Cathodoluminescence Properties of CO2-Bearing and CO2-Free Diamonds from the George Creek K1 Kimberlite Dike

Abstract

The cathodoluminescence (CL) properties of diamonds from the George Creek Kl kimberlite dike are discussed with reference to their complex growth, mantle residence, and deformation histories. Diamonds shown by infrared (IR) spectrometry to contain submicroscopic, highpressure CO2 inclusions are characterized by anomalous CL colors such as pink, pale violet, orange, and brown, instead of the blue colors typically exhibited by CO2-free diamonds. Complex intergrowth relationships between CO2-bearing and CO2-free diamond-growth generations are recognized from CL photomicrographs of CO2-bearing diamonds. CO2-free diamonds commonly exhibit octahedral growth zonation, and growth-sector zonation was identified in a single diamond of cubo-octahedral morphology. The distribution of platelets that form during prolonged mantle residence time is related to initial nitrogen concentration and thus is influenced strongly by growth zonation. The extreme heterogeneity and complex growth history of the George Creek diamonds...