Based on new mineralogical, petrographic, geochemical (ICP-MS), and geochronological (U–Pb, SHRIMP-II) data, small rapakivi intrusions and associating intermediate and acid rocks in the Allakh-Yun and Olchan-Nera tectonic zones of the southeastern margin of North Asia are combined into the Late Cretaceous Severookhotsky complex (94–88 Ma). Rocks of this complex were formed from mantle (enriched) and crustal sources in an active continental margin setting, in the back-arc of the West Okhotsk sector of the Okhotsk-Chukotka volcanoplutonic belt, after magmatism is this sector faded. 308 The magmatism of the Severookhotsky complex, including rapakivi granitoids, is regarded as a source and trigger for metasomatic processes during the formation of the adjacent and synchronous Au-Bi mineralization in the Allakh-Yun tectonic zone.

New data on the U–Th–Pb geochronology, mineralogy, geochemistry, and Sm–Nd and Rb–Sr isotopes for granitoids and the associated subalkaline rocks of the Tarbagannakh pluton of the Allakh-Yun tectonic zone in the Verkhoyansk fold-and-thrust belt are presented. These rocks, including trachyandesibasalt dikes, combined into the Uemlyakh complex, were formed about 120 Ma from a continental crust source probably with input from an enriched mantle component. Rapakivi granites are reported for the first time among them; their origin is reference for understanding the geodynamic conditions of formation of rocks in this complex. A tectonic model for the formation of these rocks due to slab break-off during the development of the active continental margin in the Aptian age is proposed. It is discussed that this magmatism was conducive for the widespread development of metasomatic processes until the end of the Aptian age and was at the same time a source of the coinciding spatially gold mineralization of the Okhotsk–Koryak metallogenic belt.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070425

—The paper presents data on the composition and age of mafic rocks of the shoshonitic series in the Irkut block of the Sharyzhalgai uplift (southwest of the Siberian Сraton). According to the U–Pb dating of magmatic zircon, the formation of monzodiorites of the Poludennyi massif and gabbro-dolerites in the endo- and exocontact zones of the Toisuk pluton occurred at 1.87 and 1.86–1.85 Ga, respectively. The intrusion of mafic magmas and their underplating into the basement of the crust under postcollisional extension resulted in the near-coeval mafic and granitoid magmatism in the Irkut block between 1.87 and 1.84 Ga. The Paleoproterozoic mafic associations belong to the shoshonitic series and are characterized by enrichment in incompatible elements, including Zr, and low negative εNd(T) values. These geochemical and isotopic characteristics point to the derivation of magma from a long-lived enriched-mantle source, such as the subcontinental lithospheric mantle. The crystallization of zircon from the last portions of the evolved mafic melt is evidenced by low zirconium saturation temperatures (710–965 °C) and zircon enrichment in U and Th with increasing Th/U, reflecting the growth of concentrations of highly incompatible elements in the residual melt.

— 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.

Abstract An U–Pb isotopic investigation combined with rare earth element data for titanites, zircons and coexisting accessories has been undertaken to gain insight into the formation of the Archean peralkaline granites of the northeastern Fennoscandian Shield and to test the stability of titanite during metamorphic and hydrothermal processes. The obtained set of isotope data shows that whereas more stable zircon retains a memory of the major episodes of granite evolution, the coexisting titanite provides additional information on crystallization, subsequent growth, cooling and alteration of the plutonic complexes. In addition to titanites formed at the magmatic stages of c. 2710 and c. 2650 Ma, the peralkaline granites contain titanite populations which have undergone major resetting at c. 1870 Ma during the burial metamorphism related to the Svecofennian orogeny and the 1760 Ma hydrothermal alteration near contemporaneous with regional metamorphism of c. 1780 Ma. The peralkaline granites which contain c. 2710 Ma titanites also include inherited titanite grains of an age of 2795 Ma. These data support the concept that the titanite can remain a closed system to Pb diffusion at temperatures of peralkaline granite melt (<800°C) as long as the crystals escape magmatic or metamorphic recrystallization.

In this paper, we discuss new data obtained by petrographical, geochemical, geochronological, and isotopic–geochemical study of magmatic rocks within the Malmyzh and Gion gold–copper-porphyry ore fields. Geochronological data show a Late Cretaceous age of their magmatic crystallization: Cenomanian (97–99 Ma) and Campanian (76–82 Ma) ages, respectively. Based on a comparative analysis of the studied samples igneous rocks with each other and with magmatic rocks of worldwide porphyry deposits, the results of a study using a secondary ion mass spectrometer of the patterns of distribution of trace elements (REE + Y, Hf, Ti, U, Th, and Pb) in accessory zircons from igneous rocks of the Malmyzh and Gion ore fields are discussed in order to estimate their potential ore content in the gold–copper-porphyry mineralization. Despite the fact that economic gold–copper ore mineralization within the potential Gion ore field was previously unknown, an analysis of the results shows, that according to the obtained values of indicative geochemical parameters of accessory zircons, the granitoids involved in its geological structure practically do not differ from the granitoids of both the neighboring Malmyzh deposit and most of the worldwide porphyry gold–copper deposits.

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).

Mountain frame of the Denman Glacier is a little explored and at the same time an most essential region of East Antarctica in the context of studying the Precambrian geological history and geodynamic evolution of the Archean protocratons of East Antarctica. Present paper provides original U–Pb isotope geochronology data from zircons of metamorphic and intrusive rocks sampled from the Denman Glacier western flank outcrops. Geodynamic interpretation of geochronology data are also presented. For the first time, for such East Antarctic location, crystallization time (3355 ± 5.4 Ma) for plagiogneisses magmatic protolith was obtained. The Davis Paleoarchean protocraton in the Archean time interval of evolution was subject to multistage polymetamorphism in the intervals ~3100–3000, 2900–2800 Ma ago. The late stage is associated with crustal extension, which is marked by syntectonic intrusion of ultramafic dikes and pyroxenite sills (2827 ± 6 Ma). The formation time of granite veins and subalkaline granitoid pluthons corresponds to the time of tectono-thermal activisation in the interval of 550–510 Ma traced also along significant part of East Antarctic (the Pan-African tectono-thermal event). The Davis terrane shows a significant similarity in the time of formation and evolution of geodynamic processes with the Paleo-Mesoarchean protocratons of East Antarctica, as well as India and Australia.

Gabbro-dolerite dikes were studied in the junction zone between two structures of different ages of the Fennoscandian shield: the Archean Fenno-Karelian craton and the Raakhe–Ladoga zone. Their composition was analyzed and U-Pb baddeleyite and zircon age was determined for the first time for the Russian territory. The Paleoproterozoic age has been established both for the gabbroic rocks of the Fenno-Karelian craton (previously considered Archean) and for the gabbro-dolerites of the Raakhe–Ladoga zone. The dike swarms within the Fenno-Karelian craton were formed in two stages: within 2091 ± 9–2086 ± 6 Ma near the Raakhe–Ladoga zone and in the central part of the studied area and within 1938 ± 6–1933 ± 26 Ma in the northern part. Sills of the Raakhe–Ladoga zone (2081 ± 7 Ma) were formed simultaneously with the earlier dikes of the Fenno-Karelian Craton (2091 ± 9–2086 ± 6 Ma). Primary magmas were derived from different sources. Most of the bodies of the Fenno-Karelian craton have high (La/Lu) N , negative niobium anomalies, predominantly negative εNd values, which suggests a contribution of a metasomatized lithospheric mantle. Some dikes of the Raakhe–Ladoga zone have the same source, but most rocks were obtained by mixing of depleted mantle and more primitive mantle source. The studied gabbrodolerite dikes were likely formed in a rifting tectonic setting.

We report results of geological, mineralogical-petrographic, geochemical, isotope-geochemical (Sm–Nd, Rb–Sr), and geochronological (U–Pb, 40Ar/39Ar) studies of acid and intermediate intrusive rocks (granodiorites, leucocratic granites, subalkaline granites, and subalkaline leucocratic granites, diorites, and quartz diorites) of the Bukeschen and Samyr small plutons in the western part of the Yana–Kolyma gold belt (northeast Asia). These rocks are combined with Late Jurassic (151–145 Ma) dikes of basic, intermediate, and acid compositions into a single complex of small intrusions. They intrude the Upper Triassic–Middle Jurassic terrigenous deposits of continental margin blocks in the eastern part of the Verkhoyansk–Kolyma folded area. Our new U–Pb data for zircon (SHRIMP-II) indicate that the Bukeschen and Samyr pluton granitoids formed in the Berriasian, at 144.5 and 143 Ma, respectively. The small-intrusion granitoids have geochemical and isotope (Sm–Nd and Rb–Sr) characteristics similar to those of Late Jurassic dikes of varying composition. Therefore, they can be united into a single complex of small intrusions generated from a mixed source with the participation of mantle (OIB- and E-MORB type), lower crust, and subduction components and with Paleoproterozoic–Mesoproterozoic Sm–Nd model age estimates for the magma sources. Late Jurassic–Early Cretaceous magmatic and postmagmatic events and cooling of the intrusions played an important role in the processes of gold localization in the western part of the Yana–Kolyma gold belt. This is reflected in two tectonothermal stages (accounting for closing temperatures of the U–Pb, 40Ar/39Ar, and Re–Os isotope systems for different minerals) estimated at 151–141 and 138–137 Ma. These results for the small-intrusion complex agree with the tectonic model of the evolution of an active continental margin (northeastern Siberia) in the Mesozoic era, whose final development stage in the Berriasian age saw the formation of mostly small granitoid plutons.

Data on the petrographic–geochemical and U–Th–Pb geochronological studies of granitoids of the Bukeschensky and Samyrsky massifs of small intrusions complex of the western part of the Yana–Kolyma gold belt are reported. The granitoids intruded terrigenous rocks of the Kular–Nera and Polousniy–Debin terranes and the Verkhoyansk fold and thrust belt. According to the U–Pb geochronological data obtained on zircons (SIMS SHRIMP-II), the granitoids were formed in the Early Cretaceous, in the interval of 144.5–143 Ma. Their geochemical characteristics are similar to the associated Late Jurassic (151–145 Ma) dikes of various composition of the Nera–Bokhapcha complex. The granitoids could have been formed from a mixed source with the participation of mantle (OIB- and E-MORB-type), subduction, or crustal components. The intrusion into the Early Cretaceous granitoids probably contributed to the final processes of migration and localization of gold in the Yana–Kolyma belt. Systems of tectonic faults of different orders, such as longitudinal (northwestern), Adycha–Taryn and others, and faults transverse to them (northeastern), also played in favor of this process.

U-Pb dating of magmatic zircons from the Permian meta-andesites of the Cierna Hora Mts. yielded the Concordia ages of 267.0 +/- 1.5 Ma, which correspond to the Guadalupian Epoch in the time span of the Wordian Stage. The sequence was correlated with the Northern Veporic Permian rocks from the Ciertaz Mts. From the geochemical point of view, the studied volcanic rocks belong to a peraluminous calc-alkaline magmatic suite, linked to the post-collisional lithospheric extension. Lithosphere extension and attenuation will promote upwelling of hot asthenosphere. In this context, the calc-alkaline affinity may result through extensive crustal contamination of basaltic magma. Continuous extensional setting, succeeded by overheating is indicated by the newly formed zircon rims of 252.2 +/- 3.2 Ma age at the edges of the Wordian zircon grains. The Neoproterozoic (618 +/- 8 Ma) and Paleoproterozoic (2080 +/- 13 Ma) ages were found within the xenocrystic cores in the studied magmatic zircon grains. The presented xenocrystic zircon ages indicate derivation from the Variscan basement rocks with reworked fragments of Cadomian crust.

The Baltic Shield is one of the world's largest ( ca 2500 km 2 ) provinces of alkaline granites which are confined to the Keivy segment of the Kola fold system and are represented by three series of mantle-source rocks of different origin, but close in time of formation linked to the Late Archaean mantle plume (Vetrin, 2018). We have studied by SHRIMP-II the U-Pb system of titanite from the Western Keivy and Ponoy massifs of alkaline granitoids. The studied titanite is represented by irregular-shaped fragments of crystals up to 400-500 mkm which have well-pronounced growth zoning, both oscillatory and sectorial, and contain microinclusions of accessory and rock-forming minerals. The grain partial recrystallization with unconformity to crystal forms is also noted. All studied titanites were characterized by insignificant variations in U within 10-100 ppm, whereas Th/U varied from 0 to 13, and non-radiogenic Pb from 0.1 to 60-70%. Nevertheless, all calculated ages turned out to be concardant within the error limits after correction by the non-radiogenic Pb and grouped around two figures: 2700 and 1750 Ma (Figure). The temperature of the U-Pb system closing is comparable to the crystallization temperature of granite melts (600-800°C), which makes it possible to correspondence the U-Pb age of titanite with the primary crystallization of alkaline granite massifs at 2710 Ma, but the latest titanite formed at about 1750 Ma reflects the influence of the tectonometamorphic paleoproterozoic

New data obtained by petrographical, geochemical and U-Pb geochronological studies of magmatic whole rock and zircon samples from the Malmyzh and Pony gold-copper porphyry ore fields are discussed. The trace ele-ments distribution patterns (REE + Y, Hf, Ti, U, Th, Pb) in zircons have been measured by SIMS SoMP-IIe instrument in the same spots as for local U-Pb age dating. Geochronological data show a matching Cen-omanian crystallization age of the Malmyzh and Pony magmatic rocks: 99-97 and 93 Ma, respectively. n-ary sumation REE in zircons from the Malmyzh granitoids varies from 217 to 1,158 ppm, Y - from 718 to 732 ppm, Hf - from 4,524 to 4,928 ppm, Ti - from 4.1 to 16.6 ppm, Pb - from 1.2 to 1.6 ppm, U - from 89 to 112 ppm, Th - from 58 to 76 ppm. Geochemical characteristics of zircons from the Pony monzodiorite-porphyry differ significantly from the Malmyzh granitoid zircons. Concentrations of most trace elements in the Pony zircons, especially LREE and MREE, as well as Y, Pb, U, Th, and Ti are two-three times higher than in zircons from the Malmyzh granitoids. Temperature of zircon crystallization of the Malmyzh granitoids revealed by "Ti in zircon" thermometer is estimated at 680-700 degrees C, whereas temperature of zircon crystallization of the Pony monzodiorite-porphyry is approximately 784 +/- 15 degrees C. Fertility assessment of magmatic rocks from the Malmyzh and Pony ore fields is based on geochemical characteristics of zircons like Eu/Eu* vs. Dy/Nd and Eu/Eu* vs. (Ce/Nd)/Y plots. These characteristics show that zircons from the Malmyzh granitoids fall into the field of fertile porphyry systems, whereas zircons from the Pony monzodiorite-porphyry plot within the field of barren suites. Comparative analysis of studied samples from the Malmyzh and Pony ore fields with magmatic rocks from porphyry deposits worldwide aids our understanding of the geodynamic framework of their formation and establishes links to adakitic granitoids generated under similar conditions. This result can be utilized during prognostic and metallogenic considerations not only within the limits of Sikhote-Alin territory but also within the whole Russian Far East region.

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.

Dikes of intermediate and felsic composition from the area of the Vyun deposit and the Shumnyi occurrence, both of which belong to the Yano–Kolyma gold belt (Northeast Asia), are dated for the first time, with the age of 151–147 Ma (Late Jurassic) based on U–Pb zircon dating (SHRIMP II method). The trace element distribution in the dike rocks is very similar to the previously studied Late Jurassic mafic dikes reported in similar blocks representing fragments of the Siberian Craton margin. Based on this, these dikes can constitute an unified complex. The dikes could have formed from mixed material from enriched and depleted mantle sources, probably in the northeastern part (in modern coordinates) of the Siberian Craton, in the settings of an active continental margin. This event preceded and was contemporaneous to the early (Late Jurassic) stage of the collision between the Siberian Craton and the Kolyma–Omolon superterrane.