Name of the Mine
Guanaceví mine.

Location  
The north-west portion of the Mexican state of Durango, about 3.6 km west of the town of Guanaceví and 260 km north-west of the capital city of Durango.

Mine Owner/s  
Midtier precious metals mining company Endeavour Silver Corporation (EDR), which controls the mine through its 100%-owned Mexican subsidiary, Endeavour Gold Corporation. Endeavour Gold holds the project through its two 100%-owned subsidiaries, Minera Plata Adelante and Refinadora Plata Guanaceví.

Brief Description  
The Guanaceví mine comprises the milling facility just outside of the town of Guanaceví and three active mines – Milache-El Curso, North Porvenir and Santa Cruz Sur – which are all on the Santa Cruz vein. The mines are about 5 km from the plant. 

The Milache-El Curso mines are accessed using the same portal as the old Porvenir 4 mine, while the North Porvenir and Santa Cruz Sur? mines are located 2 km and 4.5 km away respectively, south of the Porvenir 4 portal.

Brief History  
Acquired by EDR in 2004, Guanacevi is the company’s first and highest-grade silver mine. Shortly after the acquisition closed, management discovered the first high-grade orebody and production started in 2005.

Primary Metals/Minerals  
Silver and gold.

Secondary Metals/Minerals  
None stated.

Geology/Mineralisation  
The main ore at the Santa Cruz–Porvenir mines occurs in a crack-filled vein consisting of quartz and carbonate minerals. This vein is situated inside a major fault zone. Ultimately, hot mineral-rich fluids moved through a large break in the rock and left behind valuable minerals as they cooled.

This fault-and-vein system runs in a north-west direction and slopes down towards the south-west. Locally, it is called the Santa Cruz vein structure or Santa Cruz vein fault.

Geologists have traced this structure for about 5 km, and it is on average about 3 m wide. However, the mineralisation is not spread evenly along the full length. Instead, richer ore occurs in separate, steep zones (“shoots”), each up to about 200 m long along the vein.

There is also a second vein that runs almost parallel to the Santa Cruz vein, but it is less continuous. Nonetheless, it is important economically in parts of the mine, especially Porvenir Dos and the northern part of deep North Porvenir. In those areas, it is usually called the Footwall vein, and in Porvenir Dos it is also sometimes called the Conglomerate vein.

The wider Guanaceví silver/gold district is made up of classic high-grade epithermal veins, formed from hot fluids at relatively shallow crustal levels. These are low-sulphidation deposits and show a typical alteration style called adularia-sericite.

The veins are hosted mainly in older volcanic rocks (andesite flows and volcanic fragment rocks), which are overlain by younger rhyolite volcanic rocks. This rock sequence is common in many Mexican epithermal silver-gold districts.

Current evidence in Guanaceví suggests the mineralisation is closely linked to a phase of silica-rich volcanic eruptions. This phase likely marked either the end of one volcanic period (Lower Volcanic Sequence) or the start of the next (Upper Volcanic Sequence).

In many Mexican low-sulphidation systems, the best ore tends to occur in a fairly flat “ore horizon” about 300 m to 500 m thick vertically, where boiling hydrothermal fluids dropped out very rich (“bonanza”) minerals. At Santa Cruz, geologists still have not found the full upper or lower limits of that ore horizon.

Reserves
Total proven and probable reserves as December 31, 2024, were estimated at 202 000 t grading 413 g/t silver and 1.10 g/t gold equating to 506 g/t silver equivalent.

Resources  
Total measured resources as December 31, 2024, were estimated at 143 000 t grading 449 g/t silver, 1.15 g/t gold and 547 g/t silver equivalent. Indicated resources were estimated at 418 000 t grading 411 g/t silver and 0.94 g/t gold equating to 491 g/t silver equivalent. Inferred resources were estimated at 403 000 t grading 509 g/t silver and 0.95 g/t gold equating to 590 g/t silver equivalent.

Type of Mine
Underground.

Mining Method  
Ramp access, mechanised longhole and cut-and-fill mining methods.

Major Infrastructure/Equipment  
EDR has all the necessary mine and mill infrastructure to operate the Guanaceví mines to comply with all regulatory requirements.

The El Porvenir mine comprises the main access ramp and old workings that exit to the surface.

The Santa Cruz Sur ramp is served by two raises in the centre of the relatively narrow ramp, both of which are used as extraction for mine ventilation, with the ramp serving as the path for inflow of fresh air to the lowest levels of the mine. Ventilation is generally very good. 

The Porvenir 4, El Curso and Milache mining areas are a contiguous section of the Santa Cruz vein served by a single portal, which was originally designed as the access for the southernmost Porvenir 4 mine area. Later, this access was extended further north and deeper, along the Santa Cruz Fault Structure, to serve as access for the El Curso and Milache mine areas. 

An integrated ventilation system serves these areas. Intake consists of raise bores in the southernmost Porvenir 4 area and the portal and ramp. There are two  8-ft-diameter raise bores at the northernmost extreme of the area in the Milache mine, one with the fan extracting about 230 000 ft3 a minute of air and the other providing fresh air for this part of the Guanacevi mine. 

El Curso and Milache areas are dewatered using the 2163 level pumpstation, which includes six vertical turbine pumps and two inline horizontal pumps with 4 600 gallons per minute pumping capacity to handle the estimated 4 200 gallons per minute inflow. 

Water inflows collected from the Porvenir 4, El Curso and Milache areas below the 2163 level are pumped from the Milache area, the northernmost and deepest area. 

Electrical power distribution includes a series of substations connected to the public power grid, with additional underground transformers added as required. Backup substations are also available.

Prospects  
None stated.

Contact Details 
Endeavour Silver 
Tel +1 604 685 9775
Email info@edrsilver.com
Website https://edrsilver.com/