Geology and paleomagnetism of the Vendian and lower Cambrian deposits from Argun terrane (Eastern Transbaikalia)

We present new data on the geologic structure and paleomagnetism of the Vendian and Lower Cambrian deposits of the Argun River region in East Transbaikalia. We discuss the issues related to the recognition of the Argun microcontinent within the composite blocks of the south-eastern part of the Central Asian belt, which are traditionally combined in the Amuria superterrane. Our paleomagnetic determinations help us justify the equatorial position of the sedimentary basin, in which the deposits of the Argun terrane Beletuy and Bystrin formations formed 560 and 525 Ma, close to or directly on the margin of the Siberian paleocontinent. This data is essential for the reconstruction of the geodynamic evolution of Siberia and Central Asia at the Precambrian-Paleozoic boundary.     

Early Hercynides of the Baikal–Vitim Fold System,western Transbaikal region

New data on the composition, age, structure, and geodynamic settings of the Upper Silurian–lower Middle Carboniferous rocks in the Baikal–Vitim Fold System (BVFS) are reported. These rocks make up the Early Hercynian structural stage of the BVFS, within which the Uda–Vitim, Vitimkan–Tsipa, and Turka–Kurba lithotectonic zones are recognized. The Early Hercynian stage combines rocks of two stratigraphic levels: Upper Silurian–Upper Devonian (S₂–D₃) and Upper–Devonian–Middle Carboniferous (D₃–C₂¹). On the basis of lithostratigraphic and spatiotemporal relationships between sedimentary and volcanic–sedimentary complexes of the Early Hercynian stage three formations are identified, which characterize the main tectonic regimes of the early half of the Late Paleozoic. It has been established that a common paleobasin that evolved through consecutively changing geodynamic settings at the passive and active continental margins existed in the Silurian (?)–early Middle Carboniferous in the northeastern part (in present-day coordinates) of the western Transbaikal region.     

Diversity of Archaeocyaths and Sr Chemostratigraphy of the Lower Cambrian of West Transbaikalia,Uda–Vitim and Birami–Yanguda Zones

Doklady Earth Sciences - The morphology of archaeocyaths from the Oldynda Formation of the Uda–Vitim lithofacial zone and the Aikta Formation of the Birami–Yanguda Zone of West...     

The Late Riphean–Paleozoic history of the Uda–Vitim island arc system in the Transbaikalian sector of the Paleoasian ocean

New structural, petrological, chemical, isotope, and paleomagnetic data have provided clues to the Late Riphean–Paleozoic history of the Uda–Vitim island arc system (UVIAS) in the Transbaikalian sector of the Paleoasian ocean, as part of the Transbaikalian zone of Paleozoids. The island arc system consists of three units corresponding to main evolution stages: (i) Upper Riphean (Late Baikalian), (ii) Vendian–Lower Paleozoic (Caledonian), and (iii) Middle–Upper Paleozoic (Hercynian). The earliest stage produced the base of the system composed of Late Riphean ophiolite (971–892 Ma, U-Pb) and volcanic (837–789 Ma, U-Pb) and sedimentary rocks (hemipelagic siliceous sediments and dolerite sills) which represent the Barguzin–Vitim oceanic basin and the Kelyana island arc. The main event of the second stage was the formation of the large UVIAS structure (over 150,000 km2) which comprised the Transbaikalian oceanic basin, the forearc and backarc basins, and the volcanic arc itself, and consisted of many volcanic-tectonic units exceeding 100 km² in area (Eravna, Oldynda, Abaga, etc.). Lithology, stratigraphy, major–element compositions, and isotope ages of Vendian–Cambrian volcanic rocks and associated sediments indicate strong differentiation of calc-alkaline series and the origin of the island arc system upon oceanic crust, in a setting similar to that of the today’s Kuriles–Kamchatka island arc system. The Middle–Upper Paleozoic stage completed the long UVIAS history and left its imprint in sedimentary and volcanic rocks in superposed trough basins. The rocks were studied in terms of their biostratigraphic and isotope age constraints, as well as major- and trace-element compositions, and were interpreted as products of weathering and tectonic-magmatic rework of the UVIAS units.