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61.
A. A. Makhnach B. G. Pokrovsky O. V. Murashko O. L. Petrov 《Lithology and Mineral Resources》2020,55(1):24-35
The behavior of stable carbon and oxygen isotopes in carbonates during the deposition and diagenesis of sediments in the bioproductive Upper Famennian Pripyat Trough (southern Belarus) is discussed. Limestones and clayey limestones (Corg 0.92 ± 0.11%) are characterized by very low δ13C values (–9.6 ± 0.3‰). Parental sediments of these rocks were deposited in the shallow-water zone during slow downwarping episodes of the seafloor. Lithification of the sediments took place in oxidative conditions of the diagenesis zone. Organic matter was actively oxidized by free oxygen. Carbon dioxide with isotopically light organic carbon formed in this process was used during the crystallization of diagenetic carbonates that are visually indiscernible from the sedimentational variety. Marls, clayey marls, and carbonate-bearing clays (Corg 6.02 ± 0.80%) are characterized by δ13C values as high as –3.5 ± 0.6‰. In combustible shales (Corg >10%), δ13C value is ‒1.2 ± 0.6‰). The clayey rocks mark the episodes of sedimentation in relatively deep-water conditions that appear during the uncompensated sagging of the basin floor. The diagenetic zone with free oxygen was significantly decreased or absent at all. Here, oxygen of marine sulfates was the main or single oxidizer of organic matter (sulfate reduction). The sulfate oxygen is a weaker oxidizing agent than free oxygen. Therefore, much more organic matter was retained and fossilized in clayey rocks than in carbonate rocks. Organic carbon released during the sulfate reduction and mobilized later for the diagenetic carbonate formation was insufficient for the significant decrease of δ13C values relative to the marine carbonate standard. Isotopic composition of carbonate oxygen in the studied rocks is invariable and does not depend on the content of clay and organic matter. In these rocks, δ18O values are at the level (approximately –5‰) shown for the Famennian in the Global Chemostratigraphic Chart. This fact is consistent with the supposition that oxygen isotope composition of atmospheric precipitates, which influenced the rock formation via continental flow, is close to that of sea water in low latitudes where the territory of Belarus was located in the Late Devonian. 相似文献
62.
In 13 out of 14 samples of carbonate xenoliths from mud volcanic breccias of Azerbaijan, the 87Sr/86Sr values (0.70675–0.70823, 87Sr/86Srmd = 0.7073 ± 0.0005) are within the same limits as in the volcanic waters (Bujakaite et al., 2019). Genetically, they can be associated both with Mesozoic carbonate and saline deposits or with Cenozoic volcanosedimentary strata. Similarity of the Sr isotopic composition with isotopic values in carbonate extracts from terrigenous rocks of the Maikop Formation was noted only in the calcite sample from the Cheildag Volcano (87Sr/86Sr = 0.71047). The most interesting results with the lowest Sr ratios were obtained for carbonate fragments from breccias of the Byandovan Volcano. The combination of low δ13C values (down to –49.2‰), high Sr contents (up to 3108 μg/g) and 87Sr/86Sr (0.70675‒0.70690) values typical of the Late Jurassic brings them closer to caprocks of salt domes of Jurassic oil-bearing formations in the western United States. 相似文献
63.
Lithology and Mineral Resources - The results of lithological, petrographic, and C–O isotope studies of various types of the diagenetic and postdiagenetic carbonate cement in silty mudstones,... 相似文献
64.
V. I. Vinogradov G. A. Belenitskaya B. G. Pokrovsky M. I. Bujakaite 《Lithology and Mineral Resources》2011,46(1):71-84
Isotopic compositions of carbon and oxygen in carbonates and sulfur in sulfates of the Verkhnyaya Lena Formation (ε2–ε3), which terminates the Cambrian section of the Irkutsk Amphitheater of the Siberian Craton, are studied. Sulfates of the Verkhnyaya Lena Formation are marked by unusually low δ34S values (4.6–12.0‰) relative to sulfates of the underlying Angara Formation. This is likely caused by variations in the facies-paleogeographic sedimentation at the transition of the Angara and Verkhnyaya Lena formations, as well as associated variations in the water and salt alimentation budget in sedimentation basins, due to their isolation from open sea and intensification of the continental and underground discharge. The δ18O(PDB) value in carbonates decreases from ?4.4‰ at bottom to ?10.4‰ at top, reflecting variation in postsedimentary transformations and probable continuous freshening of sedimentation basin. Isotopic composition of carbon in most samples shows normal marine δ13C values (0 ± 1‰). Only in some samples, does the δ13C value increase up to ?3.8 and 2.2‰ due to specific features of postsedimentary processes. The Rb-Sr systems of the clayey component of marls from the 500-m-thick section of the Angara Formation and bottom of the Verkhnyaya Lena Formation record an age of 512 ± 10 Ma, which is close to the assumed stratigraphic age of the Verkhnyaya Lena Formation. The 87Sr/86Sr initial ratio is 0.7082 ± 0.0004. 相似文献
65.
O.S. Pokrovsky R.E. Martinez S.V. Golubev E.I. Kompantseva L.S. Shirokova 《Applied Geochemistry》2008
The purpose of the present work is to extend our knowledge of metal–cyanobacteria interactions and to contribute to the database on adsorption parameters of aquatic microorganisms with respect to metal pollutants. To this end, the surface properties of the cyanobacteria (Gloeocapsa sp. f-6gl) were studied using potentiometric acid–base titration methods and ATR-FTIR (attenuated total reflection infrared) spectroscopy. The electrophoretic mobility of viable cells was measured as a function of pH and ionic strength (0.01 and 0.1 M). Surface titrations at 0.01–1.0 M NaCl were performed using limited residence time reactors (discontinuous titration) with analysis of Ca, Mg and dissolved organic C for each titration point in order to account for alkali-earth metal–proton exchange and cell degradation, respectively. Results demonstrate that the cell-wall bound Ca and Mg from the culture media contribute to the total proton uptake via surface ion-exchange reactions. This has been explicitly taken into account for net proton balance calculations. Adsorption of Zn, Cd, Pb and Cu was studied at 25 °C in 0.01 M NaNO3 as a function of pH and metal concentration. The proportion of adsorbed metal increases as a function of culture age with cells of 44 days old having the largest adsorption capacities. A competitive Langmuir sorption isotherm in conjunction with a linear programming method (LPM) was used to fit experimental data and assess the number of surface sites and adsorption reaction constants involved in the binding of metals to the cyanobacteria surface. These observations allowed the determination of the identity and concentration of the major surface functional groups (carboxylate, amine, phosphoryl/phosphodiester and hydroxyl) responsible for the amphoteric behavior of cyanobacterial cell surfaces in aqueous solutions and for metal adsorption. Results of this work should allow better optimizing of metal bioremediation/biosequestration processes as they help to define the most efficient range of pH, cell biomass and duration of exposure necessary for controlled metal adsorption on cyanobacteria cultures. It follows from comparison of adsorption model parameters between different bacteria that technological application of cyanobacteria in wastewater bioremediation can be as efficient as other biological sorbents. 相似文献
66.
B.B. Kochnev B.G. Pokrovsky A.B. Kuznetsov V.V. Marusin 《Russian Geology and Geophysics》2018,59(6):585-605
We propose a detailed δ13C curve for the Vendian and Lower Cambrian (Tommotian) strata of the central Siberian Platform. Two positive carbon isotope excursions identified near the base of the Yuryakh Formation (up to 5.5‰) and in the lower Bilir Formation (up to 5‰) are assigned to the lowermost and middle Tommotian, respectively. This correlation is supported by paleontological data, specific 87Sr/86Sr values (0.70845-0.70856), and similar C isotope record in coeval Early Cambrian basins. The documented minor vertical oscillations (a few meters) of these isotope excursions relative to the formation boundaries in remote boreholes is presumably caused by the spatiotemporal migration of facies. A high-amplitude negative δ13C excursion (-8 to -11‰) in the upper Nepa Regional Stage putatively corresponds to the global Shuram-Wonoka negative carbon isotope excursion (Middle Ediacaran). Carbonates of the lower Nepa Regional Stage (Besyuryakh Formation) demonstrate positive δ13C values (up to 5‰) and minimum 87Sr/86Sr ratios of 0.70796-0.70832. The C and Sr isotope record of the Nepa Regional Stage provides its robust correlation with the Dal’nyaya Taiga and Zhuya Groups of the Patom Foredeep. Micropaleontological data herein reported and glacial diamictites documented at the base of the Vendian sedimentary cover both in the central Patom Foredeep and on its periphery suggest a full stratigraphic volume of the Ediacaran System in the most stratigraphically complete sections of the central Siberian Platform. 相似文献
67.
O.S. Pokrovsky A. Feurtet-Mazel R.E. Martinez S. Morin M. Baudrimont T. Duong M. Coste 《Applied Geochemistry》2010
This study addresses the interaction of Cd with natural biofilms of periphytic diatoms grown during different seasons in metal-contaminated and metal-non-contaminated streams, along a tributary of the Lot River, France. Specifically, it aims to test whether the biofilms from contaminated sites have developed a protective mechanism due to high Cd exposure. Towards this goal, reversible adsorption experiments on untreated biofilms were performed in 0.01 M NaNO3 with a pH ranging from 2 to 8, Cd concentration from 0.5 to 10,000 μg/L and exposure time from 1 to 24 h. Two types of experiments, pH-dependent adsorption edge and constant-pH “Langmuirian”-type isotherms were conducted. Results were adequately modeled using a Linear Programming Model. It was found that the adsorption capacities of natural biofilm consortia with respect to Cd do not depend on season and are not directly linked to the growth environment. The biofilms grown in non-contaminated (4.6 ppb Cd in solid) and contaminated (570 ppb Cd in solid) settings exhibit similar adsorption capacities in the Cd concentration range in solution of 100–10,000 μg/L but quite different capacities at low Cd concentration (0.5–100 μg/L); unexpectedly, the non-contaminated biofilm adsorbs approximately 10 times more Cd than the contaminated one. It is therefore possible that the strong low-abundant ligands (for example, phosphoryl or sulfhydryls) are already metal-saturated on surfaces of biofilm grown in the contaminated site whereas these sites are still available for metal adsorption in samples grown in non-contaminated sites. 相似文献
68.
V. P. Shevchenko V. B. Korobov A. P. Lisitzin A. S. Aleshinskaya O. Yu. Bogdanova N. V. Goryunova I. V. Grishchenko O. M. Dara N. N. Zavernina E. I. Kurteeva E. A. Novichkova O. S. Pokrovsky F. V. Sapozhnikov 《Doklady Earth Sciences》2010,431(2):497-501
The descent of a large quantity of dust responsible for bright colors of atmospheric precipitation in the temperate, subpolar, and polar zones of the northern hemisphere is rarely observed [1–5]. In the twentieth century and in the beginning of the twenty-first century in the northern part of European Russia, such events had not been registered right up to March 25–26, 2008. At that time in some parts of the Arkhangelsk region, Komi Republic, and Nenets Autonomous Area, atmospheric precipitation as moist snow and rain responsible for sand and saffron colors of ice crust formation on the snow surface was observed. Thus, due to detailed mineralogical, geochemical, pollen, diatom, and meteorological investigations, it was established that the main source of the yellow dust is the semidesert and steppe regions of the Northwest Kazakhstan, and the Volgograd and Astrakhan regions, Kalmykia. 相似文献
69.
B. G. Pokrovsky N. M. Chumakov V. A. Melezhik M. I. Bujakaite 《Lithology and Mineral Resources》2010,45(6):577-592
The characteristic feature of many Upper Neoproterozoic glacial sequences is their “cap carbonates” (CC) resting without visible
unconformity upon glaciogenic diamictites. Such an unusual association, peculiar structures and textures, and negative δ13C values (approximately −4 ± 2‰) that are atypical of marine carbonates provoked long debates about the nature of these carbonates,
which play an important role in the Snowball Earth hypothesis. According to this hypothesis, the Earth was entirely covered
by ice during large-scale glaciations, and CC accumulation was related to the global change in geochemical processes. In this
work, we discuss data on the chemical and isotopic (C, O, Sr) compositions of CCs, which overlie glacial sediments of the
Nichatka and Bol’shoi Patom formations accumulated in different parts of the Neoproterozoic Patom paleobasin (Central Siberia).
High concentrations of Fe (up to 6400 ppm), Mn (2320 ppm), and radiogenic Sr (87Sr/86Sr0 up to 0.7172) established in CCs indicates a strong influence of the continental flow. Extraordinary Snowball Earth conditions
are not necessary for the accumulation of these rocks, geochemical and sedimentological properties of which may be explained
by the discharge of thawing waters into partly or completely isolated near-glacier basin, their intermittent freezing, and/or
washout of “frozen” carbonates from the surface of thawing glaciers. The peculiar thin-laminated texture of CC may be related
to seasonal processes of climatic cycles. They were accumulated in the course of general (relatively long-term) depletion
of the atmosphere and hydrosphere in 13C, which has nothing to do with the CC formation as a specific type of carbonate sediments. Amplitude and duration of the
negative δ13C excursion in carbonates associated with the Lower Vendian glacial sediments (665–635 Ma) are appreciably lower than the
negative anomaly in rocks of the Zhuya Group that likely correspond to the Shuram-Vonoka Event (∼560−580 Ma ago), which probably
marks the crucial point in the Precambrian deglaciation: mass destabilization of methane hydrates and degradation of the Early
Vendian psychrosphere in oceans. 相似文献
70.
Lithology and Mineral Resources - Carbon and oxygen isotope compositions were determined in the pedogenic, sedimentary, and organogenic carbonates from Upper Permian (Vyatkian Stage) and Lower... 相似文献