The Buriticá deposits are classified as intermediate sulphidation epithermal using the terminology of Sillitoe and of Hedenquist (in Simmons et al, 2005). Corbett and Leach (1997) recognized a specific sub-class of low sulphidation epithermal deposits with high base metal contents and carbonatebearing gangue, which they named CBM association. Although such mineralization is perhaps better described as “base metal carbonate sulphide-rich”, and may occur over depth extents much larger than many low sulphidation epithermals, the Buriticá systems are referred to as the CBM association.

Mineralization at Buriticá is a porphyry related, carbonate base metal (CBM) gold vein/breccia system. High-grade precious metal mineralization in CBM systems may occur over substantial vertical intervals, to well in excess of a kilometre, from the porphyry level to below the shallow epithermal range. Compared to low sulphidation epithermal styles CBM mineralization is sulphide-rich, with abundant pyrite ± pyrrhotite + sphalerite + galena along with minor sulfosalts, chalcopyrite and quartz-carbonate gangue mineralogy. Gold in CBM systems may be free-milling or refractory. Mineralization in CBM systems typically comprises sheeted veins, stockworks and mineralogically similar breccias with some fracture-related dissemination in wallrocks.

CBM systems are widespread in circum-Pacific magmatic arcs, and include the supergiant Porgera deposits in Papua New Guinea (25 million ounce ........

Three underground mining methods were selected for Buriticá; longhole open stoping (LHOS), cut & fill (C&F), and shrinkage stoping. Mining method selection was driven primarily by geomechanical rock quality, vein geometry, depth, proximity to old workings, stope margin and vein continuity. Unless geomechanical and geometry characteristics required either C&F or shrinkage, longhole mining was the preferred mining method due to higher productivities and lower mining costs compared to either C&F or shrinkage.

There are two vein systems that will be exploited in the Buriticá mine: Yaraguá and the Veta Sur.

The Yaraguá system generally strikes to the east, and has been drill intersected over 1,125 m along strike and 1,540 m vertically. There are several veins within the system that strike to the northwest, intersecting the east-striking veins. Vein strike lengths vary from 50 to 1,100 m and vein dip distances vary from 50 to 1,300 m. The Veta Sur system strikes to the Northeast, and has been drill intersected over 1,140 m along strike and 1,600 m vertically. Vein strike lengths vary from 70 to 1,000 m, and vein dip distances vary from 150 to 1,350 m.

Cemented backfill will be used to fill stope voids to provide confinement on the waste rock pillars in the hanging wall and footwall between parallel stopes spaced close together, and as the fill develops strength, to reduce lateral loads on these pillars. This is an important aspect when mining close ........

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