Neoproterozoic metamorphism and deformation at the southeastern margin of the East European Craton, Uralides, Russia

Abstract

The eastern margin of the East European Craton (EEC) has a long lasting geological record of Precambrian age. Archaean and Proterozoic strata are exposed in the western fold-and-thrust belt of the Uralides and are known from drill cores and geophysical data below the Palaeozoic cover in the Uralides and its western foredeep. In the southern Uralides, sedimentary, metamorphic and magmatic rocks of Riphean and Vendian age occur in the Bashkirian Mega-anticlinorium (BMA) and the Beloretzk Terrane. In the eastern part of the BMA (Yamantau anticlinorium) and the Beloretzk Terrane, KAr ages of the <2-m-size fraction of phyllites (potassic white mica) and slates (illite) give evidence for a complex pre-Uralian metamorphic and deformational history of the Precambrian basement at the southeastern margin of the EEC. Interpretation of the K-Ar ages considered the variation of secondary foliation and the diagenetic to metamorphic grade. In the Yamantau anticlinorium, the greenschist-facies metamorphism of the Mesoproterozoic siliciclastic rocks is of Early Neoproterozoic origin (about 970 Ma) and the S1 cleavage formation of Late Neoproterozoic (about 550 Ma). The second wide-spaced cleavage is of Uralian origin. In the central and western part of the BMA, the diagenetic to incipient metamorphic grade developed in Late Neoproterozoic time. In postUralian time, Proterozoic siliciclastic rocks with a cleavage of Uralian age have not been exhumed to the surface of the BMA. Late Neoproterozoic thrusts and faults within the eastern margin of the EEC are reactivated during the Uralian deformation.

Permian and Triassic palaeolatitudes of the Ukrainian shield with implications for Pangea reconstructions

“…The Dniepr‐Donets‐Donbas rifting did not succeed in fragmenting Sarmatia, and hence can be considered as a classic example of an aulacogen (= failed rift; Shatsky 1946). However the rift caused the Voronezh Massif in the north and the Ukrainian Shield in the south, joined together since the Achaean (Shchipansky & Bogdanova 1996), to become two separate shield areas (Glasmacher et al 2004). During Hercynian and Uralian mountain building, there were compressional events that caused the earlier formed basins to invert, but these did not greatly impact the shield areas.…”

Ediacaran rocks from the Cadomian basement of the Saxo-Thuringian Zone (NE Bohemian Massif, Germany): age constraints, geotectonic setting and basin development

“…Nance & Murphy 1996). Baltica escaped the Avalonian-Cadomian orogenic activity, although the 'Cadomian affinity' of the late Precambrian orogenic events in the Urals and in the Timanides on the periphery of Baltica was recognized (Roberts & Siedlecka 2002;Glasmacher et al 2004).…”

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

“…Evidence of the Neoproterozoic Timanian orogeny, which is reflected by geochronological data in several other metamorphic complexes in similar tectonic settings (e.g. Beloretzk Glasmacher et al 2001Glasmacher et al , 2004Kvarkush, Beckholmen and Glodny 2004) is not present in the TC and AC.…”

“…This Timanian orogeny can be correlated with the Cadomian events in western Europe (Puchkov 1997;Scarrow 2001;Willner et al 2003). Occurrences reflecting Timanian magmatic and tectonometamorphic events are the Beloretzk complex (Southern Urals; Glasmacher et al 1999Glasmacher et al , 2001Glasmacher et al , 2004, the Kvarkush Anticlinorium (Northern Urals, Beckholmen and Glodny 2004) and the Enganepe ophiolites and calc-alkaline magmatic rocks of the Polar Urals (Scarrow et al 2001).…”