Gahcho Kue reveals dykes

Drilling by the Canadian exploration division of De Beers has encountered kimberlite intersections on the Kelvin and Faraday bodies, north of the Kennady Lake cluster, at the Gahcho Kue joint venture in the Northwest Territories.

The bodies, which are 3 km apart, appear to be associated with northeast-southwest-oriented kimberlite dyke systems that pinch and swell, resulting in thicker blowouts. Prior to drilling, De Beers carried out ground gravity and magnetic surveys.

The Kelvin and Faraday bodies are, respectivley, 9 and 12 km northeast of the Kennady Lake cluster, which includes the highly prospective 5034 and Hearne kimberlite pipes.

The Gahcho Kue project is held 51% by De Beers, 44.1% by Mountain Province Diamonds (MPV-T) and 4.9% by Camphor Ventures (CFV-V). As operator, De Beers can boost its interest to 60% by advancing the project to commercial production, leaving Mountain Province with a 36% stake and Camphor with 4%. The partners are awaiting the results of diamond valuations for the 5034 and Hearne pipes, along with an updated study of the Gahcho Kue project.

The Kelvin kimberlite was discovered in the spring of 2000. One drill hole aimed in a north-south direction under a narrow lake intersected 40 metres (estimated true width) of kimberlite, while a second, drilled in an east-west direction, cut 23 metres of kimberlite. A 2.3-metre-thick kimberlite dyke was previously intersected at a depth of 31 metres about 300 metres south-southwest of the Kelvin body under the same narrow body of water.

Kelvin was initially considered a low priority, owing to its limited size, and De Beers held off on analyzing core from the two discovery holes until last year. In total, 446 microdiamonds were recovered from 184 kg of sample from Kelvin, including nine larger stones caught between a 1-mm and 2-mm square mesh size and five diamonds exceeding a 2-mm square mesh classification.

The number of diamonds recovered and their size-frequency distribution are reportedly similar to the microdiamond counts for the 5034 and Hearne pipes. Those latter pipes have average grades of 1.64 and 1.71 carats per tonne, respectively.

This spring, De Beers completed five holes in the Kelvin area. All but one intersected kimberlite over intervals ranging from 2.4 to 25 metres estimated true width.

De Beers also drilled two holes in the Faraday area. Faraday was originally discovered in 1999. An angle hole had intersected 34 metres of kimberlite at a down-hole depth of 38-72 metres, for a true width of 23.1 metres. A 40-kg sample from the original Faraday discovery hole returned a previously reported 74 microdiamonds, including a single stone exceeding a 2-mm square mesh size.

Follow-up drilling in 1999 intersected 21 metres (or 15.5 metres true width) at a distance of 40 metres from the discovery hole. Another hole intercepted 2.5 metres of kimberlite about 160 metres northeast of the Faraday body, and a hole in 2001 cut three narrow intercepts of kimberlite, the thickest being 1.7 metres, about 600 metres to the southwest. It was suspected that the kimberlite intercepts north and south of the Faraday body were part of an extensive kimberlite dyke system. This spring, De Beers drilled two target areas along the interpreted dyke structure, intercepting 5.6 metres of kimberlite (estimated true width) about 100 metres southwest of the Faraday body, and 21.5 metres of kimberlite (estimated true width), 520 metres to the southwest.

Mountain Province President Jan Vandersande says drilling to date reveals extensive dyke systems with associated blows or small pipes, such as Kelvin, which appears to be bigger than first thought.

The recovered kimberlite from both Faraday and Kelvin will be sent for petrographic analysis and microdiamond recovery.