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31.
Hirotsugu Minami Akihiro Hachikubo Hirotoshi Sakagami Satoshi Yamashita Yusuke Soramoto Tsuyoshi Kotake Nobuo Takahashi Hitoshi Shoji Tatyana Pogodaeva Oleg Khlystov Andrey Khabuev Lieven Naudts Marc De Batist 《Geo-Marine Letters》2014,34(2-3):241-251
The isotopic and ionic composition of pure gas hydrate (GH) water was examined for GHs recovered in three gravity cores (165–193 cm length) from the Kukuy K-9 mud volcano (MV) in Lake Baikal. A massive GH sample from core St6GC4 (143–165 cm core depth interval) was dissociated progressively over 6 h in a closed glass chamber, and 11 sequentially collected fractions of dissociated GH water analyzed. Their hydrogen and oxygen isotopic compositions, and the concentrations of Cl– and HCO3 – remained essentially constant over time, except that the fraction collected during the first 50 minutes deviated partly from this pattern. Fraction #1 had a substantially higher Cl– concentration, similar to that of pore water sampled immediately above (135–142 cm core depth) the main GH-bearing interval in that core. Like the subsequent fractions, however, the HCO3 – concentration was markedly lower than that of pore water. For the GH water fractions #2 to #11, an essentially constant HCO3 –/Cl– ratio of 305 differed markedly from downcore pore water HCO3 –/Cl– ratios of 63–99. Evidently, contamination of the extracted GH water by ambient pore water probably adhered to the massive GH sample was satisfactorily restricted to the initial phase of GH dissociation. The hydrogen and oxygen isotopic composition of hydrate-forming water was estimated using the measured isotopic composition of extracted GH water combined with known isotopic fractionation factors between GH and GH-forming water. Estimated δD of ?126 to ?133‰ and δ18O of ?15.7 to ?16.7‰ differed partly from the corresponding signatures of ambient pore water (δD of ?123‰, δ18O of ?15.6‰) and of lake bottom water (δD of ?121‰, δ18O of ?15.8‰) at the St6GC4 coring site, suggesting that the GH was not formed from those waters. Observations of breccias in that core point to a possible deep-rooted water source, consistent with published thermal measurements for the neighboring Kukuy K-2 MV. By contrast, the pore waters of core St6GC4 and also of the neighboring cores GC2 and GC3 from the Kukuy K-9 MV show neither isotopic nor ionic evidence of such a source (e.g., elevated sulfate concentration). These findings constrain GH formation to earlier times, but a deep-rooted source of hydrate-forming water remains ambiguous. A possible long-term dampening of key deep-water source signatures deserves further attention, notably in terms of diffusion and/or advection, as well as anaerobic oxidation of methane. 相似文献
32.
33.
A Long-Lived Center of Gas–Fluid Emanations on the Western Slope of the Kuril Basin (Sea of Okhotsk)
Derkachev A. N. Nikolaeva N. A. Tsoy I. B. Baranov B. V. Barinov N. N. Mozherovskiy A. V. Krylov A. A. Kuznetsov A. B. Minami H. Hachikubo A. 《Lithology and Mineral Resources》2021,56(4):309-332
Lithology and Mineral Resources - The paper presents the results of multidisciplinary studies in the carbonate–barite mineralization area revealed on the western slope of the Kuril deep-water... 相似文献
34.
Isotopic composition of gas hydrates in subsurface sediments from offshore Sakhalin Island, Sea of Okhotsk 总被引:1,自引:1,他引:0
Akihiro Hachikubo Alexey Krylov Hirotoshi Sakagami Hirotsugu Minami Yutaka Nunokawa Hitoshi Shoji Tatiana Matveeva Young K. Jin Anatoly Obzhirov 《Geo-Marine Letters》2010,30(3-4):313-319
Hydrate-bearing sediment cores were retrieved from recently discovered seepage sites located offshore Sakhalin Island in the Sea of Okhotsk. We obtained samples of natural gas hydrates and dissolved gas in pore water using a headspace gas method for determining their molecular and isotopic compositions. Molecular composition ratios C1/C2+ from all the seepage sites were in the range of 1,500–50,000, while δ13C and δD values of methane ranged from ?66.0 to ?63.2‰ VPDB and ?204.6 to ?196.7‰ VSMOW, respectively. These results indicate that the methane was produced by microbial reduction of CO2. δ13C values of ethane and propane (i.e., ?40.8 to ?27.4‰ VPDB and ?41.3 to ?30.6‰ VPDB, respectively) showed that small amounts of thermogenic gas were mixed with microbial methane. We also analyzed the isotopic difference between hydrate-bound and dissolved gases, and discovered that the magnitude by which the δD hydrate gas was smaller than that of dissolved gas was in the range 4.3–16.6‰, while there were no differences in δ13C values. Based on isotopic fractionation of guest gas during the formation of gas hydrate, we conclude that the current gas in the pore water is the source of the gas hydrate at the VNIIOkeangeologia and Giselle Flare sites, but not the source of the gas hydrate at the Hieroglyph and KOPRI sites. 相似文献
35.
Xiaodong Lai Kazuhiro Norisuye Michi Mikata Tomoharu Minami Andrew R. Bowie Yoshiki Sohrin 《Marine Chemistry》2008,111(3-4):171-183
The distribution of dissolved (D) and acid-dissolvable (AD) Fe, Ni, Cu and Pb in the upper water column (0–300 m depth) was determined in the Australian sector of the Southern Ocean (140°E meridian) during three cruises conducted between November 2001 and March 2002. For Ni and Cu, there was no significant difference in concentration between dissolved and acid-dissolvable species. DNi and DCu showed significant (P = 0.01) positive correlations with silicate, phosphate and nitrate, reflecting their strong nutrient-type behaviour. For Fe and Pb, the acid-dissolvable concentration mostly exceeded the dissolved concentration, reflecting the importance of labile particulate species for these elements. DPb decreased between January and February in the Polar Frontal Zone and in Antarctic continental shelf water. ADPb maxima occurred in the Antarctic Zone, resulting in a maximum AD/D ratio of 7. The mean DFe concentration in the surface mixed layer was 0.3 nM in the sub-Antarctic zone, 0.4 nM in the Polar Frontal Zone, 0.5 nM in the Antarctic Zone and increased southward beyond the Antarctic Divergence and towards the continent. DFe did not show a clear temporal change in its horizontal distribution, which was in contrast to the other nutrients and trace metals. ADFe substantially increased in Antarctic continental shelf water where the AD/D ratio reached 11. The following conclusions can be drawn from these data. (1) Ni and Cu exist exclusively as dissolved species and their distributions are mainly controlled by their biogeochemical cycling, similar to those of the major nutrients. (2) Pb is dominated by particulate species. The distribution of DPb is temporally and spatially variable due to a sporadic source and strong scavenging. (3) DFe is rather a minor fraction of total Fe in Antarctic continental shelf water where shelf sediments and Antarctic sea-ice appear to be strong sources for Fe. There is substantial temporal variation in the supply of Fe to the upper water column. DFe in the mixed layer of the open Southern Ocean is maintained at low concentrations throughout summer due to uptake by phytoplankton and scavenging. 相似文献
36.
贝尔加湖首次发现气体水合物是1997年贝加尔钻探计划(BDP)在盆地南部海底深度121m和161m处,气体成分主要是甲烷,8δC值范围为-68.2‰~-57.6‰,表明这些气体水合物是微生物成因的。最近,在盆地南部的Malenky泥火山和盆地中部的Kukuy K-2地区海底发现气体水合物,这些站点位于抬升地形带上,并且具有流体溢出口特征。 相似文献
37.
Laboratory impact experiments were conducted for gypsum-glass bead targets simulating the parent bodies of ordinary chondrites. The effects of the chondrules included in the parent bodies on impact disruption were experimentally investigated in order to determine the impact conditions for the formation of rubble-pile bodies after catastrophic disruption. The targets included glass beads with a diameter ranging from 100 μm to 3 mm and the volume fraction was 0.6, similar to that of ordinary chondrites, which is about 0.65-0.75. Nylon projectiles with diameters of 10 mm and 2 mm were impacted at 60-180 m s−1 by a single-stage gas gun and at 4 km s−1 by a two-stage light gas gun, respectively. The impact strength of the gypsum-glass bead target was found to range from 56 to 116 J kg−1 depending on the glass bead size, and was several times smaller than that of the porous gypsum target, 446 J kg−1 in low-velocity collisions. The impact strengths of the 100 μm bead target and the porous gypsum target strongly depended on the impact velocity: those obtained in high-velocity collisions were several times greater than those obtained in low-velocity collisions. The velocities of fragments ejected from two corners on the impact surface of the target, measured in the center of the mass system, were slightly dependent on the target materials, irrespective of impact velocity. These results suggest that chondrule-including planetesimals (CiPs) can reconstruct rubble-pile bodies in catastrophic disruptions at the size of the planetesimal smaller than that of planetesimals without chondrules. 相似文献
38.
To improve the scaling parameter controlling the impact crater formation in the strength regime, we conducted impact experiments on sintered snow targets with the dynamic strength continuously changed from 20 to 200 kPa, and the largest crater size formed on small icy satellites was considered by using the revised scaling parameter. Ice and snow projectiles were impacted on a snow surface with 36% porosity at an impact velocity from 31 m s−1 to 150 m s−1. The snow target was sintered at the temperature from −5 °C to −18 °C, and the snow dynamic strength was changed with the sintering duration at each temperature. We found that the mass ejected from the crater normalized by the projectile mass, πV, was related to the ratio of the dynamic strength to the impact pressure, , as follows: , where the impact pressure was indicated by P = ρtC0tvi/2 with the target density of ρt, when the impact velocity, vi, was much smaller than the bulk sound velocity C0t (typically 1.8 km s−1 in our targets). The ratio of the largest crater diameter to the diameter of the target body, dmax/D, was estimated by calculating the crater diameter at the impact condition for catastrophic disruption and then compared to the observed dmax/D of jovian and saturnian small satellites, in order to discuss the formation condition of these large dmax/D in the strength regime. 相似文献
39.
40.
Abstract— We examined an improved system for extraction of carbon from meteorites, using a vacuum‐tight RF melting method. Meteorite samples mixed with an iron combustion accelerator, including a specific amount of carbon (0.052%), were combusted in a RF furnace (LECO HF‐10). 14CO2 extracted from the meteorite was diluted with a known amount of nearly 14C‐free CO2, evolved from the iron accelerator on combustion. The 14C activities of the recently fallen Holbrook (L6) and Mt. Tazerzait (L5) meteorites were measured by this method. The mean value was 56.5 ± 3.0 dpm/kg, which is similar to the values reported for recently fallen L6 chondrites. Furthermore, terrestrial ages were measured for four Antarctic meteorites: 1.8 ± 0.5 kyr for Yamato (Y‐) 75097 (L6), 1.8 ± 0.5 kyr for Y‐75108 (L6), and 0.1 ± 0.1 kyr for Y‐74192 (H5). For Y‐74190 (L6), an apparent age of 0.8 ± 0.5 kyr was calculated. After consideration of the shielding effect by using 22Ne/21Ne values, we obtained about 1.8 kyr for the terrestrial age of this chondrite. The five samples Y‐74190, Y‐75097, and Y‐75108, together with Y‐75102 (L6) and Y‐75271 (L6), have been reported to be paired and fragments of an L‐chondrite shower (Honda 1981; Takaoka 1987). The result of this work and literature data for the latter two samples confirmed that they are paired. More discussion and experimental work are needed for other recently fallen meteorites, both for L and H chondrites, and a correction for the shielding effect should be done to determine a more reliable terrestrial age. 相似文献