The age relationships between the alkaline rocks from the region of the rare-metal (Y, REE, Nb, Ta) Aryskan deposit have been determined. Metamict zircon with high content of U, Th was used as a geochronometer. A dedicated treatment protocol was used for sample preparation for geochronological U–Pb (ID TIMS) studies. Dating of zircon from alkaline granites of the Aryskan and nearby Astyg massifs showed that their formation occurred almost simultaneously, 448 ± 1 and 446 ± 1 million years ago, respectively. The supposed genetic relationship of alkaline granites with the accomodating alkaline-feldspar syenites formed 472 ± 2 million years ago (zircon, U–Pb, ID TIMS), has not been confirmed.

Presents the results of U–Pb geochronological (ID–TIMS) studies of garnet and U–Th–Pb (LA–ICP–MS) “screening” geochronological studies of zircon from pyroxene-carbonate rocks of the Ukduska massif. The U–Pb age of garnets (1881 ± 8 million years) and age of zircon rim (1865 ± 16 million years) indicate the early Proterozoic age of these rocks. The results of geochronological studies allow to identify a new stage of carbonate magmatism within the southeastern part of the Charo-Olekminsky geoblock.

A complex problem of dating supracrustal rocks is unavoidable by analysis of tectonic position of polymetamorphic amphibolite and granulite complexes. Geochronological dates are necessary to constrain ages of source rocks and accumulation periods of clastic sediments, while isotopic-geochemical parameters open a possibility to estimate model ages of the crust in provenances. Using the ion microprobe SHRIMP(TM) (Hiroshima, Japan), clastic zircons from metasediments of the Erzin and Moren complexes of the Tuva-Mongolian massif in accretionary collage of Central Asia are dated and the Nd model age of respective rocks are estimated. The U-Th-Pb isotopic data suggest that elastic zircons from supracrustal complexes of the Tuva-Mongolian massif were derived from the Late Riphean rocks 0.70 to 0.90 Ga old. The upper age limit is determined by synmetamorphic granitoid intrusions 536 +/- 6 Ma old, and stratigraphic range of the complexes presumably corresponds to the terminal Upper Riphean-Vendian. The Early Riphean (1.4-1.5 Ga) and pre-Riphean (1.9 and 2.56 Ga) dates that are established in particular cases characterize most likely the ages of rock complexes in provenances of classic sediments. To the first approximation, the accumulation period of protoliths for gneiss-migmatitic complexes of the Tuva-Mongolian massif is correlative with the incipient breakup of Rodinia (similar to730 Ma ago) and opening of Vendian oceans. Accumulation of respective sediments in settings of a passive continental margin was connected with erosion of volcano-plutonic rock associations formed before the Rodinia breakup and at the commencement of this event. It is possible to assume that margins of Rodinia experienced rifting with breakout of their fragments 1.0-0.73 Ga ago, whereas formation of volcanic arcs and islands was in progress within the ocean surrounding that supercontinent. In the terminal Late Riphean and Vendian, rocks originated at that time and products of their destruction formed the basement beneath terrigenous and carbonate sediments of microcontinents, the Tuva-Mongolian massif included.

The geological evolution of the junction zone between the Olekma granite-greenstone belt and Aldan granulite-gneiss terranes (OGGB and AGGT, respectively) of the Aldan Shield involved at least four episodes of Early Proterozoic granitoid magmatism. The first of them was responsible for the origin of large massifs of anorogenic granitoids of the Nelyuki Complex at 2398 +/- 4-2522 +/- 2 Ma. The sources of the parental melts were tonalite-trondhjemite gneisses of the Olekma and Western Aldan stratigraphically undifferentiated complexes. which were tectonically combined during the collision of the Olekma and Aldan microcontinents at 2.6-3.0 Ga and the origin of the Olekma-Aldan microcontinent. The second and third episodes of the Early Proterozoic granitoid magmatism gave rise to granitoid intrusions of the Verkhnii Chugino (1993-1966 Ma) and Dzhaltunda complexes (1966 +/- 4 Ma), which are collisional with respect to the collision of the Olekma-Aldan microcontinent and the Fedorovskii island arc (origin of the Olekma-Aldan-Fedorovskii microcontinent). The parental magmas of the granitoids of the Dzhaltunda Complex were most probably derived from metapelites of the Aldan granulite megacomplex and/or metapelites of the Bulgunnyakhtakh greenstone belt. The fourth episode of Early Proterozoic granitoid magmatism in the junction zone of OGGT and AGGT produced granitoid intrusions of the Amut Complex (1899 +/- 6 Ma) in response to the collision of the Olekma-Aldan-Fedorovskii and Sunnagin (?) microcontinents. The parental magmas were derived from rocks compositionally similar to the metapelites of the Aldan granulite-gneiss megacomplex and/or the tonalite-trondhjemite gneisses of the Olekma undifferentiated complex. The Sm-Nd isotopic systematics of the rocks indicate that the Early Proterozoic granitoids of different ages in the junction zone of the Olekma granite-greenstone belt and Aldan granulite-gneiss terrane of the Aldan Shield were produced by the recycling of continental crustal rocks of Late Archean and Early Archean age. No traces of juvenile granite formation of Early Proterozoic age were detected in the zone.

Based on geological, petrochemical, and geochronological data, the postcollisional nature of granitoids of the Primorsky complex in western Cisbaikalia is substantiated. The age of the Primorsky complex granites determined by U-Pb zircon dating is 1859 +/- 16 Ma. These granitoids are similar in petrochemistry to A - granites and, partly, to classical Early Proterozoic rapakivi.We have established that in geologic setting, age, and composition the Primorsky complex granitoids are similar to other Early Proterozoic postcollisional granitoid complexes on the periphery of the Siberian craton Tarak, Sayan, Shumikha, and Kodar. Some petrochemical differences between these granitoid complexes are due to regional variations in the compositions of the sources of granites and the conditions of magma crystallization rather than to different geodynamic settings of the granite formation.The conclusion is drawn that the Early Proterozoic postcollisional granitoids spread throughout the southern flank of the Siberian craton originated during the completion of accretion of large lithospheric blocks and the formation of the Siberian craton in the period 1.84-1.88 Ga.

The Variscan high-grade crystalline basement of the Western Carpathians contains granitic to granodioritic bodies transformed to various degrees into orthogneisses. The orthogneisses resemble the structures of the host regional-metamorphic rocks, indicating their syn-collisional evolution, predating the intrusion of the granitoids around 360-340 Ma. The Nizke Tatry Mountains orthogneiss, dated at similar to381 Ma (NTJ-1 sample), emplaced during early partial melting stage deformation regime. Syn-tectonic magmatic flow and emplacement is suggested by the relics of magmatic foliations and lineations. Post-intrusion evolution comprises metamorphic/ductile medium-temperature fabrics of quartz, feldspars and micas, as well as metamorphic garnet growth. The granite-tonalite plutons emplaced between similar to353 Ma (Mala Fatra Mountains) and similar to343 Ma (Nizke Tatry Mountains, DUM-1 sample) during transtensive (?) deformation of the host metamorphic complex, show distinct magmatic fabric anisotropy, especially in their marginal parts, coeval with ductile fabrics of the orthogneisses. Petrologically the orthogneisses point to S-type granite or granodiorite, while the tonalites of large granitoid plutons seem to be of igneous I-type origin.

The basement structures of the southwestern Siberian craton include the cis-Sayan and Angara-Kan marginal uplifts that are parts of the Yenisei Ridge. The postcollisional granitoids abundant within the cis-Sayan uplift were earlier assigned to the Sayan and Shumikha complexes, but there was no unanimity in interpretation of their geodynamic environments. Geochemical studies of the Sayan granitoids at the junction between the Biryusa block and the Urik-Iya graben fill and the Shumikha granitoids at the junction of the Onot greenstone belt and the Sharyzhalgai block of mafic gneisses have confirmed the postcollisional nature of both complexes. The Shumikha granitoids share some features of A-type granites, including those typical of the Primorsky rapakivi-like complex in the western Baikal region. The Sayan and Shumikha granitoids were dated by the U-Pb zircon age method as 1858+-20 and 1871+-17 Ma, respectively. Interpreted in the context of 1.8-1.9 Ga granite magmatism on the craton periphery, the intrusion of the two complexes most likely postdated the collision responsible for the formation of an Early Proterozoic supercontinent between 2.0 and 1.9 Ga. Together with the Primorsky and Taraka complexes and the Akitkan volcanoplutonic belt, the Sayan and Shumikha intrusions record rather the onset of postcollisional extension which failed to cause continent break-up and oceanic crust production than the formation of the Proterozoic supercontinent.

We report the first U-Pb dates for allochthone hypersthene granites-kuzeevites-from the Angara-Kan protrusion of the Yenisei Range. The obtained age of 1734 +/-4 Ma marks the termination of folding and metamorphism under the PT-conditions of granulite facies which determined the internal structure of the Kan crystalline rocks.