Reserves understated at Noranda/Getty bet

With 24-hour darkness drawing closer by the day and a frigid arctic air mass biting at their heels, Noranda Exploration and Getty Resources are expanding a potentially mega-size gold deposit underneath the barren sub-arctic tundra.

The discovery occurs in a structural setting that is similar to the Timmins camp in Ontario.

Mining analysts, investment brokers, and media representatives had a chance to visit the Tundra project on an N.W.T.-government sponsored tour which included visits to several advanced-stage projects. Representing approximately one- third of Canada’s land mass, the exploration potential of the Northwest Territories has barely been scratched for a number of reasons including the exceptionally high cost of exploring there.

But successes like Echo Bay Mines have shown it’s possible to develop mines in the north and make money — lots of it.

The Noranda-Getty deposit (without including any mining dilution) grades about 70% of Echo Bay’s present mill heads which now average 0.4 oz gold per ton. Published reserves at Tundra are 1.28 million tons grading 0.28 oz gold (cut) but that reserve is definitely understated, The Northern Miner can say unequivocally after visiting the property.

The deepest published intercept to date occurred at 3,500 ft where 32 ft of mineralization was returned grading 0.19 oz gold per ton (N.M., July 6/87) which will have a considerable impact on reserves.

But Noranda conceded that the four zones reach at least 4,000 ft although the sub zones might not go that far.

Noranda geologists told The Northern Miner the gold mineralization occurs in a major shear structure with arsenopyrite and quartz flooding. The mineralization is “fairly consistent down dip” and every hole in the latest program encountered gold, they noted. Drill spacing is quite wide and is currently around 325 ft in the 400 ft upper portion of the discovery. But this will be tightened up later. Noranda is trying to extend the mineralization to depth and core widths generally reach up to 25 ft, they say, adding that the “zones come and go but the signature is always there.”

There are four main zones with sub-zones included in the over-all package. Not all the zones carry from surface to depth and the package has been traced by drilling for about 4,000 ft along the north-south axis and about 400 ft east to west. Noranda said that about 63,000 ft of drilling was completed from September, 1986, to July, 1987.

Four drills are currently operating on the property which is now being remapped to tie everything together; the relogging of early drill holes is also under way.

About 8-9 holes remain to be drilled and Noranda confirmed that another shear zone has been discovered which appears to trend towards the now dormant Salmita mine property of Giant Yellowknife Mines. The gold in what Noranda designates as the Carbonate zone seems more free and not as closely associated with arsenopyrite. This is located west of the main zone. The bulk of the gold mineralization at Tundra occurs with arsenopyrite which has filled microfractures within a sericite shear zone. The arsenic content ranges from trace to 10-15% at times and the higher grades are associated closely with quartz flooding. Deposit refractory

The deposit is obviously refractory and would require roasting, pressure oxidation, or possibly bioleaching to make the gold amenable to cyanida tion. This will be a major consideration in project economics so grade and reserves (which will determine mill throughput) will be extremely important. The higher the better in each of these cases. Part of the deposit might be open pitable at a low strip ratio which would be a major plus. So would the discovery of a higher grade underground zone which could be used to justify a shaft sinking program and allow optimization of gold production during the critical early years. (Echo Bay did this at Lupin).

The metallurgical characteristics of the Tundra deposit are probably comparable to Giant Yellowknife’s Red 24 deposit which is located about 600 ft south of Noranda’s most southerly drill hole. Salmita achieved maximum recoveries of 65% from the Red 24 zone but bioleaching has yielded recoveries of 90% utilizing a 10-ton test plant. Whether these recoveries can be duplicated on a large scale basis is still unknown.

Incidentally water problems at Salmita prevented the exploitation of high grade reserves at depth which has some implications for Tundra as well. The mineralization at both properties involves a structural control (shear) which below permafrost led to heavy water inflows at Salmita from nearby lakes. All these problems are solvable but they impact on feasibility.

To date, about $8-$10 million has been spent on the gold aspect of the Tundra play, said Noranda, which also noted that 28 miles of ground was held along the Courageous Lake belt. Drilling at Tundra will go into October and possibly November, Noranda added. After that program is completed drill- inferred reserves will be calculated. Noranda has a 51% interest in the property and Getty 49%.