Reconnaissance program led to Ulu gold discovery

Diamonds are not the only mineral commodity of interest to BHP Minerals Canada in Canada’s richly endowed Northwest Territories.

For the past several years, the company has been actively exploring its Ulu gold property located about 530 km north-northeast of Yellowknife, and about 20 km north of the Arctic circle.

Ulu is a grassroots exploration discovery staked in 1988 as part of the company’s ongoing Slave Gold Reconnaissance program. From a geologic standpoint, the deposit lies in the High Lake volcanic belt within the Archean-aged Slave Structural province, a highly prospective region which also hosts a number of previously discovered gold and base metal deposits. Although no reserve estimate has ever been made public, Ulu is thought to rank high among the list of significant gold discoveries made in the North in recent years. The most commonly related rumor has the deposit as over two million tons grading about 0.5-0.6 oz. gold per ton.

The genesis of the Ulu gold discovery goes back to 1985 when Neil leNobel, manager of the company’s Vancouver office, and former senior consulting geologist, George Cargill, perceived the potential for undiscovered major deposits in the Northwest Territories’ Precambrian shield area. That same year, leNobel retained geological consultant Ted Trueman to evaluate exploration opportunities and discovery potential for gold and massive sulphide deposits. Trueman quickly confirmed BHP’s perceptions of the region as having very high potential.

In late August of 1985, Vancouver staff geologist Harry Muntanion was assigned responsibility for the Slave project, and accompanied Trueman to initiate the field program.

Muntanion and his staff undertook comprehensive data compilation, now an ongoing process in the winter months. Reconnaissance is an annual program, with an emphasis on acquisition of prospective ground.

But it was not until 1988 that the first Ulu claims were staked. In June of the following year, contract employee Eugene Flood (who joined BHP staff in June of 1992) located the gold anomaly over what was later named the Flood zone deposit.

Even more claims were staked, and a comprehensive program of mapping, sampling and geophysics was completed before a short drilling program began in 1989.

The Flood zone — with a surface strike length of 400 metres, with near surface thickness ranging from 2-5 metres, but increasing to 6-12 metres at the 240-metre and 320-metre levels — is believed to be the result of brittle-ductile failure.

The deposit is within tholeiitic basalts, and is proximal to a north-trending fold axis. The supracrustal basalts and included sequence of gabbro sills and biotite schist form an embayment into a nearby granite batholith. Feldspar porphyry dykes cross-cut the volcanic-sediment package.

Drilling continued each year, with this year’s program marking the fourth summer drill program. BHP said the goal of its current program is to establish a reserve base “of sufficient size to render the project economically viable”.

Indications are the company may be close to this goal. During the past several years, as part of its overall program, BHP has carried out a comprehensive environmental program of water quality analysis, weather data compilation, and wildlife surveys at the project site.