The Cerro Las Minitas Project in Mexico is an underground silver-polymetallic mine fully owned by Canada-based Southern Silver Exploration.
The company is working to bring the project, which is situated in one of the most significant silver producing regions in the world, into a production decision.
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The Preliminary Economic Assessment (PEA) of the project was published in October 2022.
According to PEA, the project estimates large-scale underground mining operation for 15 years with an annual average plant feed of 14.2Moz silver equivalent AgEq.
The future plan of the project is to refine target areas lying within 12km mineralised footprint and conduct drill tests on the best targets to discover a buried epithermal deposit.
The project is aimed to be developed as a silver-lead-zinc mine. In June 2023, Southern Silver Exploration confirmed the technical feasibility of recovering free cyanide-leachable gold and refractory gold from the mine following metallurgical scoping tests.
Cerro Las Minitas Project Location and Accessibility
The Cerro Las Minitas Project is located 6km northwest of Guadalupe Victoria Town in Guadalupe Victoria Municipality and 70km northeast of Durango City in the Durango State of Mexico.
The project lies at the centre of the Faja de Plata (Belt of Silver) in north Central Mexico. The Belt of Silver has current reserves or resources and historic production of more than 3 billion ounces of silver.
Overall, the property includes 26 mining concessions spread across 34,427.45 hectares (ha).
The site is situated around 1km adjacent to the Federal Highway 40D, a paved four-lane divided toll highway which runs through the Guadalupe Victoria.
A road starting from the Guadalupe Victoria connects the site via a bridge over the highway 40D. A FFCC rail service is also available to Guadalupe Victoria.
Cerro Las Minitas Project History
Most of the mining activity at Cerro Las Minitas was conducted between 1970 and 1981, with intermittent mining continuing.
Minerales Noranda optioned the areas and completed an exploration campaign from 1999 to 2000.
The leases on the concessions in the Santo Niño-Puro Corazón area were acquired by Minera Real Victoria (MRV) in 2005. The company also commenced an exploration and development programme in the same year.
In December 2005, Silver Dragon entered into agreements to purchase 100% interest in the Cerro Las Minitas property. The landholdings of the property were consolidated in March 2006, while Silver Dragon Mining de Mexico, a wholly owned Mexican subsidiary of Silver Dragon, held the claims.
In June 2009, Silver Dragon entered into a toll-milling agreement with Besmer of Mexico to process up to 12,000 tonnes of ore over 12 months from Cerro las Minitas.
Southern Silver signed an option agreement in December 2010 to acquire the mining concessions.
In September 2021, Southern Silver completed final payment to acquire 100% interest in the Cerro Las Minitas Silver Project.
Geology and Mineralisation
Southern Silver conducted drilling, sampling, and surveys from 2010 to 2021 at Cerro Las Minitas. This led to the delineation of six mineral deposits including El Sol, Las Victorias, Skarn Front, South Skarn, and Mina La Bocona deposits.
The Blind, El Sol, and Las Victorias deposits consist of semi-massive to massive sulphide mineralisation. The mineralisation lies in the skarnoid-and hornfels-altered margins of felsite and monzonite dykes.
The sulphide mineralisation at the Skarn Front deposit lies at the edge of the skarnoid alteration zone. It surrounds the Central Monzonite Intrusion at/near the transition to the marmorised zone (recrystallised or marbleised carbonate sediments).
Drilling carried out between 2020 and 2022 confirmed lateral and extensive skarnoid-style mineralisation around the central intrusion in the La Bocona, South Skarn, and North Felsite deposits.
The drilling also confirmed manto-styled mineralisation within the La Bocona deposit. The mineralisation includes predominantly silver enriched with lead, arsenic, and gold. The upper part of the mineralisation is strongly oxidised.
Cerro Las Minitas Mineral Resource Estimate
According to the PEA, the indicated sulphide mineral resource estimate of the project at $60 Net Smelter Return (NSR) cut-off is 12,325 kilo tonnes (kt) containing average grades of 106g/t silver, 0.07g/t gold, 1.3% lead, 3.3% zinc, 0.16% copper, 347g/t silver equivalent (AgEq) at a NSR of $130/t.
The property contains inferred resources of 19,605kt containing average grades of 117g/t silver, 0.12g/t gold, 1.2% lead, 2.3% zinc, 0.23% copper, 334g/t silver equivalent at a NSR of $123/t.
Mining Methods and Ore Processing
Long-hole open stoping (LHOS) was selected as the preferred method at Cerro Las Minitas assessing the parameters of the project.
It includes two variations- longitudinal long-hole open stoping to mine areas with narrower mineralisation and transverse long-hole open stoping for wider mineralisation. Both methods will use paste backfill.
Ore material will be mined using a large and modern fleet consisting of 63-tonne trucks and 21-tonne loaders.
The processing will be carried out in a processing plant with an average daily mill feed rate of 4,500t/d and an average life of mine (LOM) head grade of 0.2% Cu, 1.07% Pb, 110 g/t Ag, and 2.57% Zn.
The metallurgical process comprises a two-stage grinding circuit, a single ball mill grinding circuit, and selective copper, lead, and zinc flotation circuits sequentially. This process produces copper, silver or lead, and zinc concentrates separately which are shipped off-site to the market.
After dewatering and filtration, the tailings are stored in a tailing storage facility or in the tailing paste backfill plant which is placed underground.
Power and Water Supply
The silver-polymetallic mine will receive process make-up and a domestic water supply from sub-surface wells. It is expected to require approximately 1,500m3/d of water.
The mine and processing plant will have a 20MW demand load. A 10.4km-long overhead transmission line of 115kV on self-supported steel towers will connect the site to the CFE Substation Guadalupe Victoria.
Cerro Las Minitas Contractors
The PEA of the Cerro Las Minitas Project has been prepared by M3 Engineering & Technology, Entech Mining, Kirkham Geosciences, and Metallurgical Process Consultants.
Kirkham Geosciences also prepared the technical report of the project dated February 2018.
BD Drilling Mexico and Intercore Operaciones carried out core drilling at the property between 2011 and 2018, and during 2020 and 2021, respectively.
The mineral resource estimate for the project was filed by Kirkham Geosystems.
