| The discovery of microdiamonds from bulk samples obtained from three Proterozoic lamprophyre dikes (dated 1.85-1.83 Ga) in the Gibson-MacQuoid Lake Belt (GMLB) has determined a potential diamond association with lamprophyric hosts. This is the first recorded region in the Churchill Province known to contain a rich concentration of microdiamonds in a host other than kimberlite or lamproite. The diamondiferous lamprophyre dikes are ultrapotassic with high K;Bulk sampling has indicated the microdiamonds to be colour-variable consisting of pink, red, orange, blue, black, yellow-brown, and predominantly yellow-green stones (N-bearing) that are consistent with their absorption in the infrared spectrum by association of defect centres. Microdiamonds obtained form the Akluilak dike display a mixed type Ib-IaA signature (20-50% aggregated type IaA) with a stronger type Ib component rare in natural diamond. Nitrogen concentration in the diamonds is extreme, ranging from 900 to 5400 ppm, which are among the highest ever recorded in natural diamond. The microdiamonds nucleated at stable low temperatures (850-950... |
