Vol 478, No 1 (2018)
- Year: 2018
- Articles: 30
- URL: https://journals.rcsi.science/1028-334X/issue/view/12051
Geology
The Age of Transformation of Rare-Metal Alkaline Granites of the Katugin Massif (Aldan Shield)
Abstract
The U–Pb (ID TIMS) geochronological studies of single zircon grains and their fragments have made it possible to establish that rare-metal alkaline granites of the Katugin massif (2055 ± 7‒2066 ± 6 Ma) underwent high-temperature transformations at age levels of ~1921 ± 5 and 1876 ± 7 Ma.
Some Aspects of Evolution of Microbial Rock-Formation in the Earth’s History
Abstract
Under a relatively constant system and morphology of microbiota, sedimentary rocks produced by microbial organisms (microbiolites) evolved intensively during the geological history of the Earth. The parameters that changed were the composition, extraction form, and formation environments.
The Age of Rift-Related Basalts in East Antarctica
Abstract
The Lambert Rift, which is a large intracontinental rift zone in East Antarctica, developed over a long period of geological time, beginning from the Late Paleozoic, and its evolution was accompanied by magmatic activity. The latest manifestation of magmatism is eruption of alkaline olivine–leucite basalts on the western side of the Lambert Rift; Rb–Sr dating referred its time to the Middle Eocene, although its genesis remained vague. In order to solve this problem, we found geochronometer minerals in basaltic samples and 68 apatite grains appeared to be suitable for analysis. Their ages and ages of host basalts, determined by the U–Pb local method on the SIMS SHRIMP-II, were significantly different (323 ± 31 Ma) from those assumed earlier. This age corresponds to the earliest stage of crustal extension in East Antarctica and to most of Gondwana. The new data crucially change the ideas about the evolution of Lambert Rift and demonstrate the ambiguity of К–Ar dates of the alkali effusive formed under long-term rifting.
Shrilankite Inclusions in Garnets from Kimberlite Bodies and Diamondiferous Volcanic–Sedimentary Rocks of the Yakutian Kimberlite Province, Russia
Abstract
Pyrope–almandine garnets (Mg# = 28.3–44.9, Ca# = 15.5–21.3) from a heavy mineral concentrate of diamondiferous kimberlites of the largest diamond deposit, the Yubileinaya pipe, along with kimberlite- like rocks and diamondiferous volcano–sediments of the Laptev Sea coast, have been found to contain polymineral, predominantly acicular inclusions, composed of aggregates of shrilankite (Ti2ZrO6), rutile, ilmenite, clinopyroxene, and apatite. The presence of shrilankite as an inclusion in garnets from assumed garnet–pyroxene rocks of the lower crust, lifted up by diamond-bearing kimberlite, allows it to be considered as an indicator mineral of kimberlite, which expands the possibilities when searching for kimberlite in the Arctic.
Prospects of Oil-and-Gas Contents from the Paleozoic in the Southern Flank of the Voronezh Anteclise by Analyzing Data of Recent Regional Seismic Surveys
Abstract
Based on the materials of regional seismic surveys, general structural maps of the basement roof and the carbonate stratum, as well as a map of the carbonate formation isopachytes, are plotted. Using statistical methods, the trend-component for the basement roof is determined and the map of isolines characterizing the II-order structural-tectonic elements is obtained.
230Th/U Chronology and Geochemistry of Irinovskoe Hydrothermal Field (Mid-Atlantic Ridge)
Abstract
The results of 230Th/U dating and mineralogical–geochemical studies of sulfide ores from the Irinovskoe hydrothermal field and the Severo-Zapadnoe ore occurrence (Mid-Atlantic Ridge) are presented. Sulfides are represented primarily by copper–sulfide ores with 12–30% Cu content; sulfur- and zinc-sulfide ores are distributed less frequently. The analysis of a change in the composition of sulfides over time has made it possible to identify three stages of formation. Each stage assumes that mineral associations are changed from high-temperature (sulfur and copper sulfide) to medium temperature (Zn–Cu and Zn-sulfide) sulfide ores. The whole age range of formation of the hydrothermal deposits falls within the time interval of about 58000–8000 for the Irinovskoe field and 69000–11000 years ago for the Severo-Zapadnoe ore occurrence.
Paleoproterozoic Granitoids of the Yurovka Swell Basement (Okhotsk Massif): First U–Pb SIMS Geochronological and Nd–Sr Isotope–Geochemical Data
Abstract
The first results of U–Pb SIMS geochronological and Nd–Sr isotope–geochemical studies of the Yurovka Complex metavolcanics and granitoids of the Luktur Complex belonging to the Yurovka Swell yielded a Paleoproterozoic age of their formation pointing to a considerable Paleoproterozoic continental crust formation event. These data allow us to reconsider existing ideas about the similarity of the composition and age of the basement of the Yurovka Swell and that of the Paleoarchaean Kukhtui Swell of the Okhotsk Massif.
Geological and Isotope–Geochemical Criteria for the Existence of the Ancient Continental Crust in Basement Complexes of Primorye
Abstract
The problem of the development of the ancient continental crust in the Primorye Region is discussed. It is substantiated by geological and isotope-geochemical criteria: a granite–metamorphic mineral composition of different-aged terrigenous deposits and pelagic cherts, occurrence of arkoses, as well as Proterozoic model age datings of sedimentary complexes and the occurrence of early Proterozoic zircons and monazites. The manifestation of potassium, high-Ba, LREE- and Nb-rich basite–ultrabasite magmatism, typical of Sino-Korean and Okhotsk Ba-bearing nuclears, of lengthy age intervals (Jurassic–Paleogene) in Primorye and the Amur Region is an important criterion.
The Influence of the Ufimian Tectonic Concentric Structure on the Hydrocarbon Migration and Ore Genesis
Abstract
The Ufimian tectonic concentric structure (UTC) is a regional structure with concentric and zonal structure of the internal gravity field. In the Neoproterozoic this structure was at higher hypsometric level relative to the Bashkir Meganticlinorium. The most significant uplift of this tectonic concentric structure happened at the beginning of the Karatau time (~825 Ma) and was accompanied by the formation of a ring fractured zone, favorable for hydrocarbon migration from the Lower Riphean black shales. Due to this, bitumens with higher Mo content in the Neoproterozoic and Paleozoic deposits are confined spatially to this zone. The bitumenosity of the Neoproterozoic deposits on the southern slope of the Ufimian tectonic concentric structure could have contributed to the formation of complex Cu–Ag–Mo–Re ores (copper sands) at the upper boundary of terrigenous red deposits of the Zilmerdak Formation. Positive structures identified in the Neoproterozoic deposits near the margin of the Ufimian tectonic concentric structure are considered to be promising for searching for hydrocarbon fields.
The Phosphates of Pleistocene–Holocene Sediments of the Eastern Gallery of Denisova Cave
Abstract
Authigenic phosphate mineralization was first studied on the territory of Russia on the basis of the Holocene and Pleistocene deposits of Denisova Cave. The formation of phosphates in the eastern gallery is related to biodegradation of the horizons of guano of insectivorous bats, which inhabited the cave in the absence man. The results confirmed the archaeological record of the Holocene and the upper part of Pleistocene sequences of the eastern gallery.
Geochemistry
Rare-Earth Elements from Modern Mineral–Organic Associations in the Zone of Sulfide Ore Hypergenesis
Abstract
The REE composition of modern mineral–organic associations in the sulfide ore hypergenesis zone of the Berezitovoe deposit in the Russian Far East was studied for the first time. It is shown that the mineral–organic associations widely abundant in the valley of Konstantinovskii Creek and represented by bright brown crusts on the surface of deluvial deposits were formed at the expense of the influence of acid highly mineralized mine waters from the Berezitovoe deposit. The mineral–organic associations found in the Creek valley may be considered as a new indicator for evaluation of the geoecological state of modern technogenic landscapes.
Polychronous Zirconology of Navysh Volcanics of the Ai Formation (Southern Urals)
Abstract
In order to resolve the age of Navysh volcanics (NV), which is usually attributed to the Lower Riphean of the Ai Formation, we have used geochronological, petrologic, and mineralogical methods of zirconology, apart from the SHRIMP isotopic data of single zircon grains. Moreover, TIMS isotope age analyses have been conducted, the results of which can be regarded as both controlling and providing the most correct information. The TIMS and SHRIMP data make it possible to suggest a polychronous character of the NV, which include not only Riphean, but also Paleozoic groups of volcanics. In this situation, an assessment of the scales of such polychroneity of NV and, correspondingly, of the Ai Formation as a whole becomes urgent.
Regularities in Low-Temperature Phosphatization of Silicates
Abstract
The regularities in low-temperature phosphatization of silicates are defined from long-term experiments on the interaction between different silicate minerals and phosphate-bearing solutions in a wide range of medium acidity. It is shown that the parameters of the reaction of phosphatization of hornblende, orthoclase, and labradorite have the same values as for clayey minerals (kaolinite and montmorillonite). This effect may appear, if phosphotization proceeds, not after silicate minerals with a different structure and composition, but after a secondary silicate phase formed upon interaction between silicates and water and stable in a certain pH range. Variation in the parameters of the reaction of phosphatization at pH ≈ 1.8 is due to the stability of the silicate phase different from that at higher pH values.
Properties of Reduced Carbon Dioxide Fluid: Evidence from Experimental and Thermodynamic Modeling
Abstract
It is shown experimentally that fluid mostly consisting of CO2 and CO is a good solvent for many petrogenic and ore components under high P–T parameters. Siderite decomposed to oxides and a mixture of CO2 and CO was the source of the fluid in the experiment. It is demonstrated that an ultrapotassic alkaline melt was formed on the oxide matrix as a result of fluid transport of the components of the basaltic melt at 2–5 kbar and 900–1000°C. This melt is characterized by high concentrations of Rb, LREE, Sr, and Ba. The mechanism of solubility of metals in the carbon dioxide–reduced fluid includes the formation of volatile carbonyls. As is evident from thermodynamic modeling, the stability of Ni(CO)4 at high pressure reaches magmatic temperatures. The finding of native nickel in aerosols during eruption of the Tolbachik Volcano in 2012–2013 is explained by decomposition of carbonyl from fluid of a deep origin during magma ascent.
The First U–Pb Isotopic Systematics of Natural Aeschynite and Coexisting Monazite
Abstract
We have been the first to study in situ the U–Pb isotopic system of aeschynite identified in the gold-bearing magnetite–chlorite–dolomite rocks of the Karabash serpentine massif in the Southern Urals. In the concordia diagram, the U–Pb LA–ICP–MS data on aeschynite are characterized by a considerable discordance, which is consistent with the regression line, the lower crossing of which with the concordia corresponds to an age of 298 ± 18 Ma, whereas the figurative ellipses of coexisting monazite reveal an almost concordant cluster corresponding to the U–Pb age of 317.3 ± 3.3 Ma. It has been established that the closure temperature of the aeschynite system is lower than that of the coexisting monazite.
Xenoliths of Eclogites with Diamonds from the Yubileinaya Kimberlite Pipe, Yakutia
Abstract
The first results of study of minerals and diamonds of diamond-bearing eclogites from kimberlites of the Yubileinaya pipe with a variable percent amount of clinopyroxene and garnet are presented. Samples with a garnet content from 30 to 90% of the xenolith volume are dominant among the round to oval xenoliths with diamonds. Five eclogite samples contain grains of accessory rutile, as well as corundum and kyanite. Some samples host two or more diamond crystals.
Occurrence Forms of Carbon, Sulfur, and Noble Metals in Deposits of the Black-Shale Formation by the Example of the Degdekan Gold-Ore Deposit (Northeastern Russia)
Abstract
Pyrite crystals and ore-bearing shales of the Degdekan deposit were studied by means of XPS, SEM–EDX, EPMA, and AAS. Five peaks of carbon organic forms were identified, conforming to polymer compounds containing either double bonds of carbon or alkyne groups and compounds containing C–OH and C=O bonds, as well as, probably, small amounts of S-containing compounds and those with functional groups of carboxylic acids. Sulfate prevails over sulfite in pyrites; among the surface sulfide forms, disulfide prevails over monosulfide; the presence of polysulfide is registered. The occurrence of various chemical forms of sulfur on the surface might provide for concentrating of microelements including the noble metals (NMs) in their surface-bound forms. The regular behavior of NMs (Au, Pt, Pd, and Ru) depending on the grain sizes (specific surfaces) of pyrite crystals along with the narrow range of the ratios of structural and surface components of the concentrations of different NMs points to NM coprecipitation with pyrite during the same productive stage. No capture of NM-containing carbonaceous phases took place, which should violate the regularity of Au distribution in pyrites of the Sukhoi Log deposit.
Foidite and Meimechite Lavas of Polar Siberia (Some Questions of Petrogenesis)
Abstract
For the Permian–Triassic foidite and meimechite lavas of Polar Siberia, both the whole-rock petrochemistry and geochemistry and that of melt inclusions in olivine phenocrysts from the same rocks have been demonstrated to be similar. In addition, their isotope characteristics imply the possibility of their generation from an abyssal parental melt compositionally resembling a high–Mg alkaline picrite.
Indicator Isotope–Geochemical Characteristics of Sulfides from the Satka Magnesite Ore Field (South Urals Province)
Abstract
The stable enrichment of pyrite from magnesite ores in δ34S isotope (from 5.4 to 6.9‰) compared with pyrite from the host (sedimentary and igneous) rocks was established in the classical Satka sparry magnesite ore field. Concretionary segregations of fine-grained pyrite in dolomite are depleted in the heavy sulfur isotope (δ34S, from–9.1 to–5.8‰). Pyrite from dolerite is characterized by δ34S values (–1.1 and 1.7‰) close to the meteorite sulfur. The δ34S values in barite from the underlying dolomite horizon vary in the range of 32.3–41.4‰. The high degree of homogeneity of the sulfur isotope composition in pyrite from magnesite is a result of thermochemical sulfate reduction during the syngenetic crystallization of pyrite and magnesite from epigenetic brines, formed during dissolution of evaporite sulfate minerals at the stage of early catagenesis of the Riphean deposits.
Tantalo–Niobate from the Apollo-17 Regolith
Abstract
Particles of tantalo–niobate of the ferrotantalite-manganotantalite series are discovered for the first time in two lunar regolith fragments delivered by the Apollo-17 mission. Allochtonous and autochtonous mineralization that accompanies tantalo–niobate in the regolith is described. An attempt is made to explain the formation of tantalite in anorthosites of the continental region of the Moon.
An Archaean Tonalite–Trondhjemite–Granodiorite Association of the Kursk Block (Voronezh Massif): Composition, Age, and Correlation with the Ukrainian Shield
Abstract
Framing of the Archaean greenstone belts of the Kursk Block (KB) of the East Sarmatia preserves rocks of the TTG association: those do not form massifs with distinct boundaries, but occur as fields gradually transiting into gneisses and migmatites. According to Sm–Nd isotope–geochemical data, the TTG are characterized by positive values of εNd(2960) = +0.3…+1.6 and protolith model ages of ТNd(DM) = 3100–3200 Ma. Magmatic protoliths of the Kursk Block TTG were formed about 2960 Ma by melting from a juvenile basite source. These age estimates are significantly younger than heterochronous (3.19, 3.13 and 3.07 Ga) TTGs of the Middle Dnieper granite–greenstone terrane. On the other hand, the similarity of εNd(T) implies a single source of their protoliths. Consequently, the KB TTGs, apparently, are a result of transformation of an older sial crust preserved within the Middle Dnieper Block.
Geophysics
Velocities of Ultrasonic Waves in Sand Samples Containing Water, Ice, or Methane and Tetrahydrofuran Hydrates (Laboratory Measurements)
Abstract
We analyze the results of investigations of acoustic properties (velocities of longitudinal and transversal waves) in sand samples containing different amounts of water, ice, and methane or tetrahydrofuran hydrates in the pores using a special laboratory setup.
The P-Wave Focusing Effect in a Low-Velocity Core of the Earth: Analytical Solution
Abstract
This paper reports the calculation data on wave fields for the Earth’s model including the mantle and external and internal core with real parameters. The investigation has made it possible to identify physical phenomenon unknown previously such as the formation of the wave field focusing region in the Earth, emerging to the day surface before the first PKP-wave. This is due to the fact that spherical bodies (in this case, the low-velocity core of the Earth) are characterized by the collecting lens properties.
Geography
Coastal Geographic Structures in Coastal-Marine Environmental Management
Abstract
It has been proposed to distinguish the coastal geographic structures consisting of a spatial combination of three interconnected and mutually conditioned parts (coastal-territorial, coastal, coastal-marine), which are interlinked with each other by the cumulative effect of real-energy flows. Distinguishing specific resource features of the coastal structures, by which they play a connecting role in the complex coastalmarine management, has been considered. The main integral resource feature of the coastal structures is their connecting functions, which form transitional parts mutually connecting the coastal-territorial and coastalmarine environmental management.
Eutrophication of an Urban Forest Ecosystem: Causes and Effects
Abstract
The combined use of methods of passive dosimetry of the status of atmospheric air, phytoindication, and cartographic visualization of data made it possible to elaborate and substantiate approaches to evaluation of the effect of atmospheric air contamination on the eutrophication of forest ecosystems under urban conditions.
About New Maps of Surface Currents of the World Ocean
Abstract
Using the example of the surface currents map сonstructed for the Northern Atlantic on the basis of data of modern observations by means of drifting buoys, it is shown that the previously published maps of ocean surface currents, based on ship drift data, have become outdated and require an update. The influence of the bottom relief on the directions of surface layer currents is shown.
Oceanology
Effects of the Influence of a Wave on an Underwater Obstacle by a Stratified Flow of Finite Depth
Abstract
Equations are obtained for a hydrodynamic load on an obstacle, which is modeled by a point dipole during its circulated flow of a two-layered liquid of finite depth. The correlations between the wave resistance and rising force and the rate of the flow and circulation are studied. Examples of numerical calculations for real marine conditions are given. It is shown that the account of circulation can significantly change the value of the hydrodynamic reaction, which impacts the dipole.
Erratum
Erratum to: “New Data on the Age and Nature of the Khan–Bogd Alkaline Granites, Mongolia”
Abstract
The list of authors and their affiliations should read as follows:
A. Gerdesa, Academician L. N. Kogarkob,*, and N. V. Vladykinc
aInstitute of Earth Sciences, Goethe University, Frankfurt, Germany
bVernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
cVinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia
*e-mail: kogarko@geochi.ru