Corriente cuts new copper at Mirador (September 08, 2003)

Drilling by Corriente Resources (CTQ-T) has uncovered a new zone of high-grade copper mineralization about 3 km to the northwest of its Mirador copper-gold deposit in southeastern Ecuador.

Two angled holes collared on the northwest geochemical soil anomaly cut an enriched copper zone beneath a 75-metre-thick leached cap.

Hole MN-3 returned 12 metres (from 110 metres below surface) grading 1.5% copper and 0.1 gram gold per tonne. The subsequent 176.7 metres of primary mineralization graded 0.35% copper and 0.1 gram gold.

Hole MN-4, drilled in the opposite direction from the same platform, yielded 10 metres (from 120 metres) running 1.5% copper and 0.2 gram gold, followed immediately by 120 metres of primary mineralization averaging 0.4% copper and 0.2 gram gold.

The enriched copper intersections (comprising chalcocite mineralization) are about 100 metres apart and remain open in all directions. Follow-up drilling will aim to outline the size of the new zone.

Meanwhile, two angled holes collared on the southeast soil anomaly cut typical Mirador-style mineralization

Hole MN-1 returned 298 metres (from 24 metres) averaging 0.5% copper and 0.1 gram gold, including 18 metres (from 89 metres) of 0.8% copper and 0.1 gram gold. Hole MN-2, drilled in the opposite direction from the same spot, cut 143 metres averaging 0.6% copper and 0.1 gram gold.

Corriente believes the holes suggest the presence of a new porphyry system separate from the Mirador deposit. The zone remains open in all directions and additional drilling is planned.

The latest holes are part of an ongoing prefeasibility study at Mirador. The company says the high-grade discovery may significantly improve Mirador’s economics, and could impact on the design of the project’s proposed tailings storage facilities.

Recent metallurgical test work on representative drill core samples from Mirador by Japan’s Sumitomo Metal Mining indicates:

— copper recovery of up to 92% can be obtained via rougher flotation followed by regrinding and cleaning;

— copper concentrate is devoid of any deleterious elements, and can grade more than 30% copper; and

— there is a moderate power requirement for grinding of 15.4 kWh per tonne.

Earlier this year, Corriente tabled an independent study of a proposed, scaled-down 20,000-tonne-per-day operation at Mirador. A previous mining plan called for a 50,000-tonne-per-day operation (T.N.M., Mar. 17-23/03).

The smaller operation generates a pre-tax net present value of US$153 million and a pre-tax internal rate of return of 30%, based on a copper price of US80 per lb. and a gold price of US$325 per oz.

Total capital cost are pegged at US$134 million, including a conventional flotation plant and semi-autogenous-grinding mill. Corriente hopes the reduced capital costs will attract a broader base of potential partners.

Mining would focus on an inferred resource of 98 million tonnes grading 0.78% copper and 0.22 gram gold per tonne in the northern portion of the deposit. Total resources at Mirador stand at 182 million tonnes grading 0.76% copper and 0.22 gram gold.

Corriente is currently studying the economics of contract mining, copper concentrate transport and port operations at Mirador. The company is also looking at its options for funding a subsequent feasibility study.

Shares in Corriente jumped 13 to $1.28 in late-afternoon trading following the news on Sept. 2.