Petrology and retrograde P‐T path for eclogites of the Maksyutov Complex, Southern Ural Mountains, Russia

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 (Ml-J and two stages of deformation (S, and S,) were observed in thin sections: MI) garnet (Alm53-60, Prp,, 2 x , Grs,,-,,,) + omphacite (Jd4& + phengite (Si z 3.5) + rutile; M,) garnet + glaucophane f lawsonite + white mica; and M,) epidote + chlorite k albite k 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.

A moderate exhumation rate for the high‐pressure Maksyutov Complex, southern Urals, Russia

“…Grey boxes represent uncertainties of the P±T estimates. The P±T estimates are discussed in the text and are based on petrological data from Beane et al (1995), Dobretsov et al (1996), Hetzel et al (1998). The age of 378 AE 6 Ma for eclogite-facies peak-metamorphic conditions results from critical evaluation of all available geochronological data as discussed in the text.…”

“…Two eclogites from Antingan yielded peak pressure estimates of 1.6 and 1.7 GPa. In addition, peak pressures of 1.5 and 2.1 GPa have been calculated for two eclogites from Karayanovo and Shubino using mineral data of Beane et al (1995). Due to the scatter in the pressure estimates, we consider 2.0AE 0.3 GPa as an appropriate estimate for the peak pressure in the lower unit 1.…”

Ultrahigh-pressure minerals and metamorphic terranes – The view from China

“…Maksyutov Complex, South Urals: This complex contains boudins of eclogite, layers of eclogitic gneiss, and rare ultramafic bodies within host metasedimentary mica schist and quartzite recrystallized at 594-637°C at a minimum P of 1.5-1.7 GPa (Beane et al, 1995;Leech and Ernst, 1998). Documentation of UHP index minerals in the Maksyutov Complex has been more elusive (e.g., Beane and Leech, 2007).…”

Role of a phase: Change Moho in stabilization and preservation of the Southern Uralide orogen, Russia

“…The protolith and the metamorphic age of the rocks forming the Maksyutov Complex remain a subject of controversy [e.g., Zakharov and Puchkov, 1994;Hetzel, 1999;Leech and Stockli, 2000]. However, metamorphosed mafic and quartz-rich rocks exposed in the Maksyutov Complex preserve evidence for a Paleozoic high-pressure meta morphic event during thc asscmbly of the Southcrn Uralidcs [Matte ct al., 1993;Beane et al, 1995Beane et al, , 1997Hetzel et al, 1998;Beane and Connelly, 2000;Leech and Stockli, 2000].…”