The modern theory of the evolving Earth is based on integrated isotopic data obtained for the accessible part of the planet and cosmic bodies, in which the U–Pb isotope system plays a key role. The theory is tested by the isotope systematics of oceanic basalt sources. The origin of continental volcanic rocks is often interpreted in terms of the isotopic systematics of oceanic basalts. However, such interpretations, as a rule, reveal contradictions arising from differences in the history and current mantle dynamics of oceans and continents. Under the oceans, a mantle material has long lost connection with the accessible Earth tectonic units; under the continents such a connection is often established. The nature of the evolution of deep‐seated processes under the continents remains uncertain and, by analogy with the oceans, requires deciphering in terms of the components of the mantle sources for volcanic rocks. In modern lithospheric plates of the Earth, there are regions ranging in width from hundreds to thousands of kilometers, which are characterized by high strain rates and, consequently, at least one to two orders of magnitude lower viscosity relative to that of the internal stable parts of the plates. This gives them a special structural status of “dispersed plate boundaries”. The isotope‐geochemical studies of volcanic rocks from regions of the unstable Asia revealed the different nature of components in sources, for which particular interpretations have been proposed. In this paper, a general systematics of sources is defined for volcanic rocks of the latest geodynamic stage in Asia through estimating the incubation time on the 207Pb/204Pb versus 206Pb/204Pb diagram. Two domains are designated: (1) low 238U/204Pb (LOMU) derived from the viscous protomantle (VIPMA), and (2) elevated 238U/204Pb (ELMU). The mantle domains evolved from the Earth's primary material between 4.51 and 4.36 Gyr ago, 4.0 and 3.7 Gyr ago, 2.9 and 2.6 Gyr ago, 2.0 and 1.8 Gyr ago, about 0.66 Gyr ago and <0.09 Gyr ago. Melting anomalies of ELMU sources characterize the unstable mantle of Southern Asia, and those of LOMU sources belong to the Japan‐Baikal geodynamic corridor of the transitional region between the unstable mantle of Asia and its stable core. The Late Cenozoic evolution of the Japan‐Baikal geodynamic corridor resulted in cutting the LOMU domain by the Jeju‐Vitim ELMU source line.

We present results of lithogeochemical, diatomic and palynological studies of sediments from the Tunka-13 well that was drilled in the southeastern part of dry Tunka basin in the Baikal rift zone. At the base of the section, there is an eroded basaltic flow of 16-15 Ma. From lithogeochemical signatures, we identify nine sedimentary units. The seven lower ones (interval 7.2-86.5 m) belong to the Tankhoi formation, the eighth (interval 2.7-6.6 m) to the Anosov formation, the ninth (interval <2.4 m) to the sandy stratum. We determined local sources of clastic material of basaltic and silicic compositions for units 1 and 2, respectively, and remote sources of silicic compositions for the overlaying units. The section shows a change from alluvial facies (units 1-3) through avandelta (unit 4) and lacustrine ones (units 5-7), again to alluvial facies (unit 8) and then to lacustrine-eolian ones (unit 9). Spore and pollen spectra from sediments of units 1-7 are divided into three palynozones (PZ), reflecting the vegetation change in the Late Miocene -Early Pliocene: PZ-1 -coniferous and deciduous forests with a small participation of thermophilic broadleaved species in moderately warm, humid climatic conditions; PZ-2 -enhancing the role of hemlock and more diverse thermophilic deciduous rocks in more humid and warm conditions; PZ-3 -a gradual reduction in the number of hemlock and other dark coniferous species, removing broadleaved species by birch and alder, growing grassy communities in wetlands due to climate cooling. We identified layers of lacustrine facies by occurrence of fossil diatoms that are absent in the layers of the alluvial and avandelta facies. In lacustrine sediments, we distinguish four diatom zones: DZ-1 denotes a relatively deep Late Miocene paleolake, marked by planktonic species, DZ-2, DZ-3 and DZ-4 -a shallow Early Pliocene lake with a developed littoral zone and short transgression. The Late-Miocene paleolake transgression, indicated by changing facies, is associated with structural reorganization, accompanied by volcanic extinction in the Tunka valley about 9-8 Ma, and the Early Pliocene short transgression with a new reorganization, reflected in volcanic rejuvenation about 4.0 Ma.

It is revealed that highMg lavas (MgO=11.0-15.8 wt. %) are spatially controlled by linear zones extending for more than 90 km and demonstrate chemically distinct differences from moderatelyMg compositions (MgO=3.0-11.0 wt. %), which occupy the isometric area of the Dariganga volcanic field. From the major and traceelement data on the rocks in the field under study, we have justified a petrogenetic mode of the uniform onelevel mantle magmatism. Our model differs from the contrasting magmatism model of the processes that developed at two levels beneath the Hannuoba volcanic field. Based on tomography images showing the East Mongolian local lowvelocity anomaly in the upper mantle, we suggest that magma tism of Type 1 occurred in the mantle sources at the asthenosphere-lithosphere boundary and the underlying asthenosphere as a reflection of a relatively weak mantle flow that may have ascended from a depth of ~250 km. Magmatism of Type 2 occurred in the isolated sources of the sublithospheric mantle and the asthenosphere-lithosphere boundary as an evidence on the initially strong mantle flow that may have ascended from a depth of ~410 km. Аннотация: Установлен пространственный контроль высокомагнезиальных вулканических пород (MgO=11.0-15.8 мас. %) линейными зонами протяженностью более 90 км и резкие отличия их химического состава от умеренно магнезиальных (MgO=3.0-11.0 мас. %) пород, занимающих всю изометричную территорию вулканического поля Дариганга. При сравнительном анализе петрогенных и малых элементов пород этого поля обоснована петрогенети ческая модель мантийного магматизма одного глубинного уровня, в отличие от модели контрастных магматических процессов, проявленных на двух глубинных уровнях под вулканическим полем Ханнуоба. С учетом томографиче

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Devonian dikes of the Urik-Belaya and Shagayte-Gol-Urik zones and Miocene lavas of the Urik volcanic field are spatially associated with each other at the structural junction between the Neoproterozoic Tuva-Mongolian massif and Siberian craton. The former dike belt is represented by basalts and basaltic andesites of tholeiitic series and the latter one by trachybasalts, trachyandesitic basalts of moderately alkaline series and trachybasalts, phonotephrites of highly alkaline one. The Urik volcanic field is composed of trachybasalts and trachyandesitic basalts of moderately alkaline series. A partial similarity between magmatic series of different age is found in terms of major oxides, trace elements, and Sr, Pb isotopes. The common component corrected for age was defined through its converging mixing trends with those of the lithospheric mantle and crust. The component identification was a basis for deciphering the nature of isotopic and geochemical heterogeneity of evolved magmatic sources. It was inferred that the common component characterizes either a modified (depleted) reservoir of the lower mantle or, more likely, a local region of the convecting asthenospheric mantle that underlies the Tuva-Mongolian massif. The latter interpretation assumes the formation of a locally convecting asthenosphere in the middle Neoproterozoic, along with the development of the Oka zone at the massif, and puts constrains on later sufficient processing of the asthenosphere due to rising plumes or subducting slabs.