MINERALIZATION

 

Buriticá is the northernmost significant deposit in the upper Miocene Middle Cauca belt, one of the three major gold belts identified in Colombia. The belt contains porphyry and vein style mineralization in addition to the porphyry-related carbonate base metal gold vein/breccia system seen at Buriticá. Numerous gold systems are developed along the 300 km belt and all appear to be related to relatively small, high level intrusions of intermediate composition.

 

Three potentially economicstyles of mineralization are developed within the Buriticá project area, high grade veins, mineralized intrusive breccias, and replacement mineralization. In the Yaragua mine area both high grade veins and mineralized breccias occur. Replacement mineralization has been identified on the contact between the volcanoclastic sequence and the Buriticá complex. The mineralization at San Augustin and La Mano fall into this type. Details of the Buriticá geological setting are described in the presentation New High Grade Gold discoveries in the Buriticá District, Antioquia, Colombia presented at Mineral Exploration Roundup in Vancouver, January 2010.

 

Mineralization at Buriticá is a porphyry-related carbonate base metal gold vein/breccia system. The veins in these systems typically have characteristics intermediate between classic epithermal and mesothermal veins and they are developed at vertical levels above the porphyry horizon but below the epithermal range. Mineralogically they are characterized by free gold and small amounts of sphalerite (Zn), galena (Pb), and chalcopyrite (Cu) in a carbonate-quartz gangue. They can have economic vertical extents in excess of one kilometer. Breccias in these systems typically have similar mineralogical characteristics to the veins. The main difference between Buriticá and the idealized system is the lack of known porphyry-style Au-Cu mineralization and the telescoping of the veins down into the horizon of porphyry-style alteration.

 

The sequence of geologic events involved in the mineralization process at Buriticá appears to be:

• Emplacement of the Buriticá complex in upper Tertiary time
• Formation of a system of ENE-trending fractures
• Zoned, porphyry-style alteration affecting the entire complex
• Emplacement of the intrusive breccias with associated retrograde silica-sericite alteration controlled by the pre-existing fracture system
• Reactivation of the ENE fractures and Phase 1 gold-base metal mineralization in the breccias and veins
• Initiation of N-S faulting
• Phase 2 native gold, stibnite mineralization superimposed on Phase 1 veins