| Abstrakt: |
Rare-metal granite pegmatites of the lithium-cesium-tantalum (LCT) type are widely distributed in Early Precambrian Greenstone belts worldwide, including the Canadian and Australian shields. However, the Middle Dnipro Granite-Greenstone region, which includes a lot of greenstone belts such as Sura, Verkhivtseve, Konka, Sofiivka, Chortomlyk, etc., remains insufficiently studied in terms of these pegmatites. This article presents previously unpublished data on the pegmatites of the Sura and Verkhivtseve greenstone structures or belts, obtained through a meticulous study, analysis, and reinterpretation of repository and archive materials. It reveals their geological-structural setting, distribution limits, mineralogical and geochemical characteristics, and their connection with granite complexes and massifs. Furthermore, the article outlines the prospects for rare-metal mineralization in these pegmatites. Pegmatites within the Sura greenstone structures or belts were discovered on its northern flank within the Karnaukhivka synclinal branch, associated with the ultramafic massif of the same name. Over 60 pegmatite veins were encountered during the 1961 exploration for silicate nickel, with most veins intruding serpentinized ultrabasites. The extension of the veins aligns with the general extension of the Karnaukhivka ultramafic massif, and their average length ranges from 150 to 250 m. The majority of the pegmatite bodies likely dip subvertically and exhibit a zonal structure comprising aplite, multi-grained granite, pegmatoid, blocky quartz, and microcline. The northwestern part of the Sura greenstone structures or belts presents a promising Pravda-Karnaukhivka pegmatite field. The Verkhivtseve greenstone stroctures or belts displays a complex block structure, suggesting the presence of deeply eroded pegmatite-bearing blocks. Isolated bodies of pegmatites have been found on the southeastern flank of the structure, primarily within the Shmakove branch and its surrounding granitoids. A series of pegmatite and aplite veins with anomalous contents of rare metals and rare earth elements are localized in plagiogranites of Sura, granites of Demuryne, and plagiomigmatites of Dnipropetrovsk complexes. The highest niobium content of 0.048% and tantalum content of 0.005% were determined in drill-hole 0151. These pegmatite-bearing greenstone formations in the Shmakove branch and the associated granitoids are designated as the Hrushivka-Rudytsynske pegmatite field. Specialized prospecting for rare-metal mineralization associated with pegmatites within the Pravda-Karnaukhivka and Hrushivka-Rudytsynske pegmatite fields is recommended. [ABSTRACT FROM AUTHOR] |
