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This paper reports the results from an investigation on the geochemistry and petrogenesis of the Aptian Li-F granites from the Omchikandya, Burgali, and Arga Ynnakh Khaya ore fields in the northern Verkhoyansk–Kolyma orogenic belt in eastern Russia. Li-F microcline–albite granites intrude the Late Jurassic to Early Cretaceous syn-collisional granitoids. According to their geochemical composition, they are close to A-type granites and can be subdivided into low-P and high-P varieties, differing in their geochemistry and genesis. The low-P microcline–albite granites (Omchikandya massif) intrude syn-collisional biotite granites. It is assumed that the formation of their parent melt occurred at deep levels in the same magma chamber that produced biotite granites. The high-P granites (Verkhne–Burgali ethmolith and Kester harpolith) are supposed to have been derived from melts originated from a high-grade metamorphosed lower crustal protolith under the influence of deep-seated fluid flows related to diapirs of alkaline-ultrabasic or alkaline-basic composition. It is supposed that their formation was related to post-collisional extension during the early stages of the evolution of the Aptian–Late Cretaceous Indigirka belt of crust extension. All studied Li-F granites are enriched with rare metals and have associated Li deposits with accompanying Sn, W, Ta, and Nb mineralization. In the low-P Li-F Omchikandya massif, mineralization tends to occur within greisenized granites and greisens in their apical parts. In the high-P granite massifs, mineralization is found throughout their volume, and, therefore, the Verkhne–Burgali ethmolith and Kester harpolith can be considered as large ore bodies. There is a direct dependence of the content and reserves of Li2O on the content of P2O5. Minimum Li2O reserves are established in low-P Li-F microcline–albite granites of the Polyarnoe deposit of the Omchikandya ore field, whereas in the high-P granites of the Verkhne–Burgali and Kester deposits, the Li2O reserves are significantly higher. [ABSTRACT FROM AUTHOR]

This article considers the mineralogical and geochemical features of the Early Cretaceous gold ore deposits in the Northern Okhotsk region, that is, the southeastern flank of the Yana-Kolyma orogenic belt and the Okhotsk sector of the Okhotsk–Koryak orogenic belt. Dating results are reviewed and the general and distinctive geological, mineralogical, and geochemical features of different mineralization types are shown. A close genetic link of ore mineralization with Early Cretaceous magmatism and formation of the Uda-Murgal magmatic arc is assumed. [ABSTRACT FROM AUTHOR]

The results of geological, geochemical, and geochronological studies of granophyre rocks from the Jarva-Varaka Massif (Kola region) are presented. The 2-km section of the massif is composed of mafic and felsic norites, hypersthene diorite, pigeonite-augitic diorite, quartz diorite, and granodiorite. All these rocks contain a variable amount of granophyre (micropegmatite), from ~10% in norites that compose the lower part of the massif, to ~45% in quartz diorite and granodiorite of the upper part. The Sudbury Igneous Complex (SIC) is the only known case of a similar 2-km thick section of granophyre rocks whose composition varies from mafic at the bottom to felsic at the top. The SIC has an impact origin, which suggests a similar formation mechanism for the Jarva-Varaka Massif. The norites contain micro-xenoliths of the host high-alumina gneisses, which were transformed to rocks of the high-grade hornfels facies. Such gneisses are absent among the country rocks of other mafic intrusions in the area, and it suggests that the parental melt for mafic norites could have assimilated the host rocks. Given the relatively small size of the massif, the formation of hornfelses could have occurred if the xenoliths would be entrained by a melt under near-surface conditions, and the melt was hot enough to cause the formation of hornfelses. Spinifex-like structures in the diorites of the very marginal contact zone of the Jarva-Varaka Massif indicate very rapid cooling of a high-temperature melt, which is typical of near-surface conditions. A pseudotachylitic breccia, planar deformations in quartz, kink-bands in biotite and clinozoisite, zircon and inclusions of sillimanite and plagioclase all transformed into diaplectic glasses detected in the host rocks of the Jarva-Varaka Massif are interpreted as distinct signs of shock metamorphism. Geophysical data show no signs that beneath the Jarva-Varaka Massif there exists a large mafic intrusion that could have contaminated large volumes of crustal material, and magmatic differentiation of which could have produced a large volume of enriched melt whose crystallization could resulted in the formation of granophyre rocks from the bottom to the top of the magma chamber. All of the aforementioned data indicate that the impact origin of the 2.5 Ga Jarva-Varaka Massif is very likely. [ABSTRACT FROM AUTHOR]

Long-term and continuous lake sedimentary records offer enormous potential for interpreting paleoenvironmental histories and for understanding how terrestrial environments might respond to current global warming conditions. However, sedimentary records that contain the Late Glacial and Holocene epochs are scarce in deep continental high-mountain regions. A 150 cm sediment core was obtained from Lake Kaskadnoe-1 in the East Sayan Mountains (South Siberia, Russia, 2080 m above sea level), containing a unique record of the last 13,200 calibrated years (cal yr). Chronological control was obtained by AMS 14C dating. Here, we show the first detailed X-ray fluorescence (XRF) geochemical record, with the goal of broadening our knowledge of the paleoenvironmental history of the East Sayan Mountains in the past. The determination of major compounds and trace elements (Sr, Zr) was performed from each centimeter of the Lake Kaskadnoe-1 sediment core. The inorganic geochemistry indicates significant variations in elemental composition between two major lithological units of the sediment core: the Late Glacial dense grey silty clay (150–144 cm), and the upper interval (0–143 cm) mostly consisted of dark biogenic-terrigenous silt, accumulated during the Holocene. The Late Glacial sediments accumulated 13,200–12,800 cal yr BP are characterized by high values of CIA, Mg/Al, K/Al, and Mn/Fe, and are depleted in Si/Al, Fe/Al, and Ca/Al. During the Younger Dryas cold episode, LOI enrichment was probably caused by the presence of less oxic conditions, as seen in lower Mn/Fe values, due to a longer period of lake ice-cover. The Early Holocene (12,000–7500 cal yr BP) is associated with a decreasing trend of mineral matter with fluvial transport to Lake Kaskadnoe-1 (low K/Al, Mg/Al) and stronger chemical weathering in the lake basin. The increase in Ti/Al, K/Al and CIA values over the last 7500 years suggests an increase in the terrigenous input into the lake. Low LOI values can be possibly explained by the presence of less dense vegetation cover in the basin. In summary, our data indicate that the geochemical indices and selected elemental ratios mirror the sedimentation conditions that were triggered by environmental and climate changes during the Late Glacial and Holocene. [ABSTRACT FROM AUTHOR]

This study presents the results of lithological, diatom, geochemical analyses and radiocarbon chronology of the bottom lake sediments and peat bogs in the central part of the Onega Peninsula (the southern coast of the White Sea): Lake Maloye Murakanskoye (11.0 m a.s.l.), Lake Zhirovskoye (9.5 m a.s.l.), Lake Murakanskoye (7 m a.s.l.), and the Gorbovatiy Mokh bog (6.5 m a.s.l.). The bottom topography and sediments of Lake Murakanskoye were examined using sonar and ground penetration radar (GPR) survey, whereas in the other locations only the water depth was measured. Then, the digital models of the lake bottom topography were created. As an additional indicator of the relative sea-level (RSL) position, we used data on the altitude of the coastal terraces. Evidences of two transgressions in the White Sea (late glacial and Middle Holocene) are revealed. The transgressions were interrupted by two regressions (Early and Late Holocene). Our studies do not allow us to make a clear conclusion about the time and maximum level of the late glacial transgression. However, we may suggest that its level was above 11 m a.s.l. The regression of the Early Holocene started before 10.6–10.2 ka cal BP when the water level in the study area dropped below the altitude of 11m. At 9.4–9.1 ka cal BP the RSL was at an altitude of ca 7m. The Middle Holocene transgression (Tapes) started after 8.4 ka cal BP. The maximum level was reached before 7.4 ka cal BP and did not exceed an altitude of 9.5 m. The RSL stabilized at an altitude about 8.5–8 m during 7.4–6.0 ka cal BP. During 6.0–3.9 ka cal BP RSL very slowly decreased or fluctuated by the level of 8–7 m. RSL began to fall from the 7 m altitude about 4.0–3.9 ka cal BP and by 2.7–2.3 ka cal BP the sea-level reached 4.5 m. After that RSL dropped to its modern position. During the last 4.0 ka cal BP the rate of RSL fall was approximately 0.17–0.18 cm/year. [ABSTRACT FROM AUTHOR]

The evolution of hypergene and technogenic processes occurring in tin sulfide, copper–tin, and tin-polymetallic deposits of the Komsomolsky district of the Russian Far East is described. The results of long-term field observations and studies of hypergene and technogenic minerals collected in mine workings (ditches, quarries, galleries) and tailings, their natural associations, sequences, and zonality, and staging of mineral formation are given. The sulfide oxidation process in the bulk ore and tailings was simulated in a wide temperature range from –25 to 45°C using Selektor software package, which made it possible to determine physicochemical parameters of the resulting technogenic water solutions, but their ionic and molecular composition. The obtained data expanded our knowledge about hypergene and technogenic processes and conditions for the precipitation of secondary minerals during the appearance of a mining technogenic system in the course of exploitation of tin sulfide deposits and ore enrichment. The results of our studies have demonstrated negative impact of technogenic waters on the hydrosphere of the region. [ABSTRACT FROM AUTHOR]

Understanding the tectonic evolution of the Yenisei Range offers important clues not only for the tectonic evolution of orogenic belts at margins of ancient cratons but also for solving the problem of the incorporation of the Siberian craton into the Rodinia supercontinent. Results of mineralogical−petrological, geochemical, and isotope–geochemical studies provide an insight into the petrogenesis, geotectonic settings, thermodynamic parameters of formation, and the ages of the metamorphism and protoliths for the contrastingly compositionally different rocks of the Garevka metamorphic complex. The paper discusses the possible models for the origin of the rock complexes and the geodynamic settings in which they were formed. The western margin of the Siberian craton was determined to have been affected by two pulses of Neoproterozoic endogenic activity, which were related to the origin of the Rodinia supercontinent (930–900 and 880–845 Ma), and which correlated with Grenville and post-Grenville processes responsible for Valhalla folding. The regional geodynamic history is correlated with the coeval sequence and similar style of tectono−thermal events in the peripheries of the large Precambrian cratons Laurentia and Baltica, which is consistent with the proposed Neoproterozoic paleogeographic reconstructions of close spatiotemporal relationships between these cratons and their incorporation into Rodinia configuration. [ABSTRACT FROM AUTHOR]

A new promising source of mineral deposits is found in the southern part of the Far East of Russia: the Ti-bearing intrusions of ultramafic rocks of the Sikhote-Alin orogenic belt. The main mineralogical–geochemical features of antimonite–quartz veins are determined at the external contact of the Ariadnoe intrusion. It is shown that mantle and crustal processes were involved in the formation of Au–Ti and Au–Sb ores. The typomorphic properties of native gold in ultramafic rocks open new possibilities for re-estimation of the prospects of a mineral base of strategic metals of Primor'e. [ABSTRACT FROM AUTHOR]

The article presents the results of studying the aegirine–arfvedsonite granites of the Somnitelnyi massif within the Tommot ore field located in the Verkhoyansk–Kolyma orogenic belt (NE Asia). Along with the crustal signatures, the rocks display features of mantle contamination at their origin. Their affinity for A-type granites characteristic of continental rifts and hot spots is shown. The associated Tommot REE deposit is the only one discovered in NE Russia. New data are presented for the previously studied Tommot massif within the same ore field, with a wide compositional range from alkaline-ultrabasic rocks to alkaline syenites. It is established that despite a common geochemical enrichment of both massifs' rocks with REEs, the Somnitelnyi massif granites cannot be interpreted as the final phase of the Tommot massif emplacement. Specific REE mineralization and high crystallization temperatures (up to 1045 °C) of the Somnitelnyi granites may be explained by the existence within the study area of an undepleted mantle source ("hot spot"), whose maximum activity occurred during the granitic melt generation. The ore bodies of the Tommot deposit consist of fenitized albitites, granite gneisses, and, more rarely, the cross-cutting pegmatite veins. They are confined mostly to exocontacts of the Somnitelnyi massif, are less often in its endocontacts, and are not found in the host rocks and in the inner part of the massif away from the contacts. Principal ore minerals are chevkinite, yttrialite, gadolinite, and fergusonite. Based on the data obtained, the deposit is classified as a metasomatic complex Ce–Y–Nb–Zr deposit associated with the alkaline granites. [ABSTRACT FROM AUTHOR]

This paper presents the results of geochemical research on the Kamyshovoe Lake sediments (Kaliningrad oblast, Russian Federation). The study of Pb, Ni, Zn, As, Co and Cu concentration and enrichment factors (EF) combined with the results of the lithological, geochronological, magnetic susceptibility and microcharcoal studies revealed possible anthropogenic sources of metals in southeastern Baltic lake sediments from the Neolithic to the Medieval period. Increasing Co EF value and peaks of the Pb EF in Kamyshovoe Lake sediments, starting from ~6000 cal yr BP in the Neolithic, probably show the growing role and usage of metals as dyes and fixatives. Since ~3100 cal yr BP, in the end of the Bronze Age, a simultaneous increase in the content of indicators of metallurgical production Pb, Ni, Zn and As, coinciding with growth of the microcharcoal curve, can show a growing demand for metal objects in the southeastern Baltic region and the input of the local or regional ancient metallurgy into the metal pollution of the lake sediments. [ABSTRACT FROM AUTHOR]

Karavannoe is a pallasite found in Russia in 2010. The mineralogy, chemistry, and oxygen isotopic composition indicate that Karavannoe is a member of the Eagle Station Pallasite (ESP) group. Karavannoe contains mostly olivine and subdued interstitial Fe,Ni‐metal. Zoned distribution of FeO in small, rounded grains of olivine and FeO and Al2O3 in chromite shows that the cooling rate of the melt was fast during the crystallization of the round olivine grains. Siderophile element distribution and correlations of Au‐As and Os‐Ir concentrations in Karavannoe and the other ESP metal record its magmatic origin. FeO‐rich composition of olivine, low W and Ga, and high Ni abundances in the Karavannoe metal indicate the formation of the metal from an oxidized chondrite precursor. Model calculations demonstrate that the ESPs' metal compositions correspond to the solids of the fractional crystallization of CV‐ or CO‐chondrite‐derived metallic liquids. The Karavannoe metal composition corresponds to the solid fraction crystallized after ~40% fractional crystallization. The Mg/(Mg+Fe) atom ratio of complementary silicate liquid corresponds to Fo70, possibly indicating that the olivine is not in equilibrium with the metal and could have been a product of the late evolutionary processes in the Karavannoe parent body mantle. In any ESP genesis Karavannoe was not in equilibrium with its metal and is a product of mantle differentiation processes. Olivine of Karavannoe and ESPs is similar in composition, while the metal is different. We propose a model of ESP formation involving an impact‐induced intrusion of liquid core metal into a basal mantle layer, followed by fractional crystallization of the metal. The metal textures and chemical zoning of Karavannoe minerals point to remelting and rapid cooling due to a later impact event. [ABSTRACT FROM AUTHOR]

Origin of abundant alkaline and related lamproite massifs and dykes in Aldan shield have no explanation and the geochemistry of rocks and their xenocrysts is used for the explanation. Bulk-rock geochemistry, mineral chemistry data of the Kayla lamproites of Russia and mineral chemical data (trace and rare elements) of the mantle xenocrysts found in these lamproites was studied using ICP MS and electron microprobe analyses (EPMA). The trace element spectrum of Kayla tuffs and breccias show the similarity with the olivine lamproites and belong to the orogenic type according to Th–U–Nb systematics. Primitive mantle normalized trace element (TRE) spider diagrams show right-leaning patterns with the peaks in large ion lithophile elements Sr, Pb, U, and troughs in Ta, Nb suggesting melting of original peridotites mixed with the ancient EMI (according to Nd, Sr isotopes) source probably belonging to eclogites or lower crust. The age of the emplacement is 132–134 Ma, similar to the Chompolo lamprophyres and many other alkaline Aldan complexes. Thermo-barometric estimation from Cr-diopsides and chromites xenocrysts suggest the origin from the spinel-garnet transition in the lithospheric mantle region. The P–T estimates derived from low-Cr-clinopyroxene xenocrysts, and related to lamproites show a high heat flow of 90 mW/m2 due to interaction with the plume-related magma. The Cr-diopsides and chromites give 45 mW/m2 geotherm similar to regional heat flow. The chondrite normalized rare earth element (REE) pattern for chrome-diopsides is steeper, compared to the low-chrome varieties. Primitive mantle normalized spidergram of Cr-diopsides displays peaks for Sr, U, and Th, and deep troughs of Nd, Nb, Ta. REE. The trace element spider diagrams of both types of xenocrysts show that they were equilibrated with the lamproitic melts and reconstructed parental melts of low-Cr-clinopyroxene coincides with the lamproite spectrums. [ABSTRACT FROM AUTHOR]

In this paper, we present a new point of view on the deposit geology and genesis of the largest gold deposit in Eastern Sayan, Zun-Kholba. Quartz–sulfide replacement ores and shallow quartz veins are of great economic importance. At the deposit, quartz–pyrite ore bodies are dominant, whereas paragenetically late base metal-bearing quartz veins occur only at shallow levels. The study of the fluid inclusions, stable isotopes (C–O–S), and mineral geothermometry allowed us to determine the P–T conditions of ore deposition. It is established that the temperature of ore formation changed from 380 to 433 °C at the deepest levels of the deposit to 316 °C at the shallowest levels. The pressure estimates for gold deposition at 570–950 bar were calculated for the 1490-m level in the center of the deposit. The determined P–T conditions can help estimate the average depth of deposit formation at about 3.6 km. Ore mineral assemblages were formed from homogeneous fluids of low to moderate salinity (2.4–7.9 wt.% eq. NaCl). The sulfur isotope composition of sulfide minerals (δ34S = 0–4.6‰), as well as pyrite geochemistry, corresponds to that of older volcanogenic massive sulfide (VMS) occurrences, which are widespread within the Eastern Sayan ophiolitic belts. Lens-like fragments of metamorphosed VMS-type sulfide ores are also present in the Zun-Kholba deposit. The oxygen isotope data indicate a metamorphic origin for the ore-forming fluids. Migrating metamorphic fluids may have become enriched in gold, sulfur, and other metals during the flow through the complex ore-hosting lithologies, including ophiolitic bodies with sulfide-rich VMS fragments that are characterized by a relatively high content of gold and related ore elements. The obtained data allow us to suggest a metamorphic devolatilization model for the genesis of the Zun-Kholba gold deposit. [ABSTRACT FROM AUTHOR]

The paper presents results of petrological and geochemical studies of sulfide-bearing rocks from a bottom apophysis in the central part of the Yoko-Dovyren massif, northern Transbaikalia, Russia. It is composed of plagioperidotite and was sampled in a bulge up to 300 m thick throughout the whole vertical section, from its upper to lower contact. The observed diversity of sulfide-bearing rocks is subdivided into four types: (1) picrodolerite with droplet-shaped sulfides, (2) olivine gabbronorite with sulfides varying from droplet-shaped to irregular globules, (3) olivine gabbronorite with larger globules and patchy net-textured domains, and (4) net-textured ores. These varieties occur in the basal zone of the apophysis, in the interval up to 30 m inward from the lower contact. Petrographic features of these rocks correspond to olivine ortho- and mesocumulates, with the only exception of the quenched picrodolerite with an ophitic groundmass. The association of sulfides (pyrrhotite, chalcopyrite, pentlandite, and cubanite) has a pretty little varying composition, except only a relative decrease in the proportion of chalcopyrite in samples with more than 5% sulfides. The results of X-ray computed tomography show an increase in the sulfide connectivity in the rocks (from 25 to 95%) with increasing sulfide abundance. These characteristics, supported by visualized 3D models, allowed us to identify a morpho-structural trend tended from the rocks with sulfide droplets to the net-textured ores. The first ever data were obtained on the chemostratigraphy (PGE and tellurium) of rocks composing this apophysis. Covariations of Au, Pt and Pd with S and Te indicate that the precious metals have a single sulfide precursor. The 100%-sulfide compositions calculated for these rocks indicate that the most primitive and PGE rich sulfides correspond to droplets it the lowerest part of the apophysis, whereas the net-textured ores are depleted in these elements. The geochemical estimates are supported with COMAGMAT-5 modeling which made it possible to calculate the average Au, PGE, and Te contents in the protosulfide melt (in ppm): 2.9 Au, 14.4 Pt, 25.1 Pd, and 44.3 Te. Results of the geochemical studies of different fragments of the net-textured ores reveal a heterogeneity in the form of domains relatively enriched in copper, PGE, and tellurium, whose characteristic size is a few dozen centimeters. This can be considered as a signature of the porous migration and accumulation of the crystallization products of the original sulfide liquid at the subsolidus stage of cooling down the ore-bearing cumulates. [ABSTRACT FROM AUTHOR]

• Some Fe-oxide grains crystallized from silicate melt were incorporated into downward percolated sulfide liquid. • Fe-oxide in massive ores crystallized from the sulfide liquid pool mingled with the downward percolated sulfide liquid. • Downward percolation of sulfide liquid is crucial in the formation of the net-textured and massive ores. The mineralogy and chemical composition of magnetite and chromite series (simplified as magnetite) can provide valuable insights into the formation processes of magmatic Ni-Cu-(PGE) sulfide deposits. Previous studies mainly focus on magnetite in disseminated ores and massive ores, but very little is known about the magnetite in net-textured ores. In this study, magnetite in net-textured ores (type 1 magnetite) and massive ores (type 2 magnetite) from the Zhdanov Ni-Cu-(PGE) deposit in the Pechenga ore field, were recognized and analyzed using scanning electron microscope (SEM), electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Both the type 1 and type 2 magnetite grains show zoned textures with Cr concentration decreasing from the core to the rim. Type 1 magnetite has higher Al and Mg concentrations than type 2 magnetite. These observations indicate that type 1 and type 2 magnetite crystallized from and record the solidification process of silicate melt and sulfide liquid, respectively. Type 1 magnetite within sulfides of net-textured ores has identical chemical composition to that within silicates, which suggests that the chemical composition of magnetite is not significantly affected by sub-solidus re-equilibrium with sulfide minerals. It also suggests that the type 1 magnetite within sulfides was incorporated into sulfide liquid later during the downward percolation of sulfide liquid through the magnetite-bearing olivine crystal mush. On the other hand, type 2 magnetite has comparable concentrations of W, Sc, Ga, Cr, Mo, and Mn to the type 1 magnetite. Such compositional similarity can be explained by the crystallization of type 2 magnetite from the sulfide liquid pool that have been mingled with the downward percolated sulfide liquid. Accordingly, the downward percolation of sulfide liquid plays an important role in the formation of net-textured ores and massive ores in the Zhdanov deposit. [ABSTRACT FROM AUTHOR]

Lamprophyric (lamproitic) diatremes in Chompolo field, NE Aldan shield, Siberia dated 132 Ma contain abundant mantle xenocrysts studied by EPMA and LA-ICP-MS. The deepest rocks ~6.5 GPa determined with thermobarometry are phlogopite eclogites. Thermobarometry on pyrope garnets, Cr-diopside and chromites yield a relatively low-temperature geotherm of 35 mW/m2 at the base to 55 mW/m2 at the Moho, while orthopyroxenes give 55 mW/m2. Amphiboles vary from magmatic Cr-hornblendes to metasomatic richterites. Trace element patterns for the host monchiquite are inclined with HFSE minima and are common for all Aldan lamprophyres but there are also more strongly inclined lamproitic varieties with ten times higher LREE contents. The geochemistry of Cr-diopsides, pyrope garnets and phlogopites reveal ancient multistage metasomatism of an originally depleted mantle keel related to both continental subduction and mantle plume activity. The lithospheric mantle is composed of harzburgites, roughly layered with rare dunites. Garnets appear widely at depths from 5.5 to 4.5 GPa. Trace element patterns show four groups from dunites to pyroxenites, related to low degree melting of hydrous and carbonatite melts. Clinopyroxenes reflect various melting degrees and variable trace element contents. The high-temperature orthopyroxene-based branches of the geotherm resulted from the percolation of hydrous plume-related melts. The high temperature 90 mW/m2 geotherm from 2.5 GPa to the Moho reflects fractionation of Fe-rich plume-related siliceous melts. Eclogites and metasomatites melting at the lithosphere base produce lamprophyres rich in LREE (100/C1), LILE, Zr and Ta–Nb minima. The Mg-lamproites are more LREE-enriched to 1000/C1. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Pasha-Ladoga Basin is located at the margin of the Karelian Craton and Svecofennian Belt in northwest Russia. It is the only basin in Russia that is currently recognized to host unconformity-type uranium mineralization (e.g., Karku deposit). Mineralization is associated with the Priozersk Formation which comprises a basal sequence of immature arkosic sandstones and conglomerates interpreted as high-energy braided stream channel and channel bar facies within an alluvial fan depositional environment. Diagenetic and hydrothermal alteration of the Priozersk sandstones is similar to that observed in unconformity-related uranium deposits of the Athabasca Basin (Canada) and includes three main stages: (1) an early diagenetic assemblage comprising illite-smectite (K-rectorite), calcite, minor chlorite, and kaolinite precipitated at 100–150 °C; (2) a peak diagenetic-hydrothermal assemblage composed of kaolinite-dickite, Fe- and Fe-Mg chlorite, calcite, and sulfides formed at 150–250 °C; (3) late diagenetic-hydrothermal event involving fracture-controlled kaolinite and late hematite. Similar to the Athabasca Basin type uranium mineralization, the Karku deposit exhibits anomalous concentrations of LREE, Nb, Pb, and positive correlations between U and Cu, Zn, Ag, and Pb that is a geochemical signature of unconformity-type uranium mineralization. Based on oxygen and hydrogen stable isotope study, it was found that fluids in equilibrium with early and peak diagenetic clays were consistent with oxidized basinal brines and reduced basement fluids. In contrast to the Athabasca Basin, mineralizing fluids at the Karku area were more reduced and potassic. A new geological model for the Karku deposit is proposed based on petrographic observations and sandstones geochemistry. The proposed model envisages the permeable rocks of paleoregolith and the coarse-grained basal part of the Priozersk Formation as the main pathway for migration of uraniferous fluids responsible for the formation of Karku uranium deposit. From the perspective of the geological setting, the Karku deposit differs from deposits of the Athabasca Basin in that it occurs in a rapidly deposited rift-related basin with associated mafic magmatism, the host sandstone sequence is relatively thin (e.g., Priozersk Formation) and exhibits abrupt lateral facies variations, and the widespread presence of early diagenetic interstitial swelling clays. Based on these sedimentological characteristics, it is considered that the Karku deposit setting precludes optimum conditions to create high tonnage high-grade unconformity-type U deposits as found in the Athabasca basin. [ABSTRACT FROM AUTHOR]

Some geochemical features of fine-grained clastic/clayey rocks are considered for a series of formations of the Yudoma–Maya region, southeast Yakutia. The following conclusions were drawn from a comparison of the distribution of the chemical composition of samples and average composition of clayey rocks of various formations on (La/Yb)N–Eu/Eu* and (La/Yb)N–Th diagrams, which show the compositional areas of the bottom sediments of the mouth parts of various present-day rivers. As an example, the individual compositions on the (La/Yb)N–Eu/Eu* diagram are mostly focused in areas of the bottom sediments of the mouth parts of the present-day rivers, which are supplied by erosion products of mostly sedimentary (types 1 and 2) and volcanic (type 4) rocks, as well as in zones of their overlapping. The average composition of clayey rocks of Trekhgornaya Formation on this diagram corresponds to the area of the bottom sediments of the mouth parts of the present-day rivers, which drain the igneous/metamorphic terranes/complexes/provinces (type 3). The average compositions of clayey shales of the Dim, Talyn, and Svetlinskaya formations tend to the overlapping zone of the areas of the bottom sediments of the mouth parts of the present-day type 1, 2, and 3 rivers, i.e., they contain the erosion products of both sedimentary rocks and igneous and metamorphic complexes. This is in agreement with the real geological setting. At the same time, the erosion products of igneous/metamorphic terranes/complexes/provinces in clayey rocks of the higher levels of the Riphean of the Yudoma–Maya region are either absent or they are minor. On the (La/Yb)N–Th diagram, most compositions of the Riphean clayey rocks also tend to areas 1, 2, and 4. The average compositions are mostly confined to the overlapping zone of the bottom sediments of the mouth parts of the present-day type 1 and 2 rivers. The average composition of clayey rocks of the Ust-Kirba Formation occurs in the area of the bottom sediments of the mouth parts of the present-day rivers, which are supplied by the erosion products of rocks of volcanic provinces. This is also consistent with the regional geological setting. [ABSTRACT FROM AUTHOR]

Hydrocarbon reserves of the order of 1140 MM brl oe have been identified in the northern foreland of the eastern Greater Caucasus, principally in the Terek‐Caspian fold‐and‐thrust belt and the Prikumsk Swell in the north of the Terek‐Caspian foredeep. Despite the great economic significance of these areas and their long exploration history, the origin of the hydrocarbons is still poorly understood. In the present paper, geochemical data from 73 oil samples representing 28 fields are used to investigate the presence of oil families and to correlate the oils with potential source rocks. Biomarker composition of oils in Cretaceous and Miocene reservoirs in the Terek‐Caspian fold‐and‐thrust belt is mainly controlled by reservoir depth (100‐5700 m) and maturity (0.70‐1.15 %Ro), and it is therefore difficult to separate maturity and facies effects. For example, a downward increase in diasterane/sterane ratios may indicate a change in source rock facies or may be attributed to increasing maturity. Some shallow oils are biodegraded. The presence of short‐chain n‐alkanes in biodegraded oils indicates recent hydrocarbon migration. Biomarker data (e.g. the presence of oleanane) and compound‐specific isotope data suggest that the Khadum Formation in the lower part of the Maikop Group is the main source rock. However data from Cretaceous and Paleogene organic‐rich rocks, which may also have contributed to the accumulated oils, are urgently needed in order to quantify their possible input. In the Prikumsk Swell, at least two oil families, characterized by low and high C28/C29 sterane ratios respectively, can be distinguished in reservoir rocks of Triassic to Cretaceous age. Most oils are characterized by low C28/C29 sterane ratios and the absence of oleanane ("Group B oils"). These characteristics suggest a pre‐Upper Cretaceous source for the oils, which is also supported by the geological setting. Hierarchical cluster analysis suggests the presence of four sub‐groups (Sub‐Groups B1 to B4). Typically, biomarker ratios in oils in Cretaceous reservoirs are more uniform than those in Triassic and Jurassic reservoirs. Potential source rocks include Lower Triassic deep‐water clayey limestones and shales as well as Middle Jurassic and Aptian‐Albian marine shales. Three oil samples from Triassic and Cretaceous reservoirs form a separate oil family ("Group A"), which is genetically related to oils from the Terek‐Caspian fold‐and‐thrust belt. Group A oils have high C28/C29 sterane ratios and in general contain at least some oleanane. A contribution by Cenozoic source rocks to Group A oils is likely. [ABSTRACT FROM AUTHOR]

Petrological, whole-rock major and trace element, and Sr–Nd–Pb isotopic data are reported for the late Mesozoic Dzheltula alkaline igneous complex in the Aldan–Stanovoy Shield, Russia. The alkaline rocks are emplaced into the Tyrkanda mélange zone. The Dzheltula complex consists of monzonites, foid monzonites, and alkaline syenites; granite dykes intrude the complex. All alkaline rocks have high LILE contents (e.g., Ba and Sr), high light REE/HFSE ratios, strongly fractionated REE patterns, and typically lack Eu anomalies. Granite shows different major and trace-element characteristics in comparison to monzonites and syenites. The major and trace-element characteristics of the Dzheltula complex rocks and minerals are consistent with formation by combined assimilation and fractionation processes of an alkaline parental magma of lamproitic composition. The alkaline rocks have moderately radiogenic Sr (87Sr/86Sr(t) = 0.7057–0.7065) and unradiogenic Nd (ɛNd(t) = − 11.3 to − 15.2) and Pb (206Pb/204Pb = 17.17–17.26); granite has more enriched 87Sr/86Sr(t) value (0.707408) but similar ɛNd(t) = − 12.93 The trace element and Sr–Nd–Pb isotopic data for the Dzheltula complex indicate its mantle source experienced ancient metasomatic enrichment, probably associated with subduction. [ABSTRACT FROM AUTHOR]

The paper presents petrochemical, geochemical, and mineralogical data on rocks of the phoscorite–carbonatite complex in the Kovdor alkaline–ultramafic massif, Kola Peninsula, Russia. In contrast to what is usually thought, trace elements were determined to be concentrated not in the carbonatites themselves but in the related phoscorites. The paper presents data on the evolution of the compositions and zoning of minerals in successive generations of both rock types as a result of the fractional crystallization of their parental magmas, and data on general trends in the concentrations of trace elements. The Fe-rich phosphate–carbonate melt seems to have separated from the primitive alkaline–ultramafic silicate melt during its advanced differentiation. The Fe-rich phosphate–carbonate magma was parental for the phoscorite–carbonatite complex. The possibility of its splitting into immiscible Fe-rich phosphate and carbonatite melts is discussed. [ABSTRACT FROM AUTHOR]

The article presents the results of a study on sediment deposition processes in the palaeolake shore zone, at the multilayered Serteya II archaeological site in Western Russia. In recent years, geomorphological, palaeopedological and palaeoecological research was undertaken in strict cooperation with archaeological fieldwork. The Serteya II site occupies a substantial area of a kame terrace and biogenic plain within a palaeolake basin. From an archaeological point of view, the site is represented by few Mesolithic artefacts, but mostly by remnants of hunter-gatherer-fisher communities attributed in the Russian scientific tradition to the Neolithic period and dated from 6300 BC to 2000 BC. Later, the area was used by people in the Bronze Age, Early Iron Age and Early Middle Ages. The integration of archaeological and multidisciplinary palaeoenvironmental research allowed the natural and human induced deposition of mineral-organic and minerogenic sediments to be reconstructed, as well as the development of structures in the lake shore zone. The changes from lacustrine to fluvial system were documented and the human impact is recorded mostly in the acceleration of slope processes. [ABSTRACT FROM AUTHOR]

The Vuoriyarvi Devonian carbonatite-ijolite-pyroxenite-olivinite complex comprises several carbonatite fields: Neske Vara, Tukhta-Vara, and Petyayan-Vara. The most common carbonatites in the Tukhta-Vara and Neske-Vara fields are calciocarbonatites, which host several P, Fe, Nb, and Ta deposits. This paper focuses on the Petyayan-Vara field, in which the primary magmatic carbonatites are magnesian. The least altered magnesiocarbonatites are composed of dolomite with burbankite and are rich in REE (up to 2.0 wt. %), Sr (up to 1.2 wt. %), and Ba (up to 0.8 wt. %). These carbonatites underwent several stages of metasomatism. Each metasomatic event produced a new rock type with specific mineralization. The introduction of K, Si, Al, Fe, Ti, and Nb by a F-rich fluid (or fluid-saturated melt) resulted in the formation of high-Ti magnesiocarbonatites and silicocarbonatites, composed of dolomite, microcline, Ti-rich phlogopite, and Fe-Ti oxides. Alteration by a phosphate-fluoride fluid caused the crystallization of apatite in the carbonatites. A sulfate-rich Ba-Sr-rare-earth elements (REE) fluid (probably brine-melt) promoted the massive precipitation of ancylite and baryte and, to a lesser extent, strontianite, bastnäsite, and synchysite. Varieties of carbonatite that contain the highest concentrations of REE are ancylite-dominant. The influence of sulfate-rich Ba-Sr-REE fluid on the apatite-bearing rocks resulted in the dissolution and reprecipitation of apatite in situ. The newly formed apatite generation is rich in HREE, Sr, and S. During late-stage transformations, breccias of magnesiocarbonatites with quartz-bastnäsite matrixes were formed. Simultaneously, strontianite, quartz, calcite, monazite, HREE-rich thorite, and Fe-hydroxides were deposited. Breccias with quartz-bastnäsite matrix are poorer in REE (up to 4.5 wt. % total REE) than the ancylite-dominant rocks (up to 11 wt. % total REE). [ABSTRACT FROM AUTHOR]

Ediacaran and Permian‒Triassic stages of plagiogranite magmatism are distinguished for the Ust-Bel'sky and Algansky terranes of the West Koryak fold belt, NE Russia. The U‒Pb ages of Ediacaran plagiogranites are 556 ± 3 Ma (SIMS data) and 538 ± 7 Ma (LA–ICP–MS data), respectively, and 235 ± 2 Ma (SIMS data) for the Permian‒Triassic plagiogranites. The Ediacaran and Permian‒Triassic plagiogranites are low-K igneous rocks. Sr‒Nd isotopy and REE patterns of both plagiogranite suites allow suggesting their formation via partial melting of primary mantle material or fractional crystallization of basaltic magma. Ediacaran plagiogranites were formed in the oceanic arc setting contemporaneously with the volcanic-sedimentary complex of Otrozhnaya slice, Ust-Bel'sky terrane. Tuffaceous conglomerates in the lower part of this complex contain Ediacaran zircons with a peak age of 571 Ma. Formation of the Permian‒Triassic plagiogranites took place within the Ust-Bel'sky segment of the Koni‒Taigonos arc via partial melting of melanocratic ophiolite material in the accretionary structure of this arc or fractional crystallization of basaltic magma, melted from such substrate. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous Kanguk Formation of the Sverdrup Basin, Canadian Arctic Islands, contains numerous diagenetically altered volcanic ash layers (bentonites). Eleven bentonites were sampled from an outcrop section on Ellesmere Island for U–Pb zircon secondary ion mass spectrometry dating and whole-rock geochemical analysis. Two distinct types of bentonite are identified from the geochemical data. Relatively thick (0.1 to 5 m) peralkaline rhyolitic to trachytic bentonites erupted in an intraplate tectonic setting. These occur throughout the upper Turonian to lower Campanian (c. 92–83 Ma) outcrop section and are likely associated with the alkaline phase of the High Arctic Large Igneous Province. Two thinner (<5 cm) subalkaline dacitic to rhyolitic bentonites of late Turonian to early Coniacian age (c. 90–88 Ma) are also identified. The geochemistry of these bentonites is consistent with derivation from volcanoes within an active continental margin tectonic setting. The lack of nearby potential sources of subalkaline magmatism, together with the thinner bed thickness of the subalkaline bentonites and the small size of zircon phenocrysts therein (typically 50–80 μm in length) are consistent with a more distal source area. The zircon U–Pb age and whole-rock geochemistry of these two subalkaline bentonites correlate with an interval of intense volcanism in the Okhotsk–Chukotka Volcanic Belt, Russia. It is proposed that during late Turonian to early Coniacian times intense volcanism within the Okhotsk–Chukotka Volcanic Belt resulted in widespread volcanic ash dispersal across Arctic Alaska and Canada, reaching as far east as the Sverdrup Basin, more than 3000 km away. [ABSTRACT FROM AUTHOR]

In this paper, new main and trace elements and isotopic data are presented for 14 coarse-grained eclogite xenoliths from the V. Grib kimberlite pipe in the central part of the Arkhangelsk Diamondiferous Province. Based on reconstructed whole rock MgO content, this suite is divided into high-MgO and low-MgO varieties. Eclogitic groups have a similar range of variations in the trace element compositions of garnet, clinopyroxene and reconstructed whole rock. All eclogites show positive Eu anomalies in garnet and Sr anomalies in the whole rock. The negative correlation between the Mg#, Sr/Lu ratio and HREE in a whole rock points to upper and lower oceanic crustal rocks as a protolith for eclogites with high and low whole rock HREEs, respectively. Low-MgO eclogites with higher whole rock HREEs have the basaltic upper oceanic crustal protolith, whereas the protoliths of eclogites with lower whole rock HREEs could be of gabbroic composition from the lower oceanic crust. High-MgO eclogites could represent MgO-rich portions of oceanic crustal rocks: picritic/MgO basalt portions in the upper oceanic crust and troctolite portions in the lower oceanic crust. The Sr and Nd isotope compositions suggest a complex history of eclogites during their residence in the lithospheric mantle. Similarities in the Nd isotope compositions and two-point Sm-Nd isochron ages are evidence for re-equilibration of the Sm-Nd isotope system between the eclogite garnet and clinopyroxene via a pre-kimberlite thermal event at 396 ± 24 Ma. The subset of clinopyroxenes from four eclogites has a Sr isotope composition that plots on the isochron at an age of 2.84 Ga, which reflects the time of the subduction event and emplacement into the lithosphere and corresponds to the time of the Belomorian Eclogite Province of Baltic Shield formation. [ABSTRACT FROM AUTHOR]

The first data on five primary molybdenite sources within the gabbro-dolerite complex of Pay-Khoy (Pay-Khoy Ridge, Yugra Peninsula, Russia) are presented. The mineral is extended areally in Devonian ore-bearing gabbro-dolerites, contact rocks, and quartz veins. This paper considers the mineralogical–geochemical features of molybdenite, its occurrence, the composition of host rocks, and spectroscopic studies. [ABSTRACT FROM AUTHOR]

Abstract–New geochemical, mineralogical, and Rb–Sr and Sm–Nd isotopic data have been obtained on corundum plagioclasites–kyshtymites from the 5th Versta deposit (South Urals, Russia). The genetic link of miaskites and kyshtymites is shown. The formation of the kyshtymites is associated with the redistribution and accumulation of aluminum, calcium, HFSE, and LIL-elements at the stage of tectonic-metamorphic deformations of the Ilmenogorsky–Vishnevogorsky alkaline complex. [ABSTRACT FROM AUTHOR]

Secondary quartzites on Tyuters Island in the Gulf of Finland host long linear zones, up to 3 m thick, that are easily discernible in detailed satellite imagery. The zones consist of sillimanite–magnetite–kaolinite metasomatites, rocks that were first found in these zones. The metasomatites were produced at shattering of the quartzites and subsequent fluid introduction of material enriched in various components. The metasomatites are enriched in Al2O3 (16–23 wt %, as compared to 2–5 wt % in the quartzites). In contrast to the quartzites, iron in the metasomatic is contained mostly in the form of ferric oxide (whereas it occurs dominantly as ferrous oxide in the quartzites). The metasomatites contain practically no alkalis and alkali-earth elements and are enriched in Zn (146–199 ppm) and some other trace elements, including REE, first of all Ce (34 ppm) and La (17 ppm). Both the metasomatites and the quartzites show similar and insignificant REE fractionation: (La/Yb)n = 6.55 and 6.17. The metasomatites consist of the same minerals as the quartzites, but the proportions of these minerals and their composition in these rock types are different. It is worth mentioning magnetite of the metasomatites: it hosts abundant quartz inclusions with kaolinite rims. The quartz inclusions host, in turn, inclusions of magnetite crystallites. The metasomatites were produced in a number of stages of a metasomatic process, with changes in the fluid composition and its pH. The development of the metasomatites in the linear zones, the disintegration of their protolithic quartzites, and the high kaolinite contents in the rocks make these metasomatites similar, in a sense, to weathering crusts. However, the facts that the metasomatites and their protolithic quartzites consist of the same minerals, that the metasomatites contain absolutely no sulfides and sulfur but contain magnetite with complicated mineral inclusions make these rocks different from classic weathering crusts. [ABSTRACT FROM AUTHOR]

Long-term disposal of coal combustion residues (CCR) in the environment could change the geochemistry of soils and surface waters of adjacent territories. Aiming to evaluate the environmental impact of CCR we investigated soils and surface waters (12 and 18 sampling points, respectively) in the vicinity of the aged settling pond of the Cherepetskaya Thermal Power Plant in the Tula Region (Russia). The research reports and discusses changes in the composition of readily soluble salts in sod-podzolic soils (Retisols) as well as the content of carbonates and the distribution of potentially hazardous elements (Ni, Cr, V, Sr, Pb, Zn) in soil profiles. The mineralization of surface waters was also measured. For performing analyses, methods of HPLC, XRF, ICP-AES, and ICP-MS were used. The research revealed that the introduction of technogenic material into soils had 1.5–3 times increased the content of readily soluble salts compared to natural Retisols and changed the composition of ions. Carbonates in amounts of up to 1.9% were determined in all Retisols with introduced CCR which is never observed in natural acid soils. Differentiation in the content of V, Cr, Ni, Zn, Sr, Pb in soil profiles corresponded to leaching patterns of these elements from the CCR stated by the other researchers. Their concentrations in soils generally did not exceed the standards stated in the Russian Federation. Natural waters and waters with technogenic impact had the well-defined differentiation in the ratio of sodium and potassium in total cations. The study showed that the area of the environmental footprint of the settling pond with CCR differed in soils and surface waters. Changes in the geochemistry of surface waters were noticeable at greater distances and probably reflected the transformation of the geochemistry of groundwater. Changes in the geochemistry of soils were very local and were observed at a distance of fewer than 200 m from the settling pond. • Settling ponds can impact the geochemistry of soils and surface waters. • Soils with coal combustion residues (CCR) had elevated concentrations of readily soluble salts. • The distribution of V, Cr, Ni, Zn, Sr, Pb in soil profiles reflected the presence of CCR. • Natural waters and waters with technogenic impact were differentiated in the composition of ions. • Wastes from thermal power engineering leave a long-term environmental footprint. [ABSTRACT FROM AUTHOR]

Abstract Complex studies of soil cover within the urbanized areas represent one of the main research directions in environmental geochemistry. Urban soil geochemistry depends on a combination of natural and urbanization factors unique to each urban environment. Although Tyumen, in Western Siberia, is an intensively developing urban city, a detailed geochemical survey of its soils has never been performed. In this study, we conducted a systematic geochemical soil survey across the urbanized area of Tyumen, Russian Federation. Surface soil samples (0–10 cm) were collected from 241 sampling sites: 1 × 1 km regular grid for highly urbanized areas, and 4 × 4 km grid for peripheral parts of the city. The contents of V, Cr, Co, Ni, Cu, Zn, As, Sr, and Pb were determined using XRF analysis. Data were interpreted using GIS and multivariate statistical analyses, including hierarchical cluster analysis and principal components analysis. The results showed a non-uniform spatial distribution of individual metals, associated with natural soil-lithological conditions and urban environment characteristics. Our data showed that variation in soil element content was origin dependent: V, Cr, and Co contents were related to their natural origin; As and Pb to their anthropogenic origin; and Ni, Cu, and Zn to their mixed origin. Elevated V, Cr, Co, Ni, Cu, and Zn contents correlated with proximity to motorway networks and machinery. Strong As and Pb anomalies were associated with the activity of battery enterprises. The spatial distribution of Sr was significantly different from other studied elements — anomalous content of this metal was confined to hydromorphic boggy landscapes of the city's northern part. In general, Tyumen territory was slightly polluted with metals. Zn and Pb contents were slightly lower than in most cities with similar population levels, while those of V and Co were higher. Other metal contents were comparable to those in large cities, with a long history of industrial development. Elevated Cr, Ni, Zn, Cu, As, Pb, and Co contents were observed in areas that developed during mid last century. Highlights • Systematic geochemical survey of soils for the large Siberian city is presented. • Spatial distribution of chemical elements in soil were examined. • Parent rocks and soils defined the contents of V, Cr, Co and Sr. • Ni, Cu and Zn in soils had a mixed origin, As and Pb had anthropogenic origin. • Contents of Cr, Ni, Zn, Cu, As, Pb, Co correlated with urbanization factors. [ABSTRACT FROM AUTHOR]

The results of comprehensive (geological, geochemical, geochronological, and petro- and paleomagnetic) study of the Aptian–Albian rocks of the Kema Terrane and the northeastern Udyl segment of the Kiselevka–Manoma Terrane are presented. The obtained results suggest that the studied volcanogenic–terrigenous complexes of rocks formed in a suprasubduction zone at about the same time (early Albian, 110 Ma ago) at close latitudes but in different island arcs unequally distant from the continent: the complexes of the Kema Terrane at a latitude of 36° ± 6° N in the island arc close to the continent as evidenced by the petro–geochemical characteristics of the volcanites and the presence of ancient zircons in the sediments; and the rocks of the Udyl segment of the Kiselevka–Manoma Terrane at a latitude of 33° ± 5° N in an intraoceanic island arc separated from the volcanic arc of the Kema terrane by an interarc basin, which was wide and deep enough to avoid the influence of the continental source areas in the sediment accumulation zone of the Kiselevka–Manoma Terrane. Based on the conclusions, the geodynamic reconstruction is developed for the formation and history of motions of the studied rock complexes during the oceanic plate movement, their displacement along the transform margin, as well as post-accretionary movements at various distances to the current position with the following coordinates: Udyl 52° N, 140° E; Kema 45°–46° N, 136°–137° E. [ABSTRACT FROM AUTHOR]

The article presents new geological, geochronological, mineralogical, geochemical, and isotopic data on the Early Cretaceous granitic rocks of the southern part of the Zhuravlevka Terrane (Sikhote-Alin). It is shown that four intrusive complexes containing significant amounts of granitic rocks were formed almost simultaneously in this area in the Early Cretaceous (about 100 Ma). These magmatic associations differ in rock set, their mineralogical characteristics, and chemical composition, varying from medium-potassium tonalites and granodiorites depleted in incompatible elements to shoshonitic monzonitic rocks enriched in HFSE and REE. The geochemical and isotopic characteristics of the granitic rocks indicate that the source of their melts was dominated by essentially juvenile metabasite crust with a limited contribution of the upper-crustal metasedimentary rocks. The diversity of geochemical types of the granitic rocks is explained by variable metabasite and metapelite contributions to their source, upper crustal contamination during magma ascent, as well as the variable contribution of the mantle source and different mechanisms of mantle–crust interaction. [ABSTRACT FROM AUTHOR]

Migmatites on the western shore of Ol'khon Island host unusual rocks: zoned lenses of hedenbergite–garnet–epidote–anorthite metasomatites coupled with the migmatites. No intrusive granites were found nearby. The skarn-forming process operated at the interface of the granite gneiss and skarn protolith (perhaps, carbonate rocks). The composition of the metasomatites is analogous to that of calcic skarns with high Al2O3, FeO, and CaO concentrations. The compositions and relations of the minerals provide evidence of the successive development of the hedenbergite–anorthite outer zone, dominantly anorthite–garnet main zone, and quartz-enriched inner zone, with all of the zones parallel to contact with the granite gneiss. The granite gneiss itself is also likely of metasomatic nature, as follows from its supraeutectic concentration of potassic feldspar in the leucosome and low crystallization temperatures. A minimum of the Gibbs free energy (calculated with the SELECTOR-C program package) was reached at 8 kbar and temperatures of 600–625°C. These parameters are lower than the melting temperature of the granite eutectic, and the absence of melt is confirmed by the absence of melt inclusions in minerals of the granite gneisses. This indicate that the driving force of the process was migmatizing silicic–potassic solutions. The P–T parameters of the skarns are close to the foregoing values. The very high Sr and Ca and low Mg concentrations suggest that the protolith of the skarns was calcite marble. The enrichment of the skarns in the granitophile elements suggests that the skarns were produced simultaneously with and in genetic relation to the migmatization processes. The metasomatites were formed before the partial melts were derived, early in the course of the granite-forming processes and provide important information for better understanding the metasomatic process responsible for the exchange of chemical elements between the rocks. [ABSTRACT FROM AUTHOR]

Abstract—: Data on mineral-hosted inclusions indicate that the charoite rocks crystallized in a heterogeneous medium of carbonate-silicate and carbonate melts, gaseous and H2O-salt fluids. Our results indicate that the early rock-forming minerals of the charoite rocks started to crystallize at high temperatures (>800°C), and crystallization may have terminated at lower temperatures (600-450°С). Data on the melt and fluid inclusions confirm the conclusion that the charoite rocks are of magmatic origin. The facts that these rocks are typically found as vein- and lens-shaped bodies, the composition of these rocks does not correlate with the composition of the host rocks, and the occurrence of chilled fine-grained domains of the charoite rocks also suggest that these rocks crystallized from magmatic melt. [ABSTRACT FROM AUTHOR]

Apatite is a concentrator of F and Cl, which play a significant role in the formation of minerals of platinum-group elements of pneumatolitic origin. There are three apatite generations in Norilsk magmatic sulfide ores. Apatite I occurs in sulfide bodies and rims of fluid alteration above sulfide droplets in disseminated ores. Its composition evolved from hydroxyl-chlorapatite to chlorapatite. Apatite I associates with Tiрbiotite, titanomagnetite, ilmenite with baddeleyite lamellae, anhydrite, Ti-poor kaersutite, Cl-bearing hastingsite and edenite, djerfisherite, bartonite, and minerals of the Pt and Au groups. Apatite I contains up to 2.3 wt % lanthanides, primarily Ce, La, and Nd. Apatite I is overgrown and replaced by apatite II, the composition of which evolved from hydroxyl-chlor-fluorapatite to fluorapatite. Apatite II often occurs also as individual crystals in massive sulfides and contains up to 0.9 wt % lanthanides. The pneumatolitic chlorapatite and fluorapatite contain ~0.5 wt % SiO2. The composition of apatite indicates discrete evolution of fluids released during the crystallization of Norilsk sulfide melts: from water-chloride to chloride at the first state, and from water-chlorite-fluoride to essentially fluoride at the second stage. The lanthanides released during the replacement of chlorapatite I by fluorapatite II were probably incorporated in pneumatolitic zoned orthite-(Ce). In the areas affected by prehnite-pumpellyite metamorphism, apatite I and apatite II within metamorphosed sulfide ores are partly or completely replaced by apatite III, which varies in composition from hydroxyl-chlorapatite to hydroxylapatite poor in fluorine and lanthanides. The lanthanides released during the replacement of apatite I and II by metamorphic hydroxylapatite III were probably incorporated in metamorphic unzoned orthite-(Ce). [ABSTRACT FROM AUTHOR]

Anomalous concentrations of dissolved gases, exceeding their background values by an order of magnitude or more, are recorded in the surface and ground waters of the Birofeld Graben of the Middle Amur sedimentary basin. The main geological factors that influence the formation of the gas composition and gas saturation of waters are determined. The gas-geochemical indicators for the dissolved hydrocarbon gases, which make it possible to estimate their genesis and prospects for the oil-and-gas contents of the Birofeld graben, are specified. [ABSTRACT FROM AUTHOR]

Data on the petrography, geochemistry, and isotopic geochronology of granites from the northern part of the Taimyr Peninsula are considered. The Early-Middle Carboniferous age of these rocks has been established (U-Pb, SIMS). Judging by the results of 40Ar/39Ar dating, the rocks underwent metamorphism in the Middle Permian. In geochemical and isotopic composition, the granitic rocks have much in common with evolved I-type granites. This makes it possible to specify a suprasubduction marginal continental formation setting. The existence of an active Carboniferous margin along the southern edge of the Kara Block (in presentday coordinates) corroborates the close relationship of the studied region with the continent of Baltia. [ABSTRACT FROM AUTHOR]

For an improved understanding of metal behavior in soils, studies on geochemical changes occurring in a specific grain-size fraction during pedogenesis and lateral translocation of soil material are needed. In the present research we analyzed the concentrations and vertical distributions of Fe, Mn, Cu, Ni, Co, Cr, Zn, Pb, Ti, Zr in coarse and medium sand fraction of the major soil types of the middle Protva basin, situated in the mixed forest zone of European Russia, and described patterns of downslope (lateral) distribution of metals in the humus horizons along two catenas and two types of small erosional systems. The observed concentrations for all metals in the fraction 1–0.25 mm, except of Mn, conform to the natural geogenic concentrations reported previously in literature. The majority of the metals exhibit high natural variability in concentrations in the sand fraction. Higher metal concentrations are found either in the topsoil horizons or in parent material and underlying stratum. Studying lateral aspects of metal distribution in the sand fraction of humus horizons revealed a decrease in Mn, Zn, Pb, Co, Ti and an increase in Fe, Cr and Ni levels of the lower sections of the slopes. The similarity of metal concentrations in the sand fraction in these positions across two catenas implies the importance of the geochemical convergence processes operating in downslope direction. The small erosional landforms, a gully and a dry U-shaped valley, show similar patterns in lateral distribution of Fe, Cu, Ni, Cr, Zr, Zn, but they differ in terms of Pb, Co and Mn behavior across their elementary units: adjacent areas, slopes and bottom. The results imply that the features of vertical (within the soil profiles) and lateral (along catenas and small erosional systems) distributions of metals are significantly controlled by the provenance of the sand fraction, although at the same time some variations in metal contents seem are attributed to chemical transformations of the sand fraction due to pedogenic processes and during downslope translocation of soil material. [ABSTRACT FROM AUTHOR]

Upper Eocene and Lower Oligocene rocks in the northeastern Caucasus were examined in the most representative Chirkei section (Sulak River basin). Sharp lithogeochemical distinctions between them were revealed. The results of the study of nannoplankton demonstrated that the Eocene/Oligocene interface occurs slightly below the boundary between the Belaya Glina and Khadum formations. The studied section revealed a series of nannoplankton bioevents facilitating its stratigraphic subdivision. It has been established that organic matter (OM) in rocks of the Khadum Formation is characterized by a relatively high degree of maturity. Probably, the material of mainly marine genesis contains a terrigenous OM admixture. Positive oxygen isotope anomaly in the upper part of the Belaya Glina Formation reflects global climate changes (cooling) near the Eocene/Oligocene interface. Limitation of the anomaly by the upper boundary of the Belaya Glina Formation is likely related to changes in water salinity variations in the Early Oligocene basin and intense early diagenetic processes in rocks therein. Lithological, geochemical, and paleoecological data suggest that the Khadum paleobasin was depleted in oxygen. Such environment was unstable with periodic intensification or attenuation. Paleoecology in the Belaya Glina basin was typical of normally aerated basins. [ABSTRACT FROM AUTHOR]

This paper presents new geochemical, U–Pb geochronological, and Sm–Nd isotopic data for early Paleozoic granitoids and acidic volcanic rocks within the Mamyn Terrane that constrain the early Paleozoic tectonic evolution of the eastern central Asian orogenic belt (CAOB). The Mamyn Terrane is usually considered part of the Argun Massif, although our new geochronological data indicate the presence of two magmatic events within the terrane that occurred at the Ediacaran–Cambrian boundary (∼541 Ma) and the late Cambrian–Early Ordovician boundary (507–488 Ma). Field observations indicate that all of the late Ediacaran–Early Cambrian (∼541 Ma) volcanic rocks are deformed whereas the Late Cambrian–Early Ordovician (507–488 Ma) intrusive and volcanic rocks are either deformed or undeformed. The ∼541 Ma magmatic event in the study area produced rhyodacite, trachyrhyodacite, and trachyrhyolite units that are either high-K calc-alkaline or shoshonitic. These units have ε Nd(t) values from −7.4 to −8.7, t Nd(DM) ages of 1.9–1.8 Ga, and formed from primary magmas generated by the partial melting of Mesoproterozoic continental crustal material in a suprasubduction zone setting. The Late Cambrian–Early Ordovician (507–488 Ma) magmatic event in this area formed gabbrodiorite, diorite, granodiorite, granite, trachyrhyodacite, and rhyodacite units that are medium-K and calc-alkaline, and have arc-like trace element compositions that are enriched in the large ion lithophile elements (LILEs) and depleted in the high field strength elements (HFSEs). These units have initial 87 Sr/ 86 Sr (i) ratios and ε Nd(t) values that range from 0.7048 to 0.7067 and from −3.3 to −0.2, respectively, yielding t Nd(DM) ages of 1.6–1.1 Ga. These features indicate that the magmas that formed these units were generated in a subduction zone setting, most likely by the partial melting of Mesoproterozoic crustal material with the addition of some younger juvenile material. In addition, the Late Cambrian–Early Ordovician trachyrhyodacite and rhyodacite units in this area are high-K and calc-alkaline or are shoshonitic and are enriched in K, Rb, the rare earth elements (REE), Y, Nb, Ta, and Zr, and are depleted in Sr and have A-type granite affinities. However, these units do not contain alkali amphibole or pyroxene and have high FeO tot /MgO ratios (6.7–12.7) that indicate they formed from highly fractionated magmas. Therefore, these volcanic rocks represent extreme melt differentiates that also formed the coeval granites. The early Paleozoic magmatic events within the Mamyn Terrane have also been identified in the Argun, Bureya, and Jiamusi areas of the eastern CAOB, suggesting that all of these areas have a common geodynamic history. [ABSTRACT FROM AUTHOR]

The work reports on the results of geochemical studies of the bottom sediments on the shelf of the East Siberian Sea. The sediments' gas content, gas composition, and gas geochemical and isotopic characteristics are determined. Abnormal zones of distribution of methane, hydrocarbon gases, and carbon dioxide are revealed within the studied areas, along with the general geological factors affecting gas formation. Areas of distribution of hydrocarbon gases of varying origins are distinguished. The potential for oil-and-gas content is estimated. [ABSTRACT FROM AUTHOR]

The study presents new data on the geochemistry coal deposits of the Cretaceous, Paleogene, and Neogene age in the Sakhalin Basin. A wide range of trace elements were studied in 240 coal samples and 138 coal-bearing rock samples from the main fields of the Basin that are under development and available for study. This study demonstrated that the coals in the Sakhalin Basin are generally characterized by concentrations of most trace elements close to the average estimates for the world coals along with, in addition, a mixed chalcophile-siderophile and lithophile geochemical assemblage typical for the transition areas of the continent-ocean zone. On average for the Basin, the coals are enriched in Sc, V, Co, Br, Sr, and Ba compared to the world average. Ash of coals from the Sakhalin Basin is characterized by the above-Clarke content of rare alkali metals (Li, Rb, Cs), Cr, Ni, Cu, Y, and Zr, in addition to the above elements. HREE, Br, Cu, Ag, Hg, Nb, Ge, Mo, W, As, Ni, and Pb specialization was identified for some coalfields. The levels of accumulation of Sc, Y, Sr and heavy lanthanides in coal ash in some coalfields exceed the minimum possible commercial concentrations. The study demonstrated that the geochemical trace element characteristics of coal-bearing sediments in the Sakhalin Basin reflects the peculiarities of the geological evolution of this crustal block. Despite the high tectonic activity and volcanism in the Cenozoic, the specific composition of the rocks in the flanks and the basement of the coal-bearing depressions defined the low rare-metal potential of the basin. Scandium, V, Co, Ni, Ba, and Sr anomalies are associated with the predominantly basic composition of the flanks of the depressions, while local Hg, Sb, W, Cu, and Ge anomalies are connected to the hydrothermal activity. • The coals in the Sakhalin Basin have a geochemical specialization typical for transition areas of the continent-ocean zone. • The coals are enriched with Sc, V, Co, Br, Sr, Ba, Br, Cu, Ag, and Hg relative to the average estimates for the world coals. • Some coals have high concentrations of Sc, Y, Sr, Hg, and medium and heavy lanthanides reaching commercial values. • Distribution of Sc, Y, Sr, Hg, M and HREE with high concentrations suggest a hydrogenous mechanism of their accumulation. [ABSTRACT FROM AUTHOR]

Three styles of platinum-group element mineralization occur within the Ural-Alaskan type complexes of the Uralian Platinum belt: chromite-platinum, noble metal, and noble metal-copper ones. They are associated with dunite and chromitite (chromite-platinum), pyroxenite (noble metal) and gabbro (noble metal-copper). Three common platinum group element distribution patterns are observed for dunite and chromitite: (1) M-shaped (defined by positive Ir and Pt anomalies); (2) with positive Ir-Rh(Pt) anomalies; and (3) W-shaped with positive Os and Pt, or Os and Rh anomalies. In contrast, pyroxenite and gabbro are enriched in Pd and Au. The PGM assemblages correlate to the PGE + Au distribution patterns as exemplified by the predominance of Ir-rich Pt-Fe alloys within dunite and chromitite. The noble metal assemblages of pyroxenite and gabbro comprise tellurides, arsenides, and various Pd minerals, as well as native gold and Au-Ag alloy. An indicative Pd/Ir ratio in a succession dunite-chromitite-gabbro increases from 0.04 to 148 with a maximum value of ~5000 in massive sulfide ore of the Volkovsky that is attributable to the contrasting magma compositions defining chromite vs sulfide controls over PGE concentration. • Three PGE mineralization styles are linked to specific lithologies in the Ural-Alaskan type complexes. • Three types of PGE patterns (M-, W-shaped and Ir-Rh ± Pt) are typical of dunite and chromitite. • Pyroxenite and gabbro show sulfide-controlled patterns with enrichment in Au and Pd. • Platinum-group mineral assemblages correlate to the PGE + Au distribution patterns. [ABSTRACT FROM AUTHOR]

The lower continental crust, representing up to 50% of the continental mass, is largely inaccessible, making its composition difficult to constrain. Previous composite models based on geophysical evidence and geochemical data of granulite terrains and xenoliths have proposed varying results, from a mafic, relatively refractory lower crust to an intermediate-felsic, more enriched composition. Here, we investigated the mineralogy and geochemistry of predominantly mafic granulite xenoliths from eastern Australia and the Kola Peninsula, Russia, using an in situ analytical approach that minimises host magma contamination. The resulting xenolith compositions are variably and often strongly depleted in most highly incompatible trace elements, including the heat-producing elements. These xenoliths represent an extremely refractory component of the lower continental crust, likely formed after high degrees of partial melting or crystallisation from a depleted source. A lower crust composed solely of this refractory endmember would be too exhausted in heat-producing elements to satisfy heat-flow constraints. However, a volumetrically significant component of the lower crust is this mafic and refractory material, combined with undifferentiated material and a felsic or metapelitic portion. Using geophysical constraints on proportions of refractory (55%), undepleted (38%) and enriched (7%) components, a new estimate for average lower continental crust that satisfies heat flow limits was calculated, including for elements such as Be, B, Cs, W and Tl, where previous estimates relied on very few data. Finally, we show that because much of the lower continental crust is so refractory and depleted in incompatible elements, it is unlikely to be a reservoir that can balance radiogenic isotope (unradiogenic Pb) and trace element ratios (e.g. Rb/Cs, Nb/Ta) for which bulk silicate Earth departs from chondritic ratios. • Granulite xenoliths are investigated to constrain the composition of the deep crust. • Most of the lower crust is extremely depleted in highly incompatible trace elements. • An updated compositional estimate for the lower crust is presented. • Deep crust has limited potential as a "hidden" reservoir for mass balance issues. • Only ancient delaminated deep crust can contribute significantly to the bulk Earth. [ABSTRACT FROM AUTHOR]

• The Pre-Eifelian paleosol on rhyolite demonstrates surprisingly deep development. • Rhyolite contains allochthonous substituted by pyrite inclusions of nematophyte. • Pyrite oxidation drives the acid sulfate paleosol development. • Gypseous acid sulfate paleosol was developed under warm humid climate. During Late Devonian Voronezh Land was one of the main volcanic centers of Central Devonian Field. Earlier eruptions on the given territory have not been documented. This paper presents the detailed multidisciplinary study of the Pre-Eifelian paleosol developed from rhyolite lava deposited on the contact with the Proterozoic basement in Shkurlat granite quarry (Voronezh region, Russia). Discovered paleosol includes abundant coalified and partly substituted by pyrite allochthonous remnants of Nematasketum and Prototaxites. Main part of them had an outstanding preservation of tissues. Along with typical for rhyolite a quartz dominance, paleosol contains in situ developed kaolinite, gypsum, goethite, jarosite. Abundant Fe-nodules concentrated in the second half part of the shallow (∼50 cm) paleosol profile are composed of gypsum, goethite and metastable Fe-sulfates - jarosite and voltaite. Based on a complex of analytical characteristics, the discovered paleosol was attributed to acidic sulfate soil. The development of paleosol was initiated by pyrite oxidation which played the role of trigger. Being gypseous, paleosol bears the characteristics which are typical for paleosol of humid type. Based on geochemical data (CIA, CIA-K, PWI indexes) the obtained climatic parameters correspond to a subtropical climate with MAP 1200–1300 mm and MAT ∼ 17 °C. [ABSTRACT FROM AUTHOR]

Calcareous tufa deposits have been discovered in the Chibitka River valley near Lake Cheybek-Kohl, at the junction of the Kurai and Teletsk-Kurai large active faults in the southeastern Gorny Altai, Russia, at an altitude of 1800–2000 m. Fossil tufa is composed of calcite and cements Holocene grey colluvium and glacial till deposited by the Late Glacial Chibitka Glacier. Current tufa precipitation has been observed from a low-flow spring with cold (10 °C) HCO 3 -SO 4 –Ca-Mg water, рН = 6.86. The stable isotope composition of spring water is − 5.8‰ VPDB δ 13 C of dissolved inorganic carbon and − 14.5‰ VSMOW δ 18 O. Modern tufa consists of thin laminated Mg-calcite and Sr-aragonite crusts, with abundant algae and biofilms on their surfaces. Both modern and fossil tufas are depleted in REE (a total of 0.40–16.4 ppm and 0.40–3.80 ppm, respectively) and share similar PAAS-normalised REE + Y spectra with HREE enrichment and slight progressive LREE depletion. The modern tufas show positive δ 13 C values of 0.1‰ to 0.9‰ VPDB while the fossil ones have an isotopically lighter composition of δ 13 C = − 4.1‰ to − 1.9‰ VPDB; the δ 18 O range is very narrow (− 13.0 to − 13.8‰ VPDB). Both stable isotope and trace-element signatures (including REE patterns) of the tufas indicate precipitation from cold groundwaters subjected to prolonged interaction with a carbonate aquifer (the Baratal Group of limestone and dolostone) in a cold continental climate similar to the present conditions. Tufa deposition in the Lake Cheybek-Kohl area began with the onset of post-Late Glacial global warming and permafrost degradation. Unlike the fossil tufa formation, current precipitation of freshwater carbonates has been microbially mediated. The discovered tufa deposits provide new palaeoclimatic and active tectonic proxies in the southeastern Gorny Altai. [ABSTRACT FROM AUTHOR]