While conducting work towards a final feasibility study on the Mantua copper project in Cuba, 50% owner Miramar Mining (TSE) identified three previously unrecognized forms of gold mineralization.
One of the showings is within the copper deposit; a second is within a gossan overlying the deposit; and a third is within a shear zone parallel to the copper deposit.
The Mantua solvent extraction-electrowinning project contains a potentially open-pit resource of 3.9 million tonnes grading 3.47% copper. The project is expected to produce in the order of 18 million kg (40 million lb.) of copper per year at an average cash cost of US40 cents per lb.
While extracting a 500-tonne bulk sample for pilot mill testing, the companies encountered a shear zone parallel to the copper deposit. The shear contains disseminated pyrite over a width of 96.7 metres, and assays from a 75.8-metre section of the shear returned an average grade of 0.94 grams gold and 1.52 grams silver per tonne.
The true width of the shear is estimated at 55-60 metres and the strike length can be traced for a distance of more than 5,000 metres. Miramar sees good potential in identifying additional shear zones in the area, and the joint venture has increased its holdings in the area to 85 sq. km from 22 sq. km.
An exploration program is under way, including airborne geophysics and ground work to identify and evaluate the gold potential of the district. In addition to the shear zone, a zone of gold-mineralized gossan was identified during a 13-hole drill program in 1993.
Six of the holes were collared in a gossan, with results ranging from 0.51 grams gold and 4.63 grams silver over 4 metres up to 3.32 grams gold and 9.72 grams silver over 28.3 metres.
Miramar estimates the size of the gossan overlying the deposit at about 6.3 million tonnes, about 4.5 million tonnes of which fall within the current proposed pit limits.
An initial program of 34 holes is under way to test the gossan zone. Gold was also identified in the Mantua copper deposit itself when drill core from 1993 was recently re-assayed. The average grade of gold and silver mineralization within the copper deposit is estimated at more than 0.2 grams gold and 3 grams silver.
The joint venture expects to complete a feasibility study on the Mantua copper deposit and overlying gossan zone by June, 1995.
Results from the six holes on the gossan zone are as follows: Hole Interval Width Gold Silver
(m) (m) (g/tonne) (g/tonne)
93-1 0-38.4 38.4 0.65 6.12
93-4 0-28.3 28.3 3.32 9.72
93-5 0-33.0 33.0 0.84 6.86
93-6 0-15.0 15.0 0.76 6.20
93-7 0-10.3 10.3 0.37 8.54
93-11 0-4.00 4.0 0.51 4.63
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