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2017 year, number 8

1.
VOLATILES IN SUPRASUBDUCTION BASALTIC MELTS FROM TOLBACHIK VOLCANO (Kamchatka)

N.L. Dobretsov1,2, V.A. Simonov3,2, A.V. Kotlyarov3, S.I. Stupakov3
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Летучие компоненты, надсубдукционные базальтовые расплавы, высокотемпературная газовая хроматография, влк. Толбачик, Камчатка, Volatiles, suprasubduction basaltic melt, high-temperature gas chromatography, Tolbachik Volcano, Kamchatka

Abstract >>
Vitreous basalts and plagioclase lapilli from Tolbachik Volcano studied by high-temperature gas chromatography reveal features of a fluid regime uncommon to suprasubduction melts. Prominent depletion in volatiles confirms the anomalous behavior of the Tolbachik fluid systems. Vitreous basalts contain minor amounts of water (0.16-0.27 wt.%) and carbon dioxide (95-440 ppm). New data on volatiles in the Tolbachik plagioclase lapilli show very low contents of CO2 and total gas (exclusive of H2O) and enrichment in reduced fluids (CO and CH4) relative to the basalts. In general, analysis of basalts and plagioclase lapilli from different eruptions trace a progressive increase in reduced fluids (CO and CH4) and decrease in CO2 and total gas from past to present events. The concentrations of CO2 decrease, while those of CO and CH4 in basalts and plagioclase lapilli increase systematically with an increase in FeO/MgO ratios and K2O contents in the lavas and in anorthite component in plagioclase.



2.
MINERAL COMPOSITION OF ALKALINE LAMPROPHYRES OF THE TOMTOR MASSIF AS REFLECTION OF THEIR GENESIS

L.I. Panina, E.Yu. Rokosova, A.T. Isakova, A.V. Tolstov
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Щелочные лампрофиры, зональность вкрапленников, низкомагнезиальная натриевая и высокомагнезиальная калиевая магмы, смешение расплавов, Alkaline lamprophyre, zoned phenocryst, lowly magnesian sodic and highly magnesian potassic melts, mixing of magmas

Abstract >>
The influence of parental melts on the chemical composition of rock-forming minerals of alkaline lamprophyres (monchiquites) referred to as the volcanic series of porphyritic potassic alkaline-ultrabasic rocks was studied in the Tomtor alkaline-ultrabasic carbonatite massif (Yakutia) hosting a unique deposit of Sc-REE-Y-Nb ores. Previous fluid-melt inclusion study showed that these rocks formed from two mixing alkaline-basic melts of different alkalinity. A detailed study of the chemical composition of minerals revealed a repeated irregular zoning in most of phenocrysts, which reflects the influence of different parental magmas and their mixing. It was established that the cores of diopside phenocrysts (Di I) with inclusions of Na-Fe-rich silicate melts have a low Mg-number and low contents of Ti, Al, and Ca and high contents of Na and Mn. The intermediate zones of phenocrysts (Di II) containing inclusions of K-Mg-rich silicate melts show a high Mg-number and are rich in Ti and Al and poor in Mn and Na. Groundmass grains and rims (and, sometimes, intermediate zones) of diopside phenocrysts often have a mixed Di I-Di II composition with slightly elevated contents of Mg, Ti, and Al. Amphibole phenocrysts, like the diopside ones, have both zones with low Mg contents and high Na/K ratios and Mn contents and zones with high Mg contents, low Na/K ratios, and low Mn and elevated Ti contents. Phlogopites are also of two varieties: highly magnesian, with high contents of Si and K and low content of Mn, and lowly magnesian, with low contents of Si and K and high content of Mn. Ilmenite, titanomagnetite, and fine grains of femic minerals are mostly of mixed varying composition. The chemical composition of rock-forming minerals, especially zoned phenocrysts, evidences that they crystallized with the participation of two alkaline-basic melts: Na-Fe-rich silicate melt enriched in Mn and K-Mg-rich silicate melt enriched in Ti but depleted in Mn.



3.
AGE AND MINERALOGICAL AND GEOCHEMICAL PARAMETERS OF ROCKS OF THE CHINA ALKALINE MASSIF (western Transbaikalia)

I.A. Izbrodin1, A.G. Doroshkevich1,2, M.O. Rampilov1, G.S. Ripp1, E.I. Lastochkin1, V.B. Khubanov1, V.F. Posokhov1, N.V. Vladykin3
1Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakh'yanovoi 6a, Ulan Ude, 670047, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
Keywords: Щелочные и нефелиновые сиениты, высококалиевые породы, позднепалеозойский магматизм, источники, Западное Забайкалье, Alkali and nepheline syenites, high-K rocks, Late Paleozoic magmatism, sources, western Transbaikalia

Abstract >>
Geochemical and U-Pb geochronological studies have shown that the alkali syenites of the China massif have an age of 311.4 ± 1.8 Ma and potassic specialization in contrast to most massifs of the Vitim alkaline-magmatism zone. The rocks are similar in geochemistry to the nepheline syenites of the Synnyr massif, dated at 289.5 ± 3.5 Ma. The alkali syenites of the China massif formed, most likely, from crustal protoliths.



4.
FOSSIL TRAVERTINES AND QUASI-TRAVERTINE IN THE MINUSA BASIN (West Siberia): STRUCTURE, COMPOSITION, AND COMPARATIVE ANALYSIS

G.S. Fedoseev1,2, A.A. Vorontsov3,4, A.A. Orekhov5
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
4Irkutsk State University, ul. Karla Marksa 1, Irkutsk, 663033, Russia
5Far East Geological Institute, Far East Branch of the Russian Academy of Sciences, pr. 100-letiya Vladivostoka 159, Vladivostok, 690022, Russia
Keywords: Палеотравертин, малоглубинные силлы, долерит, базальт, квазитравертин, спарит, пренит, керит, Минусинский прогиб, Fossil travertine, shallow sill, dolerite, basalt, quasi-travertine, sparite, prehnite, Minusa basin

Abstract >>
We study a carbonate body looking like a classical fossil travertine which was discovered in the Chebak-Balakhta basin within the Minusa Trough Basin (Khakassia, Russia) and called quasi-travertine . It is a thin layer sandwiched between a basalt-dolerite sill and calcareous siltstone. Comprehensive studies of the quasi-travertine and its comparison with Devonian fossil travertines located a few kilometers away in terms of structure and composition have made the basis for its formation model. According to this model, the quasi-travertine has had a two-stage history: deposition and subsequent hydrothermal metasomatism. Laminated limestone coexisting with calcareous siltstone of the Early Devonian Shunet Formation formed during the first stage and then experienced hydrothermal metasomatism with precipitation of secondary calcite, prehnite, and pyrobitumen (kerite).



5.
GEOCHEMISTRY OF PRECAMBRIAN VOLCANOSEDIMENTARY ROCKS OF THE KARSAKPAI GROUP in southern Ulutau (Central Kazakhstan)

N.V. Dmitrieva1,2, E.F. Letnikova1,2, I.A. Vishnevskaya1,2, P.A. Serov3
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Geological Institute, Kola Scientific Center of the Russian Academy of Sciences, ul. Fersmana 14, Apatity, Murmansk Region, 184209, Russia
Keywords: Поздний докембрий, вулканогенно-осадочные породы, осадочные породы железорудной формации, рифтогенные вулканиты, Sm-Nd изотопия, Центральный Казахстан, Late Precambrian, volcanosedimentary rocks, sedimentary rocks of iron formation, rift volcanics, Sm-Nd isotope composition, Central Kazakhstan

Abstract >>
We have analyzed the isotope-geochemical features of volcanosedimentary rocks of the Karsakpai Group in southern Ulutau (Central Kazakhstan): mafic volcanics, siliceous and siliceous-ferruginous sediments, and quartz-sericite-chlorite schists. The close association of ferruginous quartzites with intraplate volcanics indicates that they formed in a tectonically active basin. The Nd isotope composition of ferruginous quartzites was governed by synchronous underwater volcanism, whereas the 143Nd/144Nd value of schists was additionally controlled by the Nd isotope composition of older sources. The Mesoproterozoic Nd model ages and positive εNd(t) values of the metaterrigenous rocks of the Karsakpai Group indicate the presence of Mesoproterozoic juvenile material in the provenance. The minimum Nd model ages suggest the lower boundary of sedimentation of 1.3 Ga.



6.
COCRYSTALLIZATION COEFFICIENTS OF Cr, V, AND Fe IN HYDROTHERMAL ORE SYSTEMS (from experimental data)

V.L. Tauson, N.V. Smagunov, S.V. Lipko
A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
Keywords: Хром, ванадий, железо, марганец, распределение, магнетит, пирит, халькопирит, сфалерит, полифазные ассоциации, коэффициент сокристаллизации, гидротермальные системы, Chromium, vanadium, iron, manganese, distribution, magnetite, pyrite, chalcopyrite, sphalerite, multiphase associations, cocrystallization coefficient, hydrothermal systems

Abstract >>
The cocrystallization coefficients of Cr, V, and Fe ( D Me/Fe) in magnetite and sulfide minerals (pyrite, chalcopyrite, and Fe-containing sphalerite) in multiphase associations are determined in hydrothermal-growth experiments with internal sampling at 450 °C and 100 MPa (1 kbar). The results are compared with previous data on D Mn/Fe. Magnetite and pyrite are characterized by the highest D Me/Fe values for both Cr (1.2 and 2) and V (6.6 and 1.1). These minerals also show the highest mineral/solution distribution coefficients of Cr and V. For V and Cr in chalcopyrite, much lower D Me/Fe values (0.03 and 0.04, respectively) were obtained, which, however, are slightly higher than those for Mn in magnetite (0.01). Although the deposition of magnetite and iron sulfides has no significant effect on the evolution of Mn in solution and Mn-Fe partitioning, crystallization of magnetite and pyrite favors a decrease in Cr and V contents relative to Fe content in solution. The data obtained can be used to reconstruct the chemical composition of paleofluids. Spinel minerals with close contents of Mn, V, and Cr can form through a hydrothermal process provided that the solutions are highly enriched in Mn relative to Fe and have V and Cr contents close to the Fe one. Such solutions seem to be exotic. Usually, a magnetite-forming hydrothermal fluid contains V and Cr as millionths of Fe, while the content of Mn in it can be of the same order of magnitude as the content of Fe. The data obtained may be of interest for reconstructing the evolution of the chemical composition of the World Ocean in different geologic periods. The study has shown that the bulk distribution coefficient of variable-valence elements between mineral and hydrothermal solution varies over a wide range of values even at constant pressure<M>, temperature, and solution composition and can be used only for qualitative estimation of the element compatibility. In contrast, the bulk cocrystallization coefficient of chemically similar elements is less dependent on physicochemical conditions, has a nearly three times lower variation coefficient, and permits an element partitioning analysis in heterogeneous mineral-fluid systems.



7.
NEW DATA ON BETEKHTINITE: REFINEMENT OF CRYSTAL STRUCTURE AND REVISION OF CHEMICAL FORMULA

S.V. Krivovichev1, V.N. Yakovenchuk2
1Department of Crystallography, Institute of Earth Sciences, Saint-Petersburg State University, Universitetskaya nab. 7/9, Saint-Petersburg, 199034, Russia
2Nanomaterials Research Centre, Kola Science Centre, ul. Fersmana 14, Apatity, Murmansk Region, 184200, Russia
Keywords: Бетехтинит, кристаллическая структура, сульфид, медь, Джезказган, Казахстан, Betekhtinite, crystal structure, sulfide, copper, Dzhezkazgan, Kazakhstan

Abstract >>
The crystal structure of betekhtinite from the Dzhezkazgan copper ore deposit, Kazakhstan, has been refined to R 1 = 0.047 for 1321 unique observed reflections. The mineral is orthorhombic, Immm , a = 3.9047 (6), b = 14.796 (2), and c = 22.731 (3) Å, and V = 1313.3 (3) Å3. The structure refinement revealed five additional partially occupied Cu sites compared to the previous structural study. The structure contains one Pb and thirteen Cu sites. The coordination of the Pb site is sevenfold. Coordination geometries of the Cu sites are variable: The Cu1, Cu2, Cu3 Cu6, Cu7, Cu8, and Cu9 sites are tetrahedrally coordinated, whereas Cu4, Cu5, Cu10, Cu11, and Cu13 have a triangular coordination. The Cu12 site is coordinated by two S atoms to form a CuS2 dumbell. The crystal structure of betekhtinite is based upon complex Pb-Cu sulfide rods running parallel to the a axis. The rods have a rhombus-like cross section with lateral dimensions of ca . 11·16 Å2. The core of the rod is composed from the CuS4 tetrahedra and may be considered a module extracted from the archetype structure of fluorite, CaF2. The tetrahedral columns are further incrustated by the Cu4S3 and Cu5S3 triangles and Pb atoms to form the [Pb2Cu16S15] rods, which are linked to each other along the b axis via S6 atoms. The low-occupied Cu sites are located in between the rods. The structural formula determined on the basis of the crystal-structure refinement can be written as Pb2Cu22.18Fe1.04S15, which is in agreement with the chemical analyses of betekhtinite and disagrees notably with the formula Pb2(Cu,Fe)21S15 suggested by Dornberger-Schiff and Höhne. The general crystal chemical formula of betekhtinite can be written as Pb2(Cu,Fe)22-24S15. Information-based structural complexity parameters for betekhtinite are: IG = 3.696 bits/atom and IG,total = 144.131 bits/cell. Decomposition of betekhtinite into a mixture of galena (PbS; IG = 1.000 bits/atom; IG,total = 2.000 bits/cell) and chalcocite (Cu2S; IG = 1.500 bits/atom; IG,total = 12.000 bits/cell) at temperatures above 150 ºC is associated with the loss of structural complexity and the rise of configurational entropy of the system.



8.
PROBLEMS OF SELECTION AND CORRELATION OF STRATOTYPE SECTIONS OF THE NEOCOMIAN IN WEST SIBERIA IN THE CONTEXT OF ITS CLINOFORM STRUCTURE

S.V. Ershov
A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Неоком, стратотип, клиноформа, секвенция, корреляция, индексация пластов, Западная Сибирь, Neocomian, stratotype, clinoform, sequence, correlation, bed indexing, West Siberia

Abstract >>
This paper discusses the problems of selection of stratotype sections and correlation of marker beds in the Neocomian productive complex of West Siberia in the context of its clinoform structure. In this paper we present a conceptual sequence stratigraphic model and a correlation chart for beds from different lithofacies regions of the Berriasian-Lower Aptian deposits of West Siberia.



9.
REFERENCE SECTION OF NEOGENE-QUARTERNARY DEPOSITS IN THE UIMON BASIN (Gorny Altai)

G.G. Rusanov1,2, E.V. Deev3,4, I.D. Zol’nikov5,4,6, L.B. Khazin3, I.V. Khazina3, O.B. Kuz’mina3
1Gorno-Altaisk Expedition JSC, ul. Sovetskaya 15, Maloeniseiskoe Village, Altai Territory, 659370, Russia
2Shukshin Altai State Humanities Pedagogical University, ul. Korolenko 53, Biysk, 659333, Russia
3A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
5V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
6Institute of Archeology and Ethnography, Siberian Branch of the Russian Academy of Sciences, pr. Lavrentieva 17, Novosibirsk, 630090, Russia
Keywords: Неоген, плейстоцен, остракоды, палинология, Уймонская впадина, Горный Алтай, Neogene, Pleistocene, ostracods, palynology, Uimon Basin, Gorny Altai

Abstract >>
An extraordinary-thick (400 m) section of the Neogene-Quaternary deposits is for the first time exposed by well 1 in the central Uimon Basin. The Miocene-Pliocene lacustrine Tueryk Formation is recognized at the base of the continuous section, verified by new paleontological data (ostracods, spores, and pollen). As assumed, overlaying deposits are represented by the Lower Pleistocene lacustrine-alluvial Beken Formation, Middle Pleistocene alluvial-proluvial Bashkaus Formation, undifferentiated Middle Pleistocene glacial, fluvioglacial, and alluvial deposits, and Upper Pleistocene lacustrine-glacial deposits. The data obtained from the core of well 1 undisputably demonstrate that the Uimon Basin had been developed prior the beginning of the Miocene Epoch, when it was characterized by accumulation of the lacustrine Tueryk Formation, incompletely exposed within the studied section. The presence of thick unexposed lower-Ohm interval of sedimentary filling of the basin suggests that the Uimon Basin was developed as early as the Paleogene. Therefore, the tectonic evolution and sedimentation history of the basin are assumed to have features similar to those of the Chuya and Kurai Basins of Gorny Altai.



10.
NATURAL ELECTRIC FIELDS IN SiberiaN gold deposits: structure, ORIGIN, AND RELATIONSHIP with golD OREBODIES

L.Ya. Erofeev, A.N. Orekhov, G.V. Erofeeva
National Tomsk Research Polytechnical University, pr. Lenina 30, Tomsk, 634050, Russia
Keywords: Электроразведка, естественное электрическое поле, золоторудные месторождения, Сибирь, Electrical prospecting, natural electric field, gold deposits, Siberia

Abstract >>
Characteristics of the constant natural electric field in the Siberian gold ore areas. The regularities of spatial variations in the electric-field potential and the parameters and properties of anomalies have been established. The cause of the natural electric field in deposits of major genotypes has been elucidated. It is shown that the electric field is induced mainly by physicochemical processes running in electron-conducting syn-ore metasomatites and by circulation of groundwaters. Orebodies do not influence significantly the structure of the observed electric fields. We give recommendations on application of the electric-field method at various gold ore objects.



11.
Structure and physical properties of natural sphalerites and galena from THE Dal’negorsk DEPOSIT in the temperature range 4-300 K

R.I. Gulyaeva, E.N. Selivanov, G.A. Dorogina, S.A. Uporov, S.V. Pryanichnikov
Institute of Metallurgy, Ural Branch of the Russian Academy of Sciences, ul. Amundsena 101, Yekaterinburg, 620016, Russia
Keywords: Сфалерит, галенит, структура, состав, электрическое сопротивление, магнитные свойства, Sphalerite, galena, structure, composition, electrical resistance, magnetic properties

Abstract >>
The structure and physical properties of natural sphalerites and galena from the Dal’negorsk ore massif were investigated. A nonlinear temperature dependence of the unit-cell parameters of sphalerite in the range 80-300 K was established by X -ray diffraction. The microstructure and elemental composition of sphalerites with different contents of iron were studied. The results show that an increase in iron content in sphalerite solid solution leads to an increase in the unit-cell parameters. We have established that sphalerites are insulators in the temperature range from 4 to 300 K, as their absolute electrical resistivity is greater than 1 MOhm·m. The temperature dependence of sphalerite magnetization has a peak corresponding to the mineral transition from antiferromagnetic to ferrimagnetic state with a Neel temperature of about 90 K in fields of 0, 0.15, and 1.00 T. The magnetic state of natural galena is due to a sphalerite impurity: The extrema in the temperature magnetization curve are typical of sphalerite.