Vancouver Re-analysis of low-to-mid grade core samples from the Dolores project in Mexico has increased the silver grades by 36.3% for owner Minefinders (MFL-T).
The boosted assay results are based on total digestion analysis of samples taken from mineralized drill intercepts, compared to the previously reported aqua-regia digestion analytical results. Some intervals containing abundant silver-halide minerals increased in grade by more than 100%. Hole D98-114 saw its silver grade jump 132% to 102.1 grams silver per tonne over 16.2 metres from 156 metres down-hole.
The junior re-analyzed 560 oxide samples resulting in a jump of 61.2% to 41.7 grams silver, from the previously reported 25.9 grams silver. Some 492 re-analyzed samples of mixed oxide-sulphide ore resulted in a 22.4% jump in silver values to 35.3 grams, from the previously posted 28.8 grams. The re-assay of 277 sulphide samples showed a 12.9% increase in silver grades to 28.6 grams, from 25.3 grams.
The revised assay data results in an overall higher silver grade for the deposit causing an increase in the total resource. The projected impact of higher silver grades on the current Dolores mine model is an increase in silver production, lower strip ratios, reduced production cost per oz. and accelerated cash flows.
Located in Chihuahua state, the Dolores gold-silver project is Minefinders main asset. An updated model of the Dolores open pit, based on gold and silver prices of US$300 and US$5 per oz., respectively, indicates the presence of 67.2 million tonnes grading 0.96 gram gold and 53.6 grams silver per tonne at a stripping ratio of 4.2-to-1. This is equivalent to 2.1 million contained ounces gold and 115.8 million contained ounces silver.
Minefinders has proposed processing the higher-grade mineralization (23.4 million tonnes grading 2.09 grams gold and 124.5 grams silver), representing about 35% of the open-pit resource, through a mill grinding circuit. The residual pulp would then be agglomerated with lower-grade material for standard heap-leach processing. Tests by McClelland Laboratories of Sparks, Nev., projects overall recoveries of 86-89% for gold and 57-65% for silver.
A mine life of 13 years would result in annual production of 138,359 oz. gold and 6.3 million oz. silver, or 242,900 oz. gold-equivalent, at an estimated cash cost of US$149 per oz. and a total cost of US$184 per oz. gold-equivalent. Capital costs are pegged at US$77 million.
Additional infill drilling and engineering work will be required to upgrade the open-pit model to the final feasibility stage. Minefinders believes there is good potential for expanding the project’s overall resource with further drilling beneath the pit and along strike.
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