DIAMONDS OF UKRAINE: RESULTS AND GOALS

Abstract

Diamonds from Ukraine were studied in terms of their separation into their geological and genetic types, distribution and occurrence, the ages of their host rocks, and their nature in Proterozoic and Neogene age sediments. The diamonds are variable in morphology, internal structure, concentration and degree of aggregation of nitrogen centers, carbon isotopes and mineral inclusions. Placer diamonds, primarily from Neogene sands, are anomalous in many respects. They are mostly extremely small, polyhedral, and morphologically diverse showing octahedral, rhombic dodecahedral and cubic forms and they have various colors. In addition to the large heterogeneity in nitrogen concentrations, many diamonds are characterized by a low degree of aggregation of nitrogen centers, which indicates short mantle residence times. Depending on the nitrogen impurity content, the degree of aggregation of nitrogen centers and the possible temperatures of crystallization, several types of diamonds are distinguished in the studied sedimentary placers. According to new isotope-geochemical data, placer diamonds are characterized by a wide range of carbon isotopic composition. This may indicate isotopic inhomogeneity of diamond carbon, different modes of formation and chemical variability in their source regions. Impact diamonds from meteorite craters and Neogene sedimentary deposits of Ukraine are paramorphoses from graphite with similar morphological, isotopic and structural characteristics. The goals of future research of Ukrainian diamonds are discussed.