Cominco Res. active in Latin America

One of the more active foreign mining companies in Latin America is Cominco Resources International (TSE). It has copper projects in Mexico and Chile, a wollastonite project in Mexico, a gold property in Honduras and gold and zinc-lead properties in Bolivia.

The company’s 49% owned Maria high-grade copper mine and concentrator is situated 8 km northwest of Cananea in northern Mexico. In 1991, the mine produced 138,000 tonnes of ore grading 13% copper, most of which was sold or toll-milled. The concentrator, which cost $7.1 million, was commissioned late in the fourth quarter.

At year-end, minable reserves of high-grade ore were 330,000 tonnes grading 12.8% copper, 0.25% molybdenum and 62 grams silver per tonne. In addition, there are 390,000 tonnes of low-grade ore containing 1.8% copper and 0.67% molybdenum. The mine is expected to continue production utilizing the low-grade copper-molybdenum ore after the high-grade ore is mined-out in late 1993.

The Quebrada Blanca project in northern Chile is designed to produce 75,000 tonnes (165 million lb.) per year of low-cost cathode copper for 14 years, using a heap-leaching and solvent extraction-electrowinning (SX-EW) process. Copper produced at Quebrada Blanca will be in cathode form and will not be subject to smelter treatment charges.

Project construction costs are estimated to be US$300 million (1991 dollars). Construction is expected to take about 2.5 years, with copper production commencing in 1994. At full production, the operation will process 17,400 tonnes of enriched copper ore per day.

Ore will be crushed to minus one-quarter inch and agglomerated before being placed on the leach pads. Copper will then be leached from the ore and recovered in the SX-EW plant in the form of high-purity copper cathodes. The cathodes will be trucked about 250 km to the port of Iquique and shipped to customers. Teck (TSE) has agreed to acquire a 32.5% interest in the project from Cominco Resources.

No on-site work was done in 1991 at the Mariquita copper project in Mexico, but the pre-feasibility study completed in 1990 was re-assessed using operating experience gained from the nearby Maria mine and metallurgical experience gained at Quebrada Blanca in Chile, the company says. This update continues to suggest that the Mariquita copper deposit could be a profitable open pit, solvent extraction and electrowinning operation producing 10,000 tonnes (22 million pounds) of cathode copper per year. From the San Martin project in Mexico, a hand-sorted 60-tonne sample grading 90% wollastonite was shipped to Europe for use in marketing studies. Preliminary results have been encouraging, the company says. Exploration continues in northern Mexico, particularly in the Cananea district of Sonora. The company says additional properties have been acquired that have good potential to host both high-grade copper deposits similar to Maria and porphyry-style copper and gold mineralization.

In Honduras, a total of 900 metres of diamond drilling in 11 holes was completed on the Chaparrales gold property. This work was funded by a joint venture partner which can earn 49% of Cominco Resources’ interest in the property, under an agreement signed in mid-1991.

The drilling identified narrow, discontinuous zones of high-grade gold mineralization within broader zones of low-grade gold mineralization in deeply weathered schists.

In Bolivia, the company has acquired a number of gold and zinc-lead properties during the last few years. In 1991, two separate joint venture agreements were signed which entitled Cominco Resources’ partners to earn a 49% interest in a number of properties.

Drilling is planned on at least five gold properties which have been joint-ventured with an unrelated major Canadian resource company. Regional exploration and property work will be conducted for zinc under a separate joint venture agreement with Cominco Ltd.

Cominco Resources expanded its Chilean exploration group in 1991 and increased its level of activity. The Company’s principal exploration targets continue to be large-tonnage copper deposits and several land positions were acquired in 1991 covering targets in northern and central Chile. Breccia bodies that could host significant copper deposits have been identified on the company’s Bolsico property, located near Copiapo in northern Chile. In 1991, the company’s

100% owned Inca de Oro gold prospect near Copiapo was tested by trenching and limited drilling and more drilling is being considered for 1992. At the San Felipe area properties in the Andes, 100 km northeast of Santiago, a joint venture partner has commenced exploration for porphyry copper deposits. Cominco Resources is not contributing funds to the current exploration program, which will result in the reduction of the company’s ownership of the properties from the current level of 41%.