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51.
52.
Mineralogy of the Boroo Gold Deposit in the North Khentei Gold Belt,Central Northern Mongolia 下载免费PDF全文
Mineral assemblages and chemical compositions of ore minerals from the Boroo gold deposit in the North Khentei gold belt of Mongolia were studied to characterize the gold mineralization, and to clarify crystallization processes of the ore minerals. The gold deposit consists of low‐grade disseminated and stockwork ores in granite, metasedimentary rocks and diorite dikes. Moderate to high‐grade auriferous quartz vein ores are present in the above lithological units. The ore grades of the former range from about 1 to 3 g/t, and those of the latter from 5 to 10 g/t, or more than 10 g/t Au. The main sulfide minerals in the ores are pyrite and arsenopyrite, both of which are divisible into two different stages (pyrite‐I and pyrite‐II; arsenopyrite‐I and arsenopyrite‐II). Sphalerite, galena, chalcopyrite, and tetrahedrite are minor associated minerals, with trace amounts of bournonite, boulangerite, geerite, alloclasite, native gold, and electrum. The ore minerals in the both types of ores are variable in distribution, abundance and grain size. Four modes of gold occurrence are recognized: (i) “invisible” gold in pyrite and arsenopyrite in the disseminated and stockwork ores, and in auriferous quartz vein ores; (ii) microscopic native gold, 3 to 100 µm in diameter, that occurs as fine grains or as an interstitial phase in sulfides in the disseminated and stockwork ores, and in auriferous quartz vein ores; (iii) visible native gold, up to 1 cm in diameter, in the auriferous quartz vein ores; and (iv) electrum in the auriferous quartz vein ores. The gold mineralization of the disseminated and stockwork ores consists of four stages characterized by the mineral assemblages of: (i) pyrite‐I + arsenopyrite‐I; (ii) pyrite‐II + arsenopyrite‐II; (iii) sphalerite + galena + chalcopyrite + tetrahedrite + bournonite + boulangerite + alloclasite + native gold; and (iv) native gold. In the auriferous quartz vein ores, five mineralization stages are defined by the following mineral assemblages: (i) pyrite‐I; (ii) pyrite‐II + arsenopyrite; (iii) sphalerite + galena + chalcopyrite; (iv) Ag‐rich tetrahedrite‐tennantite + bournonite + geerite + native gold; and (v) electrum. The As–Au relations in pyrite‐II and arsenopyrite suggest that gold detected as invisible gold is mostly attributed to Au+1 in those minerals. By applying the arsenopyrite geothermometer to arsenopyrite‐II in the disseminated and stockwork ores, crystallization temperature and logfs2 are estimated to be 365 to 300 °C and –7.5 to –10.1, respectively. 相似文献
53.
Hiroaki Matsuo Masahide Kawano Koji Omori Kiyonori Nakajima Ichiro Takeuchi 《Marine pollution bulletin》2009,58(11):1615-1623
Organisms collected from a coastal ecosystem in Japan were analyzed for concentrations of 205 polychlorinated biphenyls (PCBs) congeners; analyses were guided by δ13C and δ15N measurements. The regression slopes of log PCB concentration on δ15N value are regarded as indices of biomagnification in food webs. The slope (wet weight basis) of ΣPCBs was +0.104; the slope (lipid weight basis) was close to zero. Lipid content increased from 0.06% in a primary producer to 8.32% in the highest trophic level consumer. Hence, biomagnification of ΣPCBs (wet weight basis) can be attributed to increase of lipid content through the food web. For most of the congeners, the slopes (wet weight basis) exceeded those (lipid weight basis) by ca. 0.10. Slopes increased with increasing PCB chlorination levels between chlorine numbers 1–6; slopes decreased at higher chlorination levels. This decrease is likely caused by a decrease in membrane permeability with increasing molecular weight. 相似文献
54.
Reiko Matsumoto Nguyen Phuc Cam Tu Shinsuke Haruta Masahide Kawano Ichiro Takeuchi 《Marine pollution bulletin》2014
We collected two subspecies of masu salmon: Oncorhynchus masou masou from four localities (southern Sea of Japan northward to Hokkaido) and O. masou ishikawae from upstream from Ise Bay close to a heavy industrial area. All 209 PCB congeners were analyzed using HRGC/HRMS. PCA ordination of congener concentrations divided data into three groups: (i) ssp. masou from Hokkaido, (ii) ssp. masou from the other regions and (iii) ssp. ishikawae. The highest ∑ PCB concentration (40.39 ng/wet wt) was in ssp. ishikawae followed by ssp. masou from southern waters; however the TEQdioxin-like PCBs was highest in ssp. masou from southern water (1.96 pg-TEQdioxin-like PCBs/g wet wt.) due to the high proportion of congener #126 in its complement (#126 has the highest toxic equivalency factor among congeners). There is likely a contamination source offshore in the southern Sea of Japan and/or along the migratory route of ssp. masou. 相似文献
55.
Steric sea level changes estimated from historical ocean subsurface temperature and salinity analyses 总被引:13,自引:0,他引:13
Masayoshi Ishii Masahide Kimoto Kenji Sakamoto Sin-Iti Iwasaki 《Journal of Oceanography》2006,62(2):155-170
An historical objective analysis of subsurface temperature and salinity was carried out on a monthly basis from 1945 to 2003
using the latest observational databases and a sea surface temperature analysis. In addition, steric sea level changes were
mainly examined using outputs of the objective analyses. The objective analysis is a revised version of Ishii et al. and is
available at 16 levels in the upper 700 m depth. Artificial errors in the previous analysis during the 1990s have been worked
out in the present analysis. The steric sea level computed from the temperature analysis has been verified with tide gauge
observations and TOPEX/Poseidon sea surface height data. A correction for crustal movement is applied for tide gauge data
along the Japanese coast. The new analysis is suitable for the discussion of global warming. Validation against the tide gauge
reveals that the amplitude of thermosteric sea level becomes larger and the agreement improves in comparison with the previous
analysis. A substantial part of local sea level rise along the Japanese coast appears to be explained by the thermosteric
effect. The thermal expansion averaged in all longitudes from 60°S to 60°N explains at most half of recent sea level rise
detected by satellite observation during the last decade. Considerable uncertainties remain in steric sea level, particularly
over the southern oceans. Temperature changes within MLD make no effective contribution to steric sea level changes along
the Antarctic Circumpolar Current. According to statistics using only reliable profiles of the temperature and salinity analyses,
salinity variations are intrinsically important to steric sea level changes in high latitudes and in the Atlantic Ocean. Although
data sparseness is severe even in the latest decade, linear trends of global mean thermosteric and halosteric sea level for
1955 to 2003 are estimated to be 0.31 ± 0.07 mm/yr and 0.04 ± 0.01 mm/yr, respectively. These estimates are comparable to
those of the former studies. 相似文献
56.
The seasonality of the vertical air temperature profile in an urban area in the vicinity of the coast was studied. The vertical air temperature profile showed the characteristic seasonality. In the summer, the atmosphere was thermally stratified in the 60–100 m layer, while the 20–60 m layer was unstable or weakly stable throughout the day due to the strong solar radiation. On the other hand, no temperature inversion layer was observed in the winter presumably due to the heat supply from the sea as well as the strong wind speed in the vicinity of the coast. The vertical air temperature profiles at nighttime in the spring and autumn were transitional between the summer and the winter. In contrast, the vertical air temperature profile in the daytime in the spring was similar to that in the summer, while that in the autumn was comparable to that in the winter. Characteristic findings in the study due to the site location, i.e., in the vicinity of the coast, can be summarized as follows: (1) the elevated temperature inversion layer at noon was observed in the summer, and (2) no temperature inversion layer was observed in the winter. 相似文献
57.
58.
An overview of decadal climate predictability in a multi-model ensemble by climate model MIROC 总被引:1,自引:1,他引:0
Yoshimitsu Chikamoto Masahide Kimoto Masayoshi Ishii Takashi Mochizuki Takashi T. Sakamoto Hiroaki Tatebe Yoshiki Komuro Masahiro Watanabe Toru Nozawa Hideo Shiogama Masato Mori Sayaka Yasunaka Yukiko Imada 《Climate Dynamics》2013,40(5-6):1201-1222
Decadal climate predictability is examined in hindcast experiments by a multi-model ensemble using three versions of the coupled atmosphere-ocean model MIROC. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity with prescribed natural and anthropogenic forcings on the basis of the historical data and future emission scenarios in the Intergovernmental Panel of Climate Change. Results of the multi-model ensemble in our hindcast experiments show that predictability of surface air temperature (SAT) anomalies on decadal timescales mostly originates from externally forced variability. Although the predictable component of internally generated variability has considerably smaller SAT variance than that of externally forced variability, ocean subsurface temperature variability has predictive skills over almost a decade, particularly in the North Pacific and the North Atlantic where dominant signals associated with Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation (AMO) are observed. Initialization enhances the predictive skills of AMO and PDO indices and slightly improves those of global mean temperature anomalies. Improvement of these predictive skills in the multi-model ensemble is higher than that in a single-model ensemble. 相似文献
59.
60.
Masahide?WakitaEmail author Shuichi?Watanabe Yutaka?W.?Watanabe Tsuneo?Ono Nobuo?Tsurushima Shizuo?Tsunogai 《Journal of Oceanography》2005,61(1):129-139
The dissolved inorganic carbon (DIC) and related chemical species have been measured from 1992 to 2001 at Station KNOT (44°N, 155°E) in the western North Pacific subpolar region. DIC (1.3∼2.3 µ mol/kg/yr) and apparent oxygen utilization (AOU, 0.7∼1.8 µmol/kg/yr) have increased while total alkalinity remained constant in the intermediate water (26.9∼27.3σθ). The increases of DIC in the upper intermediate water (26.9∼27.1σθ) were higher than those in the lower one (27.2∼ 27.3σθ). The temporal change of DIC would be controlled by the increase of anthropogenic CO2, the decomposition of organic matter and the non-anthropogenic CO2 absorbed at the region of intermediate water formation. We estimated the increase of anthropogenic CO2 to be only 0.5∼0.7 µmol/kg/yr under equilibrium with the atmospheric CO2 content. The effect of decomposition was estimated to be 0.8 ± 0.7 µmol/kg/yr from AOU increase. The remainder of non-anthropogenic CO2 had increased by 0.6 ± 1.1 µmol/kg/yr. We suggest that the non-anthropogenic CO2 increase is controlled by the accumulation of CO2 liberated back to atmosphere at the region of intermediate water formation due to the decrease of difference between DIC in the winter mixed layer and DIC under equilibrium with the atmospheric CO2 content, and the reduction of diapycnal vertical water exchange between mixed layer and pycnocline waters. In future, more accurate and longer time series data will be required to confirm our results. 相似文献