Detection and Evaluation of Gas Hydrates in the Eastern Nankai Trough by Geochemical and Geophysical Methods   总被引：2，自引：0，他引：2  

Ryo Matsumoto    Hitoshi Tomaru  Hailong Lu 《Resource Geology》2004,54(1):53-67

Abstract: Interstitial waters extracted from the sediment cores from the exploration wells, “BH‐1” and “MITI Nankai Trough”, drilled ～60 km off Omaezaki Peninsula in the eastern Nankai Trough, were analyzed for the chloride and sulfate concentrations to examine the depth profiles and occurrence of subsurface gas hydrates. Cored intervals from the seafloor to 310 mbsf were divided into Unit 1 (～70 mbsf, predominated by mud), Unit 2 (70–150 mbsf, mud with thin ash beds), Unit 3 (150–250+ mbsf, mud with thin ash and sand), and Unit 4 (275–310 mbsf, predominated by mud). The baseline level for Cl “concentrations was 540 mM, whereas low chloride anomalies (103 to 223 mM) were identified at around 207 mbsf (zone A), 234–240 mbsf (zone B), and 258–265 mbsf (zone C) in Unit 3. Gas hydrate saturation (Sh %) of sediment pores was calculated to be 60 % (zone A) to 80 % (zones B and C) in sands whereas only a few percent in clay and silt. The total amount of gas hydrates in hydrate‐bearing sands was estimated to be 8 to 10 m³ of solid gas hydrate per m², or 1.48 km³ CH₄ per 1 km². High saturation zones (A, B and C) were consistent with anomaly zones recognized in sonic and resistivity logs. 2D and high‐resolution seismic studies revealed two BSRs in the study area. Strong BSRs (BSR‐1) at ～263 mbsf were correlated to the boundary between gas hydrate‐bearing sands (zone C) and the shallower low velocity zone, while the lower BSRs (BSR‐2) at～289 mbsf corresponded to the top of the deeper low velocity zone of the sonic log. Tectonic uplift of the study area is thought to have caused the upward migration of BGHS. That is, BSR‐1 corresponds to the new BGHS and BSR‐2 to the old BGHS. Relic gas hydrates and free gas may survive in the interval between BSR‐1 and BSR‐2, and below BSR‐2, respectively. Direct measurements of the formation temperature for the top 170 m interval yield a geothermal gradient of ～4.3d?C/ 100 m. Extrapolation of this gradient down to the base of gas hydrate stability yields a theoretical BGHS at～230 mbsf, surprisingly ～35 m shallower than the base of gas hydrate‐bearing sands (zone C) and BSR‐1. As with the double BSRs, another tectonic uplift may explain the BGHS at unreasonably shallow depths. Alternatively, linear extrapolation of the geothermal gradient down to the hydrate‐bearing zones may not be appropriate if the gradient changes below the depths that were measured. Recognition of double BSRs (263 and 289 mbsf) and probable new BGHS (～230 mbsf) in the exploration wells implies that the BGHS has gradually migrated upward. Tectonically induced processes are thought to have enhanced dense and massive accumulation of gas hydrate deposits through effective methane recycling and condensation. To test the hypothetical models for the accumulation of gas hydrates in Nankai accretionary prism, we strongly propose to measure the equilibrium temperatures for the entire depth range down to the free gas zone below predicted BGHS and to reconstruct the water depths and uplift history of hydrate‐bearing area.  相似文献   

Summer Water Balance Characteristics of Koryto Glacier, Kamchatka Peninsula, Russia     

Takane Matsumoto  Renji Naruse  Keiko Konya  Satoru Yamaguchi  Tomomi Yamada  Yaroslav D. Muravyev 《Geografiska Annaler: Series A, Physical Geography》2004,86(2):181-190

The daily water balance for the drainage basin of Koryto Glacier, Kamchatka Peninsula, Russia, was calculated during the period from August to September 2000. The result shows that 14×10⁶ m³ of meltwater and 2×10⁶ m³ of rainwater entered the basin, while 26×10⁶ m³ of water drained from the basin through proglacial streams. Thus, about ?9×10⁶ m³ of water storage reduction occurred in the basin. Vertical displacements of the glacier surface showed that the volume change due to contraction of subglacial cavities was nearly 20% of the total storage change. The remaining fraction of water storage during the period is thought to be stored in englacial and supraglacial locations. The estimate of water balance components in the early ablation season in 2000 indicates that meltwater was already stored within the glacier before the spring, even during the previous year, and that the stored water drained through the ablation season.  相似文献   

Late cretaceous to early paleogene paleomagnetic results from Sikhote Alin, far eastern Russia: implications for deformation of East Asia   总被引：1，自引：0，他引：1  

Yo-ichiro Otofuji  Takaaki Matsuda  Tetsumaru Itaya  Takeshi Shibata  Michiko Matsumoto  Takahiro Yamamoto  Chiyo Morimoto  Ruslan G. Kulinich  Petr S. Zimin  Anatoly P. Matunin  Vladimir G. Sakhno  Katsuhiro Kimura 《Earth and Planetary Science Letters》1995,130(1-4):95-108

Welded tuffs in the Bogopol and Sijanov groups were sampled at 27 sites from 12 caldera formations in the Sikhote Alin mountain range around Kavalerovo (44.3°N, 135.0°E) for chronological and paleomagnetic studies. KAr age dates show that the welded tuffs erupted between 66 Ma and 46 Ma. All sites yield reliable paleomagnetic directions, with unblocking temperatures higher than 560°C. The high-temperature component at 12 sites and the medium-temperature component at 3 sites in the Bogopol Group show reversed polarity (D = 193.7°, I = −57.6°,₉₅ = 8.1°). The high-temperature component at 11 sites in the Sijanov Group showed both reversed and normal polarities and its mean direction reveals no detectable deflection from north (D = −2.9°, I = 59.6°,₉₅ = 11.2°). The combined paleomagnetic direction of the two groups yields a paleomagnetic pole of 250.5°E, 84.1°N (A₉₅ = 8.8°), which falls near Cretaceous paleomagnetic poles from Outer Mongolia, Inner Mongolia, the North China Block and the South China Block. The Sikhote Alin area appears not to have been subjected to detectable motion with respect to East Asia since about 50 Ma. This implies that the Sikhote Alin area behaved as an integral part of East Asia during the opening of the Japan Sea at about 15 Ma. However, significant separation between the paleomagnetic poles of East Asia and Europe during the Jurassic-Paleogene implies a major relative movement between these two blocks since the Paleogene.  相似文献   

Loch Macumber (early Carboniferous) of Atlantic Canada     

Paul E. Schenk  Ryo Matsumoto  Peter H. von Bitter 《Journal of Paleolimnology》1994,11(2):151-172

Following the Acadian Orogeny, Atlantic Canada accommodated several, large, relatively deep lakes within a wrench-fault basin complex called the Maritime Basin. Late Devonian and Tournaisian lakes were hydrologically open, shallow to deep, mainly fresh water bodies. Middle Visean lakes, here collectively called Loch Macumber, were closed, deep, and meromictic. Their deposits comprise the first and thickest of five sequences in the Maritime Basin. Salinity in the loch increased with time from restricted marine or penesaline, to saline. Basin-centre facies consist of a thin, but extensive, sheet of black, peloidal laminated lime mudstones and an overlying thick evaporite complex. The carbonate sheet grades laterally into both laminated to thinly bedded marlstones, siliciclastic sandstones, and microbial, biocementstone mounds. Laminae consist of alternating carbonate and either silty carbonaceous shale or siliciclastic clay and silt. The mudstone and marlstone are locally interbedded with siliciclastic and carbonate turbidites, resedimented (?deep water) breccias, and olistostromes. Seasonal changes in anoxia and/or carbonate production produced rhythmic laminae of carbonate and carbonaceous shale. Carbonate grains consist of silt-sized microbial clots and rare arthropod carapaces and brachiopod shells. The mounds originated as tufa precipitated around subaqueous hydrothermal springs that supported chemosynthetic communities. Resedimentation processes including incipient brecciation, sliding, slumping, debris flows, and turbidity currents were common. The mounds trapped hydrocarbons from the surrounding laminite and sulphides from underlying hydrothermal vents. Increasing salinity with time resulted in sulphate and chloride precipitation that filled the basins and ended the life of Loch Macumber. After the deposition of thick evaporites the topography became less accentuated, the seas less saline, and the faunas more normal marine.  相似文献   

Gravity anomaly in and around Antarctica and its tectonic implications     

Jiro Segawa  Takeshi Matsumoto  Katsutada Kaminuma 《Journal of Geodynamics》1986,6(1-4)

During the nineteen-seventies, the geophysical satellites EOS-3 and SEASAT-1 provided very accurate sea-surface heights, which could be employed as information on the marine geoid. Geoid height can easily be converted to gravity anomalies, and since the tracks of GEOS-3 and SEASAT-1 were extremely dense, the gravity anomaly data thus obtained were the densest and of the widest coverage ever obtained for gravity measurements.The authors completed a self-consistent free-air gravity anomaly map in the Antarctic region, covering from 45°S to the South Pole, using all the gravity data available at present: namely, those obtained by satellites and the ground-truth data obtained by land gravimeters and ship borne gravimeters (Segawa et at., 1984).The bouguer anomaly was also calculated, from which estimates of crustal and lithospheric structures were made. This has resulted in clarifying the relationships among sub-bottom structures between the mid-oceanic ridges surrounding the Antarctic plate and the Ross Sea.  相似文献   

基于绕月单卫星和双星测量的月球重力场恢复仿真分析   总被引：5，自引：0，他引：5       下载免费PDF全文

鄢建国  平劲松  李斐  松本晃志  王广利  史弦 《地球物理学报》2007,50(2):425-429

月球重力场是月球科学研究的重要部分，是进一步了解月球内部结构和构造的基础，也是我国探月计划“嫦娥工程”一个重要的科学研究内容.本文针对“嫦娥工程”，利用GSFC/NASA/USA的GEODYNII/SOLVE轨道分析软件，分析计算了利用单星跟踪数据恢复月球重力场的能力，同时模拟计算了双星跟踪数据在恢复月球重力场方面的能力，结合可能的工程环境我们对两种情况分别给出了30天、60天和90天的计算结果.计算表明双星相比于单星对月球重力场的中低阶位系数有比较显著的改善.  相似文献   

Pseudosection analysis for talc-Na pyroxene-bearing piemontite-quartz schist in the Sanbagawa Belt, Japan     

Taro  Ubukawa  Akiko  Hatanaka  Keisaku  Matsumoto  Takao  Hirajima 《Island Arc》2007,16(4):553-574

Abstract Various modes of occurrence of talc were identified in piemontite‐quartz schists collected from schist and eclogite units in the Kotsu area of the Sanbagawa Belt, eastern Shikoku, Japan. They can be classified into the following types: (A) matrix and (B) pull‐apart talc. The matrix talc is associated with aegirineaugite or glaucophane in the eclogite unit and with albite or chlorite in the schist unit. The pull‐apart talc is developed at the pull‐apart of microboudin structures of Na‐amphibole, along with albite or chlorite in samples from both units, suggesting that the pull‐apart talc was formed by Na‐amphibole consuming reactions in both units. The talc–aegirineaugite–phengite association is found in a thin layer (a few millimetres thick), with higher Na₂O/(Na₂O + Al₂O₃ + MgO) ratio in the ANM (Al₂O₃–Na₂O–MgO) diagram projected from phengite, epidote and other minerals, in the eclogite unit. Crystals of aegirineaugite have decreased jadeite content [= 100 × Al/(Na + Ca)] and increased aegirine content [= 100 × (Na – Al)/(Na + Ca)] from the core (ca Jd₄₀Aeg₄₀Di₂₀) to the rim (ca Jd₂₃Aeg₅₃Di₂₄), and are replaced by winchite and albite in varying degrees at the crystal margins. Na‐amphibole is glaucophane/crossite, commonly rimmed by Al‐poor crossite or winchite at the margin in the eclogite unit, although it is relatively homogeneous crossite in the schist unit. These textures suggest that the talc‐phengite‐(aegirineaugite or glaucophane) assemblage equilibrated during an early stage of metamorphism and the pull‐apart talc was formed at a later stage in the eclogite unit. A plausible petrogenetic grid in the NCKFe³⁺MASH system with excess piemontite (regarded as epidote), hematite, quartz and water, pseudosection analysis for the aegirineaugite‐bearing layer and the observed mineral assemblages suggest that the talc‐aegirineaugite‐phengite assemblage is stable under high pressure conditions (ca 560–580°C and 18–20 kbar). The pull‐apart talc was formed at ca 565–580°C and 9.5–10.5 kbar by the reaction of glaucophane/crossite + paragonite = talc + albite during the decompression stage, suggesting that the piemontite‐quartz schist in the eclogite unit experienced high‐pressure metamorphism at ca 50–60 km depth and was then exhumed to ca 30 km depth under nearly adiabatic conditions.  相似文献   

Diffuse reflection and transmission of radiation by finite atmospheres with specular reflectors     

M. Matsumoto  S. Ueno 《Astrophysics and Space Science》1976,43(2):475-490

It is supposed that solar rays are incident uniformly on the top of a plane-parallel, anisotropically scattering, and homogeneous atmosphere, whose bottom is bounded by a specular reflector. An initial-value solution for the scattering and transmission functions is obtained, starting with an auxiliary equation. Some results of numerical experiments for given optical parameters are presented in Figures.  相似文献   

A Theoretical Light-Curve Model for the 1999 Outburst of U Scorpii     

Hachisu I  Kato M  Kato T  Matsumoto K 《The Astrophysical journal》2000,536(2):L97-L100

We report the detection of the Pb i lambda4057.8 line in the very metal-poor (&sqbl0;Fe&solm0;H&sqbr0;=-2.7), carbon-rich star, LP 625-44. We determine the abundance of Pb (&sqbl0;Pb&solm0;Fe&sqbr0;=2.65) and 15 other neutron-capture elements. The abundance pattern between Ba and Pb agrees well with a scaled solar system s-process component, while the lighter elements (Sr-Zr) are less abundant than Ba. The enhancement of s-process elements is interpreted as a result of mass transfer in a binary system from a previous asymptotic giant branch (AGB) companion, an interpretation strongly supported by radial velocity variations of this system. The detection of Pb makes it possible, for the first time, to compare model predictions of s-process nucleosynthesis in AGB stars with observations of elements between Sr and Pb. The Pb abundance is significantly lower than the prediction of recent models (e.g., Gallino et al.), which succeeded in explaining the metallicity dependence of the abundance ratios of light s-elements (Sr-Zr) to heavy ones (Ba-Dy) found in previously observed s-process-enhanced stars. This suggests that one should either (1) reconsider the underlying assumptions concerning the (13)C-rich s-processing site ((13)C pocket) in the present models or (2) investigate alternative sites of s-process nucleosynthesis in very metal-poor AGB stars.  相似文献   

An organic geochemical study of KP-2 core on the mud volcano at Nankai Trough     

Shigenori Ogihara  Ryo Matsumoto  Yifeng Chen   《Journal of Geochemical Exploration》2007,95(1-3):81

Organic geochemical data was collected from a KP-2 piston core sample obtained from a mud volcano in the Nankai Trough, off the southeast coast of Japan. The Nankai Trough was investigated geologically and was found to have a large amount of methane hydrates. Biomarkers indicating anaerobic oxidation of methane (AOM) were expected to be found in the sediment of the mud volcano collected by KP-2 core. But the gas chromatography-mass spectrometry (GC-MS) analysis of the samples showed only one biomarker related to the methane-oxidizing Archaea, namely 2,6,10,15,19-pentamethyleicosane (PME), could be detected throughout the KP-2 core. Phytane was predominant in the upper part of the KP-2 core; however, a series of 2,2-dimethylalkanes (2,2-DMAs) were characterized in the lower part of KP-2 core. The individual δ¹³C values of 2,2-DMAs, which were − 29.1 to − 27.3‰ indicate that the origin of 2,2-DMAs was not related to methane-oxidizing Archaea.  相似文献