Overview

Deposit type

• Epithermal
• Vein / narrow vein
• Breccia pipe / Stockwork

Summary:

Six principal areas of mineralization are identified on the Pallancata Property within an area of 3 km by 2 km. These comprise Virgen del Carmen/San Javier, Mariana, Mercedes, San Cayetano, Pallancata and Huararani.

Low sulfidation, epithermal silver-gold mineralization is present in a complex array of veins, breccias (both hydrothermal and tectonic), stockworks and silicified zones. Vein zones comprise vein breccia with in-situ clasts of bladed carbonate replacement and partial leaching. Crustiform and colloform banding is also common. The matrix generally consists of milky-white to coarse-grained semi translucent drusy quartz. Multiple phases of veining are apparent. Breccias range from simple tectonic breccias to complex multiple event hydrothermal breccias. These include black silica breccia (rich in sulfides) to massive white quartz breccias.

The main Pallancata Vein System is the principal target area and hosts a west-northwest to east-southeast trending zone of complex multiphase veining and faulting that generally has well-defined conduits that underwent major dilation. The system pinches, splits and has a sinuous nature. It is apparent that the vein system is en echelon in form, both horizontally and vertically.

The dip of the vein system is generally sub-vertical, with a down-throw to the south. The alteration style of the clay components changes from smectitic to illitic towards the main structure, but it is often hard to distinguish hydrothermal-related clay alteration from diagenetic alteration due to the high pumice content of the lapilli tuffs. There is a distinct silicified halo around the veins which is more prominent on the north side of the vein.

The main Pallancata Vein structure, as currently recognized has a strike length of approximately 2 km and is up to 40 m wide at its widest, including the intensely silicified wall rocks. Individual veins or splays are more typically 0.5 m to 3 m wide. Mineralization has been delineated to depths up to 500 m below surface. Portions of the system are dominated by in situ quartz altered, bladed carbonate. Elsewhere it shows jigsaw breccia, commonly with black chalcedonic silica and sulfide fill. Other parts are true hydrothermal breccias with complex textures and multiple phases of banded chalcedonic silica and euhedral drusy quartz.

Much of the high-grade mineralization on the Pallancata Property is seen in the West Vein. This zone is located in the western part of the main Pallancata structure, and comprises an intensely silicified body with a strong stockwork of quartz veins, typically striking northeastsouthwest to north-south. High-grade zones occur where these veins intersect the northwestsoutheast striking main Pallancata Vein System. In the West Vein, fracture movements are seen to be normal and sinistral, while in the Central Vein they are normal and dextral. The main structure displays mineralized cimoides (duplex veins) and tensional veins principally in the footwall of the West Vein, and in both footwall and hanging wall in the Central Vein.

Mining Methods

• Mechanized Cut & Fill
• Bench & Fill
• Sub-level stoping

Summary:

Hochschild is currently use several different mining methods for this area. There are Mechanized Cut & Fill, Bench & Fill and Sub-level stoping with cemented backfill.

Ore is then hauled by LHDs to ore-passes located at one of the internal access ramps. From these ramps, ore is loaded into road-type haul trucks for transportation to surface.

Extracted ore is stored on surface at the Pallancata mine site in one of a series of stockpiles to enable ore blending to take place.

Comminution

Crushers and Mills

Summary:

In 2009, the Selene flotation plant capacity was expanded to a rated throughput of 3,000 t/d ore and no further expansion of the processing plant is planned.

The plant modifications that were required to increase capacity to 3,000 t/d of ore are summarized below:

Crushing Circuit
The circuit has been modified from two-stage to three-stage crushing and a washing circuit is being considered to remove clays from primary crushed ore ahead of secondary crushing. The circuit includes:
- Aprimary crushing system comprising a grizzly screen and a Metso C100 jaw crusher, nominal capacity of 145 t/h at a three-inch setting, is retained.
- A single, standard HP200 crusher is installed as a new secondary crusher.
- The existing secondary HP200 shorthead crushers are converted to tertiary crushing duty and a third HP200 has been added to the circuit.

Grinding Circuit
- Milling Circuit No. 1 remains unchanged.
- Milling Circuit No. 2 is expanded by installing a 9.5 ft by 15 ft diameter ball mill to provide secondary grinding following the existing primary mill.

Milling to a target grind size of 60% less than 200 mesh is carried out in two parallel circuits. Milling Circuit No1, based on the original plant design, consists of a primary SAG mill, Comesa 9.5 feet by 8 feet, operating in closed circuit with a hydro cyclone. The cyclone underflow returns to the primary mill circuit whilst the cyclone overflow is fed to the secondary mill sump and combined with the secondary mill product. The combined stream is pumped to a Derrick screen; the oversize from which is returned to the secondary milling circuit comprising, one seven feet by seven feet Comesa ball mill and one seven feet Denver ball mill, operating in parallel. Undersize from the Derrick screen is fed to the flotation circuit.

Milling circuit No 2: a Comesa 9.5 feet by 12 feet mill with a nominal capacity of 77 tph has been installed as a secondary mill to work in series with the existing Comesa ball mill, 9.5 feet by 15 feet with classification provided by a new Derrick screen, operating in closed circuit with hydrocyclones. The cyclone overflow reports to the flotation circuit whilst underflow material returns to the ball mill.

Processing

• Vacuum filtration
• Crush & Screen plant
• Flotation
• Dewatering
• Filter press

Summary:

All ore from the Pallancata Mine is toll treated at the Selene flotation plant, 22 km to the north by road.

In 2009, the Selene flotation plant capacity was expanded to a rated throughput of 3,000 t/d ore and no further expansion of the processing plant is planned.

The flowsheet for mineral processing for Pallancata ore involves:
x Three stage crushing
x Grinding
x Flotation
x Concentrate de-watering
x Tailings disposal.

In 2009, the Selene flotation plant capacity was expanded to a rated throughput of 3,000 t/d ore.
The plant modifications that were required to increase capacity to 3,000 t/d of ore are summarized below:

Flotation Circuit
- A third flotation circuit is installed including one conditioner tank and additional rougher, scavenger and cleaner flotation cells.

Concentrate Dewatering and Tailings Handling
- The capacity for concentrate dewatering is increased by the addition of a 20-ft diameter concentrate thickener and a new twenty plate, one-meter by one-meter pressure filter.
- A third, 50-ft diameter tailings thickener has been added.

There are three flotation circuits, each consisting of a conditioner tank, rougher and scavenger cells. The concentrate stream is combined and upgraded in two phases of column cell cleaning. The cleaned concentrate is partially dewatered in a thickener vessel and then filtered using a pressure filter and a vacuum disc filter. Selene concentrate has a moisture content of approximately 12%, whereas Pallancata concentrate having higher clay content is more difficult to filter and has a moisture content of 19% when using the pressure filter and approximately 28% from the disc filter. The pressure filter, installed during the last expansion project, was intended to handle all filtration duties. However, due to the poor filtration characteristics of Pallancata concentrate, the disc filter was retained.

The concentrate is loaded manually into bags weighing 50 kg and transferred to the port of Matarani for dispatch to a smelter.

Tailings are partially de-watered in two thickener vessels and the thickened slurry is classified to separate the coarser material for use as backfill in the mine. The fine particle size material is drained under gravity via pipeline to the tailings storage facility (TSF) located approximately one kilometer from the plant. Clarified water is pumped from the TSF to the plant.

The plant is relatively new and the equipment appears in good condition. Selene reported a plant feed of approximately 80 tph when treating Pallancata ore. This is lower than the nominal capacity due to the hardness of the ore and the difficulties experienced from the high moisture content during the wet season.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Mine Manager	Giancarlo Aldo Gonzales Aguilar		Aug 31, 2023
Mine Superintendent	Jose Granda		Aug 31, 2023
Plant Superintendent	Juan Guillen Cantoral		Aug 31, 2023
Process/Metallurgical Manager	Luis Vargas Hurtado		Aug 31, 2023