The second part of the publication "Lithium in the subsoil of Ukraine" highlights the mineralogy of rock-forming quartz from lithium-bearing objects of Ukraine: chamber pegmatites of the Korosten pluton, Perzhansky ore district, rare-metal granites and pegmatites of the Azov region, rare-metal pegmatites of the Inhulsky megablock, hydrothermalites of the Nagolny Ridge (Donetsk basin). In all these objects, quartz is characterized mostly from the point of view of its typomorphic value. The conclusion was as follows: the habit of quartz crystals has a typomorphic value, but cannot be described for all genetic situations by one simple scheme of the evolution of simple forms; so the main typomorphic information is "hidden" in the middle of quartz crystals. Point defects of its crystal structure are of greatest importance, primarily Al-O– centers and hydrogen defects, which are the most common in the mineral. They are best studied in crystals of chambered pegmatites and hydrothermal veins of the Nagolny ridge. The dependence of these defects on the action of external factors has been clarified. In particular, in chambered pegmatites, in contrast to crystal-bearing veins, a paradox occurs: with a decrease in the temperature of quartz growth, which is accompanied by an increase in the concentration (activity) of Li in the environment of mineralization, the number of lithium-hydrogen defects in the late zones of quartz decreases. It is assumed that in productive pegmatites this is due to the competing action of lithium micas — the main Li absorbers, the role of which increased with a decrease in the temperature of the solutions and an increase in their pH. In the quartz of rare-metal pegmatites, a high concentration of Al-Li centers has been established, which reaches a maximum in the quartz of the central zones and is therefore a criterion for the degree of differentiation of pegmatites. The luminescent properties of quartz from the petalite pegmatites of the Inhulsky megablock, caused by superimposed metasomatic processes and metamorphism, are unusual.
The structural properties and composition of metamict minerals, namely allanite, chevkinite, and britholite, occurring as inclusions in allanite from feldspar syenites of the Velyka Vyska massif (Korsun-Novomyrgorod pluton, Ukrainian Shield) were investigated by X-ray diffraction and electron probe microanalysis (EPMA). The age of the syenites is 1.7-1.8 Ga, which corresponds to their formation ages within the Ukrainian Shield. X-ray analysis shows that of the original samples of chevkinite and allanite give a broad diffraction peak between 16—28° 2Θ as well as Bragg reflections in the region of the most intense reflections of semimetamict allanite and britholite, indicating the metamict state of chevkinite and the semimetamict state of allanite. The content of radioactive Th found in the chevkinite (0.25-0.33 apfu) is higher compared to its amount in allanite (0.024-0.033 apfu). Calculated unit-cell parameters of the chevkinite and allanite samples showed that their structures underwent significant changes after annealing. There is a slight distortion of the chevkinite unit cell related to a decrease in the a and an increase in b and c edges. A decrease in b and the increase in c in the allanite is caused by a redistribution of cations in the structure and an oxidation of iron, Fe2+ → Fe3+, during heating. Thereby the stability of the allanite structure decreases and it ultimately breaks down. The structural sites A and A2 in chevkinite and allanite are mainly occupied by REEs of the cerium group. The amount of Y is minor. The substitution mechanism А2(REE)3+ + М3М2+ → А2Са2+ + М3М3+(allanite) and M2Fe3+ + M3,4Ti4+↔ M2Fe2+ + M3,4Nb5+ (chevkinite) occur. The M2 site in the structure of chevkinite and M3 in allanite contain more Fe2+ than Fe3+. This leads to a weakening of the bonds in their structures, and a stepwise breakdown and partial or total metamictization of their structures. The britholite inclusions in allanite belong to the Y variety. They were probably formed much later than allanite and chevkinite in the Velyka Vyska massif. According to the EPMA results, namely BSE-images and REE content determinations, allanite and chevkinite formed almost simultaneously.
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