PRE-ORDOVICIAN TECTONIC EVOLUTION AND VOLCANO-PLUTONIC ASSOCIATIONS OF THE TIMANIDES AND NORTHERN PRE-URALIDES, NORTHEAST PART OF THE EAST EUROPEAN CRATON

Abstract

The Pre-Uralides and Timanides are Pre-Ordovician complexes, located at the east and northeast portion of the East European Craton. They combine two large groups of rocks of different composition: (1) The southwestern Timanides and southern Pre-Uralides consisting mostly of sedimentary rocks; (2) The northeastern Timanides and northern Pre-Uralides are composed of volcanic–sedimentary series and volcanogenic series, granitoids and rare ophiolites. The granitoids and associated volcanics of the second group are subdivided into I- and A-types. Rocks considered from the I-type are parts of a continuous basalt–andesite–dacite–rhyodacite and gabbro–granodiorite–granite series showing a calc-alkaline affinity. They are dated within a time range of 700 to 515 Ma and they are interpreted to be subduction-related and/or affected by collision magmatism. In contrast, A-type granitoids are parts of bimodal gabbro–granite and basalt–rhyolite associations, and dated from 565 to 500 Ma. A-type granitoid massifs show elongated shapes within linear tectonic zones and are interpreted to reflect an extensional/transtensional setting.The southwestern Timanides and southern Pre-Uralides were formed in the Neoproterozoic passive Timan margin of the Baltica. In contrast, the northeastern Timanides and northern Pre-Uralides were formed in the Late Neoproterozoic active Bolshezemel margin of Arctida and in the Baltica–Arctida collision zone during the Ediacaran–Middle Cambrian.