Tectonic Setting of the Permo-Triassic Chiang Khong Volcanic Rocks, Northern Thailand Based on Petrochemical Characteristics   总被引：1，自引：0，他引：1  

Yuenyong Panjasawatwong  Burapha Phajuy  Shigeki Hada 《Gondwana Research》2003,6(4):743-755

The inferred Permo-Triassic Chiang Khong volcanic belt is composed of felsic to mafic volcanic rocks and their pyroclastic equivalents. Almost all the least-altered mafic volcanic rocks are lava flows; a few might have occurred as dykes. These mafic volcanic rocks are non-foliated to weakly foliated, and mostly have porphyritic textures. The phenocrysts/microphenocrysts in porphyritic samples are commonly plagioclase, and may include clinopyroxene, olivine, Fe-Ti oxide, apatite and amphibole. The matrix of lava flows ranges texturally from felty to trachytic but a few samples show felty to ophitic/subophitic, and glassy textures, whereas that of possible dyke samples is holocrystalline. The primary matrix constituents are largely plagioclase and variable proportions of clinopyroxene, Fe-Ti oxide, amphibole, olivine, apatite, quartz, alkali feldspar and/or glass. All the studied samples have been subjected to greenschist-facies regional metamorphism. Chemically, the samples show narrow ranges of least-mobile incompatible-element ratios and range compositionally from dacite to basalt of tholeiitic series. These samples are chemically analogous to those of the Tertiary andesite from Sardinian Rift, Sardinia, Italy, particularly in terms of least-mobile incompatible-element ratios. Accordingly, the studied mafic volcanic rocks are interpreted to have formed in a continental volcanic arc. However, the problem related to the geometry of plate convergence, giving rise to the continental volcanic arc, still exists.  相似文献   

Structure of Cu-bearing orthopyroxene, Mg(Cu.56,Mg.44)Si2O6, and behavior of Cu2+ in the orthopyroxene structure     

T. Tachi  H. Horiuchi  H. Nagasawa 《Physics and Chemistry of Minerals》1997,24(7):463-476

Cu-bearing pyroxene, Mg(Cu.₅₆,Mg.₄₄)Si₂O₆, has been synthesized by a flux method and crystal structure refinement has been performed by single crystal X-ray diffraction. It is found that the crystal structure is orthorhombic (space group Pbca) with unit cell dimensions of a=18.221(4), b=8.890(1), c=5.2260(7)Å and the cell volume of 846.5( )3ų. In the M2-site one of the M-O bonds(M-O3B) is extremely expanded from 2.444(2) in enstatite to 2.732(2), thus the coordination polyhedron around M2-site is regarded as square pyramidal rather than square planar or octahedral. It is also found that the M1-site in the pyroxene structure is occupied almost exclusively by Mg, while the M2-site is almost evenly occupied by Mg and Cu. The observed extreme site preference shown by Cu²⁺ is unusual among the divalent cations with similar ionic sizes.  相似文献   

Attenuation of coda waves and Q _c value beneath the Chengdu telemetered seismic network     

Jian Zeng  Tian-Chang Chen  Wei-Bin Han  Jun Fan  Si-Hua Zheng  Akira Hasegawa  Shigeki Horiuchij  Satoshi Matsumoto 《地震学报(英文版)》1997,10(3):313-320

Based on the single scattering model of coda power spectrum analysis, digital waveform data of 50 events recorded by the real-time processing system of the Chengdu telemetry network are analyzed to estimate the Q _c values of earth medium beneath the Chengdu telemetry network for several specified frequencies. It is found that the Q _c shows the frequency dependency in the form of Q _c = Q ₀ f ⁿ in the range of 1.0 to 20.0Hz. Estimated Q ₀ ranges from 60.83 to 178.05, and n is found to be 0.713 to 1.159. The average value of Q ₀ and n are 117 and 0.978 respectively. This result indicates the strong frequency dependency of the attenuation of coda waves beneath the Chengdu telemetry network. Comparing with the results obtained in other regions of the world, it is found that Q ₀ ⁻¹ value and its change with frequency are similar to those in regions with strong tectonic activity. This subject is supported by the Ministry of Personnel, China for partly sponsoring.  相似文献   

Effect of ocean acidification on coastal phytoplankton composition and accompanying organic nitrogen production     

Takeo Hama  Shoko Kawashima  Koichi Shimotori  Yuhi Satoh  Yuko Omori  Shigeki Wada  Taiki Adachi  Shun Hasegawa  Takashi Midorikawa  Masao Ishii  Shu Saito  Daisuke Sasano  Hiroko Endo  Tsuyoshi Nakayama  Isao Inouye 《Journal of Oceanography》2012,68(1):183-194

The effect of ocean acidification, caused by the increase in pCO₂ in seawater, on phytoplankton population and on related organic nitrogen production was experimentally examined by use of a natural coastal microbial population. pCO₂ and pH were controlled by aeration with air in which pCO₂ was at the current level (control), for which ambient air was used, and with air in which pCO₂ was ??800?? and ??1200?? ppm, in 500-L culture vessels. The experiment was continued for 15?days after addition of the inorganic nutrients such as nitrate, phosphate, and silicate. During most of the experimental period, a minor increase in phytoplankton biomass was noted, probably because of low irradiance, an increase in phytoplankton biomass was observed at the end of the experiment. Flow cytometric and microscopic observations revealed that this increase was because of Chrysochromulina sp. (Haptophyceae). The growth of Chrysochromulina sp. was most obvious in the control vessel, and tended to be obscured by increasing pCO₂ (decrease in pH), indicating the possibility that ocean acidification inhibits the growth of specific phytoplankton groups, for example Chrysochromulina sp. Production of particulate organic nitrogen (PON), determined by the ¹⁵N tracer method, also diminished under acidified conditions compared with that at the current level.  相似文献   

‘Thailand was a desert' during the mid‐Cretaceous: Equatorward shift of the subtropical high‐pressure belt indicated by eolian deposits (Phu Thok Formation) in the Khorat Basin,northeastern Thailand     

Hitoshi Hasegawa  Suvapak Imsamut  Punya Charusiri  Ryuji Tada  Yu Horiuchi  Ken‐Ichiro Hisada 《Island Arc》2010,19(4):605-621

The Tibetan Plateau is a key factor in controlling the present‐day climate and atmospheric circulation pattern in Asia. The pattern of atmospheric circulation after the uplift of the plateau is well known, whereas direct evidence is lacking regarding the nature of the circulation pattern prior to the uplift. The distribution of desert directly reflects the position of the subtropical high‐pressure belt, and the prevailing surface‐wind pattern recorded in desert deposits reveals the position of its divergence axis. Cretaceous eolian sandstone of the Phu Thok Formation is extensively exposed in the northern Khorat Basin, northeastern Thailand. We conducted a sedimentological study on this formation to reconstruct temporal changes in the latitude of the subtropical high‐pressure belt in low‐latitude Asia during the Cretaceous. Spatio‐temporal changes in the paleo‐wind directions recorded in the Phu Thok Formation reveal that the Khorat Basin mainly belonged to the northeast trade wind belt and subtropical high‐pressure belt was situated to the north of the Khorat Basin during the initial stages of deposition, shifted southward to immediately above the basin during the main phase of deposition, and then shifted northward again to the north of the basin during the final stages of deposition. The paleomagnetic polarity sequence obtained for the Phu Thok Formation comprises three zones of normal polarity and two of reversed polarity, correlating to chrons M1n to C34n of the geomagnetic polarity time scale. This result suggests that the Phu Thok Formation is mid‐Cretaceous in age (from c. 126 Ma to c. 99–93 Ma), similar to the age of eolian sandstone in the Sichuan Basin, southern China (the Jiaguan Formation). These results, in combination with paleo‐wind direction data, suggest the development of low‐latitude desert and an equatorward shift of the subtropical high‐pressure belt (relative to the present‐day) in Asia during the mid‐Cretaceous.  相似文献   

Levels and distribution of polybrominated diphenyl ethers and organochlorine compounds in sea turtles from Japan     

Malarvannan G  Takahashi S  Isobe T  Kunisue T  Sudaryanto A  Miyagi T  Nakamura M  Yasumura S  Tanabe S 《Marine pollution bulletin》2011,63(5-12):172-178

Three species of sea turtles (green, hawksbill and loggerhead turtles) stranded along the coasts or caught (by-catch) around Ishigaki Island and Kochi, Japan were collected between 1998 and 2006 and analyzed for six organohalogen compounds viz., PBDEs, PCBs, DDTs, CHLs, HCHs and HCB. The present study is the first and foremost to report the occurrence of organohalogen compounds in the sea turtles from Japan. Among the compounds analyzed, concentrations of PCBs, DDTs and CHLs were the highest in all the turtle samples. PBDEs were ubiquitously present in all the turtle species. Comparing with the other two species, concentrations of organohalogens in green turtle were relatively low and decreasing trend in the concentrations were noted with increasing carapace length. Concentrations of OCs in sea turtles from the coasts of Ishigaki Island and Kochi were relatively low as compared to those from other locations in the world.  相似文献   

Shaking Maps for Scenario Earthquakes by Applying the Upgraded Version of the Strong Ground Motion Prediction Method ��Recipe��     

Nobuyuki Morikawa  Shigeki Senna  Yuzuru Hayakawa  Hiroyuki Fujiwara 《Pure and Applied Geophysics》2011,168(3-4):645-657

The strong ground motion prediction method ??Recipe?? was published by the Headquarters for Earthquake Research Promotion (HERP) of Japan. HERP has applied this method to prepare shaking maps for scenario earthquakes in specific active faults. Recently, Recipe was updated following its verification by simulations of strong ground motions associated with the Mw?=?6.6 off-shore earthquake west of Fukuoka prefecture in 2005, which occurred in the northwest part of the Kego fault zone located in northern Kyushu, Japan. One of the prominent changes in the upgraded version of Recipe is the inclusion of a procedure to evaluate seismic intensities on the ground surface from waveforms of S-wave velocity of 400?m/s on the engineering bedrock. By applying the upgraded version of Recipe, we have made shaking-maps for earthquakes in the southeast part of the Kego fault zone, which is located directly below the mega-city of Fukuoka. We assume four source models for scenario earthquakes; the locations of the asperities and the hypocenters vary between the models. The results show that in all cases, disastrous seismic intensities can strike a wide area of Fukuoka city. Differences in the distributions of seismic intensities among the four cases can be clearly observed in the area located on the extension of the source fault. Furthermore, we construct a velocity-layer structure model on the engineering bedrock for the central area of Fukuoka city. We assess not only the distribution of seismic intensities but also waveforms on the ground by using an equivalent linear method for the central area of Fukuoka city.  相似文献   

Response of a phytoplankton community to nutrient addition under different CO2 and pH conditions     

Takeo Hama  Tomoki Inoue  Risa Suzuki  Hiroto Kashiwazaki  Shigeki Wada  Daisuke Sasano  Naohiro Kosugi  Masao Ishii 《Journal of Oceanography》2016,72(2):207-223

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Ship berthing and mooring monitoring system by pneumatic-type fenders     

Shigeki Sakakibara  Masayoshi Kubo   《Ocean Engineering》2007,34(8-9):1174-1181

Ship berthing and mooring monitoring system by using pneumatic-type fenders has been proposed. This system consists of present berth monitoring system including a mooring line load monitoring system, and a fender load monitoring system. The fender loads such as fender deflection and reaction force are calculated by measuring inner air pressure of the pneumatic fenders, which have unique characteristics in performance. Furthermore both loads for the mooring lines and the fenders can be used to estimate moored ship motions simultaneously. Total ship monitoring system at jetty can be achieved and contributes safe ship berthing and mooring.  相似文献   

Application of a 3-D chemical fate prediction model (FATE3D) to predict dioxin concentrations in the Tokyo Bay     

Norihiro Kobayashi  Tomomi Eriguchi  Kisaburo Nakata  Shigeki Masunaga  Fumio Horiguchi  Junko Nakanishi 《Estuarine, Coastal and Shelf Science》2006,70(4):621

A 3-D chemical fate prediction model (FATE3D) was applied to predict the dioxin concentrations in the seawater of Tokyo Bay, Japan. The simulations were carried out for a period of one year (from September 2002 to August 2003). Parameters such as meteorological data, flow field conditions, concentrations and sinking rates of organic particulate matter, initial and boundary conditions, and loading fluxes and physico-chemical properties of dioxins were used as the model inputs.The simulation results compared favorably with the field measurements of dioxin concentrations in the bay for both the particulate and dissolved phases, indicating the validity and predictive capability of the model. Furthermore, the differences in the seasonal cycles and distributions between the particulate- and dissolved-phase dioxins in the bay were estimated from the simulation results.However, the particulate-phase dioxin concentrations in the bottom layers (+1 m from the bottom) were underestimated, probably because the resuspension process was not taken into account in the model. The improvement of the model's predictive capability, including the resuspension process, shall be the focus of our next study.  相似文献