Tahuehueto

The property contains four main rock types: lower volcanic series andesite, granodiorite stocks, polymictic conglomerate, and felsic ash-flow tuffs of the upper volcanic series. The majority of the project area is underlain by andesite flows, tuffs, and volcaniclastic rocks of the lower volcanic series.

The lower volcanic series remains generally undifferentiated. A volcaniclastic unit distinct from the andesite flows exists in the Texcalama and Cinco de Mayo areas and an andesite lithic lapilli tuff exists in the footwall of the El Creston structural zone. Granodioritic stocks intrude the andesites and are exposed at surface in the footwall of the El Creston structural zone and the El Rey mine area.

The andesites and granodiorite are overlain by a basal polymictic conglomerate unit that is tens of meters thick and marks the unconformity between the lower and upper volcanic series. Amygdaloidal basalt flows occur locally within the conglomerate unit. In some areas, thin units of ignimbrite were deposited before the conglomerate. Late Tertiary or Quaternary landslides obscure outcrop patterns in the El Creston-El Perdido area and are likely to be present in other areas of steep topography within the project area.

A series of northeast-striking veins that formed within a series of normal faults with subordinate left-lateral displacement hosts the Mineral Resources described in Section 14. The principal, through going veins have a general strike of 045° to 060° and dip between 65° and 80° to the southeast. This vein set includes Cinco de Mayo, El Catorce, and El Perdido and extends northeastward to Santiago. Other veins with the same orientation include El Rey, Dolores, Tahuehueto, Texcalama, El Espinal, and Tres de Mayo. Within the core area of the Mineral Resources, the El Creston series of veins, striking about 035° and dipping 60° to 80° east, formed in a strongly dilatant zone between the through-going El Perdido and El Rey structures.