Four Stages of the Thermal Evolution of Eclogites from the Maksyutov Complex (South Urals)

Fedkin, V.V.

Автор: Fedkin V.V.
Журнал: Russian Geology and Geophysics
Том: 61
Номер: 5-6
Год издания: 2020
Издательство: ELSEVIER SCIENCE BV
Местоположение издательства: PO BOX 211, AMSTERDAM, NETHERLANDS, 1000 AE
Первая страница: 543
Последняя страница: 558
DOI: 10.15372/RGG2019182
Аннотация: Abstract—Based on a detailed electron probe microanalysis of the composition and zoning of coexisting minerals (garnet, clinopyroxene,and plagioclase), we have studied the P–T conditions of formation of high-pressure (HP/UHP) rocks of the Maksyutov eclogite–blueschist complex in the South Urals. We have established its periodic evolution and have determined the specific thermodynamicparameters of mineral formation at each stage of its geodynamic history, from the conditions of crystallization of the protolith to the finalstages of retrograde greenschist metamorphism. The new analytical data on the composition of coexisting phases confirm the high-pressureformation of eclogites present as numerous lenses, boudins, and interlayers among blueschist and feldspar–mica schists in the lower partof the complex. Thermobarometric calculations of metamorphism parameters were performed for the Grt + Cpx ± Pl + Qz paragenesisusing a Grt–Cpx geothermometer and a Pl–Cpx–Qz geobarometer. Garnet in eclogites of the Maksyutov Complex, being conservativeto changes in the Р–Т conditions, has a direct, reverse, or inverse chemical zoning. Under equilibrium of garnet with omphacitic clinopyroxene,this zoning records conjugate progressive and regressive Р–Т paths reflecting the thermodynamic conditions at the certainstages of the terrane evolution. Based on the data obtained, we have recognized at least four P–T stages of progressive metamorphictransformations of the Maksyutov Complex: (1) >800–910 °C/~2.5–3.5 GPa; (2) 540–790 °C/2.0–3.5 GPa; (3) 410–690 °C/1.1–2.5 GPa;and (4) 310–520 °C/1.0–1.2 GPa. The estimated P–T parameters of the conjugate regressive stages of metamorphism are as follows: (1)870–625 °C/3.5–2.5 GPa; (2) 745–615 °C/3.5–2.0 GPa; (3) 690–550 °C/1.5–1.0 GPa; and (4) 590–460 °C/1.2–0.6 GPa, respectively. Theage data for the certain stages, along with the parameters of metamorphism, form a single P–T–t path of the complex, which determines theposition of the gradient of the metamorphic field during the complex exhumation.
Добавил в систему: Федькин Валентин Васильевич

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Four Stages of the Thermal Evolution of Eclogites from the Maksyutov Complex (South Urals)статья

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