Stepanyuk L.M.1, Kurylo S.I.1, Dovbush T.I.1, Ziultsle O.V.1, Syomka V.A.1, Bondarenko S.N.1, Kovalenko N.A.1, Gintov O.B.2, Mychak S.V.2
1 – M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine
2 – S.I. Subbotin Institute of Geophysics of the National Academy of Science of Ukraine
Language: Ukrainian
Geochemistry and ore formation 2018, 39: 24-35
https://doi.org/10.15407/gof.2018.39.024
Uranium-lead isotopic dating is carried out on monazite of crystalline rocks outcropped along sides of the Yatran river valley, from Korzhova to Pokotilovo villages. The monazites of bifeldspar granites show the ages of 2042.7 ± 1.2 Ma for non-altered granite (Davidovka village) and 2036.2 ± 4,7 Ma for tectonized granite (Korzhov village). The uranium-lead isotopic system of monazite of tectonized pegmatitic granite (Dubov village) is more complex than two-stage. It is possibly caused by disturbance of isotopic system closeness due to superposition of tectonic deformations. The largest value (2019.3 Ma) calculated on the 207Pb/206Pb ratio might be treated as the maximum possible age of monazite. Unexpectedly smaller values of age are obtained for monazites of charnockitoids. These are 2014.6 ± 4.5 Ma for plagiocharnokite and 2037.9 ± 1.3 Ma for enderbitegneiss (gneissic charnokite) of Peregonovka village (open pit) as well as 2028.8 ± 2.8 Ma for garnet-bearing enderbitegneiss (garnet-bearing enderbite) of Pokotilovo village. Likewise the cataclized pegmatitic granite (Dubov village) uraniumlead isotopic system of monazite of enderbitegneiss (diorite-charnokite) of Lebedinka village is more complex than two-stage. The largest value (1998.9 Ma) calculated on 207Pb/206Pb ration might be treated as the maximum possible age of this monazite. It is most likely caused by tectonic deformations. Some delay (more later start) of monazite crystallization in small xenoliths of crystalloschists which are present in the sample is not improbable.
Keywords: Yatran block, monazite, uranium-lead isotopic age, granite, charnockitoids.
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