The age of monzonites of the eastern part of the Korsun-Novomirgorod pluton (Ingul megablock of the USh)

Authors

  • E. Shestopalova S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
  • L.M. Stepanyuk Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine, Ukraine
  • T. Dovbush Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine, Ukraine
  • I.N. Kotvitskaya Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine, Ukraine

DOI:

https://doi.org/10.24028/gzh.0203-3100.v37i4.2015.111132

Keywords:

monzonites, zircon, generations, dating, isotopic age, Korsun-Novomirgorod pluton

Abstract

The article presents the results of monzonites research of the eastern part of Korsun-Novomirgorod pluton. The pluton is situated in the northwestern part of the Ingul megablock. Besides basic rocks varieties — gabbro-anorthosite and rapakivi granites the rocks of monzonite composition of different genesis are widely presented here. Small bodies of monzonites form outputs among rapakivi granites of Shpola massif at the junction of tectonic structures of different rank. Monzonite is a hybrid rock which contains xenoliths of frame rock and possibly ancient dyke formations. Zircon is represented by several generations, which are distinguishable by optical studies, as well as by different U / Th ratio. Some grains contain a nuclei and zircon inclusions, appearance of which was determined by the process of contamination. All fractions obtained discordant zircon age values.  Dating calculated by isotope ratio 207Pb / 206Pb has been taken as the most reliable. Due to the presence of relict zircons received isotopic age of the figures are overstated and do not reflect the formation of monzonite. As the maximum possible monzonite age we can take a minimum age, calculated by 207Pb / 206Pb — 1.740 Ma. The assumption about the formation of monzonite melt as a result of contamination of basic magma by ancient crustal rocks of acid composition has been given, which does not contradict the results of the study of the isotopic composition of strontium, neodymium, and geochronological data.

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Published

2015-08-01

How to Cite

Shestopalova, E., Stepanyuk, L., Dovbush, T., & Kotvitskaya, I. (2015). The age of monzonites of the eastern part of the Korsun-Novomirgorod pluton (Ingul megablock of the USh). Geofizicheskiy Zhurnal, 37(4), 114–125. https://doi.org/10.24028/gzh.0203-3100.v37i4.2015.111132

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