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As the gem trade has evolved, origin information has become a major consideration in nephrite commerce, affecting the price heavily. Accurate origin determination of nephrite is difficult due to similarities in appearances, mineral composition, major chemical components, and spectroscopy. In addition, the diversification of new nephrite deposits in the world leads to an increase in class numbers and complexity in the classification model, making it more difficult to determine the origin of nephrite. To tackle the large-class-number classification (LCNC) origin determination problem, laser inductively coupled plasma mass spectrometry (LA-ICP-MS) was utilized to detect the content of 45 major and minor elements in the nephrite sample. In addition, three different linear discriminant analysis (LDA) strategies for multi-class classification, One-off (OO), One-Versus-Rest (OVR), and One-Versus-One (OVO), were examined to evaluate the potential of a comprehensive multivariate chemometric strategy to determine the origin of nephrite samples from seven localities in three different countries (China, Russia, and South Korea) and compare their capability to improve the performance of the classification model. The results demonstrated that LA-ICP-MS coupled with multi-strategy LDA can be used to determine the origin of nephrite with a high level of accuracy. The One-off LDA model achieved classification accuracies of 95.8% and 93.3% in original classification and leave-one-out cross-validation (LOOCV), respectively. Nonetheless, this method has poor capabilities in solving large-number class classification problems, and the data of the classes in discriminant models overlap. OVR-LDA and OVO-LDA were used to handle multiclass problems by transforming multiple classes into a set of binary cases. These two strategies both were demonstrated to be capable of differentiating the origin and achieved improved performance in dealing with the multi-class problem. Most importantly, we critically analyze the performance of the three LDA strategies in classification models and reveal their appealing properties, matters that need attention, and application prospects. We also investigate the element combinations that contribute greatly to classification functions and discuss the rationale of nephrite origin performance in the origin determination model from a geological perspective. [ABSTRACT FROM AUTHOR]

The paper presents results of petrographic, geochemical, mineralogical, and isotope-geochronological studies of metagabbro-dolerites of the central part of the Kara Depression, located in the middle course of the Sopcha-Yu River in the Yugorsky Peninsula, Nenets Autonomous District, Russia. Two varieties of metagabbro-dolerites are distinguished: quartz-bearing and quartz-free. The influence of an impact event on rock-forming and accessory minerals is considered. It is proved that the impact event has not modified the isotope system of zircon in the metagabbro-dolerites. The U–Pb (LA-ICP-MS) isotope–geochronological dating of the zircons gives an age of the magmatic minerals within the range of 365.3 to 390.8 Ma, which seems to correspond to the age of the massif. The weighted mean age is 375.5 ± 2.6 Ma and likely corresponds to the age of the Hengur complex. [ABSTRACT FROM AUTHOR]

To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals (Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed. The trace element compositions in clinopyroxenes indicate the existence of the mantle protolith of two types. The first protolith type, represented by lherzolites and diopside harzburgites, was originated from the partial melting (5%–10%) under the spinel fades conditions, while the second one, represented by diopside harzburgites, was formed under the polybaric partial melting (17%–19%) under garnet and spinel fades conditions. Subsequently, the mantle peridotite protolith was subject to fluid-induced partial melting in the suprasubduction setting that was resulted in the formation of harzburgites. Being affected by penetrating melts and fluids peridotites experienced the refertilization (LREE enrichment of clinopyroxenes) and high-temperature hydratation with subsequent development of pargasite and Mg amphibole. The high-T fluid-induced metamorphism at the subduction zone was accompanied by the formation of metaperidotites with clinochlore and REE-depleted tremolite. [ABSTRACT FROM AUTHOR]

The isotopic U–Pb ages are estimated for zircons (for the first time by the LA–ICP–MS method) from biotite (Eldzhurty) granites and for the first time from the rhyolites at the giant Tyrnyauz Mo–W deposit (North Caucasus). The weighted mean isotopic U–Pb age of zircon from the Eldzhurty granites is 2.10 ± 0.08 Ma, with variations from 1.78 to 2.53 Ma, whereas that of zircon from the rhyolites is 2.05 ± 0.04 Ma, with variations from 1.81 to 2.42 Ma. These data confirm the Neogene (Pleistocene) age of the rock crystallization, are in agreement with the emplacement sequence, and emphasize the short time span (~50 ky) between them. [ABSTRACT FROM AUTHOR]

The first data of a U–Pb isotopic study (LA-ICP-MS method) of zircon from leucocratic granites of the giant Tyrnyauz Mo–W deposit (North Caucasus) are presented. The emplacement of this granite separated the formation stages of Mo–W skarns and younger large stockworks with Mo-mineralization. Two types of zircons are distinguished among the grains identified. The first type is represented by rare tabular and short-prismatic crystals (xenocrysts) of an ancient zircon, with large variations of the U–Pb isotopic age (from about 300 Ma to almost 1500 Ma). The second type includes more abundant long-prismatic crystals of a young zircon; its weighted average U–Pb isotopic age (2.67 ± 0.04 Ma) corresponds to the time of leucocratic granite crystallization. [ABSTRACT FROM AUTHOR]

Demantoid is a rare Cr-bearing variety of andradite garnet historically mined in the Middle Urals of Russia, where its mode and time of formation remain controversial. A first direct in situ U-Pb LA-ICP-MS dating of demantoid was carried out on samples with extremely low U content obtained from the Karkodinskoe and Poldnevskoe deposits, both of which are located in the Karkodin meta-ultramafic massif of the Middle Urals. In both locations, demantoid mineralization occurred within cracks in ca. 400 Ma serpentinite host rocks composed of chrysotile and antigorite, calcite and aragonite, and magnesite. Magnetite, chromite, and pyrite occur as accessory minerals. The results yielded ages of 343 ± 4 Ma and 292 ± 1 Ma for the Karkodinskoe and Poldnevskoe deposits, respectively. These ages correspond to the times of continental collision and subsequent exhumation in the Middle Urals during the Uralian orogeny. Geochronology combined with trace element data of Uralian demantoid suggests that mineralization was induced by hydrothermal processes at T < 300 °C. But trace-element signatures point to different origins for the two hydrothermal fluids. Rare-earth element (REE) patterns in garnet from Karkodinskoe deposit appear to be inherited from syenitic rocks, whereas REEs in demantoid from Poldnevskoe show affinities with skarn environments. During the collision stage, magmatic fluids that were probably associated with syenitic rocks of the Kozlinogorsky complex were re-activated leading to the re-working of the meta-ultramafic protolith of the Karkodin massif. Metamorphic processes during the exhumation stage subsequently resulted in the mobilization of hydrothermal fluids likely linked to skarns. Their migration into fractures within meta-ultramafic rocks developed the demantoid mineralization in Poldnevskoe occurrence. • U-Pb LA-ICP-MS dating of andradite (var. demantoid) with extremely low U and high common Pb. • U-Pb ages cluster at ca. 343 ± 4 Ma and 292 ± 1 Ma for two neighbouring occurrences with similar mineralization. • Two ages correspond to the continental collision and exhumation stages occurred during the Uralian orogeny. • The REE patterns of demantoid garnets of two occurrences showed similarities to those found in skarn and syenitic rocks. [ABSTRACT FROM AUTHOR]

Abstract: Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) is applied to determining the concentrations of radioactive isotopes (87Rb, 232Th, 234U and 238U) in soil samples from Lake Baikal, Russia, for an annual dose estimation for luminescence dating. After an examination of pellet making procedures, the dried sediments were pressed into pellets. The concentrations of radioisotopes were successfully measured taking the National Institute of Standards and Technology standard glass (SRM 610 from NIST) as an external standard (reference material) to convert the signal intensity to a concentration. When the laser ablation setting is chosen to send a significant amount of material to the mass spectrometer (e.g., the repetition frequency of 20 Hz and spot diameter of 140 µm), a very small quantity of 234U (~10 ppb order) could be measured, and the resultant concentration agreed with the result obtained by conventional alpha-spectrometry analyses. Radioisotopes, along with other major elements measurable by LA-ICP-MS, can be measured quickly on fine-grained sediments (e.g., lake and deep-sea sediments) of small quantity by the simple procedure proposed here. [Copyright &y& Elsevier]

Information on Pu in environmental samples is traditionally based on the determination of the (240+239)Pu activity via Alpha Spectrometry (AS). A large number of alpha spectrometry sources (planchettes) containing radiochemically separated Pu are therefore stored worldwide and are available for further analyses. These archive samples represent a resource from which valuable information on isotopic composition of alpha emitters including Pu can be obtained. The relative abundances of Pu isotopes can be used to trace specific Pu sources and characterize the relative contributions of different Pu sources in a sample. Thus, in addition to the total (239+240)Pu activity, determination of the (240)Pu/(239)Pu ratio can provide valuable information on the nature of the Pu emitting sources. The Pu isotopic ratios can be determined by mass spectrometry techniques such as Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICPMS) or Accelerator Mass Spectrometry (AMS) that require dissolution and complete destruction of the material deposited on the planchettes. In this study Laser Ablation (LA)-quadrupole-ICP-MS has been employed for the analysis of (239)Pu/(240)Pu ratios from alpha-planchettes prepared from samples originating from the Mayak PA nuclear facility, Russia. The results are compared with data from AMS and show that the (240)Pu/(239)Pu ratios obtained by LA-ICP-MS can be utilized to distinguish weapons-grade Pu from civil reprocessing sources. Moreover, isotope ratio mapping can also be performed across the planchettes, allowing e.g. the visualization of possible inhomogeneities in the Pu-isotope distribution on their surface. Thus, this solid sample technique can be applied to extract additional information from existing archives of samples.

The article offers information regarding the modern concepts on the structure and evolution of the Uralian thrust fold. It discusses the age of two groups of geological structures the Uralides and Pre-Uralides-Timanides which are widespread in the Urals. It uses the mass uranium-lead isotope dating for the paleogeography and paleotectonics analysis. It mentions that Pre-Uralides-Timanides compose the submeridionally extended range of large salients lying among the Paleozoic complexes of the West Uralian megazone. It states that the upper structural element of Pre-Uralides-Timanides in the Bashkirian uplift is represented by a complex of terrigenous, terrigenous-carbonate, and carbonate rocks.

This study presents the first comprehensive investigation of perovskite from its type locality (Mineral Mines of Southern Urals, Russia), where this mineral was first described by Gustav Rose in 1839. The new data includes results from precise chemical analyses (electron-probe microanalyzer, LA-ICP-MS) and U-Pb ages (SHRIMP-II) of perovskite. Perovskite occurs in silicate-carbonate veins that transect the marginal parts of the Middle Riphaean Kusinsko-Kopanskaya layered intrusion, previously thought to be skarns. The perovskite crystals range from micrometer-scale grains to up to 11 cm in size. Chemical investigations revealed a low content of trace elements (rare earth elements, Y, Nd, U, Th) compared to perovskites from alkaline ultramafic rocks, silica-undersaturated basic rocks, carbonatites, and kimberlites. The determined age of the perovskite, 535 ± 43 Ma, significantly differs from the 1379 ± 8 Ma age of the Kusinsko-Kopanskaya intrusion, challenging the skarn-origin hypothesis for perovskite. Instead, the findings suggest a carbonatite origin for the perovskite mineralization. This timing indicates a previously unknown stage of endogenic activity on the Western Slope of the Southern Urals. [ABSTRACT FROM AUTHOR]

The distributions of trace elements in pyrite were studied in samples of high-grade gold ores from the Talatui, Teremkyn, and Darasun deposits. The paper presents LA-ICP-MS data on concentrations of trace elements in pyrite in gold ores from mineral deposits of the Darasun goldfield, which were produced by a single fluid–magmatic system at various temperatures. The high-temperature pyrite was found to be enriched in Co, Se, and W, whereas the medium-temperature pyrite was enriched in Cu, Zn, Ag, Te, As, and In. The behaviors of some elements (Ni, Au, Bi, Sb, and Pb) seem to be independent of temperature. The identified trends and relations in the behaviors of elements can be used in studying the Au-Bi mineralization of the intrusion-related type. [ABSTRACT FROM AUTHOR]

This paper presents petrography, X-ray electron probe energy-dispersive (EDS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and Raman spectroscopy data to characterize the mineral associations and composition of apatite group minerals from anorthosites of the Kievey deposit, North platinum group-element (PGE) Reef, Fedorova-Pana Complex, Kola Peninsula, Russia. The mineralized coarse-grained anorthosite belongs to the most common rock type of the main ore body, and hosts irregular interstitial sulfide disseminations of 5–7 vol.%. Apatite in the anorthosite occurs as (a) euhedral grains included in the marginal parts of cumulus plagioclase laths, and (b) xenomorphic grains associated with intercumulus minerals. The composition of apatite evolves along a narrow trend from fluorapatite to hydroxylapatite. The F content of apatite reaches 2.21 wt.%; the maximum Sr and rare earth element (REE) concentrations are 257 and 5623 ppm, respectively, while the average ratio of La/YbN = 11.78, Sr/Sr* = 0.01, and Eu/Eu* = 0.06. Compared to classic PGE reefs in layered intrusions, such as Bushveld in South Africa and Stillwater in the United States, the mineralized anorthosite is distinguished by apatite with an unusually low chlorine concentration of only 0.46 wt.%. A suggested reason for this difference is the percolating nature of sulfide liquid, which has not been enriched in PGE in situ. [ABSTRACT FROM AUTHOR]

The first study on the distribution pattern and features of the "invisible" gold concentration in pyrite and arsenopyrite was carried out for a typical gold–quartz deposit of the Kolyma region. It was established that the main concentrator of "invisible" gold on the Pavlik deposit is the Late Arsenian pyrite-2. The method of Laser Ablation-Inductivity Coupled Plasma-Mass Spectrometer (LA-ICP-MS) gives an Au content up to 478 g/t; the Electron Microprobe Analysis (EMPA) gives up to 570 g/t by. The As content, determined by LA-ICP-MS is up to 4.1 wt % and up to 3.4 wt % by EMPA. Pyrite-2 overgrows and replaces the early pyrite-1 with a reduced content of As and Au. Microinclusions of the Pb–Zn–Cu–Sb–Ag–Bi–containing phases are concentrated at the boundaries of the pyrite-1 and pyrite-2 blocks. Pyrite-2 is depleted by an order in Cu, Zn, Ag, Sb, Pb, and Bi in comparison with pyrite-1. The max Au/As molar ratio in pyrite-2 is 0.006, which suggests the presence of Au in the form of a solid solution. In another case, pyrite, depleted by trace elements, is cemented with As, Ag, Sb, Au, and Pb-rich marcasite with native gold. In arsenopyrite, there is a homogeneous distribution of gold at low concentrations (up to 3 g/t) in euhedral crystals and a heterogeneous distribution (up to 7 g/t) in deformed fissured grains. [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]

Based on both major and trace element chemistry, the occurrence of the intergranular component in mantle-derived xenoliths from far eastern Russia has been constrained. Whole-rock trace element measurements of one xenolith show apparent negative anomalies in Ce, Th, and high field strength elements on normalized trace element patterns. The trace element pattern of the whole rock differs from those of constituent minerals, indicating that the anomalies in the whole rock are attributable to the presence of an intergranular component. That assumption was confirmed using in situ analysis of trace elements in the intergranular substance and melt inclusion using laser ablation inductively coupled plasma–mass spectrometry. Both the intergranular component and the melt inclusions have identical trace element patterns, which mean that these materials are a cognate metasomatizing agent. The anomalies are regarded as mantle metasomatism related to an aqueous fluid. Hydrous minerals were observed on the wall of the melt inclusions using micro-Raman spectroscopy, indicating that the melt inclusions contained a large amount of water. Thus, this study reveals a trace element composition of a hydrous metasomatizing agent in the mantle. [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]

Abstract: The Precambrian Taratash complex (Middle Urals) is one of the rare windows into the Palaeoproterozoic and earlier history of the eastern margin of the East European Craton. Monazite from intensively deformed rocks within a major amphibolite-facies shear zone in the Taratash complex has been investigated by means of electron-probe microanalysis and laser-ablation SF-ICP-MS. Metamorphic and magmatic cores of monazite from metasedimentary and metagranitoid rocks yield U–Pb ages of 2244±19 and 2230±22Ma (±2σ) and record a previously unknown pre-deformational HT-metamorphic event in the Taratash complex. Subsequent dissolution–reprecipitation of monazite, during shear zone formation under amphibolite-facies conditions, caused patchy zonation and chemical alteration of the recrystallised monazite domains, leading to higher cheralite and huttonite components. This process, which was mediated by a probable (alkali+OH)-bearing metamorphic fluid also caused a total resetting of the U–Pb-system. The patchy domains yield concordant U–Pb-ages between 2052±16 and 2066±22Ma, interpreted as the age of the shear zone. In line with previously published ages of high grade metamorphism and migmatisation, the data may point to a Palaeoproterozoic orogenic event at the eastern margin of the East European Craton. Post-deformational fluid-induced greenschist-facies retrogression caused partial to complete breakdown of monazite to fluorapatite, REE+Y-rich epidote, allanite and Th-orthosilicate.The retrograde assemblages either form coronas around monazite, or occur as dispersed reaction zones, indicating that the REE, Y, and Th were mobile at least on the thin section scale. The greenschist-facies metamorphic fluid was aqueous and rich in Ca. Monazite affected by advanced breakdown responded to the retrogression by incorporating the cheralite or huttonite components during a fluid-induced dissolution–reprecipitation process. This event did not reset the U–Pb-system but caused partial Pb loss reflected by discordant U–Pb-dates. [Copyright &y& Elsevier]

The magnetite ore bodies of the Paleozoic Glubochenskoe iron deposit (315.7 Mt at ~ 30.15% Fe) are located in the northern part of the Valerianovka arc zone ("Turgai belt") within the Transuralian Megazone, Russia. They occur in calcareous-volcaniclastic rocks, exhibit layered textures, and contain primary seafloor hematite ores. The sequence of mineral formation reflects the diagenetic to metamorphic evolution of the iron ores: (i) finely dispersed hematite-1; (ii) tabular hematite-2 crystals; (iii) pseudomorphic magnetite-1 after hematite-2; (iv) zoned magnetite-2 crystals with relict hematite-2 (or magnetite-1); (v) thin oscillatory zoned magnetite-3 crystals; and (vi) magnetite-4 porphyroblasts. A gangue assemblage of Fe-rich and Fe–Mg chlorite, illite, quartz, albite, carbonates, rutile, and apatite with rare monazite, xenotime, and zircon occurs in ore and calcareous-volcaniclastic layers. The gangue clasts (volcanic glass, Ca–Mg and Ti minerals, and altered volcanic rocks) are replaced by hematite and further by magnetite. Low siderite δ13C values from layered magnetite ores (− 8.0 to − 19.5‰ PDB) indicate the presence of primary organic matter in calcareous-volcaniclastic rocks. Siderite δ18O values (6.5 to 17.4‰ SMOW) are evidence of isotopic exchange between minerals and fluids during metamorphism. Negative δ34S values for pyrite (down to − 4.5‰) likely indicate derivation of sulfur from organic matter in clastic sedimentary rocks. LA-ICP-MS analysis of zoned magnetite demonstrates highly variable Si, Al, Mg, Na, K, Ca, Ti, Mn, Rb, Y, Zr, Sr, U, and P contents, related to inclusions of gangue minerals. Elevated homogenous V and Ga contents and low contents of Sc, Co, Ni, Ge, As, Mo, Sn, and W (average < 5 ppm) indicate their incorporation into the structure of magnetite. All element contents (except V and Ga) are significantly higher in the inner zone of magnetite (magnetite-1) compared to the outer zone of magnetite (magnetite-2). The calcareous-volcaniclastic material, which was altered during submarine weathering and leaching, is proposed to be a major source of iron to form oxides. Altogether, the paragenetic sequence, and the mineralogical and geochemical data suggest the Glubochenskoe deposit can be characterized as a volcanic-sedimentary type of banded iron formation. [ABSTRACT FROM AUTHOR]

Black tourmalines from seven granitic pegmatites (Golodnaya, Kazennitsa, Mokrusha, Kopi Mora, Zheltyye Yamy, Buzheninov Bor and Ministerskaya) related to the Murzinka pluton, Central Urals, Russia have been investigated using electron microprobe analysis, LA-ICP-MS, Raman and Mössbauer spectroscopy. Pegmatites are hosted by serpentinites and gneisses and are classified as schorl, oxy-schorl, fluor-schorl, dravite, oxy-dravite, foitite, oxy-foitite and darrellhenryite. The possible compositional evolution of tourmalines from the Ural pegmatites is as follows: Mg-rich dravite through to Fe-rich schorl, foitite and oxy-foitite to Fe- and Mn-rich darrellhenryite. The major substitutions in the tourmalines are: (1) Fe2+ ↔ Mg; (2) Al + WO2– ↔ Fe2+ + WOH–; (3) X-site vacancy + Al ↔ Na + Fe2+; (4) Al + WO2– ↔ Mg + WOH–; (5) X-site vacancy + Al ↔ Na + Mg; and (6) Fe ↔ Mn. Statical processing of the trace- and major-element composition distinguished three tourmaline groups: (1) trace Co, Ni, Pb, and major Ca and Mg; (2) uni-, di- and trivalent traces (Li, Zn, Ga) and di- and trivalent majors (Al, Mn); (3) U, Th, Hf, Ta, Nb, Y, In, and Sn which correspond to tri-, tetra-, and pentavalent high-field-strength elements. Mössbauer data shows the Fe3+/Fe2+ ratios in tourmalines from pegmatites hosted by gneisses (0.05–0.18) and serpentinites (0.28–0.65), indicates different oxidising environments. Raman data are consistent with the composition of the tourmalines. [ABSTRACT FROM AUTHOR]

The Voykar Massif of the Polar Urals in Russia consists of an ultramafic complex (mantle section) in the northwest, followed by a late Cambrian to Silurian mafic complex (intra-oceanic primitive island arc) and early Devonian intrusive rocks of an evolved island arc to the southeast. These complexes represent tectonic nappes thrust over the East European continental margin during the late Palaeozoic Uralian Orogeny. LA-ICP-MS U-Pb dating of zircon grains (n = 42) from an antigorite-serpentinite lens within the mafic complex yielded a Concordia age of 542 ± 2 Ma with an age range of 549–527 Ma. Additionally, few grains contain inherited domains with ages between ~990 and 3277 Ma. Hafnium isotopic data of the main age group show 176Hf/177Hft from 0.28242 to 028249 and εHft ranging from +1.9 to −6.5. The evolved Hf isotope data and the trace-element composition of the zircon grains point to an involvement of a continental crustal component in the parental magma. The zircon grains originate from igneous rocks formed during the Timanian Orogeny that affected the East European margin in the latest Neoproterozoic. During the Timanian or Uralian Orogeny, the magmatic zircons were eroded and shallowly recycled into the serpentinised mantle above the subduction zone. Finally, Uralian thrusting led to juxtaposition and imbrication of the zircon-bearing serpentinite and intra-oceanic volcanic rocks of the mafic complex. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb detrital zircon isotope data from Mesoproterozoic to Lower Cambrian strata of the St Petersburg region are used to characterize the paleogeographic and tectonic evolution of the Baltica continent. We dated fifteen samples and divided them into three groups based on their distribution of detrital zircons. The first group (comprising Lower Mesoproterozoic rocks) is dominated by Early Mesoproterozoic and Late Paleoproterozoic zircons, mostly derived from weathering of proximal source region including rapakivi granites exposed across the neighboring Baltic Shield. The second group includes Upper Ediacaran samples (Redkino and Kotlin Regional Stages), with major zircon populations ranging in age between 1970–1850 and 1600–1550 Ma, respectively, correlating with magmatic and metamorphic events within the Svecofennian Orogeny and rapakivi granite igneous activity in the interior of Fennoscandia. The third group of samples, collected from both the uppermost Ediacaran and lowermost Cambrian deposits (Kotlin, Lontova and Dominopol Regional Stages), contains older Paleo-Mesoproterozoic zircons as well as Late Neoproterozoic-earliest Cambrian zircons, indicating a Timanian source area and exhibiting a age spectra similar to spectra for coeval rocks of the Scandinavian Caledonides. Therefore, we conclude that reworking and transport of continental detritus from the Timanian Orogen began during Late Ediacaran, earlier than previously supposed, with transport of Timanian detritus not only to the marginal part of Baltica (known from the Scandinavian Caledonides), but also to the distal interior of Baltica. [ABSTRACT FROM AUTHOR]

Vendian and Permian–Triassic plagiogranite magmatism is distinguished for the Ust-Belsky and Algansky terranes of West Koryak fold system. The U‒Pb zircon ages from Vendian and Permian–Triassic plagiogranites are 556 ± 3 Ma (SIMS), 538 ± 7 Ma (LA–ICP–MS) and 235 ± 2 Ma (SIMS), respectively. It is revealed that Vendian and Permian–Triassic plagiogranites are mainly low-K and low-Al. Sr‒Nd isotopy and rare earth element patterns make it possible to suggest their formation as partial melting of primarily mantle substrate or fractional crystallization of the basic magma. Vendian plagiogranites formed within active margin in ensimatic island arc simultaneously with deposition of the lower part of the volcano-sedimentary complex of Otrozhninskaya sheet. We suggest that the Permian–Triassic plagiogranites were formed within the limits of the Ust-Belsky segment of the Koni-Taigonos arc during partial melting of melanocratic ophiolite material built up as fragments in the accretionary structure of that arc or by fractional crystallization of basic magmas melted from a similar substrate. [ABSTRACT FROM AUTHOR]

The article focuses on the genetic relationship between sulfide deposits of the Urals and acid volcanism. It states that ores of volcanic eruptions of young island arcs and sulfide deposits of the Ural Mountains are associated with each other. It informs about LA-ICP-MS method which helps in performing the synchronous analysis of a large number of chemical elements with low and ultralow detection limits. It concludes with the brief information of microanalytical method, it's geological settings and results.

The origin and geodynamic settings of the Ust'-Sema Formation and the Barangol Complex are some of the most controversial issues in the Early Paleozoic history of the Altai–Sayan Fold Belt. The Ust'-Sema Formation volcanic rocks are enriched in high-Ca clinopyroxene phenocrysts and were classified as ankaramites and diopside porphyry basalts. In this work, we first present LA-ICP-MS analyses of the clinopyroxenes, along with studies of the petrography, mineral composition, and whole-rock chemistry of the Ust'-Sema Formation and related Barangol Complex rocks. An LA-ICP-MS clinopyroxene study showed a slight depletion of light rare-earth elements (La/Yb)N = 0.1–1.0 (on average 0.4); and strong depletion of the high-field-strength elements (Zr, Hf, and Nb) and large-ion lithophile (Rb) elements. An Sr anomaly showed a positive correlation with Mg#. Major- and trace-element composition of the clinopyroxene cores show that these clinopyroxene grains were not captured from the mantle rocks as previously assumed and that the Ust'-Sema Formation and the Barangol Complex rocks were formed from magma with island arc characteristics. The increased titanium and light rare-earth element contents in the phenocryst rims from Biyka volcano suggest an active interaction of the ankaramitic magma with rocks or melts of OIB type. [ABSTRACT FROM AUTHOR]

Data indicating the important role of microorganisms in the formation of nodular monazite (NM) (kularite) of the Kular Range, Republic of Sakha (Yakutia), are presented. The NM contains microorganisms (cyanobacteria) replaced by REE-bearing phosphate (monazite) in the form of stromatolitic microedifices, as well as framboidal Fe sulfides in monazite. The Corg isotopic composition of kularite corresponds to biogenic carbon: the δ13С values vary from –22.2 to –22.3‰. [ABSTRACT FROM AUTHOR]

Gold occurrence Maljavr is the first Archean conglomerate-hosted gold mineralization found in the Fennoscandian Shield. Gold-mineralized metasomatic rocks form a set of lenses within a 10 m thick linear zone, conformable to the bedding of host conglomerates. The lenses are up to 10 m long and up to 1 m thick and they clearly exhibit three alteration envelopes: the rock in the central part consists of garnet and quartz or garnet-only; biotite, garnet, and quartz make the intermediate biotite–garnet envelope; hornblende, hedenbergite, and quartz are the principal rock-forming minerals in the outer zone of the lenses. All metasomatic rocks contain sulfide mineralization up to 15–20 vol.% and up to 0.6 g/t Au. The main ore mineral is pyrrhotite, and the minor minerals are arsenopyrite, chalcopyrite, pentlandite, löllingite, and troilite. The age of zircon from biotite gneiss in the zone of alteration is 2664 ± 18 Ma, this is considered as the time of formation of lenses of metasomatic rocks. Biotite gneiss-conglomerate and metasomatic rocks were later intruded by tourmaline granite pegmatite 2508 ± 7 Ma. The injection of pegmatite caused re-crystallization of sulfides (mainly arsenopyrite and löllingite) and redistribution of gold. Visible gold in association with Bi minerals native bismuth, ehrigite, maldonite, bismuthinite, joseite-B, and hedleyite was found in inclusions in recrystallized arsenopyrite and löllingite. Au content in the rocks with recrystallized arsenopyrite and löllingite is >1 g/t, up to 30 g/t in hand samples. The 2508 Ma pegmatite is interpreted as synchronous with formation of gold mineralization in its present form. The linkage of gold mineralization with pegmatite and geochemical association Au-As-Se-Te-Bi in the mineralized rocks agree with characteristics of intrusion-related gold deposits worldwide. Biotite gneiss–metaconglomerate, hosting the mineralized altered rocks, was the probable primary source of arsenic and gold for mineralization. [ABSTRACT FROM AUTHOR]

The peculiarities of the distribution and binding forms of platinum group elements (Pt, Pd, Ru, Rh, Os and Ir) in the arsenopyrites and pyrites of the Natalkinskoe gold ore deposit (Northeastern Russia) were examined using atomic absorption spectrometry with analytical data selections for single crystals (AAS-ADSSC), a "phase" chemical analysis (PCA) based on AAS of different size-fractions of minerals, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The arsenopyrites and pyrites of the Natalkinskoe gold deposit were found to concentrate not only Au but also platinum group elements (PGEs) such as Pt, Pd, Ru and Rh. The PCA showed that the highest contents (in ppm) were found in the monofractions of arsenopyrite—Pt up to 128, Pd up to 20, Ru up to 86 and Rh up to 21—and comparably lower in monofractions of pyrite—Pt to 29, Pd to 15, Ru to 58 and Rh to 5.9. The AAS-ADSSC method revealed two forms of uniformly distributed Pt, Pd and Ru corresponding to the chemically bound element in the structure of the mineral and in the superficial non-autonomous phase (NAP). The superficially bound form dominates over the structural form and presumably exists in a very thin surface layer of the crystal (~100–500 nm). The maximum contents of these PGE, chemically bound in the structure of arsenopyrite, reached values of (in ppm) 48, 5.9 and 48; and in pyrite structure, 68, 5.2 and 34 for Pt, Pd and Ru respectively. The contents of Pt, Pd and Ru related to NAP on the surface of the crystal were significantly higher and amounted (in ppm) for arsenopyrite to 714, 114 and 1083; and for pyrite 890, 62 and 690 for Pt, Pd and Ru, respectively. Preliminary results for the Rh form in arsenopyrite crystals suggest that the surface-related form (154–678 ppm) is more abundant than the structural form (17–45 ppm). Data from studying the surfaces of sulphide minerals by SEM-EDX and LA-ICP-MS confirmed the presence of Pt, Pd, Ru and Rh on the surface of arsenopyrite and pyrite crystals. These methods generated primary data on the content of Os and Ir in arsenopyrite and pyrite in the surface layer. The maximum content of Os and Ir found in arsenopyrites was up to 0.7 wt%. PGE-enriched fluids (up to ~3 ppm Pt) may exist in the gold ore deposit. It is assumed that there is a common mechanism of impurities uptake associated with the active role of the crystal surface and surface defects for gold-bearing arsenopyrites and pyrites. The surface enrichment is due to peculiarities in the crystal growth mechanism through the medium of NAP and the dualism of the element distribution coefficient in the system of mineral–hydrothermal solution, which is higher for NAP, compared to the volume of the crystal. Although mineral forms of Pt, Pd, Ru, Rh, Os and Ir have not been found at the Natalkinskoe gold deposit, their existence in the form of nano-scale particles is not excluded. This follows from the evolutionary model of surficial NAPs, assuming their partial transformation and aggregation with the formation of nano- and micro-sized autonomous phases of trace elements. The presence of PGE in the ores and the possibility of their extraction significantly increase the quality and value of the extracted raw gold materials at the Natalkinskoe deposit, and adds to the list of known platiniferous ore formations. [ABSTRACT FROM AUTHOR]

This study is aimed at substantiating the prospects of the Pitkäranta Mining District for indium, assessing its resources and elucidating the mineralogical and geochemical features of the distribution of indium in ores. The skarn deposits genetically related to the Salmi anorthosite-rapakivi granite batholith of Early Riphean age were studied. The deposits were divided into two groups, depending on the degree of the greisen alteration of skarns: 1) Sn-Zn-Cu-Fe deposits (the Old Ore Field, Kitelä, Hopunlampi, Heposelkä and Kulismajoki) with little or no greisenization and 2) Be-Sn-Zn deposits with fluorite and magnetite (the New Ore Field, Lupikko, Uksa and Ristiniemi) with well-defined greisenization. Deposits of group 1 are located in the external zone of the Salmi Batholith with a steeply plunging roof (Kitelä), and deposits of group 2 commonly lie above Li F granite domes unexposed by erosion, and are spatially associated with the dykes of these granites and stockscheiders. The distribution of In and associated elements in skarn ores and major ore minerals (sphalerite, chalcopyrite, magnetite and cassiterite) were studied by ICP MS, LA ICP MS and electron probe microanalysis. A total of over 200 samples were analyzed. The results obtained show that In is closely associated geochemically with Zn and Cd, less closely with Cu, Bi and Te is not associated practically with Mo, W, As, Sn and Ag. The content of In in ores from various mines varies from <1 ppm to 0.33 %, and the average In content is 66 ppm. These variations are mainly due to different sphalerite contents in ores and the degree of manifestation of propylitic and greisen alteration of ore-bearing skarns. The main indium-bearing mineral is sphalerite (average In content is 1927 ppm). Other high-In minerals (stannoidite and mawsonite) are uncommon (<0.01 %) and, therefore, do not markedly affect the In balance in ore. The same applies with rare exception to roquesite, the only indium's mineral known here. In-richest (up to 1.5 %) sphalerites with 3–6 % Fe, up to 300–400 ppm Mn and 0.1–0.2 % Co were identified in ore mineral associations of propylitized skarns, which contain no or small amounts of chalcopyrite. Sphalerite-chalcopyrite association is characteristic of roquesite. It occurs mainly in low-tin aposkarn greisens with abundant arsenopyrite-löllingite-sphalerite mineralization. The formation of roquesite seems to have been supported by indium, which was released upon the decomposition of its solid solutions in chalcopyrite and sphalerite and upon the hydrothermal-temperature effect of the late intrusion phases of the Salmi Batholith, Li F granites, on ores. The indium distribution pattern in sphalerite, which is also rich Cd, Ag and Au, shows that roquesite-free propylitized skarns with Sn-Zn-Fe mineralization have the greatest potential for indium and these metals in the zones where the roof of the Salmi Batholith plunges steeply (40–50°) and Li F granites do not occur (Kitelä, Kulismajoki and Hopunlampi deposits). Predicted indium resources in the sphalerite ores of the Pitkäranta Mining District are estimated at 1585–2536 t (as shown by various calculations), cadmium resources at 18424 t, silver resources at 226 t and gold resources at 2 t. • LA-ICP-MS was used to determine In and trace elements in sphalerite from skarns. • The main indium-carrier mineral in skarns of Pitkäranta Mining District is sphalerite. • Roquesite does not contribute substantially to In balance in the ores. • Great exploration potential for In resources is suggested in Pitkäranta Mining District. [ABSTRACT FROM AUTHOR]

The Kodaro–Udokan region is a huge Cu metallogenic province in Southern Siberia, one of the largest on Earth. It contains world-class copper sandstone-hosted Udokan (Cu reserves of 26.7 Mt) and PGE-Ni-Cu Chineysky deposits related to gabbro–anorthosite pluton (Cu—10 Mt; Fe-Ti-V, 30 Gt of ore). Furthermore, there are many small deposits of sulfide ores in sedimentary and igneous rocks in this region as well. For many decades, their genesis has been hotly debated. We studied the mineral composition and the sulfur isotopes in several deposits located at different levels of the stratigraphic sequence and in gabbro intruded in sandstones of the Udokan complex. The differences in ore compositions were found. The Burpala and Skvoznoy deposits consisting of the chalcocite–bornite association are characterized only by negative δ34S. The δ34S values for the Udokan deposits are mostly <0 (up to −28‰). The positive δ34S data characterize the ores of the Chineysky and Luktursky intrusions. Two Cu sandstone-hosted deposits are characterized by complex ore composition, i.e., the Krasny deposit, comprising chalcopyrite–pyrrhotite ores, is enriched in Co, Ni, Bi, Sb, Mo, Pb, Zn, Se, Te, and U and has a wide range of δ34S = −8.1–+13.5‰, and the Pravoingamakitsky deposit (Basaltovy section), consisting of quartz–chalcopyrite veins, has high PGE contents in ores with δ34S = +2.9–+4.0‰. These deposits are located near the gabbro massifs, and it is supposed that their ore compositions were influenced by magmatic fluids. The general regularities of the localization of the deposits in rift zones, and the proximity of mineral and isotopic composition allow us to conclude that the main source of copper could be rocks of basic composition because only they contain high Cu contents. Fluids from deep zones could penetrate to the surface and form Cu sandstone-hosted deposits. [ABSTRACT FROM AUTHOR]

New data on the isotopic age of zircons from metamorphic and igneous rocks are given for the Berezitovoe and Kirovskoe deposits located in the eastern margin of the Selenga-Stanovoi orogenic belt. The zircons were studied with the LA-ICP-MS method in the State Key Laboratory of Continental Dynamics, Northwestern University, Sian, Shansi province, People's Republic of China. The results allowed us to reveal three age epochs in formation of the eastern part of the Selenga-Stanovoi orogenic belt (1.87 Ga; 380-330 Ma; 138-125 Ma), which have significant importance for understanding of the geological structure of the south-eastern framework of the North Asian craton. [ABSTRACT FROM AUTHOR]

The article discusses the composition of studied ore-forming solutions and the P-T conditions of molybdenum mineralization in the Pervomaisky stockwork deposit which is situated within the Dzhidinsky ore field (South-Western Transbaikalia, Russia). New geochronological data of zircons from granites, muscovite, and molybdenite from the ore zones indicates the association of the granite formation and ore deposition processes which occurred 119–128 million years ago. Quartz-molybdenite veins of the Pervomaisky deposit were formed at the temperature of ≥314–186 °C with some boiling periods. Fluid inclusions in these veins have total salt concentration of 6.3–12.7 wt. % NaCl equivalent (eq. NaCl). The salt solution is composed of chlorides of Na, Ca, K, and Fe. The gas phase contains CO2, CH4, and N2. A series of elements were determined in fluid inclusions by laser ablation (LA)-ICP-MS: Li, Be, B, F, Na, Mg, Al, Cl, K, Ca, Mn, Fe, Cu, Zn, Nb, Mo, Ag, Sn, La, Ce, Ta, W, Au, Pb, Th, U. The Mo content reaches 559 ppm (average of 228 ± 190 ppm) in high-grade quartz-molybdenite veinlets, whereas Mo content is up to 212 ppm (average of 25 ± 29 ppm) in the low-grade veinlets. High-grade veinlets were formed by near-neutral solutions with a higher content of Mo, S, and F, while relatively low-grade veinlets were deposited from alkaline solutions. Our results demonstrate the pH of the solutions as one of the key factors for ore deposition. [ABSTRACT FROM AUTHOR]

Kyshtymites are the unique corundum-blue sapphire-bearing variety of anorthosites of debatable geological origin found in the Ilmenogorsky-Vishnevogorsky complex (IVC) in the South Urals, Russia. Their mineral association includes corundum-sapphire, plagioclase (An61–93), muscovite, clinochlore, and clinozoisite. Zircon, churchite-(Y), monazite-(Ce), and apatite group minerals are found as accessory phases. Besides, churchite-(Y) and zircon are also identified as syngenetic solid inclusions within the sapphires. In situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb zircon geochronology showed the ages at about 290–330 Ma linked to the Hercynian orogeny in IVC. These ages are close to those of the syenitic and carbonatitic magmas of the IVC, pointing to their syngenetic origin, which is in agreement with the trace element geochemistry of the zircons demonstrating clear magmatic signature. However, the trace element composition of sapphires shows mostly metamorphic signature with metasomatic overprints in contrast to the geochemistry of zircons. The reason for this discrepancy can be the fact that the discrimination diagrams for sapphires are not as universal as assumed. Hence, they cannot provide an unambiguous determination of sapphire origin. If it is true and zircons can be used as traces of anorthosite genesis, then it can be suggested that kyshtymites are formed in a magmatic process at 440–420 Ma ago, most probably as plagioclase cumulates in a magma chamber. This cumulate rock was affected by a second magmatic event at 290–330 Ma as recorded in zircon and sapphire zoning. On the other hand, Ti-in-zircon thermometer indicates that processes operated at relatively lower temperature (<900 °C), which is not enough to re-melt the anorthosites. Hence, zircons in kyshtymites can be magmatic but inherited from another rock, which was re-worked during metamorphism. The most probable candidate for the anorthosite protolith is carbonatites assuming that metamorphic fluids could likely leave Al- and Si-rich residue, but removed Ca and CO2. Further, Si is consumed by the silicification of ultramafic host rocks. However, kyshtymites do not show clear evidence of pronounced metasomatic zonation and evidence for large volume changes due to metamorphic alteration of carbonatites. Thus, the obtained data still do not allow for univocal reconstruction of the kyshtymite origin and further investigations are required. [ABSTRACT FROM AUTHOR]

Abstract The Bureya Massif is located in the eastern segment of the Central Asian Orogenic Belt (CAOB) and its tectonic affinity and Precambrian evolution is highly controversial. Here we present mineralogical, whole-rock geochemical (major and trace elements and Sm–Nd isotopes) and zircon Hf isotopic data, together with zircon geochronological and mica 40Ar/39Ar dating of the biotite and amphibole gneisses from the Tulovchikha metamorphic complex (previously considered as Archean or Paleoproterozoic basement) in the Bureya Massif, in order to investigate their protolith, metamorphic and deformation ages, petrogenesis, and tectonic implications. LA-ICP-MS U–Pb dating of magmatic zircons from the biotite gneiss, the amphibole–biotite gneiss, and the amphibolite yields single zircon age populations cluster at ~950 Ma, ~920 Ma and ~940 Ma, respectively. The narrow zircon age ranges, together with the morphological features of the zircon crystals and the geochemical data, indicate that the studied metamorphic rocks have a magmatic origin and their protoliths were formed in the early Neoproterozoic (i.e., 950–920 Ma). The consistent formation ages further suggest that the Neoproterozoic gabbro–granitic rocks within the Nyatygran Complex in the Bureya Massif probably represent the protolith of the studied metamorphic rocks. The biotite and amphibole-biotite gneisses of the Tulovchikha metamorphic complex yield whole-rock Nd model ages (t Nd(DM)) of 2.4–1.5 Ga and Hf zircon crustal model ages (t Hf(C)) of 1.7–1.2 Ga, indicating that the precursors of the Tulovchikha Complex gneisses formed from the reworking of Meso–Paleoproterozoic rocks or mixed Neoproterozoic juvenile and Meso–Paleoproterozoic crustal sources. Considering that the Bureya and Jiamusi massifs experienced similar Neoproterozoic magmatic events, we suggest that these massifs form a contiguous crustal unit and share a common geological history. The rocks of Tulovchikha metamorphic complex in the studied area experienced epidote-amphibolite to amphibolite facies metamorphism probably in the early Paleozoic, as evidenced by the 471 ± 19 Ma age of a metamorphic zircon with a low Th/U ratio (<0.1). According to 40Ar/39Ar biotite dating of the biotite gneiss, the Tulovchikha Complex experienced a youngest thermal event at 227 ± 3 Ma. This event may be related to the final closure of the Paleo-Asian Ocean, or may have been caused by the deformation of the blocks of East Asia in connection with the initial stages of the closure of the Mongol–Okhotsk Ocean. Graphical abstract Unlabelled Image Highlights • The first geochronological data for the basement rocks of the Bureya Massif have been obtained. • The protoliths of the Tulovchikha metamorphic Complex are the Neoproterozoic magmatic rocks. • The youngest termal event affecting the Tulovchikha Complex occurred at 227 ± 3 Ma. • Bureya and Jiamusi massifs probably have a common geological history. [ABSTRACT FROM AUTHOR]

The results of application of the LA-ICP-MS method for analysis of U-Pb ages of detrital zircons from Serebryanka Group (Middle Urals) has been presented for the first time. It has been found that the detrital zircon population in tillite-like conglomerates of the Tany Formation is represented nearly in equal shares by grains with Neoarchean and Paleoproterozoic U-Pb ages. This allows the basement crystalline rocks from the eastern part of the East European Craton to be considered as the principal source of aluminosilicate clastic material in the beginning of the Serebryanka. The population of detrival zircons in sandstones from the Kernos Formation consists of Meso- and Neoarchean (approximately 15%), Paleoproterozoic (∼60%), and Mesoproterozoic (∼26%) zircon grains. Comparison of the obtained data with the materials on detrital zircons from Tonian and Ediacarian sandstones in the southern Urals has shown that the principal role in formation of Tonian and Ediacaran sedimentary sequences was played by the products of Mid- and Late Paleoproterozoic crystalline rock erosion in the craton socle. In addition to this, accumulation of the Serebryanka Group took place with visible participation of more ancient-Early Paleoproterozoic, Neo- and Mesoarchean-rock associations on the paleo-water catchment areas. The end of the Serebryanka period differed from its beginning by the additional appearance of Mesoproterozoic complexes in alimentation zones; for comparison, the role played by these complexes in formation of Ectasian-Ediacarian deposits of the adjacent southern Urals segment is insufficient, judging by the currently available data. All these facts may indicate that there are significant differences in the spatiotemporal distribution of clastic material sources for Upper Precambrian deposits in the West Megazone of the southern and middle Urals. [ABSTRACT FROM AUTHOR]

The results of complex study of silicate globules and α-quartz paramorphs after coesite in kyanite from grospydites from the Zagadochnaya kimberlite pipe, Yakutia, using optical and scanning electron spectroscopy, electron and ion microprobes, LA ICP MS and Raman spectroscopy, are presented. The existence of radial fractures diverging from silicate globules into the matrix (kyanite) attests to the fact that the content of the globules is extremely condensed. A zonal structure is usually typical for globules: a coat and a core, which can be explicitly distinguished under the electron microscope, can be differentiated in them. Compositionally, the coat of the globule corresponds to potassium feldspar (wt %: 66.4 SiO; 16.9 AlO; 0.4 FeO; 0.1 CaO; 0.2 NaO; 14.7 KO). The globules were also detected in which along with K, a high content of Na and Ca was also ascertained in the silicate coat. The globule coat is considerably enriched with Ba, La, Ce, Nb, and a number of other noncompatible elements as compared with xenolith minerals. The water content in globules is ∼0.6 wt %. As compared with the host mineral (kyanite), the core part of the globules is also enriched with Co, Ni, Zn, and Cu; their content in kyanite is negligibly low. The entire data collection attests to the fact that the formation of silicate globules could have been caused by interaction of the conservated fluid and/or water-silicate melt with the host mineral and crystalline inclusions of clinopyroxene and garnet with decreasing pressure during the transportation of grospydite xenoliths by the kimberlite melt to the Earth's surface. [ABSTRACT FROM AUTHOR]

The two world’s largest complexes of highly alkaline nepheline syenites and related rare metal loparite and eudialyte deposits, the Khibina and Lovozero massifs, occur in the central part of the Kola Peninsula. We measured for the first time in situ the trace element concentrations and the Sr, Nd and Hf isotope ratios by LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometer) in loparite, eudialyte an in some other pegmatitic minerals. The results are in aggreement with the whole rock Sr and Nd isotope which suggests the formation of these superlarge rare metal deposits in a magmatic closed system. The initial Hf, Sr, Nd isotope ratios are similar to the isotopic signatures of OIB indicating depleted mantle as a source. This leads to the suggestion that the origin of these gigantic alkaline intrusions is connected to a deep seated mantle source—possibly to a lower mantle plume. The required combination of a depleted mantle and high rare metal enrichment in the source can be explained by the input of incompatible elements by metasomatising melts/fluids into the zones of alkaline magma generation shortly before the partial melting event (to avoid ingrowth of radiogenic isotopes). The minerals belovite and pyrochlore from the pegmatites are abnormally high in 87Sr /86Sr ratios. This may be explained by closed system isotope evolution as a result of a significant increase in Rb/Sr during the evolution of the peralkaline magma. [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]

The evidences of partial melting of minerals and the possible involvement of polymetallic melts in the accumulation and redistribution of gold and other metals are shown for the large Svetlinsk gold deposit (Southern Urals). The finding of Bi and Sb minerals including new Au minerals for the deposit (pampaloite, montbrayite, and aurostibite), specific mineral intergrowths (polymineral Sb–Bi–Pb–Te–Ag–Au drop-like inclusions), enrichment of early sulfides in Low-Melting-Point Chalcophile Elements (LMCE), high formation temperatures of ore assemblages (up to 400°C), as well as metamorphism of amphibolite facies of the deposit indicate the possibility of formation of such melts. The polymetallic melts at the deposit could be formed both by partial melting of early sulfides and directly from hydrothermal fluids. The melting features also include calaverite–native gold symplectites in the marginal parts of a large montbrayite grain. [ABSTRACT FROM AUTHOR]

This work has been carried out to assess the rare-earth potential of the main ore minerals of the Lovozero and Khibiny deposits. The loparite and eudialyte deposits are associated with the giant Lovozero intrusion (Eastern Fennoscandia, Kola Peninsula). There are several deposits of apatite–nepheline ores in the Khibiny complex. All these ores take the leading position in the structure of the raw material base of Russia. The highest contents of the sum of rare earth metals (REMs) are typical of loparite ores (the content of ΣREE in loparites is about 28 wt %), light rare earths sharply dominate over heavy ones (the Ce/Yb ratio is about 78000). The sum of REEs in eudialytes is about 2 wt %. A remarkable feature of eudialyte ores is the high concentration of the heavy REM group (the Ce/Yb ratio is about 14). The apatites of the Khibiny deposits occupy an intermediate position: the Ce/Yb ratio is 680, and the average concentration of the REE sum is 0.9 wt %. The conditions of formation of apatite, loparite, and eudialyte ores are considered. [ABSTRACT FROM AUTHOR]

Speleothems are unique archives of information on climate, geomagnetism, and environmental conditions of the past, and have been successfully used for paleoclimatic and paleomagnetic studies in the last two decades. The uniqueness of these geological objects lies in the peculiarities of their formation and preservation of a wide range of geochemical, geological and geophysical proxies, and, most importantly, in the ability to obtain time series of the corresponding characteristics in an unprecedentedly accurate resolution using isotope-geochronological dating methods and incremental chronology. This paper presents the first results of dating the Vor speleothem from the Vorontsovskaya Cave (Krasnodar region), which preserved a record of the geomagnetic excursion, obtained by 230Th/U α-spectrometry, 14C dating, and incremental chronology. Such studies have been carried out in Russia for the first time. Despite the limitations of using the methods of isotope geochronology, it was possible to obtain an upper limit on the age of the excursion, which probably occurred no earlier than 5500–6000 years ago. By the method of incremental chronology, the duration of the main phase of the excursion Vor – 871 ± 16 years – was determined with great accuracy. [ABSTRACT FROM AUTHOR]

Pyrrhotite (or Cu-poor) massive ores of the Skalisty mine located in Siberia, Russia, are unique in terms of their geochemical features. These ores are Ni-rich with Ni/Cu ratios in the range 1.3–1.9 and contain up to 12.25 ppm Ir + Rh + Ru in bulk composition, one of the highest IPGE contents for the Norilsk–Talnakh ore camp. The reasons behind such significant IPGE Contents cannot simply be explained by the influence of discrete platinum-group minerals on the final bulk composition of IPGE because only inclusions of Pd minerals such as menshikovite, majakite, and mertieite II in Pd-maucherite were observed. According to LA-ICP-MS data obtained, base metal sulfides such as pyrrhotite, pentlandite, and pyrite contain IPGE as the trace elements. The most significant IPGE concentrator being Py, which occurs only in the least fractionated ores, and contains Os up to 4.8 ppm, Ir about 6.9 ppm, Ru about 38.3 ppm, Rh about 36 ppm, and Pt about 62.6 ppm. High IPGE contents in the sulfide melt may be due to high degrees of partial melting of the mantle, interaction with several low-grade IPGE impulses of magma, and (or) fractionation of the sulfide melt in the magma chamber. [ABSTRACT FROM AUTHOR]

Abstract We present results of geochronological (40Ar-39Ar, U-Pb SHRIMP-II, and LA-ICP-MS) and geochemical studies of alkaline rocks of the Amalat, Sirikta, Tsipa, Pravyi Uligli, and Verkhnii Uligli massifs in the Vitim plateau (western Transbaikalia). The formation of the alkaline rocks and the accompanying albitization are dated at 261-242 Ma. The isotope inhomogeneity (ɛ Nd (T) = + 8.4 to -1.7) of the alkaline rocks indicates the heterogeneous composition of the source of their material, having a depleted component, an enriched juvenile metasomatic fluid, and a crustal substrate. [ABSTRACT FROM AUTHOR]

Geological, mineralogical, and petrological observations are reported for hornfels-like fine-grained granular mafic rocks in the Early Paleozoic Olkhon collisional orogen (West Baikal area, Russia). The rocks are composed of orthopyroxene, clinopyroxene, amphibole, plagioclase, and ilmenite; some samples also contain olivine, phlogopite, spinel, and titanomagnetite (Opx+Cpx+Amp+Pl+Ilm±Ol±Bt±Spl±Ti-Mag). There are three occurrences of these rocks in the area: a 500 m × 1000 m field in the Shirokaya Valley, another occurrence within the Tazheran Massif (a complex of igneous and metamorphic rocks), and dismembered dikes on the southern margin of the Birkhin gabbro intrusion. The Shirokaya field is located between two 500 Ma intrusions of the Birkhin gabbro; the Tazheran occurrence coexists with syenite, including nepheline syenite, subalkaline gabbro, and marble protrusions; and the dismembered dikes coexist with carbonates and display progressive alteration of dolerite through typical granular varieties. The dikes associated with granite and marble veins mark a part of a large arc-shaped shear zone that traverses the whole intrusive body produced by rotation of a rigid gabbro block during the peak of tectonic deformation at 470–460 Ma. All three occurrences of the hornfels-like rocks lack any evident source of heat that would be responsible for the thermal alteration of the igneous protolith. We hypothesize that the precursor, subvolcanic dolerite, may have undergone autometamorphism maintained by self-generated heat. Mafic magma intruded during high-rate strike–slip faulting, which caused rapid recrystallization of magmatic minerals and produced the observed metamorphic structures. Proceeding from the controversy in the formation mechanisms, with a heat source required for hornfels but lacking from the sampled occurrences of hornfels-like rocks, we suggest identifying the latter as beerbachite, though the term has mostly fallen into disuse. The reason is that the Olkhon rocks we study have a mineralogy, structure, and texture that are perfectly identical to those of beerbachites described in publications from the first half of the 20th century. [ABSTRACT FROM AUTHOR]

Beryl is both an accessory and a rock-forming mineral in pegmatites that contain beryl, making it a major source of Be. Beryl-bearing pegmatites of the Shongui deposit, located in the Kola province of the Northeastern Fennoscandian Shield, hold beryl with a yellowish-greenish color. An investigation into the chemical composition of this beryl from pegmatite dike No. 7 has been performed for the first time via the secondary ion mass spectrometry (SIMS) technique, and the chemical composition of the beryl-bearing pegmatites has been analyzed for the first time by the inductively coupled plasma mass spectrometry (ICP-MS) method. These pegmatites have high concentrations (ppm) of Be (11.8), Li (30.9), Rb (482), Nb (50.3), Ta (14.6), Cs (66.8), and Mn (283) and low concentrations of Sr, Y, Ba, rare earth elements (REE), Zr, and Th. In the Shongui pegmatite field, concentrations of Be, Li, Rb, Cs, Nb, Ta, and Mn increase from barren to beryl-bearing pegmatites, whereas concentrations of Ba, Sr, Y, and REE decline. Rb/Ba, Rb/Sr, and Zr/Hf ratios, showing the fractionation degree, change from the barren to beryl-bearing pegmatites: Rb/Ba and Rb/Sr increase from 111 and 0.46 to 1365 and 8.06, respectively, and Zr/Hf decreases from 18.9 to 14.5. The chemical composition of beryl from the Shongui deposit is unique. This mineral has a concentration of 25,300 ppm of alkalis (Li, Cs, K, Rb, Na) and the average Li, Ce, and Na content is 4430, 5000, and 15,400 ppm, respectively. According to its chemical composition, the Shongui beryl belongs to the Li-Cs-Na type, a type that is not recognized in the available classifications. It is supposed that this beryl was mainly crystallized in the magmatic stage rather than in any hydrothermal and metasomatic stages. Two beryl groups have been distinguished in beryl-bearing pegmatite dike No. 7: beryl from the intermediate zone (Brl-I) and beryl from the core zone (Brl-II). These beryls are concluded to have crystallized in the following order: Brl-I and then Brl-II. Compared with Brl-I, Brl-II is depleted in Cs, Na, Cl, and H2O and is enriched in Fe and Mn. The Fe/Mn ratio varies from 9.18 to 16.50 in these beryls and their yellowish-greenish shades are thought to be driven by a large amount of Fe compared to Mn. [ABSTRACT FROM AUTHOR]

The Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic‒alkaline‒carbonatite complex in Northern Karelia is one of the Earth's oldest alkaline complexes. The major and trace-element compositions of minerals were used to decipher the genetic relations between ultramafic cumulates, alkaline rocks, and carbonatites. Based on detailed analysis of clinopyroxenes from ultramafic cumulates, it was assumed that they were derived from an alkaline melt. It was estimated that ultramafic cumulates and alkaline rocks were formed at close moderate pressure, which in combination with the above facts, is consistent with their cogenetic origin. The REE patterns of clinopyroxenes are characterized by the high LREE/HREE fractionation, with slightly convex-upward LREE patterns (La/Nd < 1), which are typical of deep-seated cumulates formed in an equilibrium with an alkaline basaltic melt. Two types of REE zoning were distinguished in apatite using cathodoluminescence imaging. The first type with an outward LREE decrease was found in apatite from silicate rocks of the complex and was likely produced by the closed-system overgrowth of apatite from a residual melt at the late magmatic stage. In contrast, apatite from carbonatite is characterized by a slight outward LREE increase, which is likely related to the re-equilibration of apatite with fresh batches of REE-enriched carbonatite magma. Precipitation of monazite along fractures and margins of apatite in complex with essential HREE and Y enrichment observed in syenite is indicative of the metasomatic interaction of this rock with fluid. Apatites from alkaline rocks and carbonatites define a common trend in the Y–Ho diagram, with a decrease in the Y/Ho ratio from foidolites to carbonatites. This fact together with the absence of signs of liquid immiscibility, and compositional variations in apatite in silicate rocks and carbonatites, are consistent with their origin through fractional crystallization rather than liquid immiscibility. [ABSTRACT FROM AUTHOR]

The Novy Shemur volcanic-hosted massive sulfide deposit in the North Urals, Russia, is a one of striking examples of erosion of hydrothermal sulfide mounds on the Paleozoic seafloor. The top of the ore body of the deposit hosts the rhythmically layered sulfide ores intercalated with gossanite (Si–Fe-rich) and pelitic hyaloclastic layers on the top of each rhythms. These ores are identified as lithified sulfide turbidite flows and products of their seafloor oxidation. They are characterized by gradational layering, varying size of clastic sulfide material and the presence of load casts in the bottom of the layers, signatures of their collapse and slumping, and reverse folds, discontinuities, pinches and amalgamation of layers corresponding to initial stages of sediment consolidation. The sulfide layers composed of pyrite clasts gradually transit to gossanite layers because of the seafloor oxidation of the top of the sulfide layers. In the gossanite layers, pseudomorphic hematite–quartz particles after sulfide clasts, fragments of chloritized and silicified hyaloclasts and tube fossils are emplaced in a quartz–hematite groundmass. The sulfide–gossanite layers are enriched in authigenic rare-earth element (REE)-bearing minerals (monazite, REE-bearing xenotime and epidote) associated with titanite, apatite and epidote. The REE-phosphates show textural evidence of sedimentary to diagenetic and low-metamorphic evolution of their precursors. The presence of well-preserved REE-phosphate–titanite–apatite mineral assemblage within the fossilized tube worms closely to bacterial structures in the gossanite layers indicates high microbial activity during the accumulation of REEs, which were released from hyaloclasts during alteration of primary sulfide–hyaloclast sediments. These geological, mineralogical and geochemical features suggest that the sulfide–gossanite layers are a result of seafloor mixing of sulfide and hyaloclast components, which further underwent the processes of halmyrolysis, diagenesis and low-grade metamorphism. [ABSTRACT FROM AUTHOR]

At the orogenic gold deposits of the Yana–Kolyma metallogenic belt (northeast Russia) both Au–quartz-sulfide mineralization with native gold and disseminated sulfide mineralization with invisible Au developed. The textural and mineralogical-geochemical features, isotope-geochemical characteristics of gold-bearing sulfides from proximal metasomatites, and possible forms of Au occurrence in pyrite and arsenopyrite have been studied using electron microprobe, atomic absorption, LA-ICP-MS trace element, isotope analysis, and computed microtomography. Four generations of pyrite (Py1, diagenetic; Py2, metamorphic; Py3, metasomatic; Py4, veined) and two generations of arsenopyrite (Apy1, metasomatic; Apy2, veined) have been identified at the Khangalas deposit. In the proximal metasomatites, the most common are Py3 and Apy1. Studying their chemical composition makes it possible to identify the features of the distribution patterns of typochemical trace elements in pyrite and arsenopyrite, and to establish the nature of the relationship between Au and these elements. In Py3 and Apy1, structurally bound (solid solution) Au+ prevails, isomorphically entering the crystal lattice or its defects. Isotope characteristics of hydrothermal sulfides (δ34S = −2.0 to −0.6‰) indicate that mantle/magmatic sulfur was involved in the formation of the deposit, though the participation of sulfur from the host rocks of the Verkhoyansk clastic complex cannot be ruled out. The Khangalas deposit has much in common with other gold deposits of the Yana–Kolyma metallogenic belt, and from this point of view, the results obtained will help to better reveal their gold potential and understand their origin. [ABSTRACT FROM AUTHOR]

The article discuses a study based on composition and Hafnium Isotopes of Zircons from Carbonatites of the Khibiny Mountains, Russia. It mentions that Termofinnigan Neptune mass spectrometer using the method of in situ LA ICP-MS was used to study the trace elements and hafnium isotopes in zircon along with Zircon 91 500 as a standard. It says that the distribution of radioactive elements in investigated zircon were similar to that in zircons from Carbonatites of other regions. It adds that calculations demonstrate that zircon from Carbonatites of the Khibiny massif was crystallized in a very broad temperature range.

Mount Elbrus, Europe's tallest and largely glaciated volcano, is made of silicic lavas and is known for Holocene eruptions, but the size and state of its magma chamber remain poorly constrained. We report high spatial resolution U–Th–Pb zircon ages, co-registered with oxygen and hafnium isotopic values, span ~ 0.6 Ma in each lava, documenting magmatic initiation that forms the current edifice. The best-fit thermochemical modeling constrains magmatic fluxes at 1.2 km3/1000 year by hot (900 °C), initially zircon-undersaturated dacite into a vertically extensive magma body since ~ 0.6 Ma, whereas a volcanic episode with eruptible magma only extends over the past 0.2 Ma, matching the age of oldest lavas. Simulations explain the total magma volume of ~ 180 km3, temporally oscillating δ18O and εHf values, and a wide range of zircon age distributions in each sample. These data provide insights into the current state (~ 200 km3 of melt in a vertically extensive system) and the potential for future activity of Elbrus calling for much-needed seismic imaging. Similar zircon records worldwide require continuous intrusive activity by magmatic accretion of silicic magmas generated at depths, and that zircon ages do not reflect eruption ages but predate them by ~ 103 to 105 years reflecting protracted dissolution–crystallization histories. [ABSTRACT FROM AUTHOR]