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 Geochemistry International   [SJR: 0.399]   [H-I: 18]   [2 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1556-1968 - ISSN (Online) 0016-7029    Published by Springer-Verlag  [2336 journals]
• Deep differentiation of alkali ultramafic magmas: Formation of carbonatite
melts
• Authors: I. D. Ryabchikov; L. N. Kogarko
Pages: 739 - 747
Abstract: The study of melt microinclusions in olivine megacrysts from meimechites and alkali picrites of the Maimecha–Kotui alkali ultramafic and carbonatite province (Polar Siberia) revealed that the melt compositions corrected for loss of olivine due to post-entrapment crystallization of olivine on inclusion walls (differentiates of primary meimechite magma) match well to the composition of nephelinites and olivine melilitites belonging to carbonatite magmatic series. Modeling of fractional crystallization of meimechite magmas results in the high-alkali melt compositions corresponding to the silicate–carbonate liquid immiscibility field. The appearance of volatile-rich melts at the base of magma-generating plume systems at early stages of partial melting can be explained by extraction of incompatible elements including volatiles, by near-solidus melts at low degrees of partial melting, and meimechites are an example of such magmas. Subsequent accumulation of CO2 in the residual melt results in generation of carbonate magma.
PubDate: 2016-09-01
DOI: 10.1134/s001670291609007x
Issue No: Vol. 54, No. 9 (2016)

• Isotopic characteristics of the ermakovskoe
fluorite–bertrandite–phenakite deposit (Western Transbaikalia)
• Authors: G. S. Ripp; I. A. Izbrodin; E. I. Lastochkin; A. G. Doroshkevich; M. O. Rampilov; V. F. Posokhov
Pages: 748 - 764
Abstract: Isotope-geochemical study of the Ermakovskoe fluorine–beryllium deposit was carried out to estimate the ore sources and role of host carbonate rocks in its formation. We analyzed oxygen and carbon isotope compositions in marbles, skarn carbonates, ore and post-ore parageneses; oxygen isotope compositions in oxides, silicates, apatite; and sulfur isotope composition in sulfides and sulfates. Sources of fluids participating in the rock and ore formation were determined using hydrogen and oxygen isotope compositions in hydroxyl-bearing minerals: phlogopite from marbles, vesuvian from skarns, eudidymite and bertrandite from ore parageneses, and bavenite of the post-ore stage. Isotopic studies suggest crustal source of sulfur, oxygen, and carbon dioxide, while oxygen and hydrogen isotope compositions in the hydroxyl-bearing minerals points to the contribution of meteoric waters in the formation of the fluorine-beryllium ores.
PubDate: 2016-09-01
DOI: 10.1134/s0016702916090056
Issue No: Vol. 54, No. 9 (2016)

• Zirconology of miaskites from the Ilmeny Mountains, South Urals
• Authors: A. A. Krasnobaev; P. M. Valizer; S. V. Busharina; E. V. Medvedeva
Pages: 765 - 780
Abstract: It is shown that the replacement and long evolution of miaskitic zircons led to the formation of two main age groups: 420–380 Ma (I) and 260–240 Ma (II). The age of miaskites is estimated at 440–445 Ma. Zircons I bear traces of fragmentation, dissolution, and replacement; they have “flat” REE patterns typical of metasomatic (hydrothermal) types, which is caused by allochthonous nature of the studied miaskites. Zircons II with differentiated REE patterns are similar to magmatic varieties, but have metamorphic origin. Mineralogical–geochemical and age characteristics of zircons in combination with structural–compositional features of miaskites define their metasomatic nature. The origin of the early zircon generations was related to the Ordovician rifting, while late generations were formed during shear deformations at the final stage of the evolution of the Uralian orogen.
PubDate: 2016-09-01
DOI: 10.1134/s0016702916070041
Issue No: Vol. 54, No. 9 (2016)

• Linear growth rate and sectorial growth dynamics of diamond crystals grown
by the temperature-gradient techniques (Fe–Ni–C system)
• Authors: Y. V. Babich; B. N. Feigelson; A. I. Chepurov
Pages: 781 - 787
Abstract: The paper reports data on the linear growth rates of synthetic diamond single crystals grown at high P–T parameters by the temperature-gradient technique in the Fe–Ni–C system. Techniques of stepwise temperature changes and generation of growth microzoning were applied to evaluate the growth rates of various octahedral and cubic growth sectors and variations in these rates with growth time. The maximum linear growth rates of the order of 100–300 µm/h were detected at the initial activation of crystal growth, after which the growth rates nonlinearly decreased throughout the whole growth time to 5–20 µm/h. The fact that the linear growth rates can broadly vary indicates that the inner structure and growth dynamics of single diamond crystals grown by the temperature-gradient technique should be taken into account when applied in mineral–geochemical studies (capture of inclusions, accommodation of admixture components, changes of the defective structure, etc.).
PubDate: 2016-09-01
DOI: 10.1134/s0016702916080036
Issue No: Vol. 54, No. 9 (2016)

• Y–REE-Rich zircons of the Timan region: Geochemistry and economic
significance
• Authors: A. B. Makeyev; S. G. Skublov
Pages: 788 - 794
Abstract: Mineralogical–geochemical studies of zircon from the Ichet’yu occurrence revealed unusually high Y and HREE contents (correlative with the P content) in the inner parts and zones of approximately 10% of the grains. They represent the intermediate members of the zircon–xenotime join with a heterovalent scheme of isomorphism Zr4+ + Si4+ → (Y + HREE)3+ + P5+. Geochronological and mineralogical–geochemical data suggest that the Middle Timan basement (the most probable source of zircon of the Ichet’yu occurrence) is made up of the Paleoproterozoic rocks and possibly represents a continuation beneath the Mezen syneclise and Middle Timan of the Paleoproterozoic collisional structure, to which the Arkhangelsk diamond province is confined.
PubDate: 2016-09-01
DOI: 10.1134/s0016702916080073
Issue No: Vol. 54, No. 9 (2016)

• Hydrogeochemistry at mining districts
• Authors: R. F. Abdrakhmanov; R. M. Akhmetov
Pages: 795 - 806
Abstract: The Southern Urals exemplifies hydrogeochemical environments at mining districts. Information obtained by studying the geochemistry of nonferrous-metal industrial wastes (both mine and dump drainage) is important not only because these wastes are potential sources of base metals but also in the context of geoecological problems. The Southern Urals is one of Russia’s principal producers of Cu and Zn concentrates for metallurgical processing: the region produces 12–15% Cu and 49% Zn concentrates in the country and 35% Cu and 69% Zn concentrates in the Urals. The Yubileinoe, Podol’skoe, Sibai, Uchaly, Novy Uchaly, and Gai deposits are the largest in the Urals. The ores of these deposits contain certain components (Se, Te, Cd, Co, Ga, Ge, In, Be, etc.) that are environmental contaminants. The volume of mine and dump drainage in the Southern Urals amounts to 9 million m3/year, and its mineralization varies from 3.0 to 30–40 g/L, occasionally as high as 365 g/L, with a sulfate, chloride–sulfate calcic–magnesian, magnesian–sodic, and magnesian–calcic composition of the waters. The minor and trace elements of the regional waste waters whose concentrations exceed the regional background values are Cu, Zn (one to four orders of magnitude), As, Cd (one to three orders of magnitude), Li and Be (one to two orders of magnitude). All waste waters transfer various contaminants into environmental subsystems and most actively modify the composition of the groundwaters. At the same time, dump drainage is a potentially important secondary source of valuable mineral components.
PubDate: 2016-09-01
DOI: 10.1134/s0016702916080024
Issue No: Vol. 54, No. 9 (2016)

• Geochemistry of sediments from Lake Grand, Northeast Russia
• Authors: P. S. Minyuk; V. Ya. Borkhodoev
Pages: 807 - 816
Abstract: Major and trace element distribution in the bottom sediments from Hole 13 drilled in Lake Grand, Magadan district, was studied using the method of principal components. It was established that geochemical characteristics are correlated with environmental changes. The sediments of cold MIS2 and MIS4 are characterized by the enriched TiO2, MgO, Al2O3, Fe2O3, and Cr and low Na2O, K2O contents, which is related to the grain-size composition of sediments. Sediments of warm stages show an opposite tendency. High concentration peaks of iron, phosphorus, and manganese correspond to the accumulation levels of vivianite and ferromanganese rocks. Silica is represented by biogenic and abiogenic varieties. Maximum SiO2 contents were found in the Late Holocene sediments and mark the high biological productivity of the basin. Revealed variations of some elements are correlated with the Heinrich events.
PubDate: 2016-09-01
DOI: 10.1134/s0016702916070065
Issue No: Vol. 54, No. 9 (2016)

• Geochemical features of mature hydrocarbon systems and indicators of their
recognition
• Authors: S. A. Punanova; T. L. Vinogradova
Pages: 817 - 823
PubDate: 2016-09-01
DOI: 10.1134/s0016702916080103
Issue No: Vol. 54, No. 9 (2016)

• Calculation of equilibria in CO 2 –water–salt systems using
the Frezchem model
• Authors: M. V. Mironenko; V. B. Polyakov; G. M. Marion
Pages: 824 - 828
PubDate: 2016-09-01
DOI: 10.1134/s0016702916080085
Issue No: Vol. 54, No. 9 (2016)

• Behavior of lanthanides during the formation of the Svetloe deposit,
Chukotka
• Authors: Yu. A. Popova; A. Yu. Bychkov; S. S. Matveeva
Pages: 732 - 738
PubDate: 2016-08-01
DOI: 10.1134/s0016702916060057
Issue No: Vol. 54, No. 8 (2016)

• Diamonds in the products of the 2012–2013 Tolbachik eruption (Kamchatka)
and mechanism of their formation
• Authors: E. M. Galimov; G. A. Karpov; V. S. Sevast’yanov; S. N. Shilobreeva; A. P. Maksimov
Pages: 829 - 833
Abstract: The origin of diamonds in the lava and ash of the recent Tolbachik eruption of 2012–2013 (Kamchatka) is enigmatic. The mineralogy of the host rocks provides no evidence for the existence of the high pressure that is necessary for diamond formation. The analysis of carbon isotope systematics showed a similarity between the diamonds and dispersed carbon from the Tolbachik lava, which could serve as a primary material for diamond synthesis. There are grounds to believe that the formation of Tolbachik diamonds was related to fluid dynamics. Based on the obtained results, it was suggested that Tolbachik microdiamonds were formed as a result of cavitation during the rapid movement of volcanic fluid. The possibility of cavitation-induced diamond formation was previously theoretically substantiated by us and confirmed experimentally. During cavitation, ultrahigh pressure is generated locally (in collapsing bubbles), while the external pressure is not critical for diamond synthesis. The conditions of the occurrence of cavitation are rather common in geologic processes. Therefore, microdiamonds of such an origin may be much more abundant in nature than was supposed previously.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100037
Issue No: Vol. 54, No. 10 (2016)

• Micro- and nano-inclusions in a superdeep diamond from São Luiz,
Brazil
• Authors: Hiroyuki Kagi; Dmitry A. Zedgenizov; Hiroaki Ohfuji; Hidemi Ishibashi
Pages: 834 - 838
Abstract: We report cloudy micro- and nano-inclusions in a superdeep diamond from São-Luiz, Brazil which contains inclusions of ferropericlase (Mg, Fe)O and former bridgmanite (Mg, Fe)SiO3 and ringwoodite (Mg, Fe)2SiO4. Field emission-SEM and TEM observations showed that the cloudy inclusions were composed of euhedral micro-inclusions with grain sizes ranging from tens nanometers to submicrometers. Infrared absorption spectra of the cloudy inclusions showed that water, carbonate, and silicates were not major components of these micro- and nano-inclusions and suggested that the main constituent of the inclusions was infrared-inactive. Some inclusions were suggested to contain material with lower atomic numbers than that of carbon. Mineral phase of nano- and micro-inclusions is unclear at present. Microbeam X-ray fluorescence analysis clarified that the micro-inclusions contained transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) possibly as metallic or sulfide phases. The cloudy inclusions provide an important information on the growth environment of superdeep diamonds in the transition zone or the lower mantle.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100062
Issue No: Vol. 54, No. 10 (2016)

• Fundamentals of the mantle carbonatite concept of diamond genesis
• Authors: Yu. A. Litvin; A. V. Spivak; A. V. Kuzyura
Pages: 839 - 857
Abstract: In the mantle carbonatite concept of diamond genesis, the data of a physicochemical experiment and analytical mineralogy of inclusions in diamond conform well and solutions to the following genetic problems are generalized: (1) we substantiate that upper mantle diamond-forming melts have peridotite/eclogite–carbonatite–carbon compositions, melts of the transition zone have (wadsleyite ↔ ringwoodite)–majorite–stishovite–carbonatite–carbon compositions, and lower mantle melts have periclase/wüstite–bridgmanite–Ca-perovskite–stishovite–carbonatite–carbon compositions; (2) we plot generalized diagrams of diamondforming media illustrating the variable compositions of growth melts of diamonds and paragenetic phases, their genetic relationships with mantle matter, and classification relationships between primary inclusions; (3) we study experimentally equilibrium diagrams of syngenesis of diamonds and primary inclusions characterizing the diamond nucleation and growth conditions and capture of paragenetic and xenogenic minerals; (4) we determine the fractional phase diagrams of syngenesis of diamonds and inclusions illustrating regularities in the ultrabasic–basic evolution and paragenetic transitions in diamond-forming systems of the upper and lower mantle. We obtain evidence for physicochemically similar melt–solution ways of diamond genesis at mantle depths with different mineral compositions.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100086
Issue No: Vol. 54, No. 10 (2016)

• Indicator reactions of K and Na activities in the upper mantle: Natural
mineral assemblages, experimental data, and thermodynamic modeling
• Authors: O. G. Safonov; V. G. Butvina
Pages: 858 - 872
Abstract: The paper presents a review of data on mineral assemblages and reactions that are potential indicators of K and Na activities in upper mantle fluids and melts modifying upper mantle rocks in the course of mantle metasomatism. Results of experimental modeling of these reactions are discussed. These data are utilized to calculate phase reactions in $$\log \left( {{a_{{H_2}O}}} \right) - \log \left( {{a_{{K_2}O}}} \right)and\log \left( {{a_{{H_2}O}}} \right) - \log \left( {{a_{N{a_2}O}}} \right)$$ space by minimizing the Gibbs free energy (constructing pseudosections). The calculations of this type make it possible to estimate variations in K and Na activities in processes modifying upper mantle rocks, to predict successions of mineral assemblages that are formed when these parameters vary, and to compare metasomatic processes in rocks of various composition. The approach is illustrated by examples of peridotite and eclogite xenoliths in kimberlite and alkaline basalt.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100098
Issue No: Vol. 54, No. 10 (2016)

• Spectral and structural properties of carbon nanoparticles synthesized in
natural and anthropogenic processes
• Authors: S. A. Voropaev; V. S. Sevast’yanov; A. Yu. Dnestrovskii; E. A. Ponomareva; N. V. Dushenko; V. M. Shkinev; A. S. Aronin
Pages: 873 - 881
Abstract: In this contribution, we considered the character of carbon nanoparticle formation in the cosmos and during volcanic eruptions of a certain type and compared it with existing methods of synthesis in nanotechnology. Using the methods of electron diffraction and Raman spectroscopy, we investigated nanodiamond samples synthesized by hydrodynamic cavitation in various hydrocarbon liquids. Different forms of nanometer-sized carbon were distinguished, including complex fullerenes, nanodiamonds, and a face-centered cubic (fcc) carbon phase. The synthesized nanodiamonds were doped with silicon, their photoluminescence spectra were analyzed, and application of the results for geochemistry and cosmochemistry were discussed.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100104
Issue No: Vol. 54, No. 10 (2016)

• Relationships between textural and photoluminescence spectral features of
carbonado (natural polycrystalline diamond) and implications for its
origin
• Authors: Hidemi Ishibashi; Hiroyuki Kagi; Shoko Odake; Hiroyuki Ohfuji; Hiroshi Kitawaki
Pages: 882 - 889
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100050
Issue No: Vol. 54, No. 10 (2016)

• The mineralogy of Ca-rich inclusions in sublithospheric diamonds
• Authors: D. A. Zedgenizov; A. L. Ragozin; V. V. Kalinina; H. Kagi
Pages: 890 - 900
Abstract: This paper discusses mineralogy of Ca-rich inclusions in ultra-deep (sublithospheric) diamonds. It was shown that most of the Ca-rich majoritic garnets are of metabasic (eclogitic) affinity. The observed variation in major and trace element composition is consistent with variations in the composition of the protolith and the degree of enrichment or depletion during interaction with melts. Major and trace element compositions of the inclusions of Ca minerals in ultra-deep diamonds indicate that they crystallized from Ca-carbonatite melts that were derived from partial melting of eclogite bodies in deeply subducted oceanic crust in the transition zone or even the lower mantle. The occurrence of merwinite or CAS inclusions in ultra-deep diamonds can serve as mineralogical indicators of the interaction of metaperidotitic and metabasic mantle lithologies with alkaline carbonatite melts. The discovery of the inclusions of carbonates in association with ultra-deep Ca minerals can not only provide additional support for their role in the diamond formation process but also help to define additional mantle reservoirs involved in global carbon cycle.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100116
Issue No: Vol. 54, No. 10 (2016)

• Mineralogical and geochemical patterns of mantle xenoliths from the Jixia
region (Fujian Province, southeastern China)
• Authors: G. S. Zhang; A. V. Bobrov; J. S. Long; W. H. Han
Pages: 901 - 913
Abstract: The paper discusses the results of mineralogical and petrographic studies of spinel lherzolite xenoliths and clinopyroxene megacrysts in basalt from the Jixia region related to the central zone of Cenozoic basaltic magmatism of southeastern China. Spinel lherzolite is predominantly composed of olivine (Fo89.6–90.4), orthopyroxene (Mg# = 90.6–92.7), clinopyroxene (Mg# = 90.3–91.9), and chrome spinel (Cr# = 6.59–14.0). According to the geochemical characteristics, basalt of the Jixia region is similar to OIB with asthenospheric material as a source. The following equilibrium temperatures and pressures were obtained for spinel peridotite: 890–1269°C and 10.4–14.8 kbar. Mg# of olivine and Cr# of chrome spinel are close to the values in rocks of the enriched mantle. It is evident from analysis of the textural peculiarities of spinel lherzolite that basaltic melt interacted with mantle rocks at the xenolith capture stage. Based on an analysis of the P–T conditions of the formation of spinel peridotite and clinopyroxene megacrysts, we show that mantle xenoliths were captured in the course of basaltic magma intrusion at a significantly lower depth than the area of partial melting. However, capture of mantle xenoliths was preceded by low-degree partial melting at an earlier stage.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100049
Issue No: Vol. 54, No. 10 (2016)

• Interaction of Fe and Fe 3 C with hydrogen and nitrogen at 6–20 GPa: a
study by in situ X-ray diffraction
• Authors: K. D. Litasov; A. F. Shatskiy; E. Ohtani
Pages: 914 - 921
Abstract: A method of in situ X-ray diffraction at Spring-8 (Japan) was used to analyze simultaneously the hydrogen incorporation into Fe and Fe3C, as well as to measure the relative stability of carbides, nitrides, sulfides, and hydrides of iron at pressures of 6–20 GPa and temperatures up to 1600 K. The following stability sequence of individual iron compounds was established in the studied pressure and temperature interval: FeS > FeN > FeC > FeH > Fe. A change in the unit-cell volume as compared to the known equations of state was used to estimate the hydrogen contents in carbide Fe3C and hydride FeHx. Data on hydride correspond to stoichiometry with x ≈ 1. Unlike iron sulfides and silicides, the solubility of hydrogen in Fe3C seemed to be negligibly low—within measurement error. Extrapolating obtained data to pressures of the Earth’s core indicates that carbon and hydrogen are mutually incpompatible in the iron–nickel core, while nitrogen easily substitutes carbon and may be an important component of the inner core in the light of the recent models assuming the predominance of iron carbide in its composition.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100074
Issue No: Vol. 54, No. 10 (2016)

• Manifestation of nitrogen interstitials in synthetic diamonds obtained
using a temperature gradient technique (Fe–Ni–C system)
• Authors: Yu. V. Babich; B. N. Feigelson; A. I. Chepurov
Pages: 922 - 927
Abstract: The IR-peak 1450 cm–1 (H1a-center) associated with nitrogen interstitials have been studied in nitrogen-bearing diamonds synthesized at high P-T parameters in the Fe–Ni–C system. FTIR study shows that manifestation of this nitrogen form is restricted to the regions of active transformation of C-defects into A-defects, which confirms the connection of its formation with C => A aggregation process. An examination of the dependence of the 1450 cm–1 peak on the degree of nitrogen aggregation indicates that H1a-centers are not only formed during C/A aggregation but also disappear simultaneously with the end of C => A transformation. Established facts suggest direct involving of nitrogen as interstitials in the C => A aggregation and serve as strong experimental argument in support of the “interstitial” mechanism of nitrogen migration during aggregation in diamonds containing transition metals.
PubDate: 2016-10-01
DOI: 10.1134/s0016702916100025
Issue No: Vol. 54, No. 10 (2016)

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