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This paper describes the results of geochronological studies (U-Pb method over micro lots and single grains of zircon) of autochtonous and allochtonous granitoids of the Barguzinskii complex of the Angara-Vitim batolite of the petrotypical area in the basin of the Dzhirga and Kovyli rivers (tributaries of the Barguzin River). The age of crystallization of gneissose granitoids is 297 ± 5 Ma, and that of intrusive leucocratic biotite granites is 291 ± 1 Ma. The estimates of the age finalize the discussion on the age of granitoids of the Barguzin complex and cannot be considered as “rejuvenated.” The analyses of the geochronological data that have been obtained up to the present for granitoids of the Angara-Vitim batolite with the SHRIMP and U-Pb methods for large samples of zircons show that in the majority of cases they cannot be used for precise estimation of the age of their crystallization. The geochronological data obtained with use of the U-Pb method over micro samples and single grains of zircon allow one to make a conclusion on the formation of granitoids of the described complexes of the Angara-Vitim batholite that occurred within 303 ± 7–281 ± 1 Ma. Thus, the time length of formation of the largest in the eastern segment of the Central Asian belt of the Angara-Vitim batholite is not more than 22 Ma (minimum 6 Ma), which allows us to consider it as a large granitic province and is a boundary condition for development of the geodynamic models of its formation.

The UdaZeya magmatic belt is traceable in the sublatitudinal direction along the southeastern margin of the Siberian Platform for over 1000 km being up to 100 km wide. It stitches tectonic structures of the DzhugdzhurStanovoi and SelengaStanovoi supert erranes of the Central Asian mobile belt and extends parallel to the Stanovoi structural suture and the Mongol Okhotsk fold belt.

This study discusses the results of the geochronological, geochemical (UPb), and isotopic geochemical (SmNd) investigations of granitoids from the Baikal massif, which is composed of the oldest magmatic rocks developed in the Kicher zone of the BaikalMuya mobile belt, judging from its structural stratigraphic position.

The duration of migmatite formation in the K and Na geochemical zones was first estimated for the Svecofennides of the northern Ladoga region. The U-Pb (TIMS) age of monazite was determined for the most complete sequence of leucosomes with geological control of their relations and relative age observed in the outcrops. The duration of formation of the leucosomes in two zones is different and is not overlapped by the error of the age analysis: about 5 and no less than 10–15 Ma in the K and Na zones, respectively. The different duration of migmatite formation may reflect different temperature evolution of the rocks of the two zones and also the influence of the composition and rheological properties of migmatizing sequences, which govern the conditions of liquation, transportation, and crystallization of the anatectic melt.

An important role in the formation of the Central Asia Hercynides belonged to postaccretionary processes, both orogenic and anaorogenic. The accretionary structures proper were formed in the Middle Paleozoic in response to the convergence between the Siberian and Tarim paleocontinents.

A study attempted to justify the Carboniferous age of the accretion of the Malkhan Konda terrane to the Siberian continent on the basis of geological and UPb geochronological studies of the granitoids of the Malkhan Complex. The geochronological data obtained (336 3 Ma) indicate that the granitoids of the Malkhan Complex of the MalkhanKonda zone are Early Carboniferous in age rather than Early Paleozoic or Riphean as sug gested previously.

The principal structure of the Central Asian fold belt is determined by the combination of many continental massifs and smaller fold belts of different ages. In its eastern segment, the most typical examples of the massifs are the Bureya (Turan) and Malyi Khingan (Jiamusi) massifs, which represent the main element of the Bureya-Jiamusi superterrane. The metamorphic complexes, which have been dated back to the Early Precambrian, are usually thought to form the basement of these terranes.

The age of Kuranakh Complex diabases in the western part of the Aldan-Stanovoi Shield determined by the zircon U-Pb method is virtually identical to that of basic rocks in the Chinei stratified pluton and granites in the Kodar Complex. Thus, it is possible to suggest that they form a unified bimodal magmatic association and belong to the South Siberian postcollision magmatic belt, which extends along the southwestern framing of the Siberian Craton for more than 2500 km from the Yenisei mountain range to the Aldan-Stanovoi Shield. The occurrence of the diabase dike swarms in magmatic associations of this belt testifies to formation under lithospheric extension conditions.

The formation of the Caledonian accretional-collisional area of the Central Asian Fold Belt (CAFB) is controlled by the processes of Early Caledonian tectonogenesis. In the range of 570-490 Ma, these processes resulted in the formation of the Caledonian superterrain comprising the fragments of continental massifs located within the Paleoasian Ocean, as well as Late Riphean and Vendian-Early Paleozoic oceanic and island arc structures.

The evolution of the leucosome composition from essentially plagioclase (potassium-sodium) of early generations to two feldspar or essentially K feldspar (sodium-potassium) later ones is often registered in polymigmatite complexes. Analogous evolution of migmatite leucosome matter was also confirmed for polymigmatites of the Northern Ladoga region. It is generally considered that the formation of migmatites includes various processes, though the main role usually belongs to anatectic melting, which controls the composition of leucosomes. In this paper we discuss the data providing evidence for the fact that in some cases K feldspar mineralization may be secondary, superposed on primary mineral parageneses of leucosomes and separated from the main stage of anatectic migmatite formation in time.