Lithium in the Subsoil of Ukraine. Part 2. Mineralogy of Lithium-Bearing Objects: Quartz

Abstract

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.