The Lipnyazka massif is located in the Dobrovelychkivsky district of the Kirovohrad region, v. Lipnyazka and further south. Structurally, it is located within the Bratskyy Synclinorium of the Ingul megablock and coincides with the Mikhailovsky anticline. The main petrotype of the massif rocks are porphyry-like granites, often with a gneiss-like texture, aplito-pegmatoid, pegmatoid granites and pegmatites. The latter most often form secant vein bodies. Uranium-lead isotopic dating of granitoids of the Lipnyazka granite massif has been performed, with which a number of deposits and ore occurrences of rare elements, primarily lithium, are spatially and probably genetically connected. The age of porphyry-like granites (2032 ± 6 million years), which is the main petrotype of rocks distributed in the area of the village of Limestone and pegmatoid granites (2027 ± 1 million years), which cut porphyry-like in the form of vein bodies. Aplithoid framed granites (2046 ± 8 million years old), common in the area of the mouth of the Sukhyi Tashlyk River (Dobryanka village), are somewhat older. Based on the results of determining the isotopic composition of strontium in the accessory apatite of granites, a conclusion was made about the upper crust source of granites of the Lipnyazka massif (87Sr/86Sr – 0.730-0.785).
LA-ICP-MS method was applied to investigate U-Pb and Lu-Hf isotope systematics of zircon crystals from charnockitic 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.
New results of mineralogic-petrographical and ore-geochemical research on Li-pegmatites and host rocks of Stankuvatka and Polokhivka ore fields of western part of Inhul megablock of the Ukrainian Shield are presented. Petrographic characteristics of host rocks, such as granites, metapelites, metabasites and ultrabasites are described. Aplite-pegmatoid granites related to Li-pegmatites have been dated as 2026-2042 Ma by means of U-Pb isotopic analysis of monazites. Li-pegmatites were formed during two stages: 1) magmatic, when formation of oreless quartz-albite-microcline pegmatites happened; 2) hydothermal-metasomatic, when residual fluid rich in rare elements affects previously formed minerals; it is reflected in presence of several generations of Li-bearing and rock-forming minerals. Initial magma was peraluminous, depleted with mafic components, and with water deficit. Albite was a first mineral crystallized in researched pegmatites. Then albite+quartz were crystallized. Then at the end microcline+quartz were formed in the central part of pegmatite veins. Petalite and spodumene were formed at the final hydrothermal-metasomatic stage. Practical importance of ores with secondary mineralization mainly presented with petalite and spodumene has been defined. Petalite ore type of Polokhivka deposit and petalite-spodumene mixed ore type of Stankuvatka deposit have a crucial role. Microprobe chemical analysis of accessory mineralization presented with triphylite, montebrasite, and other Lithium phosphates has been carried out. These minerals were detected in pegmatites and in metasomatically altered host rocks. They can be reliable criteria during geological exploration of Lithium at other locations of Shpola-Tashlyk ore district.
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