The paper presents the results of study of Rb–Sr isotopic system of ore-hosting granitoids, metasomatites after granites, and hydrothermalites of the Upper Karalon gold deposit, as well as the Pb–Pb isotopic system of galena of low-sulfide gold–quartz mineralization of the Karalon gold field. Three groups of ore objects with various Pb isotopic composition of galena are distinguished. Different contribution of mantle and ancient crustal sources is identified for each group. The Pb isotopic composition of galena of the Upper Karalon deposit indicates its genetic link with ore-hosting granites, the age of which (∼600 Ma) could be close to the age of the earliest stage of formation of gold–quartz mineralization. The ancient crustal source is common for the leading gold deposits of North Transbaikalia and exhibits the continental crust parameters of the Siberian Craton at the period of 500–600 Ma. It is established that the Rb–Sr system of the studied rocks and minerals of the Upper Karalon deposit was reconstructed and the Pb isotopes of galena of the Vodorazdel’naya ore zone of the Karalon ore field were redistributed at the boundary of 290–250 Ma. The isotopic data show that the processes of the formation of gold mineralization in geological evolution of the Upper Karalon deposit and Karalon ore field were characterized by long multistage character and accompanied by the regeneration of primary ore concentrations.

Geochemical, geochronological (U–Pb zircons, ID-TIMS) and isotope-geochemical (Sm–Nd) studies of the rocks of the Bambukoy volcano-plutonic association, which form the Zhanok-Bambukoy volcano-tectonic structure within the Anamakit–Muya terrane on the northern flank of the Barguzin–Vitim superterrane of the East Transbaikalian segment of the Central Asian orogenic belt. The association includes volcanic rocks of the Zhanok Suite (dacites and rhyolites mainly), as well as leucocratic and biotite granites of the Bambukoy Complex that cut through them. The granites of this complex host the Mokhovoe tin deposit, which is attributed to the tin-porphyry formation. Subvolcanic rocks of the Zhanok Suite are considered as ore-bearing. The geochemical features of the volcanic rocks of the Zhanok Suite and the granites of the Bambukoy complex bring them closer to S-type granites, and belonging to a single tin-bearing Bambukoy volcanic-plutonic association. The formation of this association is determined by the age interval 834 ± 23–818 ± 7 Ma. The isotopic data point to a source of parental magmas from the rocks of the Bambukoy volcano-plutonic association, formed as a result of mixing of the material of two crustal sources, the mature Early Precambrian and the juvenile Early Baikal. The geochemical data also point to an exclusively crustal source of the rocks of this association. Thus, the Bambukoy tin-bearing volcano-plutonic association was formed in the Neoproterozoic time (Tonian), most likely under lithospheric extension conditions due to a source with a complex and long crustal prehistory.

The article presents the results of studying the Rb–Sr isotope system of ore-bearing granitoids, apogranite metasomatites and hydrothermalites of the Verkhnekaralonskoye gold deposit, as well as the Pb-Pb isotope system in galena of the gold-quartz low-sulfide mineralization of the Karalonskoye gold ore field. Three groups of ore objects with different Pb isotopic compositions of galena associated with varying contributions from mantle and ancient crustal sources have been identified. The isotope characteristics of Pb in galena of the Verkhnekaralonskoe deposit indicate its genetic relationship with ore-bearing juvenile granites, whose age of ~ 600 Ma may be close to the age of the earliest stage in the formation of gold–quartz mineralization. The ancient crustal source is common for the leading gold deposits of Northern Transbaikalia and is characterized by the parameters of the continental crust of the Siberian craton at a time of 500–600 Ma. The rearrangement of the Rb–Sr system in the studied rocks and minerals of the Verkhnekaralonskoe deposit and the redistribution of Pb isotopes in galena of the Vodorazdelnaya ore zone of the Karalonskoe ore field at the turn of 290–250 Ma have been established. Isotope data show that in the geological history of the Verkhnekaralonskoe deposit and the Karalonskoe ore field, the formation of gold mineralization had a long multi-stage character and was accompanied by the regeneration of primary ore concentrations.

— The results of geochronological study (U–Pb SHRIMP-II) of zircons from granodiorites and plagiogranites of the main phase of the Tallai pluton of the Baikal–Vitim belt are presented. The obtained estimates of the age of the magmatic cores of zircons from granodiorite and plagiogranite coincide with each other within the limits of errors and are interpreted as the age of crystallization of rocks of the main phase of the Tallai pluton, 661 ± 6 Ma. The weighted average value of the age of the metamorphic rims of zircon from these rocks is 637 ± 5 Ma. The high positive values of ε Nd (660), +7.2 and +7.3, in the rocks of the main phase indicate a juvenile source of the parental melts. Based on new and earlier published geochronological data, a conclusion about the formation of Late Baikalian juvenile gabbro–granite associations of the same type within the Baikal–Vitim belt 660 million years ago (Tallai complex) and in the interval of 603–615 Ma (Padora complex) was made.

The results of a geochronological study (U–Pb SHRIMP-II) of zircon from granodiorites and plagiogranites of the main phase of the Tallain pluton of the Baikal-Vitim belt are presented. The obtained estimates of the age of the magmatic cores of zircon from granodiorite and plagiogranite coincide with each other within errors and are interpreted as the age of crystallization of rocks of the main phase of the Tallain pluton 661 ± ± 6 million years. The weighted average age of the metamorphic zircon shells of these rocks is 637 ± 5 million years. High positive values of ɛNd (660) +7.2 and +7.3 in the rocks of the main phase indicate a juvenile source of the parent melts. Based on new and previously published geochronological data, a conclusion is made about the formation of similar late Neoproterozoic juvenile gabbro-granite associations of the Baikal-Vitim belt at the turn of 660 million years (Tallain complex) and 603–615 million years (Padorinsky complex).

The paper presents data on the geological structure of the Kichera zone of the Baikal–Vitim belt (BVB) at the boundary between the marginal part of the Siberian craton and the Barguzin–Vitim superterrane of the Central Asian Orogenic Belt. Early Neoproterozoic (Early Baikalian) and Late Neoproterozoic (Late Baikalian) structures and complexes are identified and characterized in the Kichera zone of the BVB. Data are presented on the geochemistry of the rocks and on their U–Pb isotope age (zircon, SIMS and ID-TIMS) and on the Nd isotope characteristics of rocks from various parts of the Kichera zone, including representative rock association of the Nyurundukan migmatite–tonalite–metabasite complex with MORB-type tholeiites and tholeiites with intraplate geochemical features. It is shown that the sources of the Early Neoproterozoic complexes of the Kichera zone, which were metamorphosed at 0.76–0.74 Ga as a result of accretion events in the marginal part of the craton, were dominated by Early Precambrian recycled crustal material. The Late Neoproterozoic complexes typomorphic of the Kichera zone were formed in the Cryogenian–Ediacaran (720–545 Ma) from prevailing juvenile sources. Our data suggest that the metabasites of the Nyurundukan complex were formed in an environment of segmented troughs of the pull-apart paleorift system of the Kichera zone and can be compared with a reduced complex of continental-margin ophiolites transformed at 630 ± 7 to 615 ± 3 Ma. The destruction of the ancient continental crust of the craton ended with the formation and exhumation of deep rocks in the Late Ediacaran, the emplacement of adakite granites of the postcollisional geochemical type, and the formation of grabens filled with a terrigenous complex. The juvenile and riftogenic crust produced during the Late Neoproterozoic tectonic evolution of the Kichera rift zone does not show any features of mature continental-type crust.

New geochronological (U–Pb ID-TIMS) data on zircons from pegmatites of the Mama mica belt in the Baikal Highlands are presented. The ages obtained for the plagioclase pegmatites (388 ± 2 and 389 ± 2 Ma, Mochikit deposit) and two-feldspar pegmatites (333 ± 1 and 332 ± 3 Ma, Slyudyanka deposit) demonstrate a significant age gap (50–60 Ma) between them. Based on the entire set of geological and new geochronological data available, it is proposed to divide the Mama complex, to which they were previously assigned, into two separate granitoid complexes.

The results of U–Pb geochronological (SIMS) study of zircons from granitoids of the Konstantinovskii Stock located 6 km from the Sukhoi Log gold deposit are reported. The 206Pb/238U weighted average age for long-prismatic crystals, rims, and cores of the early stage of crystallization of zoned zircons is 303 ± 3 Ma (MSWD = 0.87). The data obtained on the age of xenogenic cores of zoned zircons of the Konstantinovskii Stock granitoids indicate consolidated basement of the Bodaibo epicratonic sedimentary basin and its intraplate tectono-thermal transformation in the Archean, Paleoproterozoic and Paleozoic.

This article presents the results of U–Pb geochronological study of gneiss-granites of the Mamskaya zone. The age estimate of 1874 ± 9 Ma (SIMS method) obtained for the magmatic protolith of gneiss-granites for the first time proves the close formation time of gneiss-granites from the Mamskaya zone and rapakivi-like granites of the Kodar complex in the Chara–Olekma block. In the Late Devonian and Carboniferous, according to preliminary data, the Paleoproterozoic protolith of the gneiss-granites underwent deep metamorphic processing during shear deformations and formation of pegmatoid granites and pegmatites.

This work presents the results of U–Th–Pb (LA–ICP–MS) geochronological study of detrital zircons from terrigenous deposits of the Olokit zone of the Baikal–Patom fold–thrust belt of the Siberian Craton. It was established that the age of deposits of the Olokit Formation is in the range of 0.86–0.72 Ga. Archean and Early Proterozoic rocks of the southern part of the Siberian Craton and the Neoproterozoic complexes of the Baikal–Muya belt were the sources of detrital zircons of the terrigenous rocks of the Olokit zone. There is no evidence of rocks that could have been the sources of Mesoproterozoic (1.08–1.46 Ga) and Late Paleoproterozoic (1.65 Ga) detrital zircons for the deposits of the Ondok paleo-uplift in the Olokit zone, in the Baikal mountain region, and in the Siberian Craton. The data obtained and the results of paleomagnetic reconstructions indicate that Siberia and Laurentia in the Meso- and Early Neoproterozoic were in a fixed position relative to each other; an unknown continental block composed of Mesoproterozoic rocks could have occupied the space between them.

New results of U–Pb zircon and Nd–isotope analyses of the Goryachinskiy Pluton adakite granites have been obtained. The pluton is exposed along the Baikal coast in the section where a section of sheared tectonic sheets of the Baikal–Muya Belt wedges out. The determined Early Cambrian (545 ± 6 Ma) age of the granitoids is unusual in the Northern Baikal region. These new geological and isotopic data are interpreted as an indication of the formation of the granitoids studied at the final stage of the Late Baikal strike–slip tectonics, which caused the pulse of the adakite magmatism within the Baikal–Muya belt.

This paper presents the results of U–Pb isotope–geochronological study on zircons from subalkali gabbros and granodiorites of the Dogaldyn intrusive massif located in the Karalon–Mamakan zone of the Baikal–Muya belt. The ages of 254 ± 2 and 256 ± 1 Ma yielded for rocks of the two main intrusion phases do not differ significantly from each other and correspond to the Late Permian period. The Nd-isotope and geochemical data indicate the relationship between the primary melts of intraplate rocks from the Dogaldyn Massif and various sources, including plume–mantle and ancient crustal ones. The manifestations of Late Permian intraplate magmatic activity in the Baikal–Muya belt could have been induced by the Iberian superplume framed by the Siberian trap province.

The paper present new data on the geology of the Karalon gold ore field in northern Buryatia, including its regional position and a brief description of the mineralization, gold–sulfide and gold–quartz–low-sulfide ore objects, host rocks, and complexes, which are components that make up juvenile Late Neoproterozoic Earth’s crust formed in the course of rifting. Paleozoic dike series are characterized, as well as the ore-controlling complex of beresite–listvenite metasomatic rocks. Regularities in the emplacement of gold objects and their control are generalized. Veins and veinlets of gold–quartz mineralization are hosted in gently and steeply dipping structures in the ore field, which formed prior to the intrusive Dogaldyn massif of subalkaline rocks 252 Ma ago.

The Kichera zone of the Baikal–Muya Belt consists of alternating tectonic plates with rocks of different metamorphic facies. Garnet–cordierite–sillimanite gneiss from the tectonic fragment in granite–gneiss of the Baikal massif with an age of 755 ± 15 Ma from the Goremyka plate and two-pyroxene schist of the granulite complex with an age of 617 ± 5 Ma from the Boguchan plate were studied. Thermobarometric studies of these key metamorphic rocks were carried out using the avPT (THERMOCALC) and TWEEQU (TWQ 2.01) methods. The P–T parameters estimated for the cordierite⎯sillimanite gneiss of the Goremyka plate correspond to the boundary between the amphibolite and granulite facies. Granulites of the Boguchan plate belong to the HT–LP type. Exhumation of metamorphic rocks could be caused by extension upon the evolution of the Late Baikal rifting.

This work presents the results of U–Pb isotope dating of zircons from granodiorites and plagiogranites of the Tallainskii gabbro–granodiorite–plagiogranite complex of the Karalon–Mamakan zone of the Baikal–Muya belt, ascribed to the Tallainskii pluton. The age datings obtained for granodiorite of the Eleninskii massif (605 ± 6 Ma) and plagiogranite of the Ust-Berezovo massif (609 ± 6 Ma) are in close agreement within the limits of error. Taking into account previously published data, the emplacement of the Tallainskii complex occurred within the age interval of 615–603 Ma in connection with postcollision extension. The “island arc” geochemical characteristics of granodiorites and plagiogranites can be explained by magmatic differentiation and (or) participation in the formation of a melt source enriched in the suprasubduction component involved in petrogenesis during the preceding Neoproterozoic period.

Geochemical and Sm–Nd isotope–geochemical studies of synnyrite and syenite from the Synnyr massif and high-K syenite from the Tas massif of the Late Paleozoic (eastern Siberia) corresponding to one of the largest provinces of high-K and ultrapotassic magmatism worldwide are performed. It is shown that their formation was controlled by transformation of the Precambrian continental crust of the Siberian Craton and Central Asian Mobile Belt under the influence of the Siberian mantle plume.

It was established that amphibolites of the Kichera zone of the Baikal-Muya belt (BMB) belong, at least, to two age groups: (I) Early Neoproterozoic large metamafic xenoliths entrapped by granitic rocks of 750 Ma and (II) Late Neoproterozoic (650-620 Ma) amphibolites, which compose individual tectonic sheets and lenses. The rocks of these groups are distinct in chemical composition: the low-Ti amphibolites of the first group with increased Al2O3 contents are similar to modern IABs, whereas the highly-Ti amphibolites of the second group correspond to MORBs and OIBs. The geochemical data showed that the igneous protoliths of amphibolites of the Kichera zone were formed during different stages of the BMB evolution distinct in geodynamic settings.

We argue that the production of mantle-derived or juvenile continental crust during the accretionary history of the Central Asian Orogenic Belt (CAOB) has been grossly overestimated. This is because previous assessments only considered the Palaeozoic evolution of the belt, whereas its accretionary history already began in the latest Mesoproterozoic. Furthermore, much of the juvenile growth in Central Asia occurred in late Permian and Mesozoic times, after completion of CAOB evolution, and perhaps related to major plume activity. We demonstrate from zircon ages and Nd–Hf isotopic systematics from selected terranes within the CAOB that many Neoproterozoic to Palaeozoic granitoids in the accreted terranes of the belt are derived from melting of heterogeneous Precambrian crust or through mixing of old continental crust with juvenile or short-lived material, most likely in continental arc settings. At the same time, juvenile growth in the CAOB occurred during the latest Neoproterozoic to Palaeozoic in oceanic island arc settings and during accretion of oceanic, island arc, and Precambrian terranes. However, taking together, our data do not support unusually high crust-production rates during evolution of the CAOB. Significant variations in zircon εHf values at a given magmatic age suggest that granitoid magmas were assembled from small batches of melt that seem to mirror the isotopic characteristics of compositionally and chronologically heterogeneous crustal sources. We reiterate that the chemical characteristics of crustally-derived granitoids are inherited from their source(s) and cannot be used to reconstruct tectonic settings, and thus many tectonic models solely based on chemical data may need re-evaluation. Crustal evolution in the CAOB involved both juvenile material and abundant reworking of older crust with varying proportions throughout its accretionary history, and we see many similarities with the evolution of the SW Pacific and the Tasmanides of eastern Australia.