Résumé
The Shumyliv area includes the Pivdennyi (South) Bouh River around the village of Shumyliv. It belongs to the Haisyn block, which is a constituent part of the Ros-Tikych region of the Ukrainian Shield. The Haisyn block is composed mainly of granitoids, which form a continuous series of rocks from diorite - quartz diorite to amphibole-biotite and biotite granites, which are known under the local name "sobite". Thin felsic dykes occur sporadically and one of them is exposed in the Shumyliv area. The U-Pb monazite age of granite, which is located to the north of the dyke, was previously defined at 2049 +/- 6 Ma and represented a minimum age for the dyke. To determine the age of the felsic dyke, zircon crystals were dated by the U-Pb LA-ICP-MS method; Hf isotope compositions were also analyzed. Zircon was extracted from the granite and plagioclase granite distributed on the left bank of the Pivdennyi Bouh River. The U-Pb age of zircon from both samples of granites is identical within error at 2087.8 +/- 5.3 Ma and 2085.3 +/- 7.3 Ma, respectively. Zircon from both samples yielded similar Hf isotopic composition (weighted average epsilon Hf values are-2.1 +/- 0.3 and-1.7 +/- 0.9, respectively and the felsic crust model age is 2800-2600 Ma). Thus, these granites, which according to their features belong to the tonalite-trondhjemite-granodiorite association, crystallized from magmatic melts formed by melting of the Meso-Neoarchean continental crust.