La Buena Project
| Location: | Northern Zacatecas, Mexico, 4km North of Goldcorp's La Negra/Noche Buena resource area, 9km North of the Peñasquito mine, 1.5km west of the Dia Bras Las Coloradas resource area |
| Area: | Three concessions, approximately 8,500 hectares |
| Minerals: | Gold, Silver and Base Metals |
| Status: | No drilling, past artisanal mining |
| Ownership: | 100% |
History:
There are at least 2 different areas on the property where artisanal mining occurred and it was done from surface cuts, shallow stopes and is mainly exploratory in nature. Kennecott staked a concession over the zone of metasediments that occurs in the northwest part of the concession in 1998, but the concession was abandoned shortly thereafter and declared open ground in November 2002. Golden Minerals (Minera de Las Cordilleras) staked much of the ground that comprises the La Buena project and received title to the concession in June 2007. Their exploration effort consisted of limited reconnaissance rock-chip sampling. San Marco acquired the Golden Minerals concessions in 2010.
Property Geology:
Shallow alluvium covers nearly half of La Buena property, however where outcrop exists, Caracol Formation (mainly calcareous siltstones) dominates the property geology. The same shelf carbonates that host ore in the Zuloaga, Noche Buena, and Providencia districts are found at the north end of La Buena property along the hinge-line of an east‑west anticline that forms a prominent ridge called the Sierra de Zuloaga. Subvolcanic pyrite‑rich monzonitic intrusives occur a few kilometers to the south of the ridge, forming a halo of metasediments in the local Caracol Formation that San Marco refers to as the Julia zone. The Julia zone is situated along the axis of an east-west syncline that is overturned to the north.
Mineralization:
On La Buena property, prospect pits and shallow workings have been found on chimneys and mantos in reef limestones, as well as along structures in metasediments and Tertiary intermediate subvolcanics. The Cupido Formation hosts the chimney-style mineralization. Within the Julia zone, gold of economic interest occurs as disseminations in Caracol Formation metasediments as well as subvolcanics. Soil sampling in the Julia zone returned anomalous values (between 50 and 665ppb gold) over an area of roughly 1km by 1km. Limited sampling of the dumps and workings found on La Buena property have returned gold assays as high as 5.56 g/t gold. Intrusive and sub-volcanic rocks are associated with ore throughout the Concepción del Oro district.
