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31.
Xavier Le Pichon Toshimishi Iiyama Jacques Boulgue Jacques Charvet Michel Faure Kenichi Kano Siegfried Lallemant Hakuyu Okada Claude Rangin Asahiko Taira Tetsuro Urabe Seiya Uyeda 《Earth and Planetary Science Letters》1987,83(1-4)
Eight submersible dives between 3000 and 4200 m water depth were made off southern Japan in the eastern Nankai subduction zone. Benthic communities associated with chemosynthetic processes were discovered along the 800 m wide active tectonic zone, at the toe of the accretionary prism. A benthic community was also discovered along a zone of active compression, at the foot of Zenisu Ridge, 30 km south of Nankai Trough. Temperature measurements within the sediments below the benthic communities confirm that upward motion of interstitial water occurs there. Studies of water samples indicate advection of methane and light hydrocarbons. Specimens of the benthic community have been shown to have included in their shells carbonate resulting from methane consumption. Thus the benthic communities are related to overpressure-driven fluid advection along tectonic zones with active surface deformation. A 300 m high active scarp at the toe of the accretionary prism is related to relative motion in a 280° direction which is close to the 305° average direction of subduction in this area. The dives establish further that compressive deformation is presently occurring at the foot of Zenisu Ridge. The previous interpretation of the Zenisu Ridge as a zone of recent north-south intraplate shortening, 40 km south of the Nankai Trench, is confirmed. We conclude that tectonic evolution might well lead to future detachment of the Zenisu Ridge and overthrusting of this large piece of oceanic crust over the continental margin. Such a process might be an efficient one to emplace ophiolites over continents. 相似文献
32.
湖南沃溪金锑钨矿床是江南造山带中金、锑、钨、均达到大型规模的典型矿床,其自然金的金成色值极高(>998)。本文聚焦湖南沃溪金锑钨矿床中金矿化作用,通过ICP- MS测试和包裹体显微测温实验查明不同矿物与围岩的元素地球化学特征和成矿流体特征,并通过热力学模拟分析自然金的成矿条件,探讨金成色值及金银比值对金矿化的指示作用和研究价值。ICP- MS测试结果显示,金银比值在白钨矿(103~520)和黄铁矿(69~673)中相对较高,在辉锑矿(6~65)和围岩(0. 3~35)中相对较低,在石英(6~199)中则变化较大。基于包裹体显微测温结果(200~350℃),本文建立了自然金成矿流体的热力学模型,分析并查明在黄铁矿与绢云母共生的自然金成矿流体中,硫离子浓度比温度更容易影响金溶解度,且金成色值主要与温度呈正相关,与硫离子浓度呈负相关。通过对比研究和讨论,认为沃溪矿床大量金矿化可能形成于温度较高和硫离子浓度较低的白钨矿成矿流体中,而极高成色值的自然金可能与高金银比值的白钨矿和黄铁矿共生。上述方法和结论可为其他金矿床的研究提供新思路。 相似文献
33.
34.
Toshihiko Masui Kenichi Matsumoto Yasuaki Hijioka Tsuguki Kinoshita Toru Nozawa Sawako Ishiwatari Etsushi Kato P. R. Shukla Yoshiki Yamagata Mikiko Kainuma 《Climatic change》2011,109(1-2):59-76
Representative Concentration Pathway 6.0 (RCP6) is a pathway that describes trends in long-term, global emissions of greenhouse gases (GHGs), short-lived species, and land-use/land-cover change leading to a stabilisation of radiative forcing at 6.0 Watts per square meter (Wm?2) in the year 2100 without exceeding that value in prior years. Simulated with the Asia-Pacific Integrated Model (AIM), GHG emissions of RCP6 peak around 2060 and then decline through the rest of the century. The energy intensity improvement rates changes from 0.9% per year to 1.5% per year around 2060. Emissions are assumed to be reduced cost-effectively in any period through a global market for emissions permits. The exchange of CO2 between the atmosphere and terrestrial ecosystem through photosynthesis and respiration are estimated with the ecosystem model. The regional emissions, except CO2 and N2O, are downscaled to facilitate transfer to climate models. 相似文献
35.
Yuki Shibazaki Eiji Ohtani Hiroshi Fukui Takeshi Sakai Seiji Kamada Daisuke Ishikawa Satoshi Tsutsui Alfred Q.R. Baron Naoya Nishitani Naohisa Hirao Kenichi Takemura 《Earth and Planetary Science Letters》2012
We have determined the density evolution of the sound velocity of dhcp-FeHx (x ≈ 1) up to 70 GPa at room temperature, by inelastic X-ray scattering and by X-ray diffraction. We find that the variation of VP with density is different for the ferromagnetic and nonmagnetic dhcp-FeHx, and that only nonmagnetic dhcp-FeHx follows Birch's law. Combining our results with Birch's law for iron and assuming an ideal two-component mixing model, we obtain an upper bound of the hydrogen content in the Earth's inner core, 0.23(6) wt.% H, corresponding to FeH0.13(3). The iron alloy with 0.23(6) wt.% H can satisfy the density, and compressional and shear sound velocities of the PREM inner core, assuming that there are no other light elements in the inner core. 相似文献
36.
Osamu Nagafuchi Neil L. Rose Akira Hoshika Kenichi Satake 《Journal of Paleolimnology》2009,42(3):359-371
Fly-ash particles comprising spheroidal carbonaceous particles (SCP) and inorganic ash spheres (IAS), produced from industrial
fossil-fuel combustion, are found in lake sediments throughout the world where they provide an historical record of atmospheric
pollutant deposition. These particles have been widely used to assess the temporal and spatial distribution of industrial
atmospheric pollution in both freshwater and terrestrial environments in Europe and the USA. However, there have been very
few palaeolimnological fly-ash studies undertaken in Japan and none in Japanese mountain lakes. Here, we present the historical
SCP and IAS records from a radiometrically dated sediment core taken from Lake Akagi-konuma (36°31′ 54″N, 139°11′ 32″E; elevation
1,470 m) located 100 km north-west of Tokyo. Meteorological data and back trajectory analyses confirm potential sources both
within Japan and further afield in China and South Korea. SCP contamination began in the 1950s and increased rapidly to a
peak in the mid-1980s. It is thought this represents contamination of Japanese origin, principally oil-fired power stations
within 150 km of the lake. The profile of IAS, almost solely coal-derived, shows a rapid increase in the 1970s, in contrast
to the record of coal consumption in Japan. The IAS record is therefore thought to reflect long-range transport from coal
combustion sources in eastern China which started to expand in the 1970s. This raises concerns over the potential impact on
Japanese mountain areas from recent rapid increases in, and predicted acceleration of, emissions from this industrial process.
The scale of SCP contamination recorded in Lake Akagi-konuma is equivalent to moderately impacted mountain lakes in Europe,
but is at the upper end of the range for remote lakes in the western United States. 相似文献
37.
Shun Yukawa Yustiawati M. Suhaemi Syawal Kenichi Kobayashi Toshiyuki Hosokawa Takeshi Saito Shunitz Tanaka Masaaki Kurasaki 《Environmental Earth Sciences》2014,71(4):1945-1952
The pollution of water by heavy metals is one of the most serious problems in the developing countries, where watercourses play important roles in transport and economic activities. The aim of this study was to examine whether Hyposarcus pardalis, a fish species widespread in the freshwater environment in Indonesia, could be used as a biomarker for environmental pollution by metals. To this effect, the concentrations of metallothioneins and metals in the livers and kidneys of H. pardalis were measured. In addition, to clarify the relationship between metallothionein concentrations and metal exposure, the concentrations of metallothioneins and metals were determined in the liver and the kidney of fish exposed to 50 and 500 ppb Cu and 500 ppb Mn, compared with those kept in clean water. Sufficient concentrations of metallothionein were detected in fish captured from Lake Rawakalong located in an industrial area in the suburbs of Jakarta. The results of exposure experiments suggested that H. pardalis retained a history of pollution in its organs for a long duration, and the metals bound to metallothioneins in the liver and kidney could be replaced with Cu following exposure. In conclusion, the hepatic and renal metallothioneins in H. pardalis are a useful candidate biomarker for monitoring heavy metal contamination. 相似文献
38.
Samples from metamorphosed pillowed basalts and related Besshi-type deposits occurring in the Sanbagawa belt of the Shikoku
Island, southwest Japan, have been analyzed for 87Sr/86Sr, 143Nd/144Nd and 40 K/40Ar. This is to investigate the tectonic settings in which the original submarine volcanism and associated Besshi-type mineralization
occurred, as well as the age of metamorphism. Eight whole-rock samples of the pillow lavas metamorphosed in pumpellyite-actinolite
facies conditions yield a Rb-Sr isochron age of 107 ± 15 Ma with an initial ratio of 0.70401 ± 0.00006, while they do not
define a Sm-Nd isochron. We interpret the results as the metamorphic age, an interpretation consistent with the previously
reported Rb-Sr whole-rock age for the Sanbagawa pelitic schists. The overall ranges of the initial epsilon values at T = 107 Ma are: ɛNd (T ) = +7.8 to +4.3; ɛSr(T ) = +2.2 to −7.0, suggesting that the most likely source for the pillowed basalts is depleted oceanic mantle, a conclusion
supported by the previous Pb isotope studies. The K-Ar ages determined for twelve mineral separates from the Besshi-type deposits
range from about 60 to 112 Ma, with a mean age of about 80 Ma, in agreement with the previous K-Ar and Ar-Ar data for the
Sanbagawa pelitic and basic schists. The youngest age, 60 Ma, was obtained for sericite from the Hinooku deposit metamorphosed
in pumpellyite- actinolite facies conditions, while the oldest one for hornblende from the spotted amphibolite in the immediate
vicinity of the Shiragayama deposit metamorphosed in albite-biotite grade. The oldest age, 112 Ma, is interpreted to date
the peak metamorphism, consistent with the Rb-Sr data, though a possibility of excess Ar cannot always be ruled out. In view
of the closure temperatures of muscovite (350 °C) in the biotite zone, it is suggested that our K-Ar age data (<about 80 Ma)
represent the age of the retrograde metamorphism or subsequent uplift. Datable microfossils found in the Sanbagawa belt of
Shikoku suggest that the submarine basaltic volcanism and related Besshi-type mineralization occurred in an oceanic basin
away from the trench region in Late Triassic (conodont) to Late Jurassic (radiolarian) times.
Received: 5 March 1997 / Accepted: 14 May 1998 相似文献
39.
40.
The granular column collapse is a well-established experiment which consists of having a vertical column of granular material on a flat surface and letting it collapse by gravity. Despite its simplicity in execution, the numerical modelling of a column collapse remains challenging. So far, much attention has been dedicated in assessing the ability of various numerical methods in modelling the large deformation and little to the role of the constitutive model on both the triggering mechanism and the flow behaviour. Furthermore, the influence of the initial density, and its associated dilatancy and strength characteristics, have never been included in the analyses. Most past numerical investigations had relied on simple constitutive relations which do not consider the softening behaviours. The aim of this study is to illustrate the influence of the constitutive model on the on-set of failure, the flow behaviour and the deposition profile using the material point method. Three constitutive models were used to simulate the collapse of two granular columns with different geometries and for two densities. The results of the simulations showed that the constitutive model had a twofold influence on the collapse behaviour. It defined the volume of the mobilised mass which spread along the flat surface and controlled the dissipation of its energy. The initial density was found to enhance the failure angle and flow behaviours and was more significant for small columns than for larger ones. The analysis of the potential energy of the mobilised mass explained the existence of two collapse regimes. 相似文献