We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochronological investigations of mafic, intermediate, and felsic igneous rocks from dikes in the Yana–Kolyma gold belt of the Verkhoyansk–Kolyma folded area (northeastern Asia). The dikes of the Vyun deposit and the Shumniy occurrence intruding Mesozoic terrigenous rocks of the Kular–Nera and Polousniy–Debin terranes were examined in detail. The dikes had diverse mineralogical and petrographic compositions including trachybasalts, andesites, trachyandesites, dacites, and granodiorites. The rocks showed significant similarities in distributions of REE, and their concentrations of most HFSEs were close to the intermediate ones between ocean islands basalts and enriched middle ocean ridge basalts. We propose that the subduction that was ongoing during the collision of the Kolyma–Omolon superterrane with Siberia led to melting in the asthenospheric wedge and in the lithosphere, which formed a mixed source for the dike systems from both an enriched and a depleted mantle source. The U–Pb SHRIMP-II dates obtained for the dikes corresponded to the Late Jurassic interval of 151–145 Ma. We present a geodynamic model for the northeastern margin of the Siberian Craton for the Tithonian age of the Late Jurassic. Full article

We report major and trace element concentrations, along with Nd isotope compositions, for Late Mesoproterozoic to Early Neoproterozoic dolerite sills from the Sette-Daban ridge (southern Verkhoyansk, south-east Siberia). Based on their major element composition, all rocks correspond to low-Ti (<3 wt% TiO₂) moderately alkaline basalts. The intrusions can be subdivided into two groups based on their trace element compositions. One group includes sills mainly distributed in the southern part of the study area (Yudoma group), with mid-ocean ridge basalt (MORB) trace element patterns enriched in aqueous fluid mobile incompatible (FMI) elements (Sr, Pb, Ba, U). The second group includes sills mostly distributed in the northern part of the study area, enriched in immobile incompatible (II) elements (Th, Nb, light rare earth elements (LREE)) and to a lesser extent, in aqueous fluid mobile elements. The Nd isotope signatures of the dolerites characterize a depleted mantle source, with a small enrichment from recycled continental crust. The geochemical characteristics of these igneous rocks are analogous to low-Ti basalts of large intraplate provinces (e.g., the Karoo and Siberian Traps). We propose that they formed by rifting-induced melting of the heterogeneous metasomatized shallow spinel-bearing mantle zone. We suggest that two different melting sources were involved in the generation of the two geochemically distinct sill groups, including the addition of two different subduction components. The southern sills were formed by melting of depleted lithospheric mantle enriched with FMI elements, corresponding to subduction-induced metasomatic alteration by fluids at shallow depths. The northern dolerites were formed by melting of depleted lithospheric mantle enriched with II elements, associated with the melting of subducted sediments at deeper depths. Full article

The paper presents new data on mineralogy, geochemistry, and Sr-Nd-Pb isotope systematics of Late Cenozoic eruption products of Uguumur and Bod-Uul volcanoes in the Tesiingol field of Northern Mongolia, with implications for the magma generation conditions, magma sources, and geodynamic causes of volcanism. The lavas and pyroclastics of the two volcanic centers are composed of basanite, phonotephrite, basaltic trachyandesite, and trachyandesite, which enclose spinel and garnet peridotite and garnet-bearing pyroxenite xenoliths; megacrysts of Na-sanidine, Ca-Na pyroxene, ilmenite, and almandine-grossular-pyrope garnets; and carbonate phases. The rocks are enriched in LILE and HFSE, show strongly fractioned REE spectra, and are relatively depleted in U and Th. The low contents of U and Th in Late Cenozoic volcanics from Northern and Central Mongolia represent the composition of a magma source. The presence of carbonate phases in subliquidus minerals and mantle rocks indicates that carbon-bearing fluids were important agents in metasomatism of subcontinental lithospheric mantle. The silicate-carbonate melts were apparently released from eclogitizied slabs during the Paleo-Asian and Mongol-Okhotsk subduction. The parent alkali-basaltic magma may be derived as a result from partial melting of Grt-bearing pyroxenite or eclogite-like material or carobantized peridotite. The sources of alkali-basaltic magmas from the Northern and Central Mongolia plot different isotope trends corresponding to two different provinces. The isotope signatures of megacrysts are similar to those of studied volcanic centers rocks. The P-T conditions inferred for the crystallization of pyroxene and garnet megacrysts correspond to a depth range from the Grt-Sp phase transition to the lower crust. Late Cenozoic volcanism in Northern and Central Mongolia may be a response to stress propagation and gravity instability in the mantle associated with the India-Asia collision. Full article

We present new structural, petrographic, geochemical and geochronological data for the late Paleozoic–early Mesozoic granites and associated igneous rocks of the Taimyr Peninsula. It is demonstrated that large volumes of granites were formed due to the oblique collision of the Kara microcontinent and the Siberian paleocontinent. Based on U-Th-Pb isotope data for zircons, we identify syncollisional (315–282 Ma) and postcollisional (264–248 Ma) varieties, which differ not only in age but also in petrochemical and geochemical features. It is also shown that as the postcollisional magmatism was coming to an end, Siberian plume magmatism manifested in the Kara orogen and was represented by basalts and dolerites of the trap formation (251–249 Ma), but also by differentiated and individual intrusions of monzonites, quartz monzonites and syenites (Early–Middle Triassic) with a mixed crustal-mantle source. We present a geodynamic model for the formation of the Kara orogen and discuss the relationship between collisional and trap magmatism. Full article

We present the first comprehensive data for the early Ediacaran stage of evolution of the western active continental margin of the Siberian Craton (Yenisei Ridge). U-Pb (SHRIMP-II SIMS) data for zircons from dikes of picrodolerites, quartz diorites, and leucocratic granites show that they were emplaced at 625 ± 5, 623 ± 8, and 626 ± 5 Ma, respectively, which indicates a narrow time window of Ediacaran magmatic events. The mafic tholeiitic rocks have OIB and E-MORB mantle components in their magmatic sources. Mineralogical and geochemical observations showed that the mantle-sourced mafic melts assimilated some crustal material, forming Th-enriched dikes of intermediate composition and K- and Rb-enriched felsic rocks. The possible geodynamic conditions for the formation of these early Ediacaran dikes are shown and a geodynamic model is presented for the development of the Yenisei Ridge orogen from the late Cryogenian to the late Ediacaran. Full article

The origin of the Siberian trap province is under discussion even though numerous models of its formation have been created over the last three decades. This situation is mainly due to lack of modern geochemical data on magmatic rocks around the province. These data are a very important tool to reconstruct of magmatic evolution within the province in time and space and to understand a mechanism of province formation. Geochemical study has only been carried out so far for the Norilsk and Meimecha–Kotuy areas. For the first time, we have studied the geochemical and mineralogical characteristics of magmatic rocks at the Kulyumber river valley located 150 km to south from the Norilsk ore district, in the junction of the Tunguska syneclise and Norilsk–Igarka zone. It comprises three sites, i.e., Khalil, Kaya, and Kulyumber. The geochemical data on the magmatic rocks of the Khalil and Kaya sites were published earlier (Part I). This article (Part II) regards geochemical and mineralogical data on igneous rocks at the Kulyumber site. Seventeen intrusive bodies (41 samples) and six samples of sedimentary rocks were studied by X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). Isotopes analyses (Sr, Nd, Pb) were conducted for 12 samples. These data were compared with data for intrusions of the Norilsk area, the Dzhaltulsky massif, Kureyka river, and intrusions in Angara river valley published earlier. The whole list of analyses includes 102 items. Three groups of intrusive rocks were recognized: (1) Mafic rocks with elevated K₂O without negative Ta-Nb and Pb-positive anomalies, with (Gd/Yb)n = 2.0 and εNd = −1.0; attributed to a new Kulyumbinsky complex; (2) subalkaline rocks with elevated SiO₂,TiO₂, P₂O_5, and K₂O with small negative Ta-Nb and positive Pb anomalies and (Gd/Yb)n = 1.8, εNd = −3.8; Ergalakhsky complex; and (3) mafic rocks with strong Ta-Nb and Pb anomalies and (Gd/Yb)n = 1.2–1.4, εNd = +0.4–+2.2. The third group is rather nonhomogeneous and includes intrusions of the Norilsk, Kuryesky, Katangsky, Ogonersky, and Daldykansky complexes differing in MgO content and trace element distribution (values of Ta-Nb, Pb, and Sr anomalies). Three groups of intrusive bodies had different magma sources and different condition of crystallization reflecting their origin in rift and platform regimes. Full article

The origin of the Siberian Traps province has been under discussion for the last three decades. Up to now, there is no real model of its formation in a good agreement with geological data on the magmatic evolution at P–T boundary in Eastern Siberia. Modern geochemical data on magmatic rocks around the province is a key to reconstructing magmatic development in time and space. Such data have been obtained for the Norilsk and Meimecha–Kotuy and not for other parts of the Siberian province. For the first time, we studied the geochemistry and mineralogy of magmatic rocks at the Kulyumber river valley, located in the intersection of the Tunguska syneclise and Norilsk–Igarka zone in the NW Siberian platform. In this article, we present data from the Khalil and Kaya sites of this area belonging to the Syverminsky, Gudchikhinsky, Khakanchansky and Nadezhdinsky formations. Their mineralogical and geochemical features (including Sr, Nd and Pb isotope data) are similar to the same formations in the Norilsk area, while the rocks belonging to the Gudchikhinsky formation show differences. The Syverminsky tuffs are also described for the first time. The intrusive rocks are attributed to four intrusive complexes, i.e., Ergalakhsky, Kureysky, Katangsky and Norilsk. The Ergalakhsky complex comprises trachydolerites similar to the trachydolerites of the Norilsk area. The rocks of the Norilsk complex at the Khalil site differ from the rocks of the same complex at the Norilsk area by the (U/Nb)n = 1.8, (La/Yb)n = 2.1 in comparison with 3.7 and 2.3 of the rocks of the Norilsk 1 intrusion. The intrusions of the Kureysky complex are more differentiated than those of the Katangsky intrusions but show comparable TiO₂ and trace elements distribution. Thus, the magmatism of the Kulyumber area is characterized by features matching those of the Tunguska syneclise and Norilsk area, i.e., suggesting rift and platform regimes. Full article

Mesozoic (125–135 Ma) cratonic low-Ti lamproites from the northern part of the Aldan Shield do not conform to typical classification schemes of ultrapotassic anorogenic rocks. Here we investigate their origins by analyzing olivine and olivine-hosted inclusions from the Ryabinoviy pipe, a well preserved lamproite intrusion within the Aldan Shield. Four types of olivine are identified: (1) zoned phenocrysts, (2) high-Mg, high-Ni homogeneous macrocrysts, (3) high-Ca and low-Ni olivine and (4) mantle xenocrysts. Olivine compositions are comparable to those from the Mediterranean Belt lamproites (Olivine-1 and -2), kamafugites (Olivine-3) and leucitites. Homogenized melt inclusions (MIs) within olivine-1 phenocrysts have lamproitic compositions and are similar to the host rocks, whereas kamafugite-like compositions are obtained for melt inclusions within olivine-3. Estimates of redox conditions indicate that “lamproitic” olivine crystallized from anomalously oxidized magma (∆NNO +3 to +4 log units.). Crystallization of “kamafugitic” olivine occurred under even more oxidized conditions, supported by low V/Sc ratios. We consider high-Ca olivine (3) to be a fingerprint of kamafugite-like magmatism, which also occurred during the Mesozoic and slightly preceded lamproitic magmatism. Our preliminary genetic model suggests that low-temperature, extension-triggered melting of mica- and carbonate-rich veined subcontitental lithospheric mantle (SCLM) generated the kamafugite-like melts. This process exhausted carbonate and affected the silicate assemblage of the veins. Subsequent and more extensive melting of the modified SCLM produced volumetrically larger lamproitic magmas. This newly recognized kamafugitic “fingerprint” further highlights similarities between the Aldan Shield potassic province and the Mediterranean Belt, and provides evidence of an overlap between “orogenic” and “anorogenic” varieties of low-Ti potassic magmatism. Moreover, our study also demonstrates that recycled subduction components are not an essential factor in the petrogenesis of low-Ti lamproites, kamafugites and leucitites. Full article

Precambrian shields and outcropped Precambrian rock complexes in the Arctic may serve as the most important sources of various types of mineral raw materials, including gold. The gold potential of the Anabar shield in the territory of Siberia has, thus far, been poorly studied. A number of primary and placer gold occurrences have been discovered there, but criteria for the prediction of and search for gold mineralization remain unclear. The main purpose of this paper was to study the typomorphic features of placer gold in the central part of the Billyakh tectonic mélange zone in the Anabar shield and to compare them to mineralization from primary sources. To achieve this, we utilized common methods for mineralogical, petrographic, and mineragraphic analyses. Additionally, geochemical data were used. As a result of this investigation, important prospecting guides were identified, and essential criteria for the prediction of and search for gold deposits were elucidated. The characteristics of the studied placer gold were specific for gold derived from a proximal provenance. These characteristics included the poor roundness of the native gold grains, a cloddy–angular and dendritic form, an uneven surface, and a high content of coarse-fraction native gold (0.5–2 mm), which was as high as 24% of the volume of analyzed native gold. In addition, we conducted a study on the mineralogical features of the gold-sulfide mineralization that was disseminated throughout a small exposure area of paleo-Proterozoic para- and orthogneisses in the Anabar shield basement. A comparison of mineral inclusions in the coarse-fraction native gold and mineral assemblages in the ore deposits showed that one of the possible primary sources for placer gold might be small bodies of metasomatically altered orthogneisses associated with large granitoid plutons. Full article

The Chiron Basin extends along the southern periphery of the Siberian Craton and the western margin of the Mongol–Okhotsk Belt. Here, we present whole-rock geochemical data (major and trace elements and Sm–Nd isotopes) along with zircon U–Pb geochronology and Lu–Hf isotopic data from Paleozoic sedimentary rocks within the Chiron Basin to investigate their provenance and tectonic history. ε_Nd(t) values of the siliciclastics rocks of the Khara–Shibir, Shazagaitui, and Zhipkhoshi formations vary from −17.8 to −6.6, with corresponding two-stage Nd model ages (t_Nd(C)) ranging from 2.56 to 1.65 Ga. Detrital zircon grains from these rocks are predominantly Archean, Paleoproterozoic, and Carboniferous–Devonian in age. The data suggest that the southern flank of the Siberian Craton is the only viable source area for Archean and Paleoproterozoic zircon grains with Hf model ages (t_Hf(C)) of >2.20 Ga. The majority of zircon grains from sandstones from the Khara–Shibir, Shazagaitui, and Zhipkhoshi formations are Devonian–Carboniferous in age. With respect to their Hf model ages, the zircon grains can be subdivided into two groups. The first group of Devonian–Carboniferous zircon grains is characterized by relatively old (mainly Paleoproterozoic) t_Hf(C) model ages of 2.25–1.70 Ga and the source was the southern margin of the Siberian Craton. The second group of Devonian–Carboniferous zircon grains is characterized by significantly younger (mainly Neoproterozoic) t_Hf(C) model ages of 1.35–0.36 Ga, which are consistent with a juvenile source, most likely eroded island arcs. Our data, show that sedimentary rocks of the Chiron Basin likely formed in a back-arc basin on the southern periphery of the Siberian Craton facing the Paleozoic Mongol–Okhotsk Ocean. Full article

The Norilsk ore region is characterized by the occurrence of numerous intrusions comprising the PGE–Cu–Ni deposits. The Turumakit area, within the Southern Norilsk Trough, also contains many mineralized mafic intrusions of probably similar economic potential to the known Norilsk deposits. We study igneous rocks from three boreholes within the Turumakit area, sampling gabbro-dolerites and trachydolerites related to the Norilsk and Ergalakh complexes, as well as an outcrop of the Daldykan gabbro-dolerite intrusion. Our petrographical, mineralogical and geochemical data, as well as the U–Pb dating of extracted baddeleyites and zircons, primarily discriminate between the sub-alkaline rocks of the main Turumakit area and the Ergalakh trachydolerites located in the Norilsk and Talnakh ore junctions. Coarser grained Turumakit trachydolerites (with pegmatite segregations) contrast finer grained Ergalakh trachydolerites by having: (1) higher TiO₂ (up to 5.5 wt %) compared with 2.2 wt %–3.3 wt % in the typical Ergalakh rocks; (2) low U, lower La/Yb and La/Sm ratios (5–7), in contrast to 8–10 ppm, 2.5–2.6 and 3.0–3.3, respectively, for the Ergalakh trachydolerites; and (3) their age was determined by U–Pb methods on baddeleyite and zircon (244.8 ± 2.7 Ma), and it appears likely that the mafic rocks traditionally attributed to the Ergalakh complex within the Turumakit area are younger than the Norilsk intrusions (250 ± 1.4 Ma). These data strongly indicate an emplacement of Turumakit intrusions during the end of a ~5 Myr magmatic evolution of the Norilsk district. It is therefore proposed that the sub-alkaline rocks of the Turumakit area belong to a separate intrusive complex within the Norilsk district. Full article