GEOCHEMISTRY AND GENESIS OF CARBONADO FROM YAKUTIAN DIAMOND DEPOSITS

Abstract

Three samples of cryptocrystalline diamond aggregates (carbonado) from Yakutian deposits were determined, with the use of analytical transmission electron microscopy, to contain micron-sized inclusions of native Fe, Cr, and Ni, rutile, sphalerite, pentlandite, muscovite, zircon, zircon-xenotime solid solution and aggregates, and epigenetic inclusions of anatase, florencite, kaolinite, and goethite. Neutron activation analysis of the samples indicates that the carbonado samples have LREE-dominated chondrite-normalized REE patterns, which are typical of kimberlites. ESR spectroscopic techniques revealed that the samples are characterized by PI paramagnetic (single nitrogen atoms) and W15 (nitrogen atoms and vacancies) centers and defects responsible for absorption bands with g ∼ 4. The detected geochemical signatures of the carbonado correspond to its kimberlite provenance. The genesis of carbonado and the systematics of polycrystalline diamond aggregates are discussed.