The Upper Jurassic basalts (150–160 Ma) described as the Ichetui Formation over the territory of the Tugnui, Margintui, and Maly Khamar-Daban volcanic structures have been studied paleomagnetically. It is shown that natural remanent magnetization still contains a component which may reflect the geomagnetic field direction at the beginning of the Late Jurassic. This is supported by reversal and conglomerate tests. Calculation of mean paleopole gives: Plat = 63.6°, Plong = 166.8°, α95 = 8.5°. These values well coincide with the data for the Badin Formation from Mogzon depression, which lies east of the study area and approximately dates from the Kimmeridgian-Oxfordian interval of the Late Jurassic. At the same time, those poles statistically differ from the European and Southeast Asian poles of the same age. The available paleomagnetic data suggest that at the beginning of the Late Jurassic the Mongol-Okhotsk Ocean was probably still open. Since the early Late Jurassic the continental blocks of Southeastern Asia and Siberian part of the Eurasian plate had been approaching, with the Siberian domain rotating clockwise. Analysis of the total of data shows that sinistral strike-slip deformations were present not only in southern Siberia but also between the Siberian and European Platforms. Thus, the deformations of the Central Asian crust in the early Late Jurassic reflect the intraplate strike-slip motions coeval with the closure of the Mongol-Okhotsk Ocean and are governed by the clockwise rotation of the Siberian part of the Eurasian plate relative to its European part.

This paper is focused on the relationship between plate-and plume-tectonic processes during the formation of Neoproterozoic and Vendian-Paleozoic island-arc systems and active continental margins in the interaction zone of the Siberian continent and Paleoasian Ocean (PAO). In this study, we use our own materials collected in the long-term research of the Central Asian Orogenic Belt (CAOB) and the published models showing convection in the asthenosphere and mantle, subduction-related and plume magmatism at the Cenozoic active margins of the Western Pacific and California types. It is clearly shown that subduction-related magmatism of the Paleoasian Ocean active margins should not be considered separately from plume magmatism. These interrelated processes played a major role in the CAOB formation. Based on the reconstructed Neoproterozoic, Vendian-Early and Middle Paleozoic paleogeodynamic features, 25 island-arc systems of PAO are characterized. These island arcs are related to the occurrence of more than 30 plume magmatism areas. At the active margin of the Siberian continent, there are numerous fields of intraplate magmatism in riftogeneous structures. Such fields of various scales not related to subduction zones, especially at the final Late Paleozoic stage. All the major stages of the CAOB development, including the Cambrian-Ordovician collision stage, are clearly correlated with plume magmatism. Considering a revealed combination of the island arcs and the plume magmatism areas, there are grounds to suggest that the development of the entire Neoproterozoic-Paleozoic region of Central Asia was related to the activity of mantle plumes.

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.

The geodynamic reconstruction using new data on the composition, age, and paleomagnetism of Neoproterozoic and Vendian–Early Paleozoic island arc complexes has provided new insights into the evolution of the subduction zone magmatism over extensive areas of the Central Asian Orogenic Belt, including eastern Altai–Sayan, Transbaikalia, and Northern Mongolia. Comparison of the igneous complexes of modern and ancient ensimatic and ensialic island arcs in the subduction zone forms a basis for possible geodynamic scenarios of the subduction zone magmatism in Neoproterozoic and Vendian–Early Paleozoic island arcs in the zone of interaction between the Siberian paleocontinent and the Paleoasian Ocean, which take into account the composition of crustal and mantle (including mantle plume) components.