Petrology and retrograde P-T path for eclogites of the Maksyutov Complex, Southern Ural Mountains, Russia |
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| Authors: | R J Beane J G Liou R G Coleman M L Leech |
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| Institution: | Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA |
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| Abstract: | Abstract The Maksyutov Complex, situated in the southern Ural Mountains of Russia, is the first location where quartz aggregates within garnets exhibiting radial fractures were identified as coesite pseudomorphs (Chesnokov & Popov 1965). The complex consists of two tectonic units: a structurally lower eclogite-bearing schist unit and an overlying meta-ophiolite unit. Both units show evidence for multiple stages of metamorphism and deformation. The high-pressure metamorphism of the eclogite-bearing schist unit, discussed in this report, is suspected to be related to a collision between the Russian platform and a fragment of the Siberian continent during the early Cambrian. At least three stages of metamorphism (M1-3) and two stages of deformation (S1 and S2) were observed in thin sections: M1) garnet (Alm55-60, Prp22-28, Grs16-20) + omphacite (Jd46-56) + phengite (Si ≅ 3.5) + rutile; M2) garnet + glaucophane ± lawsonite + white mica; and M3) epidote + chlorite ± albite ± actinolite + white mica. Observed mineral parageneses define a retrograde P-T path for the eclogite. Mineral assemblages within the most representative eclogite from the lower unit of the Maksyutov Complex indicate minimum peak pressures of 15 kbar at temperatures of approximately 600°C. If the presence of coesite pseudomorph is confirmed, the peak ultrahigh-pressure metamorphism may be as high as 27 kbar at 615°C. |
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| Keywords: | coesite pseudomorphs eclogite P-T path ultrahigh-pressure metamorphism Ural Mountains |
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