MINING IN CHILE — Ivan project near production startup

The Ivan copper project in northern Chile is scheduled for startup in the second half of 1994, reports Minera Rayrock (TSE).

Situated 40 km northeast of the seaport of Antofagasta, the operation is expected to produce 22 million lb. (9.9 million kg) per year at a cash cost of about US59 cents per lb.

The capital cost of US$31.9 million is made up of debt financing of about US$15 million and equity funding of about US$17 million. Current reserves are estimated to last at least 10 years.

The project consists of 85 sq. km of registered exploitation claims (including claims that were in the process of being registered earlier this year) and about 97 sq. km of exploration claims. Minera has been negotiating to acquire (for shares) a net smelter return royalty relating to the project. Three deposits have been identified: Ivan, Zar and Emperatriz. The company describes these as lying “within a 250-km belt of Jurassic volcanic rocks of La Negra formation paralleling the northern Chilean coast.” They are, moreover, “structurally controlled and are often associated with steeply dipping breccia-fault zones or flat-lying mantos.”

Ivan, which will be mostly mined from underground, consists of high-grade copper sulphide (chalcocite and bornite) within a breccia, partially overlain by a copper oxide zone.

The Zar and Emperatriz copper oxide (atacamite and chrysocolla) deposits will be mined by open-pit methods.

A leaching process is proposed for both types of ore — the oxides with sulphuric acid and the sulphides with bacterially assisted sulphuric acid. The oxide and leaching solutions will be kept separate up an electrowinning stage.

A “minable” reserve of 4.6 million tonnes averaging 2.5% copper breaks down into the following:

n Underground reserves at Ivan total 934,700 tonnes at 4.6% sulphide ore and 937,000 tonnes at 1.7% oxide ore; the open-pit reserves at Ivan total 311,800 tonnes at 1.4% oxide ore

n Open-pit reserves at Zar total almost 1.9 million tonnes at 2.1% oxide ore n Open-pit reserves at Emperatriz total 471,600 tonnes at 1.8% oxide ore. The company also reports additional possible reserves of 323,000 tonnes at 1.4% oxide ore and 210,500 tonnes at 2.7% sulphide ore. The three deposits remain open at depth.

Zar will provide the initial production, with mining going underground at Ivan early in 1995. The high-grade sulphides are expected to last until 1998 and lower the average operating cost to US56 cents per lb. during the first five years of the project.

The company is confident of uncovering additional reserves on the Ivan property.

Elsewhere in Chile, Minera Rayrock continues to explore its Sierra Valenzuela copper project, 40 km northeast of Ivan. Also, the company recently began drilling at its Farellon and Vaquillas projects.