Minefinders ups Dolores resource (October 23, 2000)

A new resource estimate for the Dolores deposit in Mexico’s Chihuahua state shows that the Main zone hosts about 3.2 million oz. gold and 165 million oz. silver.

Using results from 230 holes and a cutoff grade of 0.3 gram gold-equivalent, Minefinders (MFL-T) estimates that the total resource is 100.1 million tonnes grading 0.76 gram gold and 40.3 grams silver per tonne. However, extending mineralization 200 metres beyond the chosen bottom of 1,250 metres boosts the total by 750,000 oz. gold and 37 million oz. silver.

All gold assays were capped at 30 grams and all silver assays at 1,000 grams. Various cutoff grades were also employed, with the highest (5 grams gold-equivalent) resulting in a volume of 3.6 million tonnes grading 5.24 grams gold and 256.7 grams silver.

Minefinders notes that 60% of the Main zone and more than 80% of the resource within a planned open pit now fall in the measured and indicated category. For the measured category, a 30-by-22.5-by-15-metre search ellipse was used; these spacings were doubled and quadrupled, respectively, in order to estimate indicated and inferred material.

The most recent open-pit design comprises 27.8 million tonnes of oxidized material grading 0.85 gram gold and 14.8 million tonnes of sulphides grading 3.78 grams gold. The stripping ratio is projected to be 3.3-to-1.

The Dolores property covers more than 400 sq. km of the Sierra Madre Occidental, near the Sonora-state border. Between 1906 and 1929, the area yielded about 300,000 oz. gold and 14 million oz. silver to local miners; however, it has seen little in the way of modern exploration.

In 1993, Minefinders acquired an option to earn a 100% interest in the property, following which it discovered a northwesterly trending zone of mineralization extending for at least 4,000 metres along strike. Since then, more than 61,000 metres have been sunk, including 56 holes by Echo Bay Mines (ECO-T) during a short-lived period in which it held an option to earn a 60% interest.

Gold-silver mineralization is associated with north-trending latite dykes along a contact between interbedded andesites and an agglomeratic tuff horizon. The Dolores zone itself is described as a low-sulphidation deposit with gold mineralization related to brecciation and stockwork-veined volcanics.

Minefinders notes that more infill drilling is required to advance the open-pit portion of the deposit to the feasibility stage. Similarly, more drilling is required to confirm the extent and grades of the deeper mineralization.