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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: Phase I Drill Program completed
Ownership: 100% (Subject to a sliding scale NSR royalty to Golden Minerals)

Exeter Resource Corporation fulfilled its first year option obligations by expending $1.4 million in 2013 and drilling just under 2,000 metres in four holes. Having elected to withdraw from the option, San Marco will begin to entertain site visits and data review by other interested parties to joint venture the project.
Project Highlights:
  • The La Buena property is next door to one of Mexico's largest open pit mines - Goldcorp's Peñasquito Mine
  • La Buena property hosts a similar geological environment to Peñasquito and Camino Rojo
  • Detailed geological mapping, ground magnetometer surveys, IP surveys & surface geochemistry resulted in multiple drill targets
  • The Phase 1 drill program comprised just under 2,000 metres over four drill holes
  • The first two holes were drilled in the Julia zone, where geology, geochemistry and geophysics identified highly prospective targets. The holes were designed to intersect highly altered calcareous siltstone / sandstone Caracol Formation known to host several mineral deposits in the area including the nearby Penasquito mine. Drill hole LBD 13-02 produced promising results with the mineralization being consistent with surface trenching
  • A gravity survey was also recommended to augment the data set. Since approximately half of the property is overlain by alluvium, the gravity survey is a useful tool in identifying important indicators associated with stockwork, breccia pipe, disseminated and skarn mineralizing systems. Results outlined several additional targets where gravity lows were coincidental to or adjacent to chargeability highs around the Julia zone and at the Las Crucitas zone, 4 km to the east
  • The third and fourth holes drilled in late Q4 2013, tested two of these targets. LBD 13-03 located just south of the Julia zone ridge, was terminated at 340m and appears to have been stopped short of an intense I.P. chargeability high. The hole has been cased to allow for the possibility of deepening this hole at a later date. LBD 13-04, collared approximately 200m to the west of LBD13-02 targeting a gravity low which appears to be related to a north-south fault system with minimal mineralization
  • Both the mineralization confirmed by drilling and the geophysical signatures from the gravity survey continue to demonstrate the same characteristics of other deposits in the area

Action Plan:
  • Delineate additional targets as identified from the recently completed gravity survey to the south of the Julia Zone and to the east in the Las Crucitas Zone
  • Continue to build the model that supports the similarities of other deposits in the area based on geological, geophysical and geochemical work completed to date
  • Commence site visits and data review by interested JV parties, which could lead to their funding of ongoing exploration activities in 2014


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.


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.

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