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Syncollisional granite generated in zonal metamorphic complexes at 500-700°C and various pressure and in the presence of fluid of various composition are proved to differ in proportions of granite material generated by metamorphic, metasomatic, and magmatic processes. Monometamorphic low-pressure complexes devoid of the influx of foreign solutions are characterized by the most intense metamorphic differentiation: the dissolution and redeposition of quartz and plagioclase into lower pressure zones and the development of plagiomigmatites. The process starts with deformations of the schists at 500-550°C. The main factors (at a constant total composition of the rock) is an uneven pressure distribution and metamorphic solutions. This stage is followed by metasomatic granitization, which is initiated if shear motions and decompression are associated with influx of silicic alkaline solutions into the rocks and their transformation into migmatite (up to granite-gneiss). Granitization during this stage is controlled by an increase in the permeability of the rocks and the introduction of perfectly mobile Si, Na, and K and removal of Mg, Ca, and Fe, which modifies the composition of the rocks and makes them similar to granite. Metasomatic granitization may take place in low-pressure polymetamorphic complexes. Under a high lithostatic pressure and in the presence of water-carbon dioxide fluids (kyanite-sillimanite facies series of metamorphism), the magmatic process begins at higher temperatures. The early stages are dominated by metamorphic differentiation and metasomatic sodic migmatization. The rocks modified by these processes (their salic and mafic minerals are segregated) are affected by anatexis at 650-700°C (partial melting of the granite eutectic) and, at higher temperatures, by diatexis, which generates granite melts able to migrate. These processes are variably pronounced in all metamorphic complexes. [ABSTRACT FROM AUTHOR]

The central portion of the Aldan Shield hosts very widely spread Archean and Early Proterozoic granitoids, much of which are granite-gneisses. Geochemical lines of evidence, data on inclusions in minerals, and Sm-Nd isotopic geochemical data suggest that the protoliths of granite-gneisses in the central part of the Aldan Shield were granitoids that had various composition, age, and were derived from distinct sources and under different parameters and were then emplaced in different geodynamic environments. The granitoids belong to at least two types of different composition that occur within spatially separated areas. The protoliths of granite-gneisses in the western part of the Western Aldan Megablock and the junction zone of the Chara-Olekma and Aldan geoblocks (granite-gneisses of type I) had the same age and affiliated to the same associations as the within-plate granitoids of the Nelyukinskii Complex. Their parental melts were derived at 2.4-2.5 Ga by the melting of Archean tonalite-trondhjemite orthogneisses of the Olekma and Aldan complexes. The protolith of granite-gneisses in the eastern portion of the Western Aldan Megablock (granite-gneisses of type II) can be subdivided into two groups according to their composition: granitoids with geochemical characteristics of subduction- and collision-related rocks. The protoliths of the type-II granite-gneisses with geochemical characteristics of subduction granitoids were produced simultaneously with the development of the Fedorovskaya island arc (at 2003-2013 Ma), whereas the protoliths of the type-II granite-gneisses with geochemical characteristics of collision granitoids were formed in the course of accretion of the Fedorovskaya island arc and the Olekma-Aldan continental microplate at 1962-2003 Ma, via the melting of magmatic rocks of the Fedorovskaya unit and older continental crustal material. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Based on the results of Sm-Nd isotopic geochemical and U-Th-Pb geochronological LA-ICP-MS studies, it has been established that the formation of metamorphic rock protoliths of the Stanovoi Complex in the western Dzhugdzhur-Stanovoi Superterrane of the Central Asian Foldbelt took place over the following time spans: 2750-2860 Ma (Ilikan Group of the Ilikan Zone), 1890-1910 Ma (Bryanta Group of the Bryanta Zone), and ~2.0 Ga (Kupuri and Zeya groups of the Kupuri and Zeya zones, respectively). It has been shown that the western part of the Dzhugdzhur-Stanovoi Superterrane was formed ~1.9 Ga ago, as a result of collision of the Neoarchean Ilikan Terrane, the Paleoproterozoic island arc, and the Paleoproterozoic Kupuri-Zeya Terrane. The data make it possible to consider the Kurul'ta, and Zverevo blocks of the Stanovoi Structural Suture and the Ilikan Terrane of the Dzhugdzhur-Stanovoi Superterrane of the Central Asian Foldbelt as constituents of a common terrane. [ABSTRACT FROM AUTHOR]

Geochronological (LA–ICP–MS) U–Th–Pb studies of detrital zircon of the Late Cenozoic sand deposits on Ol'khon Island have been performed. It has been shown that their main source is represented by Early Paleozoic igneous and metamorphic complexes of the Ol'khon Terrane of the Central-Asian Mobile belt and Late Carboniferous–Early Permian granitoids of the Angara–Vitim batholite. Sands from the source were transported over a distance of no less than 100 km. It is supposed that it was effectuated by strong air flows, over the ice on the Lake Baikal in particular. [ABSTRACT FROM AUTHOR]

The Gilyui Complex includes sedimentary and volcanic rocks metamorphosed to amphibolite and epidote-amphibolite facies, which constitute blocks confined to the main structural sutures of the Dzhugdzhur-Stanovoi superterrane in the Central Asian fold belt. In recent stratigraphic scales, they are considered as being Neoarchean in age with Nd model age values of 1.5-3.0 Ga. The youngest detrital zircons from metamorphosed mudstone of the Gilyui Complex yield a date of 285 ± 4 Ma, which determines the lower age limit for the formation of its protolith. The age of crystallization of rhyolites from the Gilyui Complex is determined to be 231 ± 4 Ma. If the rhyolites form volcanic flow units or sills, the Gilyui Complex is approximately 230 Ma or 231 ± 4 to 285 ± 4 Ma old, respectively. [ABSTRACT FROM AUTHOR]

The basement of the Zheltav sialic massif (Southern Kazakhstan) is composed of different metamorphic rocks united into the Anrakhai Complex. In the southeastern part of the massif, these rocks form a large antiform with the core represented by amphibole and clinopyroxene gneissic granite varieties. By their chemical composition, dominant amphibole (hastingsite) gneissic granites correspond to subalkaline granites, while their petroand geochemical properties make them close to A-type granites. The U-Pb geochronological study of accessory zircons yielded an age of 1841 ± 6 Ma, which corresponds to the crystallization age of melts parental for protoliths of amphibole gneissic granites of the Zheltav Massif. Thus, the structural-geological and geochronological data make it possible to define the Paleoproterozoic (Staterian) stage of anorogenic magmatism in the Precambrian history of the Zheltav Massif. The combined Sm-Nd isotopic-geochronological data and age estimates obtained for detrital zircons indicate the significant role of the Paleoproterozoic tectono-magmatic stage in the formation of the Precambrian continental crust of sialic massifs in Kazakhstan and northern Tien Shan. [ABSTRACT FROM AUTHOR]

U-Pb zircon isotopic data on rocks from the Kandalaksha-Umba zone of the Lapland granulite belt in the Por'ya Bay area constrain the age of the protolith of the apodacite (apotonalite) Opx- Bt granulite gneisses at 2799 ± 4 Ma, and the age of the apogabbronorite Grt- Opx- Cpx- Hbl crystalline schists at 2315 ± 23 Ma. The U-Pb sphene age of the magmatic crystallization of the postmetamorphic granodiorites is 1901 ± 5 Ma. The zircon yields the U-Pb age of the contamination of xenogenic zircons, which were captured during the dissolution of xenoliths of the host Grt- Opx- Cpx- Hbl crystalline schists in granodiorite melt. The comparison of the most important attributes of the endogenic histories of the adjacent Lapland Granulite and Belomorian Mobile belts testifies to their similar evolutionary histories: (1) the protolith age of the acid Opx- Bt granulites of the Lapland Belt (2799 ± 4 Ma) coincides with the protolith age of acid gneisses in the Belomorian Belt (2890-2690 Ma); (2) the ages of the gabbronorite protolith of Grt- Opx- Cpx- Hbl granulites in the Lapland Belt (2315 ± 23 Ma) and gabbro-anorthosite in the Kolvitsa Massif (2462-2423 Ma) are close to the protolith age of eclogitized gabbronorites in the Belomorian coronite suite (2.46-2.36 Ga); (3) the age of granulite metamorphism of acid and mafic rocks in the Lapland Belt is 1912-1925 Ma, and the age of eclogite metamorphism of gneisses and metabasites in the Belomorian Belt is approximately 1.9 Ga, i.e., their metamorphism took place in Svecofennian time; (4) the peak pressure of granulite metamorphism in the Lapland Belt was 9-11 kbar at a temperature of 800-850°C, whereas the peak metamorphic parameters of eclogite metamorphism in the Belomorian Belt were 10-12 kbar and 640-700°C. This means that the metamorphic complexes of the Lapland and Belomorian belts had the same Mezo- and Neoarchean protoliths hosting bodies of Paleoproterozoic gabbroids and were completely formed largely by a single cycle of Svecofennian high-pressure zonal metamorphism within a temperature range from the lowest grade of the eclogite to the granulite facies. [ABSTRACT FROM AUTHOR]

U-Pb (LA-ICPMS) geochronological studies established the minimum age of detrital zircons from metasedimentary rocks of the Uril Formation of the Amur Group of ∼240 Ma, which approximately corresponds to the lower age boundary of formation of their protoliths. The upper boundary of accumulation of sedimentary rocks of this formation is governed by the age of superimposed structural-metamorphic transformations (220-210 Ma). It follows that the age of protoliths of metasedimentary rocks of the Uril Formation is Triassic in contrast to the previously suggested Early Precambrian age. At the same time, previous estimations of the Nd model age of metasedimentary rocks of the Tulovchikha Formation of the Amur Group and intruding gabbroic rocks are 1.7 and 0.5 Ga, respectively. In other words, the age of this formation is 1.7-0.5 Ga. All of this indicates a combination of sedimentary and volcanic rocks of different ages in the section of the Amur Group. Judging from the Lu-Hf isotopic-geochemical studies of zircons, the major sources of protoliths for metasedimentary rocks of the Uril Formation are Neoproterozoic igneous rocks and also Early and Late Paleozoic and Early Mesozoic igneous rocks, the formation of which was related to the reworking of the Neo- and Mesoproterozoic continental crust. [ABSTRACT FROM AUTHOR]

The article presents information on a study which determines the age of the protolith for metamorphic rocks of the Gonzha Group. It provides information on Gonzha Group which unites metamorphic rocks of the tectonic block located in the north-eastern part of the Argun terrane in the Central Asian fold belt. It reveals that uranium-lead (U-Pb) geochronological and Lutetium-Hafnium (Lu-Hf) isotopic-geochemical investigations of detrital zircons from metasedimentary rocks of the Gonzha Group were performed in the study. A graph with concordia for zircons from meta-sedimentary rocks of the Gonzha Group is presented. A geological map is also presented.