La Teko plans heap leaching on its Alaska gold property

Heap leach technology is now being applied to gold deposits in Alaska where climatic conditions are not that much different from many parts of Canada. Last year, La Teko Resources completed a test program on its Ryan Lode property eight miles northeast of Fairbanks.

According to J. R. Billingsley, vice-president, the company’s 1987 objective is to recover 13,000 oz of gold by heap leach methods; this would generate a cash flow of $3.7 million(US) after mining costs and royalties.

The Ryan Lode is an intensely fractured, brecciated, shear zone ranging from 20-130 ft in width which has been traced by surface trenching and geophysics for more than 4,000 ft. There are indications it could extend to almost twice that distance.

Drill-indicated reserves are estimated to be 1.9 million tons grading 0.13 oz gold and much higher tonnage but lower grade to depths of 900 ft. Approximately 3,500 tons of material grading 0.115 oz gold was agglomerated and heap leached last year.

The company produced 301.6 oz gold and the recovery rate was 73.5%. When leaching operations were concluded they were recovering 2-2.5 oz gold per day, suggesting that actual recoveries would have been higher — possibly even 80%.

La Teko expects to be leaching 0.2 oz material in the first few years and mining costs should be low because they don’t have to drill and blast.Those costs are expected to average $10-$12 per ton.

The company decided to agglomerate because it was concerned about the permeability of the material. Agglomeration speeds up recoveries which is important when the leach season is limited. Cyanide might be added at the agglomeration stage to speed things up further, he notes. The operating season for leaching is five months but they have a 12-month season for mining.

Last October 750 ft of the shear zone was stripped and sampled in preparation for 1987 production which will begin this April. Thirty six trenches were cut across the shear zone and samples taken every five feet along the trenches. In one area, 50,160 tons averaging 0.26 oz gold was located to a depth of 30 ft. By extending the boundaries, 70,200 tons grading 0.21 oz was available, he adds.

A carbon recovery test plant has been installed on the property which could be expanded to a full production facility. Conventional milling was tried by the previous operator and Mr Billingsley says the recoveries were comparable to heap leaching. Chester Millar, president of Glamis Gold, is chairman of La Teko. Glamis runs a successful gold heap leach operation in California.

La Teko has applied for a permit to run a heap leach test on its San Juan property in California. Drill- indicated reserves are estimated to be one million tons grading 0.04 oz gold to 100 ft in depth. The company expects a favorable reply within 60 days.