Conditions of metamorphism of garnet-bearing aluminous gneisses in the Orekhov–Pavlograd zone of the Ukrainian Shield
2017; Elsevier BV; Volume: 58; Issue: 11 Linguagem: Inglês
10.1016/j.rgg.2017.11.002
ISSN1878-030X
AutoresШ. К. Балтыбаев, A. V. Yurchenko, С. Б. Лобач-Жученко, V. V. Balagansky, О. Л. Галанкина, М. В. Морозов, Е. С. Богомолов,
Tópico(s)Crystal Structures and Properties
ResumoAbstract Garnet-bearing aluminous gneisses in the Vasil’kovka area of the Orekhov–Pavlograd zone of the Ukrainian Shield were studied using the THERIAK-DOMINO, THERMOCALC, and WINTWQ software and mineral geothermobarometry methods. The stability fields of parageneses formed at the initial, peak, and post-peak metamorphic stages have been estimated: T = 500–650 °C and P > 7 kbar, T = 800–850 °C and P ≈ 8 kbar, and T = 600–670 °C and P = 4.0–5.5 kbar, respectively. A “clockwise” PT path has been established. Based on the aluminous gneiss, the age of metamorphism is determined as Paleoproterozoic (2014 ± 11 Ma). Unique regularly oriented acicular goethite microinclusions were described in garnet. In contrast to other known oriented Ti-bearing mineral inclusions in garnet, these goethite inclusions suggest not only extremely high P and T values (necessary for the formation of oriented Ti-bearing inclusions) but also a high oxygen fugacity. The obtained data broaden the concepts of the ways and conditions of formation of regularly oriented mineral phases in garnet.
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