Noranda, Getty deposit could be Hemlo size

A mere six years have elapsed since news of the fabulous Hemlo discoveries rocked the mining world. Yet details of another gold discovery, which displays geological parameters of Hemlo-size proportions, are being greeted with a relatively quiet response from the mining community.

At Courageous Lake, located 130 miles northeast of Yellowknife, N.W.T., partners Noranda Inc. and Getty Resources are mounting a $6.3 million exploration program which is testing the Tundra gold deposit. More than 90,000 ft of diamond drilling will be completed by the end of August.

The project is immense in terms of both scope and logistics. In preparation for spring break-up, Noranda flew in 13 Hercules aircraft loads of equipment, Reg Comeau, project geologist with Getty, explained to The Northern Miner.

Although official published reserves stand at 1.28 million tons grading 0.28 oz gold per ton, drilling completed to date suggests reserves could be increased to well over 20 million tons of a similar grade. That’s Hemlo size in stature.

The original reserve figure is to a depth of only 400 ft. However, the potential of the massive Main zone, which is more than 600 ft wide and strikes on surface for over 4,000 ft, was revealed in April when a Noranda hole cut strong values from a depth of 1,600 ft (N.M., April 20/87). The excitement at both the Noranda and Getty offices undoubtedly peaked after hole 48 came in six weeks ago. The hole cut the Main zone at a depth of 3,500 ft returning a true width of 32 ft grading 0.19 oz gold per ton.

Results announced this week from deep holes are confirming earlier results. Hole 50 cut multiple mineralized zones of which the best was from 3,056 ft to 3,086 ft. — a 30.5-ft section grading 0.37 oz gold per ton. Included within the section is a narrower 13.1 ft of 0.75 oz gold per ton. Of importance, Noranda says the intersection correlates with results from hole 41 drilled 1,300 ft above it. The latter hole yielded some of the finest results to date from the deposit — 0.26 oz gold per ton across 42.3 ft.

The zone remains open at depth and along strike, according to officials of both companies. This summer’s program is testing a section of the Main zone on 328-ft centres (100 m) to a depth of 2,500 ft and along 4,000 ft of strike, Mr Comeau explained. Upon completion, a preliminary reserve calculation will be performed. This is expected to generate reserves in the possible- inferred catagory as a result of the wide drill spacing.

Gold mineralization is associated with fine disseminations of arsenopyrite in felsic rocks comprising the Main zone. Although the zone is stratabound, gold occurs in multiple sub-parallel zones within the much larger unit. What is remarkable about the deposit is that every hole drilled to date in the zone has assayed gold values. A majority appear to be economic over mineable widths.

An examination by The Northern Miner of a 3-dimensional model of the deposit in Getty’s Toronto office shows a near vertical package of numerous strongly mineralized zones striking north- south. According to Getty offcials, material seperating the defined zones is also mineralized with lower grading rock. The persistence and continuity of the zones across strike and to a depths exceeding 2,000 ft suggest the vertical component could be immense. This has already been proven by hole 48.

In a best case scenario, the partners could outline potential reserves across 4,000 ft of strike, to a depth of 4,000 ft and across a width of more than 30 ft. Parameters like that prompted Walter Nash, Noranda’s exploration manager in Winnipeg to speculate in The Financial Post that the Main zone could host “tens of millions of tons.”

As a result of location, development costs are expected to be higher than in other more accessible parts of Canada. Also, additional costs per ton will result from the arsenopyrite which will have to be roasted in order to free the gold. However, most industry observers feel that economies of scale, which are enjoyed by comparable large tonnage, good grade gold mines, will come into play at the Noranda/Getty deposit — more than offsetting the higher metallurgical costs.

Following an analysis of this year’s drill data and the calculation of a revised reserve figure this fall, the partners will consider an underground exploration program beginning sometime in 1988.