V.S. Shatsky1,2,3, A.L. Ragozin1, I.N. Kupriyanov1, V.V. Kalinina1 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia 3Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: Siberian craton, inclusions in diamond, mantle, subducted crust, moissanite
The article presents new data on multiphase inclusions in two diamonds sampled from placers in the northeastern Siberian craton. Diamond HLS-4 is a round variety V crystal containing a multiphase mineral inclusion with more or less strongly oxidized iron carbides and moissanite in one part and calcite and iron oxides in another part. Another sample, HI-180, is a partly dissolved yellow cuboid that hosts a multiphase inclusion and numerous submicrometer inclusions delineating the crystal zoning. Sample HI-180 is deformed, with cracks and cavities up to 200 µm in size exposed in a polished section. The submicrometer inclusions plot in the field of microinclusions in fibrous diamonds from the world database, mostly near the silicic corner. They must have a hydrous composition, judging by the water-carbonate ratio of H2O/(H2O + CO2) = 0.80-0.82 estimated from FTIR data. The multiphase inclusion consists of quartz, Fe-armalcolite, anatase, and diamond grains in an amorphous matrix, as well as moissanite and calcite detected by SEM-EDS, FTIR and Raman spectroscopy. One diamond grain in the inclusion, in turn, encloses moissanite. The coexistence of calcite and moissanite in multiphase inclusions is evidence that cracks were fully healed up under extreme redox variations, possibly, during diamond growth in a subduction setting.
S.N. Rudnev1, V.M. Savatenkov2,3, I.M. Vasilieva2 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 2Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, St. Petersburg, Russia 3St. Petersburg State University, Institute of Earth Sciences, St. Petersburg, Russia
Keywords: Granitoids, Pb and Nd isotope composition, melt sources, Central Asian Orogenic Belt, Eastern Tuva
We present the results of Nd and Pb isotope studies of late Neoproterozoic-early Paleozoic granitoids of the Kaa-Khem batholith, which formed in different geodynamic settings within the early Caledonian structures of Eastern Tuva (Altai-Sayan sialic area). Based on the obtained isotope data, we assess the role of different source materials in the formation of melts for these granitoids and compare these rocks with coeval granitoids from the Lake Zone of Mongolia. The plagiogranitoid associations of the island arc stage of the Kaa-Khem batholith formation (572-562 Ma) are characterized by mantle Nd isotope values. In contrast, the Pb isotope characteristics of these intrusive associations correspond to an upper-crust source formed predominantly by terrigenous sediments. The granitoid associations of the accretion-collision stage of the Kaa-Khem batholith formation (512-450 Ma) have a less radiogenic primary Pb isotope composition as compared with the island arc granitoids. Evidently, during the magma formation at this stage, the relative role of terrigenous material decreased, while the role of depleted mantle material increased. At the same time, the decrease in ɛNd values in the granitoids as compared with the depleted mantle indicates that, along with the upper-mantle component, the role of the lower-crust component increased. These Nd and Pb isotope characteristics of the accretionary granitoids of the Kaa-Khem batholith indicate a significant contribution of the lower-crust source to their formation. This source is the crystalline basement of the Tuva-Mongolian microcontinent. The Pb isotope characteristics of the accretion-collision granitoids of the Kaa-Khem batholith are shifted to the upper-crust compositions relative to those of the Lake Zone granitoids. The reason is that the latter formed predominantly through the transformation of early Caledonian island arc complexes, which were generated with a higher portion of mantle component.
a:2:{s:4:"TEXT";s:106:"S.V. Alexeev, L.P. Alexeeva, A.A. Svetlakov, V.A. Pellinen, A.I. Orgil’yanov, P.S. Badminov, O.S. Gutareva";s:4:"TYPE";s:4:"text";}
a:2:{s:4:"TEXT";s:99:"Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia";s:4:"TYPE";s:4:"text";}
Keywords: Cold and thermal groundwaters, surface waters, ground ice, chemical composition, trace element and REE, enrichment factor, stable isotopes
The study area is located in the Eastern Sayan hydrogeological folded area. The objects of the study were groundwaters, surface waters and ground ice in the Sentsa River basin on the Oka Plateau. Cold and thermal groundwaters are associated with Proterozoic and Paleozoic metamorphic and igneous rocks. Their discharge as springs occurs in the river valleys along fault zones. Ground ice was studied in mineral frost mounds (lithalsas) composed of clays, clayey silts and silts of lacustrine-alluvial and fluvioglacial genesis. It has been established that thermal and cold groundwaters have HCO3 Ca-Na compositions, river and lake waters, as a rule, have HCO3 Ca compositions, and ground ice melts - HCO3, SO4-HCO3 and NH4-HCO3 Ca. Thermal waters are largely enriched in Li, Be, B, Si, Mn, Ga, Ge, Se, As, Br, Rb, Sr, Cs, Ba and all REE relative to river and rain waters, and have the highest values of trace elements enrichment factor (EFREE). The latter shows that atmospheric precipitation participates in the formation of the composition of groundwaters (cold and thermal) and surface waters. The specificity of the geochemistry of ground ice is determined by the composition of precipitation, the injection of ice-forming groundwater from taliks, the interaction in the water-rock system, and the presence of organic matter in unconsolidated sediments. The participation of river water and groundwater in the formation of the frost mound ice core is also evidenced by similar values of stable isotopes (δ18O, δD) in surface water, groundwater and ground ice. The 3He/4He ratio points to a possible influx of mantle helium into thermal waters, and δ13С points to the magmatic and thermometamorphic mechanisms of carbon dioxide accumulation in thermal waters. The 87Sr/86Sr ratio in travertines indicates a significant contribution of intrusive rocks to the formation of fluid composition.
A.Yu. Popov1,2, L.G. Vakulenko1,2, B.L. Nikitenko1,2, N.A. Palchik3, K.K. Melnikov1 1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia 3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Upper Jurassic, Lower Cretaceous, petrography, lithochemistry, sedimentation conditions, and environments, Anabar-Lena sedimentary basin, Arctic
Some intervals of the Jurassic-Cretaceous strata of the Anabar-Lena sedimentary basin have a certain oil and gas production potential, which can be realized in the synchronous offshore horizons of the adjacent territories of the Arctic shelf. Among the most representative objects in this regard are the outcrops of Upper Jurassic and Lower Cretaceous formations of the Nordvik Peninsula. The main data on the composition and structure of this section were obtained mainly at the beginning of the second half of last century. The results of complex mineralogical, petrographic, and lithochemical studies of the Urdyuk-Khaya and Paksa formations of Cape Urdyuk-Khaya of the Nordvik Peninsula presented in here enabled us to identify 10 boundaries for changing of sedimentation regimes of the paleobasin. It was found that the Urdyuk-Khaya Formation was formed mainly in the conditions of the shelf transition zone (moderate deep water) with low rates of terrigenous material intake, some depletion of oxygen in bottom waters, and a trend towards an increase in the depths of the basin. The basal stratum of the Paksa Formation was formed in offshore conditions with periodically occurring dioxic conditions in bottom waters and extremely low rates of terrigenous material intake. The overlying part of the formation was formed in various parts of offshore transition conditions with a gradual decrease in the depths of the basin, an increase in the oxygen content in the bottom layer of water, and the rate of terrigenous material intake. The main provenance area was igneous rocks of mafic, possibly intermediate composition. There was some influence of felsic igneous rocks, or ancient sedimentary rocks rich in quartz. The parent strata were subjected to moderate and severe chemical weathering, in a warm humid climate. The revealed features of the studied strata are similar to the characteristics of the same-age sediments of the lower reaches of the Anabar River, which determines their high correlation potential and allows us to judge the evolution of the western part of the Anabar-Lena basin.
V.V. Pustylnikova1, V.A. Muftakhov1, A.N. Obukhov2, A.M. Kirsanov2 1Aprelevka branch of the All-Russian Research Geological Oil Institute, Aprelevka, Russia 2All-Russian Research Geological Oil Institute, Moscow, Russia
Keywords: Limestones, dolomites, skarns, Devonian sediments, sills, oil-bearing rocks
Lithological studies of sedimentary rocks are often challenged by manifestations of the superimposed processes which are related neither to the stages of lithogenesis, nor to its zonality/direction. This can be exemplified by skarns in the carbonate-terrigenous sections of the unified Yukta and Nakokhoz-Kalargon formations of Devonian age which were studied in the area of Lake Baselak and the Ambardakh River basin during the expedition works. Since the latter contain potentially oil and gas-bearing strata in the area of the Yenisei-Khatanga regional trough, special attention was paid to the dark-colored lithotypes during the research. It was revealed that among the studied samples, the dark color of some of them was of mineral nature, rather than due to the presence of OM. In these samples, the mineral composition was studied in detail, with determination of the association of newly formed minerals, which allowed us to propose hypothesized mechanism and stages of their formation. The dark color of sedimentary rocks has been shown to be not a sufficient criterion for searches for oil and gas accumulation. New results of the field studies of pre-Triassic sedimentary complexes in the northern part of Kureyka syneclise are also presented.
P.S. Minyuk
N.A. Shilo North-East Interdisciplinary Scientific Research Institute, Far Eastern Branch of the Russian Academy of Sciences, Magadan, Russia
Keywords: Olduvai event, geochemistry, Pleistocene, Lake El’gygytgyn
The paper is concerned with study of the distribution of geochemical characteristics in the sediments of Lake El’gygytgyn (Chukchi Peninsula) formed during the Olduvai event. A clear geochemical and rock-magnetic zoning of the section has been established, which reflects global climatic changes. The geochemical zones coincide with marine isotope stages MIS 75-MIS 61. The sediments of warm stages are characterized by elevated contents of mobile components (SiO2, CaO, Na2O, K2O, and Sr), high values of magnetic susceptibility, low contents of Fe2O3, MgO, TiO2, Al2O3, Rb, Zr, and Ni, and low values of LOI, paramagnetic component, and chemical indices of alteration. The reverse pattern is observed for the sediments of cold stages. The low values of magnetic susceptibility in the sediments of optimal stages MIS 63, MIS 65, MIS 71, and MIS 75 are due to the dilution of detrital material with a biogenic one. The upper boundary of the Olduvai event passes in warm stage MIS 63, and the lower boundary coincides with the boundary between MIS 74 and MIS 75. The products of weathering of the Cretaceous felsic rocks of the Pykarvaam and Ergyvaam formations located near Lake El’gygytgyn were the provenances for its sediments. According to the geochemical and rock-magnetic data, the sedimentation during the Olduvai event was a cyclic process with periods of ca. 54, 40-43, and 23 kyr. The orbital cycles of 40-43 and 23 kyr indicate global causes of geochemical changes.
G.A. Leonova1, A.E. Maltsev1, L.M. Kondratieva2, V.A. Bychinskii3, L.V. Miroshnichenko1, S.K. Krivonogov1,4 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 2Institute for Water and Environmental Problems, Far Eastern Branch of the Russian Academy of Sciences, Khabarovsk, Russia 3Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia 4Korkyt Ata Kyzylorda University, Kyzylorda, Kazakhstan
Keywords: Geochemistry, early diagenesis, organic matter, sulfate reduction, authigenic mineral formation, pore waters
Chemical composition of bottom sediments and pore waters of organic-mineral sediments (sapropel) of Lake Kotokel (Eastern Baikal region) has been studied, based on long drilling cores, 14.5 and 16.5 m. A reduction type of diagenesis has been established, during which destruction of organic matter, transformation of the chemical composition of pore waters and the formation of authigenic minerals occur. Even in the uppermost intervals of sapropel, organic matter is being profoundly transformed and differs significantly in composition from that of bioproducers (plankton). The major role in diagenetic transformations of organic matter belongs to different physiological groups of microorganisms, primarily heterotrophic, amonifying and sulfate-reducing bacteria. During diagenesis, the basic chemical composition of pore waters (HCO3-, SO42-, Cl-, Ca2+, Mg2+, K+, Na+) changes, trace elements (Fe, Mn, Sr, Ba, Pb, As, Co, Ni) redistribute, concentrations of HCO3-, NH4+, PO43- and Si increase; this is caused by destruction of organic matter. In the process of bacterial sulfate reduction in pore waters, the concentration of SO42- decreases along the depth of the section, and in the sediment the proportion of reduced forms of sulfur increases and the isotopic composition of sulphur δ34S changes. Transformation of chemical composition of pore waters and the activity of microorganisms leads to the formation of authigenic pyrite, rhodochrosite, and barite.
a:2:{s:4:"TEXT";s:222:"A.V. Sergeeva1, T.P. Tikhonov2, А.А. Аvilova3, М.А. Nazarova1, О.А. Zoben’ko1, Е.V. Kartasheva1, А.А. Kuzmina1, А.V. Gladyshkina4";s:4:"TYPE";s:4:"html";} 1Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences,
Petropavlovsk-Kamchatsky, Russia 2Lomonosov Moscow State University, Moscow, Russia 3Pirogov Russian National Research Medical University, Moscow, Russia 4Orion Regional Educational Center, Voronezh, Russia
Keywords: Montmorillonite, thermal fields, cation exchange, vibrational spectroscopy, lithium, ammonium, mercury, Kamchatka
Pages: 1732-1751
The montmorillonite samples from shallow parts of the thermal fields within the Mutnovsky hydrothermal steam deposit (the Upper Mutnovsky thermal field and the Dachny site), along with the composition of salts in the clay pore solutions have been studied in the context of ion exchange between them. This aspect represents one of the topical problems due to geothermal clays (montmorillonite) enrichment with elements transferred by steam hydrotherms and concentrating in the near- surface horizons, while montmorillonite as a natural cation exchanger will absorb them, thus acting as a geochemical barrier. The composition of the interlayer cationic complex of montmorillonite samples was studied on isolated clay fractions and from the ion-exchange experiment to determine the salt composition of clay pore solutions and the mineral composition of clay fractions. Geothermally heated soils within the studied thermal fields are dominated by kaolinite-alunite-jarosite assemblage with subordinate amounts of montmorillonite, while montmorillonite prevailing in the mud-water pots is subjected to degradation when they dry out. Crystallization of salts from pore solutions in the near-surface horizons of the studied thermal fields can be exemplified by szomolnokite FeSO4‧H2O, metavoltine K2Na6Fe2+Fe3+6O2(SO4)12·18H2O, leonite K2Mg(SO4)2‧2H2O, polyhalite K2Ca2Mg(SO4)4‧2H2O, mikasaite Fe2(SO4)3, alum and amorphous aluminum sulfate hydrate. Interaction of such solutions with montmorillonite will trigger the cation exchange reactions in the interlayer space of the layered silicate with attendant formation of predominantly Al,Fe-intercalated forms. Alumina hydrates entering the interlayer space of the montmorillonite are reflected by the band at ~ 2500 cm–1 on the infrared spectra attributed to the water coordinated to aluminum. In addition to aluminum and iron, other cations which are concentrated in the uppermost parts of geothermal clay blankets and penetrate into the interlayer space of montmorillonite are: Li+, K+, NH4+, Mg2+, Ca2+, Sr2+, Ba2+, Hg2+, etc. As a result, in the thermal field conditions, montmorillonite is intercalated with easily extractable elements, including lithium, mercury, barium and strontium, ammonium, at the level of units (the first tens of grams per ton).
A. Kamal1, M.M. Shah1, H.U. Rahim1,2, T. Zafar3, R. Khalil4, M. Shahzeb1 1Department of Earth Sciences, Quaid-i-Azam University, Islamabad, Pakistan hamadrahim@gmail.com 2Earth Sciences Division, Pakistan Museum of Natural History, Islamabad, Pakistan 3Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China 4King Abdulaziz University, Jeddah, Saudi Arabia
Keywords: Dolomites, Middle Jurassic, petrography, stable isotopes, Samana Suk Formation
Pages: 1752—1771
Diagenetically modified carbonate rocks are more common in the rock record. Among these modifications, multiphase dolomitization is the most common process. The Middle Jurassic carbonates of the Samana Suk Formation are extensively altered by the dolomitization process in the Kahi section, Nizampur Basin. The primary objective of this study is to investigate this multiphase dolomitization and to elucidate its possible mechanism.
Field investigation shows both host limestone (oolitic, fossiliferous, and massive) and dolomites. Dolomite bodies are of both beddings: parallel to and crosscutting the bedding planes. Different types of dolomites were recognized on the basis of color contrast as dark gray replacive dolomite, light gray dolomite, brownish dolomite, and yellowish dolomite. Along with the replacive phase, void- and fracture-filling cementing saddle dolomite and cementing calcites are recognized in the field. Petrographic studies show the complex diagenetic history of the Samana Suk Formation from near-surface diagenesis, including micritization, neomorphism, and several varieties of dolomites. These varieties are as follows: RD1 is very fine- to fine-grained dolomite; RD2 is medium- to coarse-grained and anhedral to subhedral dolomite; RD3 is coarse- to very coarse-grained and planar euhedral zoned dolomite; and RD4 is coarse-grained euhedral to subhedral ferroan dolomite. In addition, cementing saddle dolomite SD consists of large crystals with curved faces showing sweeping extinction. Cementing calcite phases are as follows: CC1 is granular mosaic; CC2 is twin; CC3 is fracture-filling; and CC4 is ferroan calcite. The stable isotope values of limestone (δ18O is –7.13 to –0.73‰ V-PDB, and δ13C is –0.05 to 1.32‰ V-PDB) show depletion with respect to the Jurassic marine signature. The values of multiphase dolomites RD1–RD4 and SD (δ18O is –8.65 to –3.16‰, and δ13C is –3.56 to 2.09‰) indicate multiphase dolomitization. The CC1–CC3 values (δ18O is –11.07 to –8.97‰, and δ13C is –2.14 to 0.76‰) indicate highly depleted values of δ18O, showing hydrothermal origin. From field, petrography, and geochemistry data, it is deduced that a possible source of Mg for hydrothermal dolomites is activation of faults and fractures during active tectonic regime in the area and might be related to activation and reactivation of the Kahi Thrust system.
D.A. Novikov1,2, A.N. Pyryaev2,4, A.A. Maksimova1,2, V.P. Sukhorukov4, A.S. Derkachev2, A.F. Sukhorukova1, F.F. Dultsev1, A.V. Chernykh1, A.A. Khvashchevskaya3, N.A. Medeshova5,6 1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia NovikovDA@ipgg.sbras.ru 2Novosibirsk State University,Novosibirsk, Russia 3Research Laboratory for Hydrogeochemistry of the School of Earth Sciences and Engineering,
Tomsk Polytechnic University, Tomsk, Russia 4V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 5LLP Almaty Hydrogeology, Almaty, Kazakhstan 6Kazakh National Research Technical University, Almaty, Kazakhstan
Keywords: Radon waters, stable isotopes, uranium isotope ratio, uranium, thorium, radium, radon, water–rock system, geochemical type, West Siberia
Pages: 1772—1790
We present the first results of comprehensive isotope-geochemical studies of mineral radon waters of the Tulinskoe field (Novosibirsk), aimed at identifying their stages of interaction with the host rocks. By geochemical coefficients Ca/Na, Ca/Mg, Ca/Si, Mg/Si, Na/Si, Si/Na, rNa/rCl, and SO4/Cl, the studied waters are assigned to fracture–vein waters of granitoids. The indices of carbonate mineral saturation of the radon waters show their oversaturation with aragonite, calcite, and dolomite. The waters are also saturated with diaspore, ferrohydrite, gibbsite, and kaolinite, which leads to the deposition of these minerals as secondary phases. In the thermodynamic diagrams, the points of the activities of the radon water components are localized mainly in the stability fields of clay minerals (kaolinite and Na-, Ca-, and Mg-montmorillonites), layered silicates (talc), and zeolites (laumontite). A few points fall in the stability field of silicates (Mg-chlorite). The studied waters of the Tulinskoe field are neutral fresh, with Si = 6.41–9.02 mg/dm3. According to the results of thermodynamic calculations, the radon waters of the Tulinskoe field are in equilibrium with carbonate minerals and hydromicas. Following the classification by S.L. Shvartsev, they are assigned to the Si-Na geochemical type.
