TY - JOUR

T1 - Timing and Sequence of Endogenous Events in the Bug Granulite–Gneiss Domain of the Ukrainian Shield Based on the Study of a Composite Tectono-Magmatic Breccia

AU - Лобач-Жученко, С. Б.

AU - Балтыбаев, Шаукет Каимович

AU - Егорова, Юлия Сергеевна

AU - Юрченко, А.В.

AU - Галанкина, О. Л.

PY - 2025/5/1

Y1 - 2025/5/1

N2 - In the Bug granulite-gneiss domain of the Ukrainian shield, a composite tectono-magmatic brec-cia including enderbites and various mafic rocks was studied in the gneiss-enderbite complex. Based on theassessment of the thermodynamic conditions of rock and mineral formation and the analysis of the U–Pband Lu–Hf isotope systems of zircon, the endogenous history of the gneiss–enderbite complex is deciphered.The predominant rocks are enderbites with numerous enclaves of two-pyroxene and pyroxene–amphibolecrystalline schists that were deformed under granulite facies metamorphism. The oldest zircons have a con-cordant U-Pb age of 3.6–3.7 Ga, which is close to the age of the protolith of the Bug enderbites. The zirconsare characterized by a heterogeneous structure, negative Hf(t) values from –1 to –38, and a variation in176Hf/177Hf(0) isotope ratios from 0.28035 to 0.28095, which is consistent with their different ages and origins.Based on the age, geochemistry, and isotope composition of zircon from composite breccia rocks, followinggeological events from Archean to Proterozoic are distinguished: (1) 3.67–3.60 Ga stage of magmatic crys-tallization of early mineral associations; (2) 3.0‒2.8 Ga stage of granulite metamorphism and partial melting(2.9 Ga) of the enderbites with the preservation of melt mineral phases in zircons, but with a strong distur-bance of its U-Pb isotope system; (3) 2.0–1.9 Ga stage of Proterozoic granulite metamorphism with the reor-ganization of cation and isotope systems of rock-forming and accessory minerals. The obtained data are con-sistent with the model of polychronous evolution of the continental crust of the Ukrainian Shield in thePaleo- and Mesoarchean with its strong reworking in the Paleoproterozoic.

AB - In the Bug granulite-gneiss domain of the Ukrainian shield, a composite tectono-magmatic brec-cia including enderbites and various mafic rocks was studied in the gneiss-enderbite complex. Based on theassessment of the thermodynamic conditions of rock and mineral formation and the analysis of the U–Pband Lu–Hf isotope systems of zircon, the endogenous history of the gneiss–enderbite complex is deciphered.The predominant rocks are enderbites with numerous enclaves of two-pyroxene and pyroxene–amphibolecrystalline schists that were deformed under granulite facies metamorphism. The oldest zircons have a con-cordant U-Pb age of 3.6–3.7 Ga, which is close to the age of the protolith of the Bug enderbites. The zirconsare characterized by a heterogeneous structure, negative Hf(t) values from –1 to –38, and a variation in176Hf/177Hf(0) isotope ratios from 0.28035 to 0.28095, which is consistent with their different ages and origins.Based on the age, geochemistry, and isotope composition of zircon from composite breccia rocks, followinggeological events from Archean to Proterozoic are distinguished: (1) 3.67–3.60 Ga stage of magmatic crys-tallization of early mineral associations; (2) 3.0‒2.8 Ga stage of granulite metamorphism and partial melting(2.9 Ga) of the enderbites with the preservation of melt mineral phases in zircons, but with a strong distur-bance of its U-Pb isotope system; (3) 2.0–1.9 Ga stage of Proterozoic granulite metamorphism with the reor-ganization of cation and isotope systems of rock-forming and accessory minerals. The obtained data are con-sistent with the model of polychronous evolution of the continental crust of the Ukrainian Shield in thePaleo- and Mesoarchean with its strong reworking in the Paleoproterozoic.

KW - Ukrainian shield

KW - age

KW - enderbite

KW - geochemistry

KW - metamorphism

KW - tectono-magmatic breccia

KW - zircon

UR - https://www.mendeley.com/catalogue/545ed2ed-6e42-3990-8d37-2be826a5e29c/

U2 - 10.1134/s0016702925600026

DO - 10.1134/s0016702925600026

M3 - Article

VL - 63

SP - 361

EP - 390

JO - Geochemistry International

JF - Geochemistry International

SN - 0016-7029

IS - 5

ER -