Crystallization of authigenic carbonates in mud volcanoes at Lake Baikal   总被引：1，自引：0，他引：1  

A. A. Krylov  O. M. Khlystov  T. I. Zemskaya  H. Minami  A. Hachikubo  H. Shoji  M. Kida  T. P. Pogodaeva  L. Naudts  J. Poort 《Geochemistry International》2008,46(10):985-995

This paper presents data on authigenic siderite first found in surface sediments from mud volcanoes in the Central (K-2) and Southern (Malen’kii) basins of Lake Baikal. Ca is the predominant cation, which substitutes Fe in the crystalline lattice of siderite. The enrichment of the carbonates in the ¹³C isotope (from +3.3 to +6.8‰ for the Malen’kii volcano and from +17.7 to +21.9‰ for K-2) results from the crystallization of the carbonates during methane generation via the bacterial destruction of organic matter (acetate). The overall depletion of the carbonates in ¹⁸O is mainly inherited from the isotopic composition of Baikal water.  相似文献   

Remote sensing and surface POC concentration in the South Atlantic   总被引：1，自引：0，他引：1  

Alexey V. Mishonov  Wilford D. Gardner  Mary Jo Richardson 《Deep Sea Research Part II: Topical Studies in Oceanography》2003,50(22-26):2997

Several SeaWiFS products have been compared with shipboard data to assess the possibility of using remote sensing to estimate particulate organic carbon (POC) concentration in surface waters. Transmissometer data were collected during six South Atlantic Ventilation Experiment (SAVE) hydrographic expeditions conducted between November 1987 and March 1989 from R/V Knorr, and Melville. A total of 361 beam attenuation profiles were made with a SeaTech transmissometer interfaced with a CTD/rosette. In order to calculate the POC concentration from transmissometer profiles, a regression between beam attenuation and POC for open Atlantic Ocean waters derived from our research in the North Atlantic (North Atlantic Bloom Experiment, NABE) and enhanced by data from the Bermuda Atlantic Time Series Station (BATS) was applied. The profiles were processed and examined as vertical sections of the surface 250 m. The data were collected in two successive years, during the same season, which allowed us to compile a combined data set over the austral summer for examination. Beam attenuation/POC concentrations were integrated down to one attenuation depth with the intent of making comparisons with satellite optical data. No satellite optical data were available for 1987–1989, so the only option was to compare our integrated data with SeaWiFS-derived variables from later years averaged over the same season as SAVE data. Analysis of four SeaWiFS products acquired from 1997 to 2002 demonstrated very low variations from year to year for seasonally averaged data, suggesting that making comparisons of the beam attenuation/POC fields with averaged satellite optical products from later years is a valid (though not optimal) approach for this area. The highest correlation between beam attenuation/POC concentration and remotely derived products was found with normalized water-leaving radiance at 555 nm. Other SeaWiFS-derived variables—chlorophyll concentration, diffuse attenuation coefficient at 490 nm and integral chlorophyll (integrated over one attenuation depth)—were also compared but showed a slightly less satisfactory correlation.  相似文献   

Impact of the North Atlantic Oscillation on Middle Eastern Climate and Streamflow   总被引：6，自引：0，他引：6  

Heidi M. Cullen  Alexey Kaplan  Phillip A. Arkin  Peter B. deMenocal 《Climatic change》2002,55(3):315-338

Interannual to decadal variations in Middle Eastern temperature, precipitationand streamflow reflect the far-field influence of the North Atlantic Oscillation (NAO), a dominant mode of Atlantic sector climate variability. Using a new sea surface temperature (SST) based index of the NAO and availablestreamflow data from five Middle Eastern rivers, we show that the first principal component of December through March streamflow variability reflects changes in the NAO. However, Middle East rivers have two primary flooding periods.The first is rainfall-driven runoff from December through March, regulated on interannual to decadal timescales by the NAO as reflected in local precipitation and temperature.The second period, from April through June, reflects spring snowmelt and contributes in excess of 50% of annual runoff.This period, known locally as the khamsin, displays no significantNAO connections and a less direct relationship with local climatic factors, suggesting that streamflow variability during this period reflects land-cover change, possibly related to agriculture and hydropower generation, and snowmelt.  相似文献   

Amplitude—Phase Characteristics of the Annual Cycle of Surface Air Temperature in the Northern Hemisphere   总被引：2，自引：0，他引：2  

Alexey V.ELISEEV  Igor I. MOKHOV 《大气科学进展》2003,20(1):1-16

The amplitude-phase characteristics(APC)of surface air temperature(SAT)annual cycle(AC)in the Northern Hemisphere are analyzed.From meteorological observations for the 20th century and meteorological reanalyses for its second half,it is found that over land negative correlation of SAT ACamplitude with annual mean SAT dominates.Nevertheless,some exceptions exist.The positive correlationbetween these two variables is found over the two desert regions:in northern Africa and in Central America.Areas of positive correlations are also found for the northern Pacific and for the tropical Indian and PacificOceans.Southward of the characteristic annual mean snow-ice boundary (SIB) position,the shape ofthe SAT AC becomes more sinusoidal under climate warming.In contrast,northward of it,this shapebecomes less sinusoidal.The latter iS also found for the above-mentioned two desert regions.In theFar East(southward of about 50°N),the SAT AC shifts as a whole:here its spring and autumn phasesoccur earlier if the annual  相似文献   

Prolonged postcollisional shoshonitic magmatism in the southern Svecofennian domain – a case study of the Åva granite–lamprophyre ring complex     

Olav Eklund  Alexey Shebanov 《Lithos》2005,80(1-4):229-247

The Åva ring complex is one of four Paleoproterozoic postcollisional shoshonitic ring complexes in southwestern Finland. It is composed of ring dykes of K-feldspar megacryst-bearing granite, mingled in places with a shoshonitic monzonite, and lamprophyre dykes crosscutting all the rocks in a radial pattern. A survey was undertaken to trace the magma chamber beneath the ring complex to date it and measure some intensive parameters to clarify the crystallisation conditions at depth before the granite was emplaced in the upper crust. Mineral separates were extracted from the core zones of K-feldspar megacrysts in the granite, heavy mineral fractions (including zircons) from these separates were used for P-T assessment and age determinations, and the results were compared to data obtained from bulk rock samples. It appears that magma differentiation took place in a midcrustal magma chamber (at 4 to 7 kbar) possibly 30 Ma before the emplacement of the ring complex in the upper crust (deep assemblage 1790 Ma, shallow assemblage 1760 Ma). Relatively high activity of the alkalies and a low oxygen fugacity characterised the midcrustal chamber. The juvenile Svecofennian crust was invaded by shoshonitic magmas from an enriched lithospheric mantle over a long period of time. Some of these magmas were stored and differentiated in the middle crust before transportation to the upper crust. The results also show that coarse-grained granites may provide evidence for several magmatic evolutionary episodes, e.g., differentiation and crystallisation in different environments prior to final emplacement.  相似文献   

AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?     

Florian Sévellec  Alexey V. Fedorov 《Climate Dynamics》2016,47(5-6):1497-1513

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Verification of the multi-chamber model of radioactivity migration in reservoirs     

A. L. Krylov  A. V. Nosov  V. P. Kiselev 《Russian Meteorology and Hydrology》2016,41(5):344-350

A multi-chamber model of radioactivity migration in reservoirs was developed. It describes transport of radioactive substances in water and in bed sediments taking into account sorbtion of radionuclides on suspended particles. The model provides higher resolution than simplified chamber models do. At the same time, unlike complex two- or three-dimensional dynamic models, it does not require hard-to-obtain data such as detailed data on bathymetry, currents and winds. The model was included into the Sybilla program code that was developed in the framework of the Rosatom project called PRORYV. The model was verified against the observed data on the contamination of the Kiev Reservoir with ¹³⁷Cs in 1986.  相似文献   

Upper mantle density in Europe and the North Atlantic region     

Alexey Shulgin  Irina Artemieva 《《地质学报》英文版》2018,92(Z1):106-106

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Sapphirine-Bearing Ultrahigh-Temperature Granulites of the Anabar Shield: Chemical Composition,U–Pb Zircon Ages,and <Emphasis Type="Italic">P</Emphasis>–<Emphasis Type="Italic">T</Emphasis> Conditions of Metamorphism     

A. D. Nozhkin  I. I. Likhanov  K. A. Savko  V. V. Reverdatto  A. A. Krylov 《Doklady Earth Sciences》2018,479(1):347-351

The results of thermobarometry yielded the P–T parameters of formation and evolution of sapphirine- bearing granulites in the Anabar shield with peak values of UHT metamorphism in the range of T = 920–1000°C at P = 9–11 kbar. Isotope–geochronological data indicate a polymetamorphic evolution of these rocks. Detrital zircon cores in the center of crystals yielded ages of 3.36, 2.75, 2.6, and 2.5 Ga. Later, superimposed metamorphic transformations of the detrital zircon formed rims dated to 2.4, 2.3, 2.2, and 1.83 Ga. A potential provenance source of the detrital zircons could be hypersthene plagiogneisses and metabasics of the Daldyn Group with a premetamorphic age no less than 3.32 Ga and products of their metamorphism of about 2.7 Ga old.  相似文献   

Authigenic rhodochrosite from a gas hydrate-bearing structure in Lake Baikal     

Krylov  Alexey A.  Hachikubo  Akihiro  Minami  Hirotsugu  Pogodaeva  Tatyana V.  Zemskaya  Tamara I.  Krzhizhanovskaya  Mariya G.  Poort  Jeffrey  Khlystov  Oleg M. 《International Journal of Earth Sciences》2018,107(6):2011-2022

International Journal of Earth Sciences - Early diagenetic carbonates are rare in Lake Baikal. Siderite (Fe carbonate) concretions in the sediments were discovered only recently. Here, we discuss...  相似文献