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  • Age and Thermal History of ...
    Ryazantsev, A. V.; Golionko, B. G.; Kotov, A. B.; Skoblenko, A. V.; Stifeeva, M. V.; Plotkina, Yu. V.; Salnikova, E. B.; Koreshkova, M. Yu; Machev, Ph

    Doklady earth sciences, 09/2022, Letnik: 506, Številka: 1
    Journal Article

    Lenses of eclogites (the Tulepsai complex) that formed at the peak of metamorphism at P = 15 kbar and T = 700–750°C and experienced decompression at 12 kbar (granulite-facies metamorphism) are located among the amphibolite sequences in the Eastern Mugodzhar Zone. The insignificant difference between the age of zircon cores, which, we believe, formed under the conditions of the eclogite-facies metamorphism (374 ± 4 Ma) at depths of 50–60 km (?) and the age of their rims (372 ± 6 Ma) formed during the isothermal decrease in pressure up to 12 kbar (25–35 km?) may indicate a rapid uplift of eclogites from considerable depths. Rutile extracted from eclogites yields a U–Pb age at 360 ± 2 Ma and reflects a later stage of rock transformation at 630–690 ± 40°C. The Maksyutov eclogite–glaucophane–schist and Tulepsai complexes are structural analogs of similar age and compose the lower allochthons on different branches of the Magnitogorsk synform. The complexes were formed in a similar geodynamic setting at the arc–continent collision.