O.V. Zaiats, GENESIS OF THE ISKRENE GRANITES OF THE KORSUN-NOVOMYRHOROD PLUTON (UKRAINIAN SHIELD)
https://doi.org/10.15407/mineraljournal.48.02.085
UDC 552.321.1:550.42:549.623.54(477)
GENESIS OF THE ISKRENE GRANITES OF THE
KORSUN-NOVOMYRHOROD PLUTON (UKRAINIAN SHIELD)
O.V. Zaiats 1, PhD (Geology), Research Fellow
E-mail: zaiatsolga7@gmail.com; orcid: 0000-0001-5011-029X
О.М. Ponomarenko 1, DrSc (Geology), Academician of NAS of Ukraine, Director
E-mail: pan.igmof@gmail.com; orcid: 0000-0002-5179-6091
O.V. Dubyna 1, 2, DrSc (Geology), Associate Professor
E-mail: dubyna_a@ukr.net; orcid: 0000-0002-6003-4873
І.А. Shvaika 1, PhD (Geology), Research Fellow
E-mail: ishvaika@gmail.com; orcid: 0000-0001-9585-4380
I.D. Shvaika 1, Junior Research Fellow
E-mail: igor.d.shvayka@gmail.com; orcid: 0000-0002-1908-6639
L.I. Proskurka 1, Research Fellow
E-mail: igmrproskurko@gmail.com; orcid: 0000-0001-5760-2000
Yu.O. Lytvynenko 1, Junior Research Fellow
E-mail: lisick8@gmail.com; orcid: 0000-0001-6609-0000
S.V. Kushnir 1, Research Fellow
E-mail: kushnir@nas.gov.ua; orcid: 0000-0002-3449-1261
1 M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
2 Taras Shevchenko National University of Kyiv, Institute of Geology
90, Vasylkivska Str., Kyiv, Ukraine, 03022
Language: Ukrainian
Mineralogical journal 2026, 48 (2): 85-95
Abstract: The Iskrene granites are unique fine-grained rocks located at the contact zone between the Korsun-Novomyrhorod Pluton and its host rocks. Their petrogenesis has long been a subject of debate, with hypotheses ranging from a late-stage intrusive phase of the Korsun-Novomyrhorod Pluton to xenoliths of older complexes or hybrid formations. The lack of consensus necessitates a detailed study using modern analytical methods. The study aims to constrain the genesis of the Iskrene granites by comparing their geochemical signatures and biotite chemistry with those of the surrounding rapakivi granites of the Korsun-Novomyrhorod Pluton. Petrographic analysis was combined with inductively coupled plasma mass spectrometry (ICP-MS) for trace element determination and electron probe microanalysis (EPMA) to establish the chemical composition of biotites. Petrographic analysis reveals that Iskrene granites are fine-grained rocks with a characteristic taxitic structure formed by mica clusters (0.5-2 cm). The groundmass consists of K-feldspar (40-50 %), plagioclase (15-20 %), quartz (20-25 %), and biotite (5-7 %). The presence of aplitic, poikilitic, and micrographic textures indicates rapid eutectic crystallization. A comparative study of biotite chemistry shows that Iskrene biotites are extremely peraluminous (Al2O3 = 20.68 %) and have a lower iron-to-magnesium ratio (f = 0.83) than rapakivi biotites (f = 0.91), plotting in the siderophyllite and S-type granite fields. Geochemically, Iskrene granites are depleted in Sr, Ba, Zr, Ti and REE compared to rapakivi granites. The total REE content is 204 ppm with a significantly deep negative europium anomaly (Eu/Eu* = 0.19). These geochemical signatures, along with reduced La/YbN ratios, indicate inheritance from a high-alumina crustal protolith. The Iskrene granites originated from the anatexis of peraluminous crustal rocks triggered by the heat and fluid influx from the Korsun-Novomyrhorod Pluton’s rapakivi magma. The taxitic structure and biotite chemistry confirm their restite nature, representing products of incomplete melting. Unlike the "dry" rapakivi melt, the Iskrene magma was fluid-saturated, leading to intensive autometasomatic muscovitization and chloritization. The Iskrene granites are hybrid formations where the crustal melt underwent "geochemical dilution" by the rapakivi-forming magma while retaining the signature of the host rocks.
Keywords: Iskrene granites, rapakivi granites, Korsun-Novomyrhorod pluton, biotite chemical composition of biotite, anatexis, restite.
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