Factors and Trends in the Formation of Natural–Technogenic Associations of Polycyclic Aromatic Hydrocarbons in the Snow–Soil System

Doklady Earth Sciences - The content of polycyclic aromatic hydrocarbons (PAHs) in soil and snow cover near the carbon black plants in Moscow, Omsk, and Samara regions was studied. The differences...     

Hissar–Alai and the Pamirs: Junction and Position in the System of Mobile Belts of Central Asia

The position of the Pamirs and the Hissar–Alai mountainous system in the structure of Central Asia and features of their junction are considered. It is shown that their outer contours and tectonic infrastructure are significantly distinct in the planar pattern: latitudinally linear and arched for the Hissar–Alai and the Pamirs, respectively. These structures logically match those of the Central Asian and Alpine–Himalayan belts, respectively. The Pamir orogen is a relatively autonomous structural element of the crust, which is located discordantly relative to the country lithospheric blocks. Most of the Pamirs (at least, the Northern and Central) probably form a giant allochthon on the ancient basement of the Tarim and Afghan–Tajik blocks. The junction zone of these two “hard” crustal segments is reflected in the transverse Transpamir threshold, which is expressed in the relief, deep structure, and seismicity. The specific geological structure of the junction zone of the Pamirs and Hissar–Alai (systems of the Tarim, Alai, and Afghan–Tajik troughs) is shown. It suggested that this zone is a damper, which significantly neutralizes the dynamic influence of the Pamir and the southernmost elements of the Pamir–Punjab syntax on Hissar–Alai structures.     

Phlogopite Formation in the Orthopyroxene–Garnet System in the Presence of H2O–KCl Fluid in Application to the Processes of Mantle Metasomatism

Doklady Earth Sciences - The results of experimental studies are presented for reactions in the orthopyroxene–garnet–phlogopite system in the presence of H2O–KCl fluid at...     

Daily Course of CO2 Fluxes in the Atmosphere–Water System and Variable Fluorescence of Phytoplankton during the Open-Water Period for Lake Baikal according to Long-Term Measurements

The process of gas exchange of CO₂ in the atmosphere–water system and its relation to the daily course of variable fluorescence of phytoplankton is studied on the basis of long-term (2004–2014) measurements during the open water period for Lake Baikal. It is found that the decrease in photosynthetic activity of plankton is almost synchronous to the increase in the CO₂ flux from atmosphere to water. It follows from comparison of the spring and summer data with December measurements that the daily decrease in variable fluorescence of phytoplankton is caused by the internal daily rhythm of the photosynthetic activity of plankton.

     

The Influence of Sodium and Potassium Chlorides on Phase Ratios in the Eclogite–CaCO3–H2O + CO2 System at 4 GPa and 1200–1300°C

To characterize the influence of alkaline metal chlorides on the phase ratios under melting of upper mantle eclogites, the eclogite–CaCO₃–NaCl–KCl system with Н₂О + СО₂-fluid was studied in the experiments under 4 GPa and 1200–1300°C. A low difference in temperatures (<100°C) was registered between the eclogite solidus and liquidus (>1200 and <1300°C, respectively), which is characteristic for the near-eutectic compositions. The phase proportions were peculiar for the absence of any silicate melt over the entire temperature range considered. The carbonate melt coexisted with clinopyroxene and garnet within 1200–1250°C, whereas a carbonate melt exclusively occurred under above-liquidus conditions at 1300°C. The melt quenching resulted in the formation of a multiphase fine-grained mixture of Ca, Na, and K carbonates and chlorides containing microinclusions of clinopyroxene and garnet. The occurrence of a high-calcium carbonate melt in Cl-containing eclogite systems might play a significant role in the mantle metasomatism of subduction zones characterized by the water–alkaline–chloride type of fluids.

     

Minerals of the Fe–Ni–Co–Cu–S System in Picrite Intrusions of the Southern Urals: Signatures of Liquation and Differentiation of the Sulfide Melt

Doklady Earth Sciences - New data on the minerals of the Fe–Ni–Co–Cu–S system in the differentiated intrusions of the Southern Urals are presented. Based on a detailed study...     

Melt–Fluid and Fluid–Fluid Immiscibility in a Na2SO4–SiO2–H2O System and Implications for the Formation of Rare Earth Deposits

Liquid–liquid immiscibility has crucial influences on geological processes, such as magma degassing and formation of ore deposits. Sulfate, as an important component, associates with many kinds of deposits. Two types of immiscibility, including (i) fluid–melt immiscibility between an aqueous solution and a sulfate melt, and (ii) fluid–fluid immiscibility between two aqueous fluids with different sulfate concentrations, have been identified for sulfate–water systems. In this study, we investigated the immiscibility behaviors of a sulfate- and quartz-saturated Na2SO4–SiO2–H2O system at elevated temperature, to explore the phase relationships involving both types of immiscibility. The fluid–melt immiscibility appeared first when the Na2SO4–SiO2–H2O sample was heated to ~270°C, and then fluid–fluid immiscibility emerged while the sample was further heated to ~450°C. At this stage, the coexistence of one water-saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed. The three immiscible phases remain stable over a wide pressure–temperature range, and the appearance temperature of the fluid–fluid immiscibility increases with the increased pressure. Considering that sulfate components occur extensively in carbonatite-related deposits, the fluid–fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite-related rare earth deposits.     

Laboratory Investigations of the Hydro-Mechanical–Chemical Coupling Behaviour of Sandstone in CO2 Storage in Aquifers

This paper is devoted to experimental investigations of the hydro-mechanical–chemical coupling behaviour of sandstone in the context of CO₂ storage in aquifers. We focused on the evolution of creep strain, the transport properties and the elastic modulus of sandstone under the effect of CO₂–brine or CO₂ alone. A summary of previous laboratory results is first presented, including mechanical, poromechanical and hydro-mechanical–chemical coupling properties. Tests were then performed to investigate the evolution of the creep strain and permeability during the injection of CO₂–brine or CO₂ alone. After the injection of CO₂–brine or CO₂ alone, an instantaneous volumetric dilatancy was observed due to the decrease in the effective confining stress. However, CO₂ alone had a significant influence on the creep strain and permeability compared to the small influence of CO₂–brine. This phenomenon can be attributed to the acceleration of the CO₂–brine–rock reaction by the generation of carbonic acid induced by the dissolution of CO₂ into the brine. The original indentation tests on samples after the CO₂–brine–rock reaction were also performed and indicated that the elastic modulus decreased with an increasing reaction time. The present laboratory results can advance our knowledge of the hydro-mechanical–chemical coupling behaviour of sandstone in CO₂ storage in aquifers.     

Trends in intrinsic water-use efficiency of natural trees for the past 100–200 years: a response to atmospheric CO2 concentration

To evaluate how the land carbon reservoir has been acting as a sink to the anthropogenic CO₂ input to the atmosphere, it is important to study how plants in natural forests physiologically adjust to the changing atmospheric conditions. This has been studied intensively using controlled experiments, but it has been difficult to scale short-term observations to long-term ecosystem-level response. This paper derives variations of plant intrinsic water-use efficiency from natural trees for the past 100–200 years using carbon isotope chronologies. This parameter may potentially cause an increase in plant growth rate by improving the efficiency of plant water use, especially in arid environments. Attempts were made to isolate the variations of intrinsic water-use efficiency as a function of only the CO₂ concentration of the atmosphere. The intrinsic water-use efficiency of almost all trees increased with increasing atmospheric CO₂ concentration. This is caused by an increase in the carbon assimilation rate (A) and/or a decrease in the stomatal conductance (g). The increase in plant intrinsic water-use efficiency may imply an increase in plant transpiration efficiency which may have a direct connection with changes in plant biomass.     

The Marine Cretaceous in the Western Part of the Tarim Basin of Xinjiang and Its Depositional Environments

The western part of the Tarim Basin in Xinjiang is one of the main areas in China where the marineCretaceous is well developed. The Upper Cretaceous Yingjisha Group represented mainly by sediments of lit-toral, near-shore neritic and estuarine facies is divided in ascending order into the Kukebai Formation, theOytak Formation, the Ygezya Formation and the Tuylouk Formation. For about thirty years, the basal beds of the Kukebai Formation had been considered to be the lowermostmarine horizon of the Cretaceous in the western part of the Tarim Basin, which represents the earliest trans-gression of the Cretaceous Sea into this region. Recently. marine trace fossils, Ophiomorpha nodosa, O.tuberosa and Thalassinoides? spp. were found in abundance and fine preservation from the upper subcycle andupper part of the lower subcycle of the Kezlesu Group underlying the Kukebai Formation. The fact indicatesthat the marine transgression there took place earlier than the Kukebaian. Process of transgression and regression and change of environment in the West Tarim Basin during the pe-riod from the late Early Cretaceous to the end of the Cretaceous is also discussed in this paper.     

The Geochemical Zoning of the Peschanka Porphyry–Epithermal System in the West of the Chukchi Peninsula

The results of chemical analyses and the data on core samples for 266 drill holes were used to identify the geochemical zoning of the Peschanka porphyry–epithermal system. A 3D model of geochemical zoning was developed using factor analysis and GIS technologies to represent the spatial distribution of elemental associations and mineral assemblages. The lateral and longitudinal zoning patterns are described. The AgPbZn: CuAuMo ratio is suggested as an indicator of vertical zoning that allows to evaluate the erosion level of porphyry copper stockworks.     

Experiment and Pitzer Model Prediction for the Solid + Liquid Equilibria of the Ternary System LiCl–CaCl2–H2O

正1 Introduction Lithium resources are widely distributed in the oilfield brine from the Nanyishan district in the Qaidam Basin(Fan et al.,2007).The investigation of the thermodynamics and phase diagram of the brine system is valuable in providing the theoretic foundation and scientific guidance in the comprehensive exploitation of the mixture salts effectively.Comprehensive     

Mud Volcanic Fluids of the Kerch–Taman Region: Geochemical Reconstructions and Regional Trends: Communication 2. Genesis of Mud Volcanic Gases and Regional Geochemical Trends

Lithology and Mineral Resources - The chemical and isotopic signatures of mud volcanic fluids were determined for 42 mud volcanoes of the Kerch–Taman region (Crimea–Caucasus district)....     

Metamorphic CO2 production from calc-silicate rocks via garnet-forming reactions in the CFAS–H2O–CO2 system

The type and kinetics of metamorphic CO₂-producing processes in metacarbonate rocks is of importance to understand the nature and magnitude of orogenic CO₂ cycle. This paper focuses on CO₂ production by garnet-forming reactions occurring in calc-silicate rocks. Phase equilibria in the CaO–FeO–Al₂O₃–SiO₂–CO₂–H₂O (CFAS–CO₂–H₂O) system are investigated using P–T phase diagrams at fixed fluid composition, isobaric T–X(CO₂) phase diagram sections and phase diagram projections in which fluid composition is unconstrained. The relevance of the CFAS–CO₂–H₂O garnet-bearing equilibria during metamorphic evolution of calc-silicate rocks is discussed in the light of the observed microstructures and measured mineral compositions in two representative samples of calc-silicate rocks from eastern Nepal Himalaya. The results of this study demonstrate that calc-silicate rocks may act as a significant CO₂ source during prograde heating and/or early decompression. However, if the system remains closed, fluid–rock interactions may induce hydration of the calc-silicate assemblages and the in situ precipitation of graphite. The interplay between these two contrasting processes (production of CO₂-rich fluids vs. carbon sequestration through graphite precipitation) must be considered when dealing with a global estimate of the role exerted by decarbonation processes on the orogenic CO₂ cycle.     

Specific Features in the Deep Structure of the Naryn Basin–Baibichetoo Ridge–Atbashi Basin System: Evidence from the Complex of Geological and Geophysical Data

New magnetotelluric data were obtained for the Karabuk profile crossing the Naryn basin–Baibichetoo Ridge–Atbashi basin geodynamic system (Central Tien-Shan). The complex geological–geophysical cross section along the profile provides a good agreement between the surface tectonic structures and the deep geoelectric model. The electric conductivity anomalies revealed as subvertical conductors striking along the flanks of basins may be explained by the zones of dynamic influence of faults and cataclasis of granite.     

Geochemical modelling of CO2–water–rock interactions in a potential storage formation of the North German sedimentary basin

The lower Triassic/Bunter sandstone and lower Jurassic/Rhät formations of the Northern Germany sedimentary basin constitute feasible reservoirs for the storage of CO₂ from combustion of fossil fuels or industrial production processes. This study presents analyses of geochemical interactions between CO₂, formation fluid and rock of these potential reservoirs using geochemical modelling in order to assess the short and long term impact of CO₂ sequestration. Batch equilibrium modelling was performed first for assessing the consistency of fluid and mineralogy field data and for identifying potential secondary minerals under the influence of injected CO₂. Inclusion of reaction kinetics in the batch models allowed an observation of reaction paths and to estimate the time frame of geochemical reactions. Finally, one-dimensional equilibrium reactive transport modelling was used in order to investigate the direction of reactions under conditions of fluid flow and mass transport and to quantify feedbacks of reactions on transport processes.Results of the simulations performed show that dawsonite may act as the main CO₂ storage mineral in both formations, while the carbonates calcite and dolomite dissolve over time. Also, changes in porosity and permeability are significant in the equilibrium reactive transport simulations. The time scale of kinetically controlled reactions observed in the kinetic batch modeling, however, suggests that CO₂ mineral trapping in both formations requires very long time frames, and hence other mechanisms such as structural or solubility trapping seem to be more relevant within the injection or early post-injection phase for the studied formations.     

Peculiarities of the Composition of Volatiles of Diamonds Synthesized in the Fe–S–C System: Data on Gas Chromatography–Mass Spectrometry

The first chromatography–mass spectroscopy data on volatiles in diamonds synthesized in the Fe–S–C system with 5 wt % S at 1400–1450°C and 5.0–5.5 GPa indicate the evolution of volatile composition during the diamond growth and, correspondingly, the variation in redox conditions of the reaction cell. A significant role is played by various hydrocarbons (HCs) and their derivatives, the content of which can reach 87%. Our data on possible abiogenic synthesis of HCs (components of natural gas and oil) can result in global recalculations (including climate) related to the global C cycle.     

Comparison of CO2 Dynamics and Air–Sea Gas Exchange in Differing Tropical Reef Environments

An array of MAPCO₂ buoys, CRIMP-2, Ala Wai, and Kilo Nalu, deployed in the coastal waters of Hawaii, have produced multi-year high temporal resolution CO₂ records in three different coral reef environments off the island of Oahu, Hawaii. This study, which includes data from June 2008 to December 2011, is part of an integrated effort to understand the factors that influence the dynamics of CO₂–carbonic acid system parameters in waters surrounding Pacific high-island coral reef ecosystems and subject to differing natural and anthropogenic stresses. The MAPCO₂ buoys are located on the Kaneohe Bay backreef, and fringing reef sites on the south shore of Oahu, Hawaii. The buoys measure CO₂ and O₂ in seawater and in the atmosphere at 3-h intervals, as well as other physical and biogeochemical parameters (conductivity, temperature, depth, chlorophyll-a, and turbidity). The buoy records, combined with data from synoptic spatial sampling, have allowed us to examine the interplay between biological cycles of productivity/respiration and calcification/dissolution and biogeochemical and physical forcings on hourly to inter-annual time scales. Air–sea CO₂ gas exchange was also calculated to determine whether the locations were sources or sinks of CO₂ over seasonal, annual, and interannual time periods. Net annualized fluxes for CRIMP-2, Ala Wai, and Kilo Nalu over the entire study period were 1.15, 0.045, and ?0.0056 mol C m^?2 year^?1, respectively, where positive values indicate a source or a CO₂ flux from the water to the atmosphere, and negative values indicate a sink or flux of CO₂ from the atmosphere into the water. These values are of similar magnitude to previous estimates in Kaneohe Bay as well as those reported from other tropical reef environments. Total alkalinity (A_T) was measured in conjunction with pCO₂, and the carbonic acid system was calculated to compare with other reef systems and open ocean values around Hawaii. These findings emphasize the need for high-resolution data of multiple parameters when attempting to characterize the carbonic acid system in locations of highly variable physical, chemical, and biological parameters (e.g., coastal systems and reefs).     

Distribution of CO_2 in Soil Air Affected by Vegetation in the Shilin National Park

This paper studies the CO2 distribution of soil atmosphere in the Shilin National Park. The measurement sites were chosen according to different topographic features and different vegetations. Seven measurement sites on 3 cross sections were chosen to pass through 3 karstic depressions or on the slopes of depressions. All measurement results show soils with pH values lower than 7.0 (from 5.4 to 6.6). There are 2 cases for the pH values of soil in different topographic features: the pH values of 2 profiles on the ridges or upper slopes of depressions are lower than those in the depressions; and the pH values of 2 soil profiles on the slopes of depressions are higher than those in the depressions. Most samples show relatively low humidity and CO2 contents on the ridges or slopes of depressions compared with soil profiles in the depressions. High CO2 contents occur at depths from -40 to -80 cm and high and dense grassland shows high CO2 contents in the soil atmosphere. Grass roots may grow and are distribu     

Solubility and partitioning of water in synthetic forsterite and enstatite in the system MgO–SiO2–H2O±Al2O3

The solubility of water in coexisting enstatite and forsterite was investigated by simultaneously synthesizing the two phases in a series of high pressure and temperature piston cylinder experiments. Experiments were performed at 1.0 and 2.0 GPa at temperatures between 1,100 and 1,420°C. Integrated OH absorbances were determined using polarized infrared spectroscopy on orientated single crystals of each phase. Phase water contents were estimated using the calibration of Libowitzky and Rossman (Am Mineral 82:1111–1115, 1997). Enstatite crystals, synthesized in equilibrium with forsterite and an aqueous phase at 1,350°C and 2.0 GPa, contain 114 ppm H₂O. This is reduced to 59 ppm at 1,100°C, under otherwise identical conditions, suggesting a strong temperature dependence. At 1,350°C and 1.0 GPa water solubility in enstatite is 89 ppm, significantly lower than that at 2.0 GPa. In contrast water solubility in forsterite is essentially constant, being in the range 36–41 ppm for all conditions studied. These data give partition coefficients in the range 2.28–3.31 for all experiments at 1,350°C and 1.34 for one experiment at 1,100°C. The incorporation of Al₂O₃ in enstatite modifies the OH stretching spectrum in a systematic way, and slightly increases the water solubility.