Summary:
The San Luis vein system is a typical volcanic hosted low sulphidation epithermal quartz/precious metal deposit. The deposit is very similar to numerous other volcanic-hosted epithermal vein deposits that occur in the Rocky Mountain, Sierra Nevada, Sierra Madre, and Andean cordilleras, including those in districts in Ouray/Telluride and Creede, Colorado, Silver Peak, Nevada, Guanajuato, Fresnillo, and Pachuca, Mexico, and Morococha, Quirivilca, and Casapalca, Peru.
Vein gangue mineralization in the San Luis deposit consists of quartz, chalcedony, calcite and minor adularia. Gold occurs as electrum and silver is present as acanthite, other silver sulphosalts, and electrum. Other sulphides include trace amounts of pyrite, chalcopyrite, galena and sphalerite The veins display common epithermal textures including crustiform banding that often display the interlayers of quartz and sulfide minerals described in Item 10. Bands are frequently disrupted, indicating repeated pulses of mineralization. Lattice textures in which calcite crystals have been replaced by quartz and brecciation are also common characteristics. Faulting and fracturing are key elements in the localization of mineralization in the vein system. Mineralized “shoots” typically occur in dilational zones that are the result of a variety of local stresses, and often these stresses are repeated along the length of a vein structure, resulting in multiple mineralized-shoots.
The Ayelén vein is the better mineralized of the known vein structures. Trenching and diamond drilling have traced this structure along a strike of 340° to 345° for a length of over 720m, with down-dip extensions of more than 325m. Surface mapping shows that the vein structure dips -75° to -85° west-southwesterly, but drilling results show that the controlling fault structure(s), subsurface individual vein segments and post-mineral dikes dip vertically to -80° west-southwesterly. True thicknesses of individual vein segments vary from ten’s of centimeters to more than 10m, with an average of 1.5m to 3.0m wide.
The Inéz vein, which is situated approximately 110m east of the Ayelén vein, strikes northwesterly at 320° to 340° and dips -50° to -75° to the northeast. The vein outcrops as a series of discontinuous resistant ridges for more than 2,200m along strike, with apparent widths of 2.0m to 7.5m. However, only a relatively short section of the Inéz vein contains significant amounts of gold and silver, and this section occurs where the Inéz vein is closest to the Ayelén vein.