The Platosa Silver-Lead-Zinc Mine is located in Durango, Mexico. (Credit: James St. John/ Flickr)
The map shows initial drilling targets and mine’s details. (Credit: Excellon Resources)
Platosa Mine commenced production in 2005. (Credit: Kecko/ Flickr)

The Platosa Project is an operational polymetallic underground mine located in the north-eastern part of the State of Durango in Mexico. The main commodities produced by the mine are silver, lead and zinc.

The project is owned by Minera Excellon de Mexico, a wholly owned subsidiary of Excellon Resources.

Platosa began production in 2005. It is expected to produce until September 2023 to process and remaining ore, following which, care and maintenance preparations will commence.

Excellon aims to form partnerships to convert Platosa from production to a potential exploration prospect with deposits occurring as Carbonate Replacement Deposits or mantos.

Seven mineral resource estimates have been completed since Platosa mine began production.

Excellon published a technical report on the project in June 2021. The report documented a mineral resource statement for the Platosa Mine.

Platosa Mine Location

The Platosa project is situated approximately 45km north of the Torreon city and 5km north of the Bermejillo village in Mexico. It consists of 74 mining concessions.

Overall, the mining concessions occupy a total area of 11,049 hectares.

The project can be accessed from the Torreon International Airport which is approximately an hour drive via Mexico Highway 49. Rail lines run parallel to the highway, making the project accessible throughout the year.

Platosa Project Ownership History

Before 1960s, limited and small-scale mining were conducted in the area, followed by small scale artisanal mining between 1960s and 1970s.

In 1997, Excellon acquired the concession which contained the historical Platosa Mine. At that time, Apex bought the adjacent Saltillera property and conducted reconnaissance mapping and sampling on both the properties.

Apex staked the Saltillera property lying adjacent to Platosa in 1997 and with Excellon, Apex conducted mapping and sampling.

Apex optioned the Platosa Mine from Excellon in 1998, and conducted geological mapping and geochemical sampling.

Excellon again gained control over the mine in 2001.

Geology and Mineralisation

The project is situated in the Sierra Bermejillo, an anticline-syncline and open fold pair of Mesozoic sedimentary rocks. The property has Platosa Structural Zone (PSZ) as the principal fault system.

It includes a series of fault planes, striking north to northwest and dipping towards east steeply.

The PSZ contains brecciated, crushed, and dolomitised limestone, iron and manganese oxides, travertine-filled breccias, coarsely crystalline selenite veins, and slickenside fracture surfaces.

The mineralisation in the mine consists of massive carbonate-replacement deposits, characterised as discrete pods or mantos.

The main silver-lead-zinc bearing minerals are acanthite, lesser proustite, galena, and sphalerite.

Mineralisation is also found in the form of vein, breccia, and skarn systems across different exploration prospects including San Gilberto, Jaboncillo, Saltillera North and South, Halcón, Refugio, PDN, Rincón Del Caído, La Zorra, Cañón de la Güera and Cañón Colorado.

Platosa Project Mineral Resource Estimate

As of March 2021, total indicated mineral resource estimate for the mine is 317,000t containing 4,948koz silver at a grading of 485g/t, 36,797klbs lead at a grading of 5.3%, and 38,781klbs zinc at a grading of 5.5%.

The inferred mineral resource estimate is 42,000t containing 1,007koz silver at a grading of 749g/t, 4,000klbs lead at a grading of 4.3%, and 5,002klbs zinc at a grading of 5.4%.

Mining methods and Ore processing

Currently, overhand cut and fill method is used for mining at Platosa. Drift and fill method is being used for mining mantos.

The processing is done in Miguel Auza processing facility with two circuits, one for lead-silver and the other for zinc-silver.

The Run-of-Mine (ROM) is fed to jaw crusher with 900-tonne per day crushing capacity. ROM undergoes crushing in the circuit, resulting in cyclone overflow. This overflow reaches the lead flotation circuit.

In lead flotation circuit, reagents such as Aero 3407, Methyl Isobutyl Carbonyl (MIBC), and zinc sulphate are added. The concentrate then, enters two stage cleaning circuit and tailings enter the lead scavenger circuit.

From the second stage cleaning circuit, the lead concentrate is pumped into the lead thickener.

The final lead concentrate contains approximately 80% lead and 81% silver from the mill feed.

The tails enter the two parallel zinc rougher banks where tails are directed to the zinc scavenger. Additionally, the rougher concentrate enters the two-stage zinc cleaner banks.

From second stage, the final zinc concentrate is pumped to the zinc thickener.

The final zinc concentrate contains approximately 80% zinc and 9% silver from the mill feed and is transferred to the filtration circuit.

The tails are stored in tailings management facility.

The filtration circuit filters the concentrate which is transferred into the storage warehouses where wheel loaders spread concentrate on a drying pad.

After drying, the concentrate is loaded onto 38-tonne covered trucks for transportation to a concentrate sales facility.

Contractor Involved

SRK Consulting (Canada) prepared the Platosa Mine technical report for Excellon Resources.