Based on the dating of metamorphic and igneous rocks of the northeastern part of the Khamsara terrane, the main stages of tectono-magmatic activity at the border of two large structures—the Central Asian fold belt (CAFB) and the Siberian craton—have been established. The formation of the initial volcanogenic–sedimentary formations of this terrane, which mark the continental-marginal stage of development, took place in the range of 680–640 Ma. The age of accretion–collisional events in the CAFB fragment adjacent to the Siberian platform is fixed by the intrusion of postcollisional granitoids with an age of 480 Ma. Subsequent manifestations of Ordovician intraplate volcanism (464–462 Ma) are associated with the decay of the collisional orogen under the conditions of incipient rifting. Another stage in the development of this block is also associated with the processes of intracontinental extension and is represented by Late Paleozoic basic volcanism with an age of 267 Ma. The first established manifestations of rifting processes of different age levels within the fragment of the CAFB considered are associated with its location on the border of large inland structures separated by faults that retain their activity for a long time.

The paper reports petrochemical and isotope data on the ferromanganese ores and host volcanosedimentary rocks of the Taloi–Usoi interfluve of the Ikat terrane, the Central Asian Fold Belt. Obtained data indicate that the formation of the Taloi ferromanganese mineralization was related to the explosive and volcanic activity of synsedimentation suprasubduction volcanism. The age of the volcanogenic rocks is 799 ± 3 Ma. This indicates the manifestation of Neoproterozoic (Riphean) epoch of manganese accumulation related to active continental margin setting in the Transbaikalian segment of the CAFB.

Проведено геохимическое изучение карбонатных пород раннедокембрийских и фанерозойских метаморфических комплексов и выявлены их различия. Докембрийские мраморы и кальцифиры изучены в Онотском зеленокаменном поясе, китойском и шарыжалгайском гранулитовых комплексах Присаянского и енисейской серии Ангаро-Канского выступов Сибирского кратона; беломорском и лапландском комплексах, Северо-Печенгской структуре, сортавальской свите Фенноскандинавского щита; ваханском комплексе Бадахшанского массива. Фанерозойские – в ольхонском, слюдянском, святоносском комплексах Прибайкалья, боксонской серии и иркутной свите Восточного Саяна, дербинском комплексе и алхадырской свите Присаянья, юдинской свите и Панимбинско-Рыбинском поясе Енисейского кряжа, музкольском комплексе Восточного Памира. Докембрийские карбонатные породы по сравнению с фанерозойскими обогащены Fe, Mn и обеднены Sr, Ba при близко низком уровне содержаний РЗЭ. В архее обогащение Fe, Mn протолитов мраморов и кальцифиров обусловлено доминированием основных и ультраосновных пород в питающих провинциях. В палеопротерозое по сравнению с фанерозоем доля Fe, Mn в карбонатных породах уменьшилась, а Al, K, Ba, Sr возросла за счет участия в формировании их протолитов гранитно-метаморфического слоя Земли. Распределение петрогенных и редких элементов в мраморах и кальцифирах определяется формами их нахождения: 1) в изоморфных рядах Ca–Mg карбонатов c примесью Fe, Mn, Ba, Sr, РЗЭ; 2) присутствием в мраморах минералов Na, K, Ba, Sr; 3) наличием тонких (в мраморах) и крупных (кальцифирах) фракций минералов с железом, Mn Al, Ti, Zr, Cr, V, Ni, S. По выполненным палеореконструкциям поведения РЗЭ в карбонатных породах в архее – раннем палеопротерозое доминировали интракратонные мелкие моря. Открытые океаны появились на рубеже 2–1,9 млрд лет, но широкое развитие карбонатные породы получили в мезо-неопротерозое и фанерозое. Выявленные особенности являются основой проведения возрастных палеореконструкций протолитов по петрогеохимическим характеристикам карбонатных пород докембрийских и фанерозойских метаморфических комплексов.

The first Sm–Nd isotopic data and U–Pb (LA–ICP–MS) detrital zircon ages from sandstones of the Prisayan and Kuda Formations (the Irkutsk Basin, southern part of the Siberian Platform) have been obtained. They demonstrate that during accumulation of the sediments in the Irkutsk Basin, the contribution of local erosion sources decreased over time, while input from the Paleo–Transbaikalia sources increased. The change in provenance areas was triggered by tectonic rebuilding in Paleo–Transbaikalia caused by the closure of the Mongol–Okhotsk Ocean.

The results of U—Th—Pb (LA-ICP-MS) geochronological studies of detrital zircons from terrigenous rocks of the Dzhida terrane of the Central Asian Fold Belt (CAFB) are presented. The data obtained allow us to distinguish the following age maxima (Ma): 578 and 634 (Vendian); 720, 823, and 919 (Late Riphean); 1922, 2090, 2225, and 2321 (Early Proterozoic). A number of zircons have Late Archean age in the interval of 2670–2980 Ma. Taking into account Late Cambrian age (504–506 Ma) of intrusive rocks that intruded the Dzhida terrane, a possible sedimentation period of sequences of this terrane is estimated to be in the interval of 580–510 Ma (from Vendian to Late Cambrian). The possible provenance areas of terrigenous sediments are proposed and the previously proposed models of geodynamic evolution of the Dzhida terrane are correlated with new geochronological data.

The results of geochemical, mineralogical, and isotope (U–Pb and Sm–Nd) studies of metasedimentary manganese-bearing rocks from the Itantsa Formation of the Ikat terrane are presented. It is found that the carbonate-effusive-shale complex of the Itantsa Fm. formed under the continental margin environment, with volcanic activity accompanying sedimentation, in the interval of 650–540 Ma ago.

The U–Pb age of zircons from Ediacaran sandstones of the cover of the Tuva–Mongolian microcontinent and the rocks of its Early Precambrian basement (Gargan block) was analyzed by the LA–ICP–MS method. The major stages of tectonomagmatic activity of this block include the Neoarchean, Paleoproterozoic (no younger than 2 Ga), and Neoproterozoic. Comparison of the age of zircons from Ediacaran terrigenous rocks of the Tuva–Mongolian microcontinent and sandstones of the reference sections of the Ediacaran shelf of the Siberian platform undeniably indicates their independent accumulation.

The geochemical and Sm–Nd isotope characteristics of Late Precambrian and Early Cambrian sandstones previously related to the sedimentary cover of the Dzabkhan continental block are reported. It is established that the Riphean and Vendian sedimentary rocks of the Ul’zitgol’skaya and Tsaganolomskaya Formations were accumulated within the Dzabkhan continental block as a result of recycling of the terrigenous deposits formed at the expense of destruction of basement rocks and younger granite. The formation of terrigenous rocks of the Bayangol’skaya Formation after a gap in sedimentation occurred in the sedimentary basin, where only the Late Riphean formations of the juvenile crust, probably of the Dzabkhan–Mandal block were the sources, without the contribution of the ancient crustal material. The Tsaganolomskaya and Bayangol’skaya Formations were formed in different sedimentary basins and cannot be related to the same complex.