LA–ICP–MS U–Pb DATES FOR DETRITAL ZIRCON FROM QUARTZITES OF THE TEMRYUK FORMATION (NOVOUKRAINKA IRON DEPOSIT OF THE KORSAK BLOCK, WEST AZOV AREA)

The West Azov iron district corresponds to the Korsak synclinorium or block in which iron deposits of the Kamyana Mohyla belt (Pavlivka, Novoukrainka, and Serhiivka areas), Kuksungur, and Korsak Mohyla are located. The iron– bearing units are confined to the metamorphosed volcanogenic–sedimentary rocks of the Satchky Formation of the Central Azov Group, while rocks of the Temryuk Formation form the base of the section. The group is intruded by numerous dykes of pink microcline granites and pegmatites up to 15 to 20 m in thickness. The basement for the group consists of Archean plagioclase granitoids hosting xenoliths of gneisses, crystalline schists, and amphibolites. The iron ores of the Korsak block are characterized by the same rock association and mineral assemblage as those in the Mangush and Orikhovo–Pavlohrad structures. We have conducted geochronological study of metaterrigenous rocks of the Temryuk Formation of the Novoukrainka (Kamyana Mohyla) iron deposit. The iron deposit extends along the western limb of the Korsak synclinorium for ca. 20 km. The prevailing strike of the iron deposit is NW 350°. Metamorphic rocks form separate bodies (lenses) that are continuous along the strike for 1200–1500 m with a maximum thickness of 120– 140 m. Ferruginous quartzites are represented by banded iron formation with interlayers of biotite and biotite–amphibole gneisses (Sachky Formation). Micaceous (biotite, garnet–biotite) quartzites occur in the lower part of the section, where they are interbedded with biotite, muscovite–biotite–sillimanite, biotite–amphibole, and, rarely, pyroxene–garnet–biotite gneisses and schists (Temryuk Formation). Fifty–eight grains of detrital zircon from micaceous quartzite of the Temryuk Formation were dated by LA–ICP–MS. Four crystals were dated at 3.2–3.23 Ga, three more grains have an age of 3.08– 3.11 Ga, thirty–two crystals yielded an age of 2.9–2.97 Ga, fifteen crystals had an age of 2.82–2.87 Ga, and, finally, four grains were dated at 2.76–2.78 Ga. According to the obtained data, metasedimentary rocks of the Central Azov Group, bearing iron–rich units in the Korsak synclinorium of the West Azov area were deposited on the basement with the Mesoarchean (2.9–3.1 Ga) Tonalites–Trondjemites–Granites (TTG). Archean granites with ages of 2.82–2.87 and 2.76– 2.78 Ga as well as the remnants of older TTGs provided a minor contribution from the provenance. The Central Azov Group was intruded by the 2.2 Ga Na–K–rich granites. On the Mesoarchean Azov craton, volcanogenic–sedimentary rocks of the Huliaipole Formation in the Huliaipole brachysyncline and the Vovchansk unit in the Orekhiv–Pavlohrad structure were formed during the same time interval. Deposition of this volcanogenic–sedimentary succession with thick Banded Iron Formations (BIFs) is possibly related to submarine volcanism and marine transgression.