LATE PALEOZOIC ALKALI-GRANITOID MAGMATISM OF SOUTHERN KAZAKHSTAN AND ITS ROLE IN THE FORMATION OF THE ORE-BEARING VOLCANIC STRUCTURES OF KENDYCTAS-CHU-ILI-BETPAK-DALA URANIUM ORE PROVINCE

Abstract

Areas of distribution of alkaline granitoids in southernKazakhstanhave been identified, most of which are located within the Kendyktas-Chu-Ili-Betpakdalin uranium-bearing province, traditionally considered as Late Devonian-early Carboniferous. Arguments in favor of late Paleozoic age of alkaline rocks have been given. The proximity of the petrographic composition, petrochemical and geochemical features of the alkaline granites of the Chu-Ili-West-Balkhash area and late Paleozoic alkaline granites of the Zailiysky area has been established, confirming their age and continental rift origin. Similarity in the development of magmatism and hydrothermal mineralization of ore-bearing volcanic structures of the Chui area (Kurmanshitinskoe) and North-Western Chingiz (Ulkentuz and Dostar) has been revealed. In these structures, Devonian volcanic rocks are interspersed with subvolcanic bodies of comendites and later dikes of microgabbrodiorites and microdiorites. The hydrothermal mineralization of these structures took place in multiple stages. The early stage includes secondary quartzites, which developed in Devonian volcanogenic rocks. Comendite is associated with K-feldspated and albitized rocks, as well as with zones of rare-metal (Zr, Nb, Th, U and TR) Fe-Mg metasomatites that originated in the middle stage. In the later stage, after the introduction of microgabbrodiorite dikes, berezites with U-Mo mineralization formed. Comendites in the structures of the North-Western Chingiz break through the deposits D2-3 and D3-C1 and are considered to be the comagmatic alkaline granites of the neighboring late Paleozoic massifs (Tleumbet and Kuyrektykol). The noted similarity may also indicate that the Chui area comendites are likely to be dated to the late Paleozoic age. Examples have been given to the superposition of berezites and U-Mo mineralization on the late Paleozoic granosyenites, which are widespread in the Kurdai volcanic structure, as well as on the alkaline granites of Karasai volcanic structure. Their age may also be late Paleozoic. Additional research has been recommended for the final conclusions on the age of alkaline rocks and uranium mineralization.