Mineralogical Journal

16-24

Authors: S.B. Lobach-Zhuchenko, Yu.S. Egorova, S.G. Skublov, V.V. Sukach, O.L. Galankina

An abundance of the trace elements has been determined in olivine of the Achaean spinel-bearing phlogopite harzburgite enclave (sample UR17/2) from the Bug granulite complex of the Ukrainian Shield by SIMS analysis. Major elements were analyzed in the olivine by SEM-EDS and EPMA analysis. The olivine shows a homogeneous chemical composition: MgO — 45.20-45.64 wt.%, FeO — 13.66-14.23 wt.%, with Fo85-86 and Fe/Mn ratio of 68.3-68.6 which corresponds to the ratio of 60-70 in olivine of peridotites. Ni content in the UR17/2 olivine ranges from 4730 to 5612 ppm, which is higher than in olivine from mantle peridotites, high magnesium OIB and Hawaiian picrites. The olivine has average content of Ti — 20.6 ppm, Nb — 0.03 ppm, Zr — 0.32-0.60 ppm, the low total REE (0.1-0.5 ppm). The olivine crystallization temperature, calculated using an Al-in-olivine thermometer, corresponds to ~900 °C. Enrichment in Fe and Ni is the main feature that distinguishes the UR17/2 olivine from other mantle-derived olivine. Composition of the UR17/2 olivine and host harzburgite indicates an influence of T, P, the oxygen fugacity and composition of parent magma on the partition coefficients of Fe and Ni. Composition and structure (degree of polymerization) of magma are the main factors responsible for the olivine enrichment by iron and nickel.

34-50

Authors: L.M. Stepanyuk, L.V. Shumlyanskyy, S.I. Kurylo, V.O. Syomka, S.M. Bondarenko, S.A. Wilde, А.А. Nemchin

LA-ICP-MS method was applied to investigate U-Pb and Lu-Hf isotope systematics of zircon crystals from charno-ckitic gneiss and biotite-garnet-hypersthene enderbite that occur in the lower reaches of the Yatran river (Yatran block of the Bouh river area). According to the obtained isotope data, charnockitic gneiss hosts three zircon populations. The oldest one is represented by three crystals that have isotope age between 3125 and 3300 Ma, and εHf values between –2.3 and –7.5. The next population is well-defined, it has an age of 2038 ± 25 Ma and large variations of Hf isotope composition: 176Hf/177Hf — from 0.28122 to 0.28261, εHf — from –9.3 до 4.6. However, the ages of most of the analyzed zircons spread along the concordia between 2300 and 2800 Ma. All zircons in this population have a similar Hf isotope composition 176Hf/177Hf = 0.28072 to 0.28092, which does not depend on the age. It is characteristic that the oldest (with preserved U-Pb isotope systematics) crystals have positive or slightly negative εHf values. Most of the U-Pb isotope analyses of zircons from enderbite fall on the discordia line that has an upper interception age of 2029 ± 18 Ma. A small number of discordant grains have 207Pb/206Pb ages up to 2500 Ma. Hafnium isotope composition in zircons from enderbite varies widely: 176Hf/177Hf = 0.28131 to 0.28151, and εHf from –6.2 to 1.8.

68-86

Authors: O.Yu. Palkina, O.L. Falkovich

Some important questions concerning the application of methods of searches of diamond deposits on direct search signs — finds of diamonds are considered and indicator minerals of kimberlites (IMK). The probable reasons for the low efficiency of the dressing-mineralogical method in the search for diamond deposits in Ukraine are named. The article is based on materials of research of diamonds found in different age placers of Ukraine (~1300 crystals); diamonds from kimberlites of the Arkhangelsk province (~6000 crystals); diamonds from metamorphic rocks of the Kazakhstan deposit Kumdy-Kol (~200 crystals); Yakut province (~600 crystals from root springs and ~700 from placers). A physiographic description was made for all these crystals and the intensity and color of photoluminescence (PhL) were recorded. For some crystals, about 600 spectra were taken at a temperature of 77 K. For diamonds of the "Dniester" type and some highly defective diamonds from Ukrainian placers, data from Raman spectroscopy are given. The material on indicator minerals of kimberlites is partly the result of our research, partly attracted from literature sources. Finds of diamonds in terrigenous deposits of Ukraine, their territorial and age, possible sources of income are analyzed. The comparison of diamonds from terrigenous deposits of Ukraine with diamonds of indigenous deposits of different genetic type is performed. For comparison, we studied diamonds that were obtained (with their complete removal from the gross technological samples) from some kimberlite pipes of the Arkhangelsk province. We performed a physiographic description and established the particle size distribution and morphological distribution in these pipes. Based on these studies, convincing conclusions were drawn about the signs of the industrial diamond-bearing capacity of kimberlite bodies in this province. The study of a large number of diamonds extracted from Neogene and other placers of Ukraine allowed usto perform a comparative study not only on the morphology and color of photoluminescence but also on the frequency of photoluminescence centers (spectra were taken at 77K). These diamonds were compared with crystals from the industrial kimberlite bodies of the Arkhangelsk and Yakut provinces. It was established which physical properties of Ukrainian diamonds are close to the properties of kimberlite diamonds and how they differ, contrasting features of diamond sets of different genetic types were determined. It has been established that diamonds found in the deposits of the Bilokorovichi world have signs of kimberlite, and the nature of their surfaces, a set of PhL centers, indicates a long stay in sedimentary reservoirs of different ages. A study of diamonds and IMK, which were found on the territory of the Kirovohrad block of the Ukrainian Shield (USh), revealed that the known area of Gruzka has prospects and is worth further mineral and technological testing. The chemical composition of probable IMK from the kimberlite bodies of the Priazovsky block of the USh indicates their non-diamond-bearing or non-industrial diamond-bearing capacity, which is confirmed by a few (3 crystals) finds of natural diamonds. We found that the green microdiamonds extracted from these rocks turned out to be man-made debris. Numerous diamonds from Poltava-Sarmatian placers have specific morphology and physical properties. The source of diamonds from the Black Sea coast is the Poltava-Sarmatian placers, and the source of a few diamonds with kimberlite features has not been found on the coast of the Sea of Azov. Based on the analysis, it is concluded that the territory of Ukraine has clear prospects for the discovery of diamond deposits. Taking into account the current economic feasibility and the current degree of study of the diamond-bearing territory of Ukraine, the primary search for kimberlite sources of diamonds, in the opinion of the authors should be performed in the north-western (Ovruch- Bilokorovytsia) part, as well as within the Dnieper and Kirovograd blocks. In the course of search operations, it is necessary to abandon the analysis of IMC less than 1 mm in size and pay attention mainly to pyropes as the most informative IMC. A prerequisite for further exploration work for diamond deposits should be a large-scale mineralogical and technological test aimed at detecting diamonds with a size of at least 1.0 mm. Limiting the size of the studied fractions will allow not only to reduce costs, but also to determine the feasibility of the search. Only based on the results of these works it will be possible to concludethe prospects of the industrial diamond-bearing capacity of the allocated areas.