Corriente cuts new copper at Mirador (September 02, 2003)

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

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

Hole MN-3 encountered 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 grade 0.35% copper and 0.1 gram gold.

Hole MN-4, drilled in the opposite direction from the same platform, cut 10 metres (from 120 m) running 1.5% copper and 0.2 gram gold. That was followed by 120 metres (from 130 m) averaging 0.4% copper and 0.2 gram gold.

The enriched copper intersections (chalcocite mineralization) are about 100 metres apart and remain open in all directions. Follow-up drilling aimed at outlining the size of the new zone is planned.

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

Hole MN-1 returned 298 metres (from 24 m) averaging 0.5% copper and 0.1 gram gold, including 18 metres (from 89 m) of 0.8% copper and 0.1 gram gold. Hole MN-2, drilled in the opposite direction, 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 pre-feasibility study at Mirador. The company says the discoveries may improve the project’s economics. It also says the new zones 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% via rougher flotation followed by regrinding and cleaning;
• the copper grade of the concentrate is expected to exceed 30%;
• power requirements for grinding are moderate at 15.4 kWh per tonne; and
• the copper concentrate is devoid of any deleterious elements;

Earlier this year, Corriente tabled an independent study of a proposed, scaled-down 20,000-tonne-per-day operation at Mirador. An earlier model called for a 50,000-tonne-per-day operation. Corriente hopes the reduced capital costs will attract a broader base of potential partners (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 US$325 per oz. of gold. Total capital cost are pegged at US$134 million, including a conventional flotation plant and semi-autogenous-grinding mill.

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 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 were 13, or more than 11% of value, higher at $1.28 in late-afternoon trading following the news on Sept. 2.