L.M. Stepanyuk, URANIUM-LEAD GEOCHRONOLOGY OF TWO-FELDSPAR GRANITES
https://doi.org/10.15407/mineraljournal.43.02.049
UDC 550.93
URANIUM-LEAD GEOCHRONOLOGY OF TWO-FELDSPAR GRANITES OF THE INHUL MEGABLOCK (UKRAINIAN SHIELD) BY MONAZITE
L.M. Stepanyuk, DrSc (Geology), Corresponding Member of NAS of Ukraine, Prof., Deputy Director
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
E-mail: stepaniuk@nas.gov.ua; https://orcid.org/0000-0001-5591-5169
S.I. Kurylo, Science Researcher, Earth Science Institute, Slovak Academy of Sciences
974 01, Banska Bystrica, Slovakia, Ďumbierska, 1
E-mail: kurylo.sergiy@gmail.com; https://orcid.org/0000-0003-4466-6851
O.V. Kovtun, Junior Researcher, Leading Geologist Engineer
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
Ukrainian State Geological Research Institute (UkrSGRI)
78А, Avtozavodska Str., Kyiv, Ukraine, 04114
E-mail: kovtun85@ukr.net; https://orcid.org/0000-0003-0475-8778
T.I. Dovbush, Research Fellow.
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
E-mail: tetyana.dovbush1@gmail.com; https://orcid.org/0000-0002-3512-3313
O.B. Vysotsky, Research Fellow.
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
E-mail: alek.vysotsky@gmail.com; http://orcid.org/0000-0002-3542-4685
Language: Ukrainian
Mineralogical journal 2021, 43 (2): 49-57
Abstract: In the area of the Novooleksandrivka village, the valley of the Bokovenka river crosses a powerful strip of metamorphic rocks of the Inhulo-Inhulets series with numerous small granitoid bodies of the Kirovohrad complex. In the right bank of the river valley north of Novooleksandrivka there are almost continuous rock outcrops of porphyry-like, mostly coarse-grained garnet-biotite granites, which are cut by veins of aplite-pegmatoid and pegmatoid granites. Uranium-lead isotope systems of accessory monazites from porphyry-like granite, layered body of uneven-grained granite and from veined body of aplite-pegmatoid granite have been studied. The age of the first two, more coarse-grained granite varieties, is 2043.2 ± 2.6 and 2041 ± 2.3 million years, respectively. Significantly younger are the monocytes from the vein of aplite-pegmatoid granite - 2030 ± 0.3 million years. In granites in this sequence, in addition to structural and textural characteristics (in general, decrease in grain size), there is a decrease in the amount of SiO2 (from 73.14 to 70.93%) connected with a significant increase in K2O (from 3.96 to 7.58%), (their inverse correlation coefficient is 0.98), a significant decrease in the CaO content from 2.04 to 0.97%, and a slight decrease in the MgO content from 1.14% to 0.82%. These changes are probably caused by the crystallizational differentiation of the original granite melt.
Keywords: uranium-lead geochronology, monazite, two-feldspar granites, Ukrainian Shield.
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