The mineral deposits in the Guanajuato area are classic fissure-hosted low-sulphidation epithermal gold-silver-bearing quartz veins and stockwork. Mineralization of economic importance consists of fine-grained disseminations of acanthite, electrum, aguilarite, and naumannite with accessory pyrite, and relatively minor sphalerite, galena, and chalcopyrite. Gangue minerals include quartz, calcite, adularia, and sericite. The veins are accompanied by hydrothermal alteration consisting of argillic, phyllic, silicic, and propylitic facies. Mineral textures in this zone are typically fracture-filling, drusy, and coliform masses.

Guanajuato
At Guanajuato, Cenozoic volcanic and volcanogenic sediments unconformably overlie the Mesozoic basement rocks. In the area, the oldest Cenozoic unit is the Paleocene Comanja granite, (66 Ma – 56 Ma), this was followed by the Eocene extrusion of andesite (56 Ma – 33.9 Ma) which was sporadically deposited and contemporaneous with the deposition of the Guanajuato conglomerate in localized grabens. The Guanajuato conglomerate underlies an unconformity beneath a sequence of felsic to mafic volcanic rocks that consist of Oligocene ignimbrites, lava flows and domes (33.9 Ma – 23 Ma).

The best mineralization is often found related to bends in the Veta Madre orientation (Barclay, 2007 and Rhys, 2013) such as at San Vicente in the Rayas area, and at Cata and Santa Margarita. These structural bends may be due to changes in rock ty ........

The Guanajuato Mine Compleex (the “GMC”) comprises the Guanajuato and San Ignacio operations. Typically, all zones at the GMC are extracted by the Cut & Fill mining method.

Guanajuato mine
Guanajuato consists of a series of interconnected, previously independent, mines including Promontorio, Santa Margarita, Rayas, Los Pozos, Cata, Valenciana and Guanajuatito.

Mining at Guanajuato predominantly comprises cut and fill stoping, with some pillar recovery in historic workings, and a few zones where mineralized extensions are discovered and mined over a period of a few months. Mining is generally more selective using jacklegs. However, where possible, mechanized cut and fill is utilized.

Two main shafts serve access to the active mine areas, while several other old shafts provide ventilation support. The Rayas shaft is used for transportation of personnel and supplies, while the Cata shaft, located just above the processing plant is used to transport the mineralized material for milling. These are currently de-energized and access of men and materials and egress of ore is via the Rayas ramps, San Vicente and Guanajuatito that provide the access at each end of the mine network, including for mobile equipment.

Mining is conducted by contractors, primarily sourced from nearby communities, utilizing equipment owned by the Company and the contractors. Mine contractors and equipment are alternated between the mines, including San Ignaci ........

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