Mineralization at San Felipe can be classified as a zinc-lead skarn (Einaudi et al, 1981). These skarn systems commonly occur in continental settings associated with either subduction or rifting. They are sulphide rich with Zn + Pb commonly ranging from 10-20 % and Ag from 30-300 g/t. Zinc-lead skarns are often transitional to massive-sulphide veins and often lack significant calc-silicate alteration. The San Felipe district is characterized by a strong structural control on hydrothermal fluid movement and resulting alteration / mineralization in the northern areas (Ventana, Transversales and San Felipe) and a more disseminated style to the south (Lamas). Calc-silicate alteration at San Felipe is Mn-rich including bustamite-rhodonite, piemontite, garnet and pyroxene.
The San Felipe District contains a series of easterly-trending Pb-Zn-Ag-Mn skarn veins and pipes that cut the Lower Metamorphic sequence and intrusive rocks. The district hosts five principal, westerly-striking, vein systems that include Artemisa-Cornucopia, Las Lamas, San Felipe, Transversales and La Ventana. Primary minerals are sphalerite, galena, pyrite, and magnetite with lesser native silver, chalcopyrite, arsenopyrite, scheelite, and covelite within a gangue of garnet, pyroxene, epidote, quartz, rhodonite, and carbonate (Roldan-Quintana, 1979: Calmus et al., 1996).
Three types of felsic intrusions are spatially associated with the deposits and include the San Felipe rhyolite porphyry, ........
