Cominco participates in Chile gold deposit

VANCOUVER — In its second production decision this year, Cominco Resources International will participate in the development of the Marte gold deposit in north- central Chile. The project falls within a 135-sq-mile block of concessions held under a joint venture agreement between Cominco Resources and Anglo American Chile. Construction is scheduled to begin in early 1988 and full production should commence by mid- 1989, says Cominco Resources, which has a 25.6% interest in the venture. The 8,000-ton-per-day heap leach operation should produce 95,000 oz of gold annually at full production. Mineable reserves are estimated to be 27 million tons grading 0.045 oz with a 1.2:1 strip ratio.

The concessions were acquired in 1981 following a reconnaissance program for epithermal gold-silver deposits by the joint venture and a consulting firm. An extensive zone of altered volcanic rocks was surface sampled and later drilled. A bulk sample for metallurgical test work was generated from an 850-ft- long adit and satisfactory recoveries were indicated by the work.

The joint venture concluded last year that a profitable open pit mining operation was viable if sufficient reserves grading 0.04 oz gold could be developed. This conclusion was based on a recovery rate of 60% and a production rate of 3.8 million tons annually. Ore will be crushed to — 3/8 in and capital costs are estimated at $30 million-$40 million depending on whether the joint venture uses a mine contractor or not.

Cominco Resources notes that exploration work on the nearby Lobo deposit will be resumed in early 1988 where previous drilling suggested at least eight million tons at a similar grade. These reserves are still open to expansion and they appear to be heap leachable. Assuming this to be the case, the project would be integrated into the Marte development. Cominco Resources has a 50% interest in the Lobo deposit.

The company has also announced plans to develop its Maria copper deposit in the state of Sonora, Mexico, which it discovered. Empresas Frisco, a large Mexican mining company, can earn a 51% interest in the project by providing the $4.8 million capital required to bring the mine into production.

Reserves are estimated to be 850,000 tons grading approximately 10% copper, 0.26% molybdenum and 1.6 oz silver per ton. This zone lies horizontally about 300 ft below surface and is immediately underlain by further indicated reserves of 950,000 tons grading 1.8% copper, 0.44% molybdenum and 0.3 oz silver.