Los Filos Mine Expansion

The Los Filos gold mine is situated approximately 230km south of Mexico City in the Guerrero State of  Mexico.

Leagold, a mining company based in Canada, acquired the mine from Goldcorp in April 2017 and completed the feasibility study for its expansion in January 2019.

Estimated to cost $180m, the expansion project is expected to increase the mine’s average annual production to 350,000 ounce (oz), over an estimated mine life of ten years.

Los Filos mine background

Spread over 4,246ha, the Los Filos gold property includes two high-grade underground mines namely Los Filos and Bermejal and three relatively lower-grade open-pit mines namely Los Filos, Bermejal, and Guadalupe.

Historical underground mining at the site traces back to 1930s, whereas open-pit mining was carried out for the first time by Minera Nukay in 1984.

Teck Resources acquired the property in 1993 and transferred the ownership to Wheaton River Minerals in 2003.

Goldcorp acquired the property in March 2005 and completed feasibility studies for the Los Filos and Bermejal open-pits as well as for the Los Filos underground mine by 2007.

It commenced production from the Los Filos open-pit mine using heap-leach processing method in 2008.

Los Filos mine expansion details

The Los Filos expansion plan includes the development of Bermejal underground mine, enlargement of the operating Los Filos open-pit mine, re-phasing of the Bermejal open-pit mine into two distinct open-pits namely Bermejal and Guadalupe, and construction of a carbon-in-leach (CIL) processing facility.

The expansion project is expected to produce 3.3 million ounces (Moz) of gold over its estimated project life.

Geology and mineralization

The Los Filos gold mine is situated in the Guerrero Gold Belt within the central portion of Morelos-Guerrero sedimentary basin.

Gold mineralization at the mine is hosted in skarn deposits as well as volcanogenic massive sulphide deposits.

Los Filos gold mine reserves

The Los Filos mine was estimated to hold 111.3 million tonnes (Mt) of proven and probable ore reserves grading 1.23g/t Au and containing 4.5Moz of gold, as of October  2018.

Mining at Los Filos mine

Open-pit mining is carried out with conventional drill-blast-load-haul operations, whereas the underground mining involves the  underhand drift and fill technique using cemented rock fill (CRF) as backfill.

The open-pit mining fleet comprises 31 130t haul trucks, four 32t excavators, three 18t front loaders, one 32t front loader, 12 blast-hole drill rigs, eight bulldozers, four wheel dozers, four graders, four water trucks, one hydraulic excavator, two backhoe excavators, and one vibrator compactor.

The underground mining fleet includes six jumbo drills, three rock bolters, 14 scoop trams, three wheel loaders, a raise drill, a grader, a backhoe loader, and a bulldozer.

A 1.33km ramp has been built to access the Bermejal underground ore body.

Ore processing

The run-of-mine (ROM) ore is sent to the nearby processing plant, where it undergoes two-stage crushing and is conveyed to the heap leach pads for gold recovery through adsorption-desorption-recovery (ADR) process.

The obtained gold material further undergoes clarification, electro-winning, and refining for the production of gold dore.

The processing facility is planned to include a 4,000 tonnes per day (tpd) carbon-in-leach (CIL) plant, as part of the Los Filos expansion project.

Infrastructure facilities

The Los Filos mine is accessed via a 18km paved road connecting the Federal Highway 95 at Mezcala. The mine site also houses a 1.2km private airstrip.

The mine receives power supply through an 8km-long 115kV transmission line connecting a combined-cycle natural gas-fired (CCGT) power station located in San Luis de Paz. The Los Filos expansion project entails the construction of a new 40MW substation.

The water required for the mining operations is sourced from the Rio Balsas river as well as from local bore wells.

Contractors involved

SRK Consulting provided the mineral resource estimate as well as the cost estimate during the Los Filos mine expansion feasibility study. It also undertook the heap leach metallurgical test work and processing plant review for the project.

Lycopodium Minerals provided the CIL metallurgical test work management and interpretation service as well the processing plant and related process infrastructure design during the feasibility study for the expansion project.

Call & Nicholas was the geotechnical consultant for the Bermejal underground mine development.

Suppliers involved

PEMEX is the fuel supplier, whereas Chemours supplies sodium cyanide for the on-going Los Filos mining operation.

Mexicana de Explosivos y Voladuras and Explosivos Mexicanos are the explosives suppliers.

Roca Eterna S, Holcim Mexico, and Industrial & Mining Solution provide cement, while Calidra Oriente is the lime supplier for the Los Filos mine.