De Beers, GGL confirm diamond-bearing nature of Doyle Sill

It took eight years, but De Beers Canada Exploration and GGL Diamond (GGL-V) finally returned to the Doyle Lake sill in 2003 after a federally appointed tribunal upheld an earlier 1996 decision awarding the disputed LA 26-30 claims to the joint venture.

De Beers and GGL discovered the diamond-bearing kimberlite sill through a reverse-circulation drilling program that intersected a narrow, shallow-lying, sill-like body over a strike length of 1.3 km. Kimberlite intercepts ranged from 0.2 to 5.7 metres in thickness. A composite 125.2-kg sample of kimberlite rock-chips from four holes yielded 67 microdiamonds.

Last summer, De Beers drilled 24 core holes along the strike of the sill, further extending its length to 2 km. The company collected 160 kg of kimberlite sample from these drill holes and submitted 84.5 kg to Lakefield Research for microdiamond analysis. Another 10 kg was sent to De Beers’ lab in South Africa for heavy-mineral analysis.

Lakefield recovered 114 microdiamonds at a 0.1-mm square mesh cutoff. All except one microdiamond was recovered by sieves with a 0.3-mm mesh or smaller. The lone exception was a single stone, measuring 1.4 by 1.14 by 0.59 mm, caught by the 0.85-mm screen. A detailed look at the distribution of the microdiamonds is provided in the accompanying table.

The Doyle Lake project is a 60-40 joint venture between De Beers and GGL. The project consists of 30 claims (LA 1-30) totalling 213 sq. km to the south of Gahcho Ku’s Kennady Lake cluster in the Northwest Territories.

DOYLE SILL MICRODIAMOND RESULTS

Sieve Size#Diamonds

+1.18 mm0

+0.850 mm1

+0.600 mm0

+0.425 mm0

+0.300 mm9

+0.212 mm16

+0.150 mm32

+0.100 mm56

Total Diamonds114

Sample Wt.(kg)84.5