Cathodoluminescence spectra of diamonds in UHP rocks from the Kokchetav Massif, Kazakhstan

Abstract

We propose to investigate the diamonds from the Kokchetav Massif, northern Kazakhstan, which is the best example of diamond–eclogite facies metamorphism, using cathodoluminescence (CL) techniques. CL spectra measurements of diamonds from garnet–pyroxene–quartz rocks and dolomitic marbles, made at 80 K, revealed peaks at 2.156, 2.463, and 3.188 eV and a broad band at 2.72–2.80 eV. Panchromatic and monochromatic diamond images analysed by CL reveal concentric zones of variable luminescence. This indicates that the diamond crystals grow during several metamorphic stages under ultra high pressure (UHP) metamorphism conditions. The inhomogeneous broadening and lower 2.156 eV ZPL peak suggests the presence of a higher concentration of defects and stresses in the rim compared to the core.