The processing route comprises conventional crushing, grinding, whole-ore cyanidation, Merrill Crowe and SART recovery, and dry-stack tailings disposal.
Report context
The technical report, dated 2023, presents an updated preliminary economic assessment for the Los Ricos South project. The process plant design is based on a nominal 1,750 tpd throughput for Years 1–3 and a nominal 4,000 tpd throughput for Years 4–12, treating mineralized material with average grades of 1.18 g/t Au, 125 g/t Ag, and 0.09% Cu. The report references testwork detailed in Section 13 that supports the flowsheet development and design criteria.
Processing route
Primary crushing
The proposed crushing circuit reduces run-of-mine mineralized feed from a nominal top size of 300 mm to a product of 80% passing 150 mm for the SAG mill feed. The front-end circuit includes a ROM feed hopper with a 100 t surge bin, a rock breaker, a vibrating grizzly apron feeder, a 762 mm x 1219 mm jaw crusher with 75 kW installed power processing a nominal 100 t/h, and associated conveyor transfer belts with a belt scale and belt magnet.
Crushed feed stockpile and reclaim
A stockpile with 1,750 t live capacity provides production surge capacity. Three variable-speed reclaim apron feeders discharge onto the SAG mill feed conveyor, controlling the feed rate to 80 t/h.
Grinding circuit
The grinding circuit is a two-stage process comprising a SAG mill, screen, pebble crusher, and a ball mill in closed circuit with classifying cyclones. The SAG mill is 5.65 m diameter x 2.5 m EGL with 1,400 Hp installed power and variable frequency drive. Oversize material from the classifying screen is sent to a 125 Hp pebble crusher and recirculated to the SAG mill feed belt. Screen undersize feeds the ball mill pump box. The ball mill is 4.1 m diameter x 6.4 m EGL with 2,200 Hp installed power. Cyclone classification uses three operating 6gMAX20 units. Recycled process water is added to the SAG mill feed to achieve 74% slurry density. The grinding circuit final product size has a design P80 of 74 µm.
Pre-leach thickening
Ball mill cyclone overflow at approximately 35% solids feeds an 18 m diameter high-rate pre-leach thickener with 7.5 kW drive. The cyclone overflow is thickened to a minimum pulp density of 50% solids. Thickener overflow water is recirculated to the grinding circuit. Thickener underflow feeds the cyanide leaching circuit.
Cyanide leaching circuit
The leaching circuit consists of one pre-leach aeration tank (8 m diameter x 10 m high with 25 kW agitator) and six mechanically agitated leach tanks (13 m diameter x 17 m high, each with 40 kW agitator). Flow is by gravity between tanks with bypass options. Leach residence time per tank is 16 hours for an approximate total of 96 hours. Lime addition maintains leach pH between 10.5 and 11.0. Cyanide addition at a feed concentration of 1,200 ppm is accomplished within the circuit. Air spargers with an air blower system are integral to the leach tanks.
Post-leach thickening and tailings dewatering
Slurry from the last leach tank feeds an 18 m diameter post-leach thickener for initial pregnant solution recovery. Thickener underflow at approximately 50% solids feeds three tailings dewatering filters for solution washing and dewatering. Filter discharge density is 84% solids, producing dry stackable tailings with approximately 16% moisture. The filters include a washing system to recover pregnant metal-bearing solution. Collected solution is pumped to the Merrill Crowe recovery area.
Merrill Crowe circuit and refinery
Pregnant solution containing silver, gold, and copper complexes is pumped to a conventional Merrill Crowe zinc precipitation circuit at a design flowrate of 125 m³/hr. The circuit includes two clarification filters (140 m² rotating disc units), a deaeration tower (1.56 m diameter x 6.25 m high), a high vacuum pump, a zinc addition skid with zinc cone and lead nitrate system, two precipitation feed pumps, and two precipitate filters (92 m² recessed plate units). The resultant sludge is dried, fluxed, and smelted in a 400 kW induction furnace to produce saleable doré. Barren solution is pumped to the SART copper recovery circuit.
SART circuit
SART feed solution is pumped at 125 m³/hr with a copper concentration of 800 mg/L. Sodium hydrosulphide is injected prior to the copper contactor. The solution enters a 3.5 m diameter x 4.0 m high copper contactor and is acidified with sulphuric acid to a controlled pH of 4.5. This precipitates copper sulphide (Cu₂S) and regenerates cyanide associated with soluble copper. The copper precipitate (65% Cu) overflows to a 7.5 m diameter copper clarifier, then is filtered and dewatered to 30% moisture for shipment as a saleable product. Clarifier overflow is pumped to neutralization tanks where lime solution raises pH to 10.5, producing gypsum that is removed in a downstream gypsum clarifier. Overflow solution is returned to the process.
Reagent handling
Main plant reagents include hydrated lime, sodium cyanide, flocculant, diatomaceous earth, zinc dust, lead nitrate, and fluxes. SART reagents include lime slurry, sodium hydrosulphide, sulphuric acid, anionic flocculant, caustic soda, and hydrogen peroxide.
Water supply
Make-up water is supplied from the Martin Dam, a single collection dam located approximately 3.5 km from the proposed processing site. A 200 mm diameter HDPE feed line with multiple high-head pumps is proposed. Dry-stack tailings recycle water back to the process, with tailings designed at 16% moisture.
Key reported parameters
| Parameter | Units | Value | Basis |
|---|---|---|---|
| Feed Characteristics | |||
| Specific Gravity | g/cm³ | 2.60 | Design |
| Bulk Density | t/m³ | 1.65 | Design |
| Moisture Content | % | 3.0 | Design |
| SMC Axb – design | kWh/t | 35.2 | Design |
| Bond Ball Mill Work Index – design (hard) | kWh/t | 20.8 | Design |
| Bond Abrasion Index (very abrasive) | g | 0.72 | Design |
| JKSimMet Simulation (SAG) – overall circuit | mw | 1.04 | Design |
| JKSimMet Simulation (Ball) – overall circuit | mw | 1.64 | Design |
| Milling Circuit Feed Size – F80 | mm | 150 | Design |
| Milling Circuit Product Size – P80 | um | 74 | Design |
| Leach Feed Slurry Density | % | 55 | Design |
| Pre-Aeration Residence Time (minimal) | h | 4 | Design |
| Bulk Leach Residence Time | h | 96 | Design |
| Total Cyanide Leach Consumption Rate | kg/t | 1.25 | Design |
| Total Lime Leach Consumption Rate | kg/t | 0.8 | Design |
| Au and Ag Metal Recovery System | Merrill Crowe | Design | |
| Cu₂S Recovery System and CN⁻ Regeneration | SART | Design | |
| Dewatered Tailings Moisture – Pressure Filtration | % | 16 | Design |
| Peak Wash Ratio | m³/t | 1.44 | Design |
| Plant Availability/Utilization | |||
| Overall Process Plant Feed – Nominal (Years 1-3) | tpa | 639,000 | Design |
| Process Plant Feed – Nominal (Years 1-3) | tpd | 1,750 | Design |
| Crushing Plant Feed (Years 1-3) | tpd | 1,750 | Design |
| Crusher Plant – Plant Utilization | % | 75.0 | Design |
| Grinding, Leach and Refinery Utilization | % | 92.0 | Design |
| Primary Crushing Circuit Throughput Rate | t/h | 98 | Design |
| Grinding and Leach Process Rate | t/h | 80 | Design |
| Process Plant Feed Characteristics | |||
| Gold Head Grade – Nominal | g/t | 1.18 | Design |
| Silver Head Grade – Nominal | g/t | 125 | Design |
| Copper Head Grade – Nominal | % | 0.09 | Design |
| Metal Recoveries (LOM – Abra and Eagle) | |||
| Overall Gold Recovery – design | % | 95.0 | Design (based on whole feed cyanidation) |
| Overall Silver Recovery – design | % | 86.0 | Design (based on whole feed cyanidation) |
| Overall Copper Recovery – design | % | 77.0 | Design (based on whole feed cyanidation) |
Project website: https://gogoldresources.com/properties/los-ricos/
Note: Process plant recoveries are estimated at 95% Au, 84% Ag Phase 1, 86% Ag Phase 2, and 77% Cu for leaching with 95% Cu for SART.
Technical qualifications
The report constitutes a preliminary economic assessment and includes inferred mineral resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves. The recovery methods show optimized testwork detailed in Section 13 of the report. There are no metals streaming or hedging agreements in place. Metal prices and the exchange rate are based on approximate August 31, 2023 three-year monthly trailing averages and are subject to spot market conditions. The report states that currently there are no contracts in place that are material to the Los Ricos South Project.
Source: GoGold Resources Inc., Los Ricos South Updated PEA, Report No. 448, P&E Mining Consultants Inc., 2023, Sections 1.15, 1.16, 1.17, and 17.0–17.4.
