Summary:
La Colorada Vein Mine is considered a typical hydrothermal polymetallic deposit located in a region with significant silver and base metal production from well-known vein and skarn deposits.
The La Colorada Vein Mine’s intermediate sulphidation epithermal vein model considered for exploration and mineral resource and reserve estimation transitions from silver-rich mineralization at surface to more base metalrich mineralization at depth.
Epithermal Vein Mineralization
Fractures and faults formed during the D1 to D3 deformation events acted as conduits for emplacement of epithermal vein mineralization. There are three ENE to E-W-trending principal vein structures which, from NW to SE, are named Recompensa, Amolillo and NC-HW. Each vein has second order sub-parallel splays and duplexes, and there are also several NW- to WNW-trending veins. In general, the principal veins are strongly brecciated, locally oxidized, and often exhibit irregular vein boundaries. Most of the mineralization of economic significance is located in quartz veins that average 1 metre to 2 metres wide, but may be significantly wider. The vein fillings consist of quartz, calcite, and locally barite and rhodochrosite. Galena, sphalerite, pyrite, native silver, and silver sulphosalts are present in unoxidized veins. The major mineralized veins are strongly brecciated and locally oxidized. Amolillo strikes over 1.5 km to the northeast and dips 60° to the southeast, for over 800 metres down dip. The average vein width is 2.2 metres. The NC series of veins lies around 700 m to the southeast of Amolillo. The most significant of these veins, NC2, strikes around 1.2 km to the northeast and dips 75° to the southeast, for over 1 km down dip. The average vein width is 1.9 metres. The HW series is the western continuation of the NC series, strikes east-west, and dips 50° to the south, for over 600 m down dip. The average vein width is 1.8 metres. Veta 3 runs parallel to the HW and NC series, strikes for over 900 m to the northeast, and dips 75° to the northwest, for around 400 m down dip. The average vein width is 1.7 metres. Well banded epithermal textures are rare. Vein breccias generally lack cohesiveness and consequently show very little surface expression. Veins typically occur as narrow feeders with massive sulphides in the upper portion of the system.