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11.
Subsurface Occurrence of Natural Gas Hydrate in the Nankai Trough Area: Implication for Gas Hydrate Concentration 总被引:2,自引:0,他引:2
Abstract. The Nankai Trough runs along the Japanese Islands, where extensive BSRs have been recognized in its forearc basins. High resolution seismic surveys and site-survey wells undertaken by the MITI have revealed the gas hydrate distribution at a depth of about 290 mbsf. The MITI Nankai Trough wells were drilled in late 1999 and early 2000. The highlights were successful retrievals of abundant gas hydrate-bearing cores in a variety of sediments from the main hole and the post survey well-2, keeping the cored gas hydrate stable, and the obtaining of continuous well log data in the gas hydrate-dominant intervals from the main hole, the post survey well-1 and the post survey well-3. Gas-hydrate dominant layers were identified at the depth interval from 205 to 268 mbsf. Pore-space hydrate, very small in size, was recognized mostly filling intergranular pores of sandy sediments. Anomalous chloride contents in extracted pore water, core temperature depression, core observations as well as visible gas hydrates confirmed the presence of pore-space hydrates within moderate to thick sand layers. Gas hydrate-bearing sandy strata typically were 10 cm to a meter thick with porosities of about 40 %. Gas hydrate saturations in most hydrate-dominant layers were quite high, up to 90 % pore saturation.
All the gas hydrate-bearing cores were subjected to X-ray CT imagery measurements for observation of undisturbed sedimentary textures and gas-hydrate occurrences before being subjected to other analyses, such as (1) petrophysical properties, (2) biostratigraphy, (3) geochemistry, (4) microbiology and (5) gas hydrate characteristics. 相似文献
All the gas hydrate-bearing cores were subjected to X-ray CT imagery measurements for observation of undisturbed sedimentary textures and gas-hydrate occurrences before being subjected to other analyses, such as (1) petrophysical properties, (2) biostratigraphy, (3) geochemistry, (4) microbiology and (5) gas hydrate characteristics. 相似文献
12.
Brajesh Singh Santosh Kumar Masao Ban Kazuo Nakashima 《Journal of Earth System Science》2016,125(7):1329-1352
Felsic magmatism in the southern part of Himachal Higher Himalaya is constituted by Neoproterozoic granite gneiss (GGn), Early Palaeozoic granitoids (EPG) and Tertiary tourmaline-bearing leucogranite (TLg). Magnetic susceptibility values (<3 ×10?3 SI), molar Al2 O 3/(CaO + Na2 O + K 2O) (≥1.1), mineral assemblage (bt–ms–pl–kf–qtz ± tur ± ap), and the presence of normative corundum relate these granitoids to peraluminous S-type, ilmenite series (reduced type) granites formed in a syncollisional tectonic setting. Plagioclase from GGn (An10–An31) and EPG (An15–An33) represents oligoclase to andesine and TLg (An2–An15) represents albite to oligoclase, whereas compositional ranges of K-feldspar are more-or-less similar (Or88 to Or95 in GGn, Or86 to Or97 in EPG and Or87 to Or94 in TLg). Biotites in GGn (Mg/Mg + Fet= 0.34–0.45), EPG (Mg/Mg + Fet= 0.27–0.47), and TLg (Mg/Mg + Fet= 0.25–0.30) are ferribiotites enriched in siderophyllite, which stabilised between FMQ and HM buffers and are characterised by dominant 3Fe\(\rightleftharpoons \)2Al, 3Mg\(\rightleftharpoons \)2Al substitutions typical of peraluminous (S-type), reducing felsic melts. Muscovite in GGn (Mg/Mg + Fet=0.58–0.66), EPG (Mg/Mg + Fet=0.31?0.59), and TLg (Mg/Mg + Fet=0.29–0.42) represent celadonite and paragonite solid solutions, and the tourmaline from EPG and TLg belongs to the schorl-elbaite series, which are characteristics of peraluminous, Li-poor, biotite-tourmaline granites. Geochemical features reveal that the GGn and EPG precursor melts were most likely derived from melting of biotite-rich metapelite and metagraywacke sources, whereas TLg melt appears to have formed from biotite-muscovite rich metapelite and metagraywacke sources. Major and trace elements modelling suggest that the GGn, EPG and TLg parental melts have experienced low degrees (~13, ~17 and ~13%, respectively) of kf–pl–bt fractionation, respectively, subsequent to partial melting. The GGn and EPG melts are the results of a pre-Himalayan, syn-collisional Pan-African felsic magmatic event, whereas the TLg is a magmatic product of Himalayan collision tectonics. 相似文献
13.
Koji Kakinoki Shiro Imawaki Hiroshi Uchida Hirohiko Nakamura Kaoru Ichikawa Shin-Ichiro Umatani Ayako Nishina Hiroshi Ichikawa Mark Wimbush 《Journal of Oceanography》2008,64(3):373-384
Two inverted echo sounders were maintained on coastal and offshore sides of the Kuroshio south of Japan from October 1993
to July 2004. Applying the gravest empirical mode method, we obtained a time series of geostrophic transport. Estimated transports
generally agree well with geostrophic transports estimated from hydrography. Their agreement with the hydrographic transports
is better than that of transports estimated from satellite altimetry data. The geostrophic transport is expressed as the surface
transport per unit depth multiplied by the equivalent depth. The geostrophic transport varies mostly with the surface transport
and fractionally with the equivalent depth. Seasonal variation of the geostrophic transport has a minimum in March and a maximum
in September, with a range of about one fifth of the total transport. 相似文献
14.
Masahiko Fujii Fei Chai Lei Shi Hisayuki Y. Inoue Masao Ishii 《Journal of Oceanography》2009,65(5):689-701
The oceanic carbon cycle in the tropical-subtropical Pacific is strongly affected by various physical processes with different
temporal and spatial scales, yet the mechanisms that regulate air-sea CO2 flux are not fully understood due to the paucity of both measurement and modeling. Using a 3-D physical-biogeochemical model,
we simulate the partial pressure of CO2 in surface water (pCO2sea) and air-sea CO2 flux in the tropical and subtropical regions from 1990 to 2004. The model reproduces well the observed spatial differences
in physical and biogeochemical processes, such as: (1) relatively higher sea surface temperature (SST), and lower dissolved
inorganic carbon (DIC) and pCO2sea in the western than in the central tropical-subtropical Pacific, and (2) predominantly seasonal and interannual variations
in the subtropical and tropical Pacific, respectively. Our model results suggest a non-negligible contribution of the wind
variability to that of the air-sea CO2 flux in the central tropical Pacific, but the modeled contribution of 7% is much less than that from a previous modeling
study (30%; McKinley et al., 2004). While DIC increases in the entire region SST increases in the subtropical and western tropical Pacific but decreases
in the central tropical Pacific from 1990 to 2004. As a result, the interannual pCO2sea variability is different in different regions. The pCO2sea temporal variation is found to be primarily controlled by SST and DIC, although the role of salinity and total alkalinity,
both of which also control pCO2sea, need to be elucidated by long-term observations and eddy-permitting models for better estimation of the interannual variability
of air-sea CO2 flux. 相似文献
15.
Taro Takahashi Stewart C. Sutherland Rik Wanninkhof Colm Sweeney Richard A. Feely David W. Chipman Burke Hales Gernot Friederich Francisco Chavez Christopher Sabine Andrew Watson Dorothee C.E. Bakker Ute Schuster Nicolas Metzl Hisayuki Yoshikawa-Inoue Masao Ishii Takashi Midorikawa Yukihiro Nojiri Arne Krtzinger Tobias Steinhoff Mario Hoppema Jon Olafsson Thorarinn S. Arnarson Bronte Tilbrook Truls Johannessen Are Olsen Richard Bellerby C.S. Wong Bruno Delille N.R. Bates Hein J.W. de Baar 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2075-2076
16.
Sector trilling of cordierite in hornfels in the inner part of a contact aureole at Daimonji, Japan is a new type which consists not only of six (100) sectors (a-sectors) forming trilling, but also of (001) sectors (c-sectors) and high-index sectors (h-sectors). Complex twins within and among these sectors were studied from a viewpoint of a pseudo twin. The complex texture originated from both growth and transformation processes. The c-sector consists of three groups of domains which are related by a pseudo twin. This intrasector pseudo twin indicates that the initial phase of the c-sector was hexagonal cordierite (indialite) which later transformed to orthorhombic. The a-sector is related to adjacent sectors by a rotation of 120° around the c axis, resulting in an intersector pseudo twin. The a-sector is interpreted to have formed by overgrowth of orthorhombic cordierite on prism faces of indialite. The h-sector with the dendritic texture is also interpreted to have grown as orthorhombic cordierite. In hornfels in the middle part of the aureole, cordierites with sector trilling often coexist with single crystals of cordierite, and the sector trilling has no c- and h-sectors. This trilling type suggests that nucleation of indialite was subsequently followed by growth of orthorhombic cordierite in its stable field. 相似文献
17.
Eutrophication and associated occurrence of hypoxic condition could cause significant damage to marine ecosystems, resulting in considerable economic losses to fisheries and aquaculture and is a major source of stress that fish often have to contend with in order to survive. This problem is likely to be exacerbated in the coming years, since the wastewater treatment facilities is unlikely to catch up with increasing human activities. Moreover, large-scale reclamation projects in coastal areas have recently been increased, and these activities certainly have adverse impacts on water quality and fisheries resources. Coastal construction has a significant role in the development of hypoxic water by changing the current and mixing pattern of water. Changes in species composition and decreases in species richness and diversity have been well documented in hypoxic systems. Hypoxia could cause endocrine disruption in fish and eliminate populations of sensitive species. Shallow coastal areas are of great importance for the special nursery of fish and shellfish and land reclamation in these areas cause strong damage to fisheries. Although the tolerance of aquatic life to hypoxia is known, there is no information about the mortality of fish caused by hypoxia because fish can swim around it and no modeling study has yet been carried out. Criteria that influence the movement of fish are: amounts of food, water temperature and depth, dissolved oxygen concentration and nature of seabed. However, among these, water temperature and dissolved oxygen are the most crucial parameters that affect survival, movement and growth of fish. In this paper, a model of fish preference and mortality for environmental conditions was developed and applied to the Hakata Bay where hypoxic water occurs every summer. For the purpose of this study, a field survey of fish behavior under hypoxic water was conducted by releasing marbled sale (Pleuronectes yokohamae) in the inner bay. Moreover, a series of preference tests for DO, salinity and temperature in the laboratory were conducted in order to decide preference parameters of fish. Using the results of both field and laboratory studies, a sub-module of fish preference and mortality was coded within an integrated hydrothermal and eutrophication model (CHEM) to predict the behavior and mortality of marbled sale when hypoxia would occur in the bay. The model could reasonably simulate the behavior of the fish under hypoxia. An assessment of the impact of the ongoing land reclamation project of about 401 ha in the Wajiro tidal flat zones at the head of the bay on the fisheries resources was also conducted using the model. The results showed that the artificial land lowered the mortality rate of fish under hypoxic condition in the bay during the summer period. 相似文献
18.
Concentrations of Fe, Zn, Cu, Se, Mn, Mo, Hg, Cd, Cr, Ag, Pb, Sr and V were determined in skins of Dall's porpoises (Phocoenoides dalli) of the Pacific coast truei-type population (PT population) (N=45), and the Sea of Japan-Okhotsk dalli-type population (JD population) (N=31) from the northern waters of Japan. Cutaneous Hg concentrations in both PT and JD populations were significantly correlated with age, indicating a possible alternative method of age estimation. A significant correlation was also noted between Hg concentrations in skin and liver, suggesting that biopsy samples of skin can provide a non-lethal surrogate for monitoring Hg contamination in this species. Trace element accumulation patterns differed strongly between PT and JD populations, when analyzed by principal component analysis, suggesting these patterns could be utilized as non-lethal tracers of population identification. 相似文献
19.
Masao Ohno Tsutomu Sato Kenji Notsu Hiroshi Wakita Kunio Ozawa 《Pure and Applied Geophysics》2006,163(4):647-655
Anomalous water level changes were observed at two wells associated with seismic swarm activity off Izu Peninsula on March,
1997. These are coseismic water level drops followed by gradual postseismic water level rise at the time of large earthquakes
during the swarm activity. The post-seismic water level rises, which can be fitted by an exponential function with a time
constant of about six hours, are explained in terms of the horizontal pressure diffusion due to the pressure gradient in the
aquifer induced by the coseismic static strain. 相似文献
20.
Mouradian Z. Soru-Escaut I. Hiei E. McALLISTER A. H. Shibasaki K. Ohyama M. Khan J. I. Uchida Y. 《Solar physics》1998,180(1-2):313-329
The 7 May 1992 filament disappearance in the low corona is analyzed. The cool and hot components of this event are studied, using H, soft X-ray and radio data. We first show the general effect of the disparition brusque (DB) on the life of the filament, which was a quiescent filament in the vicinity of an active region, and then give the history of the development of the 7 May event. The main stages of the event are: (i) the formation of hot arches spanning the cool filament; (ii) rise of the filament, with plasma ejection into the corona, in which we note some spreading of loops from the main body, with two distinct rising velocity phases of the H filament; (iii) formation of X-ray arches below the filament, the foot points of the arcades being two-ribbon H flare patches. The dynamics of H and X-rays features are given. 相似文献