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1.
Here we characterize the magnetic properties of the Chelyabinsk chondrite (LL5, S4, W0) and constrain the composition, concentration, grain size distribution, and mineral fabric of the meteorite's magnetic mineral assemblage. Data were collected from 10 to 1073 K and include measurements of low‐field magnetic susceptibility (χ0), the anisotropy of χ0, hysteresis loops, first‐order reversal curves, Mössbauer spectroscopy, and X‐ray microtomography. The REM and REM′ paleointensity protocols suggest that the only magnetizations recorded by the chondrite are components of the Earth's magnetic field acquired during entry into our planet's atmosphere. The Chelyabinsk chondrite consists of light and dark lithologies. Fragments of the light lithology show logχ0 = 4.57 ± 0.09 (s.d.) (n = 135), while the dark lithology shows 4.65 ± 0.09 (n = 39) (where χ0 is in 10?9 m3 kg?1). Thus, Chelyabinsk is three times more magnetic than the average LL5 fall, but is similar to a subgroup of metal‐rich LL5 chondrites (Paragould, Aldsworth, Bawku, Richmond) and L/LL5 chondrites (Glanerbrug, Knyahinya). The meteorite's room‐temperature magnetization is dominated by multidomain FeNi alloys taenite and kamacite (no tetrataenite is present). However, below approximately 75 K remanence is dominated by chromite. The metal contents of the light and dark lithologies are 3.7 and 4.1 wt%, respectively, and are based on values of saturation magnetization.  相似文献   
2.
Detailed lithological, biogeochemical and molecular biological analyses of core sediments collected in 2002–2006 from the vicinity of the Malenky mud volcano, Lake Baikal, reveal considerable spatial variations in pore water chemical composition, with total concentrations of dissolved salts varying from 0.1 to 1.8‰. Values of methane δ13С in the sediments suggest a biogenic origin (δ13Сmin. ?61.3‰, δ13Сmax. ?72.9‰). Rates of sulphate reduction varied from 0.001 to 0.7 nmol cm?3 day?1, of autotrophic methanogenesis from 0.01 to 2.98 nmol CH4 cm?3 day?1, and of anaerobic oxidation of methane from 0 to 12.3 nmol cm?3 day?1. These results indicate that methanogenic processes dominate in gas hydrate-bearing sediments of Lake Baikal. Based on clone libraries of 16S rRNA genes amplified with Bacteria- and Archaea-specific primers, investigation of microbial diversity in gas hydrate-bearing sediments revealed bacterial 16S rRNA clones classified as Deltaproteobacteria, Gammaproteobacteria, Chloroflexi and OP11. Archaeal clone sequences are related to the Crenarchaeota and Euryarchaeota. Baikal sequences of Archaea form a distinct cluster occupying an intermediate position between the marine groups ANME-2 and ANME-3 of anaerobic methanotrophs.  相似文献   
3.
We investigated the molecular composition (methane, ethane, and propane) and stable isotope composition (methane and ethane) of hydrate-bound gas in sediments of Lake Baikal. Hydrate-bearing sediment cores were retrieved from eight gas seep sites, located in the southern and central Baikal basins. Empirical classification of the methane stable isotopes (δ13C and δD) for all the seep sites indicated the dominant microbial origin of methane via methyl-type fermentation; however, a mixture of thermogenic and microbial gases resulted in relatively high methane δ13C signatures at two sites where ethane δ13C indicated a typical thermogenic origin. At one of the sites in the southern Baikal basin, we found gas hydrates of enclathrated microbial ethane in which 13C and deuterium were both highly depleted (mean δ13C and δD of –61.6‰ V-PDB and –285.4‰ V-SMOW, respectively). To the best of our knowledge, this is the first report of C2 δ13C–δD classification for hydrate-bound gas in either freshwater or marine environments.  相似文献   
4.
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5.
This study reports measurements of the Raman spectra of Lake Baikal gas hydrates and estimations of the hydration number of methane-rich samples. The hydration number of gas hydrates retrieved from the southern Baikal Basin (crystallographic structure I) was approx. 6.1. Consistent with previous results, the Raman spectra of gas hydrates retrieved from the Kukuy K-2 mud volcano in the central Baikal Basin indicated the existence of crystallographic structures I and II. Measurements of the dissociation heat of Lake Baikal gas hydrates by calorimetry (from the decomposition of gas hydrates to gas and water), employing the hydration number, revealed values of 53.7–55.5?kJ?mol–1 for the southern basin samples (structure I), and of 54.3–55.5?kJ?mol–1 for the structure I hydrates and 62.8–64.2?kJ?mol–1 for the structure II hydrates from the Kukuy K-2 mud volcano.  相似文献   
6.
Lithology and Mineral Resources - We studied the composition and isotopic characteristics (δ13C and δD) of hydrocarbon gases from the Kotelnikovsky, Zmeiny, and Goryachnisky hot springs...  相似文献   
7.
We report on the isotopic composition of dissolved inorganic carbon (DIC) in pore-water samples recovered by gravity coring from near-bottom sediments at gas hydrate-bearing mud volcanoes/gas flares (Malenky, Peschanka, Peschanka 2, Goloustnoe, and Irkutsk) in the Southern Basin of Lake Baikal. The δ13C values of DIC become heavier with increasing subbottom depth, and vary between ?9.5 and +21.4‰ PDB. Enrichment of DIC in 13C indicates active methane generation in anaerobic environments near the lake bottom. These data confirm our previous assumption that crystallization of carbonates (siderites) in subsurface sediments is a result of methane generation. Types of methanogenesis (microbial methyl-type fermentation versus CO2-reduction) were revealed by determining the offset of δ13C between dissolved CH4 and CO2, and also by using δ13C and δD values of dissolved methane present in the pore waters. Results show that both mechanisms are most likely responsible for methane generation at the investigated locations.  相似文献   
8.
Petroleum potential of Baikal deposits   总被引：1，自引：0，他引：1  
We analyzed oils, gases, and bitumens of bottom sediments from natural shows on the southeastern shore of Lake Baikal, in the mouth of the Stvolovaya River near Capes Tolstyi and Gorevoi Utes. Based on a set of geological data, we have established that: (1) the lake oils underwent biodegradation to a variable degree: “Fresh” nondegraded paraffin oil floats up near Cape Gorevoi Utes; in the mouth of the Stvolovaya River and near Cape Tolstyi, aromatic-naphthene oil lacks n-alkanes, monomethyl alkanes, and acyclic isoprenoids; (2) Cenozoic oil originated from the organic matter of fresh-water basins with significant amounts of higher land plant remains, including angiosperm plants (oleanane), which suggests the lake or delta genesis of oil source formations of Cretaceous and younger ages. Judging from the carbon isotope composition (average δ13C = −43.84‰), methane from the bottom sediments near Cape Gorevoi Utes is catagenetic. The initial in-place resources in the Baikal sedimentary basins are estimated by the volumetric-statistical method at 500 mln tons of equivalent hydrocarbons.  相似文献   
9.
We propose a new type of earthquake precursor based on the analysis of correlation dynamics between geophysical signals of different nature. The precursor is found using a two-parameter cross-correlation function introduced within the framework of flicker-noise spectroscopy, a general statistical physics approach to the analysis of time series. We consider an example of cross-correlation analysis for water salinity time series, an integral characteristic of the chemical composition of groundwater, and geoacoustic emissions recorded at the G-1 borehole on the Kamchatka peninsula in the time frame from 2001 to 2003, which is characterized by a sequence of three groups of significant seismic events. We found that cross-correlation precursors took place 27, 31, and 35 days ahead of the strongest earthquakes for each group of seismic events, respectively. At the same time, precursory anomalies in the signals themselves were observed only in the geoacoustic emissions for one group of earthquakes.  相似文献   
10.
Regime observations 017 the zoobenthos state in the Balagansk transect in 1971, 1972 and in the Odissa bay in 1987-1993 of the Bratsk Reservoir were conducted.In 1991-1993 there is a change in the zoobenthos structure of the Bratsk Reservoir. In the depth zone of 0-5 m in the Balagansk transect in 1971-1972 the bottom community was considered as Gammaridae-Chiro-nomodae, in 1991 as Gammaridae-Ephemeroptera in 1992-1993 as Chironomidae-Ephemeroptera-Gammaridae. As compared with 1968-1972 the importance of Gammaridae decreased and the role of Ephemeroptera increased in the zoobenthos structure in 1991-1993.Changes were noted in the species composition of the Ologochaeta fauna and increase of the role of Oligochaeta in the zoobenthos in 1991-1993 as compared with 1965-1972.During all studies Chironomidae played a significant role in the zoobenthos. Since 1989 Paratanytarsus baialensis, bailialian endemic, has occurred in the Chironomidae fauna.The comparison of zoobenthos has shown that aver-age number and biomass of bortom invertebrates by 3-6 times and species diversity by 2.25 are higher^ in the Odissa bay than in the Balagansk transect.  相似文献   
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