Falco’s Collahuasi rivals Escondida as top copper find

Recent surface and underground exploration on Falconbridge’s Collahuasi project in northern Chile has uncovered a copper reserve that could rival Escondida, one of the largest copper deposits in the world.

Working high in the Chilean Andes, Falconbridge has outlined a preliminary reserve containing more than one billion tonnes of primary mineralization grading 0.92% copper at the Rosario deposit. Above the primary reserve, which extends to a depth of 600 metres, lies an estimated 50 million tonnes of secondary mineralization grading 1.5% copper.

(Secondary mineralization, including sulphides such as chalcocite and bornite, is the higher-grade, supergene-enriched derivative of primary copper sulphides, namely chalcopyrite.)

About six kilometres east of Rosario, the Ujina prospect is estimated to contain another 100 million tonnes of secondary mineralization grading approximately 2% copper. The deposit forms a flat-lying blanket 160 metres below surface.

And at La Grande, 2.5 km south of Rosario, Falconbridge says recent drill holes have intersected “significant” copper mineralization.

A year ago Falconbridge referred to underground exploration on the project in a review of its 1990 activities.

Shell Chile and Chevron Minera of Chile can each earn a one-third interest in the Collahuasi project by spending US$45 million by 1993.

The Escondida mine, which lies several hundred kilometres south of Collahuasi, is Chile’s second largest copper producer. Discovered in the late 1970s by Getty Oil and the precursor to BHP-Utah International, it hosts proven open pit reserves of 377 million tonnes grading 2.12% copper as of May 31, 1991. The Escondida complex has the capacity to produce up to 360,000 tonnes of contained copper per year.

Exploration drilling and other project activities will continue at Collahuasi throughout 1992. Falconbridge expects to complete a detailed feasibility study within 2-3 years in preparation for large-scale production by 1997.