability. The 3.7 MW SAG and 5.6 MW Ball mill configuration represents a high-efficiency comminution strategy, using VFDs to optimize power draw based on ore hardness, further reducing the carbon footprint per tonne of processed ore. These technical considerations, combined with a workforce of over 1,200 personnel during construction and steady-state operations, ensure that Fidus remains a flagship of responsible and technically proficient mineral processing.
Source: Fidus
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
