BHP, Northern Orion find copper-gold-moly resource in Argentina

After only one year of exploration, the Agua Rica project in the Argentine province of Catamarca is emerging as a copper-gold-molybdenum deposit of immense proportion.

The property is held under option by a joint-venture between BHP Minerals, with a 70% interest, and a fully owned subsidiary of Northern Orion Explorations (VSE), which holds 30%.

With 39 holes drilled to date in the Mi Vida and Trampeadero areas (representing 14,500 metres), the geological resource is estimated at 1.2 billion tonnes grading 0.51% copper and 0.028% molybdenum, plus 0.22 gram gold per tonne.

The estimate includes an enriched zone containing 284 million tonnes grading 0.72% copper, 0.028% moly and 0.29 gram gold. An overlying, leached cap is estimated to host 77 million tonnes grading 0.41 gram gold.

The drilled area represents less than 25% of an alteration zone measuring 7.5 sq. km. To date, drilling has tested an area encompassing 2,000 metres east to west, up to 1,000 metres north to south, and as deep as 600 metres below surface. Mineralization remains open in all directions. At Aqua Rica, a metasediment basement of Precambrian rocks is intruded by a series of Tertiary age, andesite feldspar porphyrys and associated breccias. Sulphide mineralization occurs in the porphyrys and, to a lesser extent, in the breccias and wall rocks of the metasediments.

Until the middle of last year, BHP had focused its drilling on the Mi Vida area. However, the building of a road in the Trampeadero area exposed an intrusive porphyry that had been obscured by the metasediments. BHP tested the area with hole 18, which returned a 60-metre interval grading 2.16% copper and 0.028% moly, plus 0.14 gram gold per tonne. Recent drilling at Trampeadero on a 200-300-metre grid yielded 118 metres grading 1.06% copper, 0.25 gram gold and 0.028% moly for hole 32, and 368 metres grading 1.02% copper, 0.26 gram gold and 0.125% moly for hole 38.

At Mi Vida and Trameadero, mineralization occurs in three principal layers: an overlying, leached cap depleted in copper; an enriched zone of copper averaging 100 metres thick; and an underlying zone of primary copper mineralization.

Anomalous geochemical copper values are outlined at Agua Rica over a surface area measuring 4,000 metres north to south by 3,500 metres east to west. The highest copper values are associated not only with the Mi Vida and Trameadero areas, but with two other targets not yet drill-tested — the Melcho and Morro Alumbrera.

The areas were previously mapped as metasediments, but road construction has resulted in the discovery of new porphyry bodies. A third new target area, the Misterioso, lies outside the alteration zone but nevertheless contains significant values.

It is anticipated that four drill rigs will be turning at Agua Rica during the year. Infill and stepout drilling on the Mi Vida and Trampeadero areas will continue, as will road construction and drill-testing of the new target areas. Northern Orion is targeting a final feasibility study for completion by the end of 1997.

Northern Orion, which has 69.4 million shares outstanding on a fully diluted basis, is 54.8%-owned by Miramar Mining (TSE).