Proterozoic magmatic and tectonometamorphic evolution of the Taratash complex, Central Urals, Russia

Abstract

The Taratash Complex (TC) in the northernmost Bashkirian Anticlinorium (Middle Urals) is unique among the pre-Uralian polymetamorphic complexes along the eastern margin of the East European Craton because it experienced granulite facies peak metamorphic conditions (850-900°C/10 kbar). Herein, we constrain the post-granulite facies polystage evolution of the complex, which records various increments of the geodynamic history of the East European continental margin. Formation of granite and migmatite associated with amphibolite facies events are dated at 2,344±29 and 2,044±8 Ma (U-Pb, zircon) in different structural units. At 1,810±41 Ma, the TC was affected by a greenschist facies retrogressive metamorphism which was probably related to a stage of granite formation in the eastern part of the East European Craton. This is confirmed by a U-Pb-zircon age of 1,848±8 Ma obtained from a sheared granite in the adjacent Alexandrovskiy Complex (AC). Greenschist facies shear zones which separate different structural units of the TC formed before 1,350 Ma. Partial re-equilibration of RbSr-and K-Ar-isotope systems between 1,350 Ma and 1,200 Ma is attributed to fluid flow probably induced by anorogenic magmatism in the Bashkirian Anticlinorium. Meso-to Neoproterozoic basaltic dykes indicate that the TC had been exhumed to upper crustal levels at that time. Evidence for a Grenvillian event or for the Timanian orogeny which affected other pre-Uralian complexes in the Urals is lacking. Uralian orogenic shortening and thrusting on Devonian limestones is recorded by shear zones in the AC to the east of the TC and has been dated at 300 Ma (Rb-Sr, 40 Ar/ 39 Ar).

The early Precambrian history of rock metamorphism in the Urals segment of crust

“…Certain authors (Sindern et al 2005(Sindern et al , 2012Ronkin et al 2007) associate these ages with postgranulite magmatic and metamorphic activity (e.g. dates of 2461 ± 36 Ma and 2344 ± 29 Ma, U-Pb SHRIMH-II, zircon 2244 ± 19 Ma, 2230 ± 24 Ma, 2219 ± 21 Ma, LA ICP-MS, monazite), whereas others (Krasnobaev et al 2011a) associate them with various processes of changes in granulite zircons (2611 ± 17 Ma, 2449 ± 82 Ma, 2311 ± 20 Ma, U-Pb SHRIMH-II, zircon).…”

“…The youngest ages, which are often associated with medium-and high-temperature retrograde metamorphism and granitization, are ca. 1850 Ma (U-Pb ID-TIMS, Sindern et al 2005). Comparable data were obtained for amphibolite metamorphic manifestations and granitization in the rocks of the Selyankin complex; Pb-Pb and U-Pb SIMS ages of single zircon grains are within the interval of 1943-1818 Ma (Pystina and Pystin 2002).…”

Baltica in the Cryogenian, 850–630 Ma

“…1848 Ma, and greenschist facies metamorphism from ca. 1848 to 1350 Ma (Sindern et al, 2005). The Yumaguzino suite rhyolites of the Maksyutov complexes are mid-Mesoproterozoic in age (Krasnobaev et al, 1996).…”