At its wholly optioned Mina Rica property in western Colombia, Sur American Gold (SUR-A) has launched a drill program with the intention of testing the potential for low-to-medium-grade bulk-tonnage gold mineralization.
The 460-ha property is near Quinchia, a town in the department of Risaralda, which lies in the Cordillera Occidental (eastern range of the Andes). Mina Rica has been mined sporadically since the Spanish colonial era.
Mineralization typically occurs in the form of stockworks and disseminations in an argillically altered sequence of volcanic agglomerates, breccias and tuffs of Mio-Pliocene age. Advanced argillic alteration covers an area measuring at least 1,000 by 500 metres, with a vertical extent of 300 metres.
Sur American acquired an option to buy the Mina Rica property in May 1995.
The company has since collected 1,500 soil samples, of which 750 were assayed in a Canadian laboratory. Anomalous values of gold were recorded over most of the altered area, with numbers as high as 12 grams gold per tonne. A 200-by-50-metre area is said to have averaged 5 grams.
Scores of abandoned tunnels cut the altered area. While most have collapsed and are inaccessible, the company has managed to sample 18 tunnels over an average distance of 10 metres. Grades along the tunnel walls ranged from 0.11 to 21 grams gold and averaged 3.95 grams.
Sur American says the tunnels were driven in stockwork and disseminated mineralization, and not along structures.
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Geophysics
Geophysical work defined a coinciding, moderate-to-high resistivity anomaly over an area measuring 1,000 by 800 metres. A moderate-to-strong induced-polarization anomaly measuring 600 by 500 metres coincides with the southern portion of the resistivity anomaly.
Drilling began in September on the southeastern portion of the northwest-southeast-trending anomalous zone. The first hole encountered highly altered volcanic agglomerate interspersed with 18 metres of unmineralized andesite over the first 60.9 metres of drill core. The altered agglomerate contained one to two per cent disseminated pyrite, as well as pyrite-filled fractures, and averaged a grade of 1.7 grams gold over a total of 42.9 metres, including a 7.5-metre interval averaging 8.24 grams at a downhole depth of 11.4 to 18.9 metres.
At a depth of 60.9 metres, the hole passed into the same unaltered and unmineralized andesite, where it continued for the next 200 metres.
With up to 10 holes planned, Sur America has added a second rig to the property in order to speed up the drilling program.
All core samples are being cut into two halves with a diamond saw, with half being retained for future reference and the other half crushed to 3/8 inches and split in the company’s laboratory in Quinchia. A representative 300-gram sample is being shipped to Canada for independent analysis.
The Mina Rica property is one of six projects controlled by the company in the Marmato trend, a highly mineralized belt of porphyry and epithermal gold-silver deposits.
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Gavia
Sur American is continuing negotiations to obtain approval from the local population to begin drilling on the wholly optioned Gavia gold project, 10 km north of Mina Rica, in the west-central department of Caldas.
About half of the 250-ha property lies on an indigenous reservation. The company has proposed a joint-venture arrangement in which the local population would have a 10% carried interest in the two projects, as well as the Loma Guerrero project.
Sur American has requested that the Colombian government convene a committee to approve the drilling.
Intense sericitic and argillic alteration is outlined in the Gavia and Vende Cabezas zones. The rocks are totally bleached and are characterized by a striking yellow-white color, attributable to oxidation and leaching of the sulphides.
Coinciding soil gold anomalies measure 1,000 by 500 metres for the Gavia zone and 900 by 400 metres for Vende Cabezas. Values exceeding 1 gram gold per tonne are common in both anomalies. Chip sampling in a 300-by-200-metre area of the Gavia zone averaged 7 grams gold.
Sampling of 20 abandoned tunnels returned grades ranging from 0.5 to 313 grams. The main Gavia mine tunnel averaged 4.2 grams over 40 metres.
Preliminary metallurgical testwork on an 80-kg waste dump sample, recovered from the Gavia tunnel, indicated an overall gold recovery of 92% (16.7% by gravity concentration, and 75.2% over 48 hours by cyanidation).
Sur American has 17.6 million shares outstanding (24.5 million fully diluted) and about $1.7 million in working capital.
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