Two mineral deposit models are proposed for La Parrilla: intrusion-related carbonate replacement deposits and mesothermal fault veins.

The mineralization at La Parrilla occurs in veins, breccias, stockworks and replacements that are hosted by the Cretaceous limestones and shales of the Indidura Formation and by the granodiorite–quartz monzonite intrusion. Contact metamorphism and metasomatism resulted in the development of marble, hornfels, skarnoid, and skarn at the intrusive contact. Because the mineralization is related to the intrusive contact and skarn development, the deposits are proposed to be of the intrusionrelated hydrothermal type, and may represent mesothermal to epithermal environments.

Veins at La Parrilla are of two types: open space filling veins and fault-veins. The open space filling veins can consist of massive sulphides veins; quartz-calcite veins containing pyrite, sphalerite, and galena; and breccia veins cemented by quartz-calcite. Fault-veins consists of matrix-supported breccias or gouge containing disseminated sulphides and oxides. Open space filling veins can transition along strike into fault-veins and vice versa, and the presence of stockwork is common at the contacts of the vein with the host rock. Thus, it is interpreted that most veins were open or partially open faults and fractures, that they were flooded with hydrothermal fluids, and that some of these were reactivated by later faulting. Replacement deposits, on the o ........

The La Parrilla Silver Mine is a complex of producing underground operations consisting of the Rosarios, La Blanca and San Marcos mines which are interconnected through underground workings, and the Vacas and Quebradillas mines which are connected via above-ground gravel roads.

Both the Quebradillas open pit and Vacas were mined out in 2016.

The underground mining operations currently use the Mechanized Cut and Fill (MCF) mining method. This is the mechanized version of a classic method for mining narrow orebodies and involves extracting the ore in small slices, 2 to 4 m high, working from the bottom of the mining block upwards. As each cut is extracted, the void is filled with waste rock from development to stabilize the walls and create a working platform for the next lift.

MCF mining for a new mining block begins by driving a 4 x 4m ramp on the footwall side of the ore body and establishing sub-levels at regular vertical intervals. A typical mining block at La Parrilla will have the main haulage levels every 50 m with three sub-levels at 12 m intervals. The main haulage levels will include any ventilation infrastructure, a remuck for storing broken ore, a truck loading area, electrical substations and sumps.

To access the ore body, an initial access drift or attack ramp is driven from the lower main level to near the middle of the bottom elevation of the MCF stope. Typical development methods are then used to drive sill drifts ........

- subscription is required.

La Parrilla operates two parallel processing circuits that recover metals from the two types of ore. The two ore types are oxide ores and sulphide ores; both types are polymetallic, containing silver, lead, zinc, and gold.

The flotation plant receives sulphide ores and produces a silver-rich lead concentrate and a zinc concentrate as saleable products. Precious metals are preferably deported to the lead concentrate with both concentrates showing payable values of silver.

The leaching plant receives oxide ores and produces doré bars as a saleable product.

The processing plants were originally designed to process 1,000 tonnes per day (tpd) per circuit for a combined throughput of 2,000 tpd. Total throughput was generally maintained at 2,000 tpd until mid-2015 when production from the Quebradillas open pit neared completion. After this time, the mining operations have been unable to provide 1,000 tpd of oxide ore from the remaining underground sources. FM ........