Open AccessU-Pb geochronology by zircon of fine-grained granite of the Osnitsky complex. (Volinsky megablok US)
Author(s) -
O.B. Vysotsky,
L.M. Stepanyuk,
Т.I. Dovbush,
N.O. Kovalenko
Publication year - 2020
Publication title -
geohìmìâ ta rudoutvorennâ
Language(s) - English
Resource type - Journals
eISSN - 2617-3395
pISSN - 2224-6487
DOI - 10.15407/gof.2020.41.083
Subject(s) - zircon , geology , geochemistry , geochronology , uranium , quartz , precambrian , shield , petrology , paleontology , materials science , metallurgy
The article presents the results of uranium-lead dating of zircon from fine-grained granite of the Osnytsia block of the Volyn megablock of the Ukrainian Shield. The variety of granites of the Osnitsky complex is manifested starting from their appearance. They are dominated by massive medium-grained rocks, limitedly developed fine-grained, even less common coarse-grained varieties. The age of typical Osnitsky granites, determined by the uranium-lead method according to zircon, is 1980-1950 million years. Granitoids after gabbroids were formed, and their rooting took place in two stages. At the first stage, depending on the physicochemical and tectonic conditions, a whole range of acid rocks was formed – from leptitelike (fine-grained) to large-medium-grained granites. In the second stage, coarse-grained, typical Osnitsky granites took root. One of the most characteristic macroscopic features of Osnitsky granites is that quartz is almost always represented by lilac-gray rounded grains. According to the results of uranium-lead isotope dating, the age of zircon from fine-grained granite is 1973.6 ± 8.4 million years, and 14 ± 24 million years, according to the lower. The weighted average value of the isotopic age in the isotope ratio 207Pb/206Pb is 1969.3 ± 6 million years. The obtained age for zircon from fine-grained granite of the Osnitsky complex corresponds to the time of formation of granites of the Osnitsky block.