Mineralogical Journal

21-40

Authors: T.M. Lupashko, A.N. Tarashchan, K.O. Ilchenko, E.E. Grechanovskaya

A study was carried out in order to identify the aspects of geochemical processes occurring during the formation of green and light-blue amazonite crystals. Green, light-blue and greenish-blue amazonites from rare-metals deposits of Ukraine (Perzhanske, Ukrainian Shield), rf (Gora Parusna, Ploskogirske, Kola Peninsula; Orlovske, Western Transbaikalia), and USA (Rutherford, Virginia) were investigated using X-ray luminescence (XRL), infrared (IR) spectroscopy and X-ray diffraction. The rock-forming microcline from the Perzhanske, Orlovske and Katuginske (rf) deposits was also studied. It was found that the multi-colored crystals of amazonite have similar degrees of Si/Al ordering. They are represented by the maximum microcline with 2t1 = 0.959-1.0. The various samples only differ significantly in their lead contents that range between 2000 and 10000 ppm in green amazonite and 200 ppm in light-blue colored crystals. Differences between untreated crystals and those annealed in air (1173 K) or under a stream of He (923 K) samples were observed in terms of the composition, ratio of optically active centers and oxygen-hydrogen defects. Their composition and concentration in the untreated natural crystals reflect the genesis conditions of parent rocks, and, first of all, the redox and fO2 conditions of water-containing fluids, which affect the isomorphism of plumbum in the structures of the green and light-blue crystals, mechanisms of crystal chemical compensation of Pb2+ ions and correlates with different degree of ferum oxidation (Fe3+ → Fe2+). Changes in redox and fO2 parameters of the mineral-forming fluid are the most important factors affecting the activity and acid-base properties in the residual water fluids, the process of reduction following 2H2O + 2e– → H2 + 2OH– or oxidation via 2H2O – 4e– → O2 + 4H+. A complex combination of these factors allows the formation of certain nanosized defects in the structures of the amazonite crystals. These include impurity ([Pb2+ – Pb+]3+) and impurity-vacancy (Pb2+ – VK) clusters that serve as chromophore centers for green and light-blue color, respectively.

50-58

Authors: A.L. Larikov, O.V. Zaiats, M.M. Bagmut

The electronic paramagnetic resonance spectra of microfractions of microcline, plagioclase and albite from the Ruska Polyana granites of the Korsun-Novomyrhorod pluton located in the Ukrainian Shield were measured. The results are used together with chemical and X-ray fluorescence analyzes to study the nature of Fe and Mn in the feldspars. It is shown that structural Fe3+ in the microcline and plagioclase reflect the iron content in the melt during crystallization of the granite. At the same time, nonstructural impurities of Fe3+ and Mn2+ in the feldspar monofractions, which are part of hydroxides and carbonates along grain boundaries, do not show correlations with structural impurities of Fe3+ replacing Al3+ ions in microcline and plagioclase, and presumably reflect postcrystallization processes. The ratio of the intensities of the Fe3+ EPR lines in the spectra of microcline indicates that its ordering temperatures are close to 670 K for all studied samples.

72-82

Authors: V.G. Verkhovtsev, O.G. Musich, Yu.O. Fomin, Yu.M. Demikhov

Prospects for increasing the raw materials resources of uranium ore deposits of the albite formation of the Ingul megablock of the Ukrainian Shield and the possibility of reducing the impact of harmful waste due to the method of bacterial leaching of metals were considered. Mineral-forming systems of uranium-bearing albitites of the Ukrainian Shield have always been considered as monoelement, exclusively uranium objects. However, their out-of-balance ores and tailings contain elevated, up to industrial, concentrations of other metals, which, under conditions of hypergenic processes, pose a potential threat of environmental pollution. In order to determine the possibility of expanding raw materials resources of albite deposits of the Ukrainian Shield due to the use of the method of bacterial leaching of metals, the composition of industrial ores and host rocks was considered. In particular, our data from their mineralogical and geochemical research showed that uranium and five of its companion elements: thorium, vanadium, beryllium, zirconium and lead reach industrial content. At the same time, cobalt, nickel and zinc are characterized by an increased content close to the minimum industrial values. The most promising for bacterial leaching are rocks that contain sulfides. The rocks of the uranium ore albitite formation contain sulfur-containing compounds and, in particular, pyrite, as well as bi- and trivalent iron. We found the highest content of sulfides in albitized rocks (up to 0.82%), ore-free albitites (up to 0.81%), low-ore albitites (up to 0.61%), that is, in rocks accumulated in industrial waste. It is assumed that the use of bacterial leaching methods with the participation of chemolithotrophic microorganisms can be promising for the processing of off-balance ores and will contribute to the expansion of the raw material base of albite deposits of the Ukrainian Shield, due not only to uranium, but also to nickel, cobalt and zinc.

95-109

Authors: V.M. Kvasnytsya

The diamond mineralogy from a number of different non-kimberlitic occurrences of the world was analyzed and a comparison to diamonds from Neogene placers of Ukraine was made. Diamonds from lamprophyres of the Canadian Shield, metakomatiites of the Guiana and West African Shields, and ultra-metamorphic rocks in Asian, European and African continental occurrences were considered. In general, Ukrainian Neogene placer diamonds have many similar mineralogical features to diamonds from lamprophyres and metakomatiites, which differ little from diamonds from kimberlites and lamproites. Ukrainian placer diamonds are characterized by their micron sizes (≤0.5 mm), many of them are colored and have a cubic habit and nitrogen-free compositions, relatively frequent spectral Ib and Iаb types, and orange photoluminescence behavior. In addition, many diamonds are characterized by a relatively high content of hydrocarbons (i.e., CH2, CH3 groups and bonds >C=CH2), OH groups, also C=O, N-H, CO3, NO3-groups. This is evidence for a volatile-rich environment during the diamond crystallization. The formation of diamonds from lamprophyres and metakomatiites, as well as from kimberlites and lamproites, occurred under mantle temperatures and pressures. The relatively recently discovered diamond-bearing lamprophyres and metakomatiites have a number of similarities. They are: i) both formed on the edges of Archean cratonic structures, ii) their old ages (2.7 billion years ago and 1.83 billion years ago for the lamprophyres and 2.2 billion years ago for the metakomatiites), iii) both are strongly metamorphosed, iv) both contain many fragments of rocks of various origins, v) both contain rare xenograins of mantle minerals having diamond-bearing peridotite and eclogite associations, and vi) the diamonds themselves are often microcrystals and many are colored and have a cubic habit. The main difference between diamonds from the lamprophyres and metakomatiites is in their carbon isotopic signatures and their thermal history in the mantle. This is expressed by their different nitrogen contents and the different degree of its aggregation. Diamond-bearing ultrametamorphic rocks are mainly Paleozoic-Mesozoic in age (i.e., 531-92 million years) and occupy a tectonic setting at convergent plate boundaries unlike diamond-bearing lamprophyres and metakomatiites. Diamonds from ultrametamorphic rocks differ from diamonds from lamprophyres and metakomatiites as well as from Ukrainian placer diamonds from Neogene sands in a number of ways.