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81.
Urumu Tsunogai Kanae Kamimura Saya Anzai Fumiko Nakagawa Daisuke D. Komatsu 《Geochimica et cosmochimica acta》2011,75(16):4531-4546
In high-temperature volcanic fumaroles (>400 °C), the isotopic composition of molecular hydrogen (H2) reaches equilibrium with that of the fumarolic H2O. In this study, we used this hydrogen isotope exchange equilibrium of fumarolic H2 as a tracer for the remote temperature at volcanic fumaroles. In this remote sensing, we deduced the hydrogen isotopic composition (δD value) of fumarolic H2 from those in the volcanic plume. To ascertain that we can estimate the δD value of fumarolic H2 from those in a volcanic plume, we estimated the values in three fumaroles with outlet temperatures of 630 °C (Tarumae), 203 °C (Kuju), and 107 °C (E-san). For this we measured the concentration and δD value of H2 in each volcanic plume, along with those determined directly at each fumarole. The average and maximum mixing ratios of fumarolic H2 within a plume’s total H2 were 97% and 99% (at Tarumae), 89% and 96% (at Kuju), and 97% and 99% (at E-san). We found a linear relationship between the depletion in the δD values of H2, with the reciprocal of H2 concentration. Furthermore, the estimated end-member δD value for each H2-enriched component (−260 ± 30‰ vs. VSMOW in Tarumae, −509 ± 23‰ in Kuju, and −437 ± 14‰ in E-san) coincided well with those observed at each fumarole (−247.0 ± 0.6‰ in Tarumae, −527.7 ± 10.1‰ in Kuju, and −432.1 ± 2.5‰ in E-san). Moreover, the calculated isotopic temperatures at the fumaroles agreed to within 20 °C with the observed outlet temperature at Tarumae and Kuju. We deduced that the δD value of the fumarolic H2 was quenched within the volcanic plume. This enabled us to remotely estimate these in the fumarole, and thus the outlet temperature of fumaroles, at least for those having the outlet temperatures more than 400 °C. By applying this methodology to the volcanic plume emitted from the Crater 1 of Mt. Naka-dake (the volcano Aso) where direct measurement on fumaroles was impractical, we estimated that the δD value of the fumarolic H2 to be −172 ± 16‰ and the outlet temperature to be 868 ± 97 °C. The remote temperature sensing using hydrogen isotopes developed in this study is widely applicable to many volcanic systems. 相似文献
82.
Shuangmeng Zhai Weihong Xue Daisuke Yamazaki Shuangming Shan Eiji Ito Naotaka Tomioka Akira Shimojuku Ken-ichi Funakoshi 《Physics and Chemistry of Minerals》2011,38(5):357-361
High pressure in situ synchrotron X-ray diffraction experiment of strontium orthophosphate Sr3(PO4)2 has been carried out to 20.0 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P–V data yields a volume of V 0 = 498.0 ± 0.1 Å3, an isothermal bulk modulus of K T = 89.5 ± 1.7 GPa, and first pressure derivative of K T ′ = 6.57 ± 0.34. If K T ′ is fixed at 4, K T is obtained as 104.4 ± 1.2 GPa. Analysis of axial compressible modulus shows that the a-axis (K a = 79.6 ± 3.2 GPa) is more compressible than the c-axis (K c = 116.4 ± 4.3 GPa). Based on the high pressure Raman spectroscopic results, the mode Grüneisen parameters are determined and the average mode Grüneisen parameter of PO4 vibrations of Sr3(PO4)2 is calculated to be 0.30(2). 相似文献
83.
Takeshi Hanyu Laure Dosso Osamu Ishizuka Kenichiro Tani Barry B. Hanan Claudia Adam Shun’ichi Nakai Ryoko Senda Qing Chang Yoshiyuki Tatsumi 《Contributions to Mineralogy and Petrology》2013,166(5):1285-1304
We present the first report of geochemical data for submarine basalts collected by a manned submersible from Rurutu, Tubuai, and Raivavae in the Austral Islands in the South Pacific, where subaerial basalts exhibit HIMU isotopic signatures with highly radiogenic Pb isotopic compositions. With the exception of one sample from Tubuai, the 40Ar/39Ar ages of the submarine basalts show no significant age gaps between the submarine and subaerial basalts, and the major element compositions are indistinguishable at each island. However, the variations in Pb, Sr, Nd, and Hf isotopic compositions in the submarine basalts are much larger than those previously reported in subaerial basalts. The submarine basalts with less-radiogenic Pb and radiogenic Nd and Hf isotopic compositions show systematically lower concentrations in highly incompatible elements than the typical HIMU basalts. These geochemical variations are best explained by a two-component mixing process in which the depleted asthenospheric mantle was entrained by the mantle plume from the HIMU reservoir during its upwelling, and the melts from the HIMU reservoir and depleted asthenospheric mantle were then mixed in various proportions. The present and compiled data demonstrate that the HIMU reservoir has a uniquely low 176Hf/177Hf decoupled from 143Nd/144Nd, suggesting that it was derived from an ancient subducted slab. Moreover, the Nd/Hf ratios of the HIMU basalts and curvilinear Nd–Hf isotopic mixing trend require higher Nd/Hf ratios for the melt from the HIMU reservoir than that from the depleted mantle component. Such elevated Nd/Hf ratios could reflect source enrichment by a subducted slab during reservoir formation. 相似文献
84.
Tetsuya Tokiwa Kimikazu Tsusaka Makoto Matsubara Taiki Ishikawa Daisuke Ogawa 《地学前缘(英文版)》2013,4(1):105-111
This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan.Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone(EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks.The EDZ fractures terminate against pre-existing shear fractures.Therefore,even for excavations in soft sedimentary rocks,formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes. 相似文献
85.
Noriko T. Kita Kees C. Welten John W. Valley Michael J. Spicuzza Daisuke Nakashima Travis J. Tenner Takayuki Ushikubo Glenn J. MacPherson Linda Welzenbach Philipp R. Heck Andrew M. Davis Matthias M. M. Meier Rainer Wieler Marc W. Caffee Matthias Laubenstein Kunihiko Nishiizumi 《Meteoritics & planetary science》2013,48(4):641-655
The Mifflin meteorite fell on the night of April 14, 2010, in southwestern Wisconsin. A bright fireball was observed throughout a wide area of the midwestern United States. The petrography, mineral compositions, and oxygen isotope ratios indicate that the meteorite is a L5 chondrite fragmental breccia with light/dark structure. The meteorite shows a low shock stage of S2, although some shock‐melted veins are present. The U,Th‐He age is 0.7 Ga, and the K‐Ar age is 1.8 Ga, indicating that Mifflin might have been heated at the time of the 470 Ma L‐chondrite parent body breakup and that U, Th‐He, and K‐Ar ages were partially reset. The cosmogenic radionuclide data indicate that Mifflin was exposed to cosmic rays while its radius was 30–65 cm. Assuming this exposure geometry, a cosmic‐ray exposure age of 25 ± 3 Ma is calculated from cosmogenic noble gas concentrations. The low 22Ne/21Ne ratio may, however, indicate a two‐stage exposure with a longer first‐stage exposure at high shielding. Mifflin is unusual in having a low radiogenic gas content combined with a low shock stage and no evidence of late stage annealing; this inconsistency remains unexplained. 相似文献
86.
Aki Ito Hiroko Sugioka Daisuke Suetsugu Hajime Shiobara Toshihiko Kanazawa Yoshio Fukao 《Marine Geophysical Researches》2012,33(3):229-238
A number of seismoacoustic T-wave events were observed between January 2003 and January 2004 by broadband ocean-bottom seismometers installed on the French Polynesia seafloor at depths of 4,000?C5,000?m, well below the conjugate depth of the SOFAR channel. Using T-wave arrival times, we located 89 T-wave events along the Pacific-Antarctic Ridge. Among these, 63 events were not detected by land-based seismic observations of the United States Geological Survey (USGS), which was nearly twice the number of earthquakes reported by the USGS in the area during the observation period. We used a simple method to estimate earthquake magnitude from T-wave energy. The magnitudes of the events unidentified by the USGS ranged from 2.3 to 5.5, whereas magnitudes of the earthquakes reported by the USGS ranged from 4.1 to 6.2. Our study suggests that T-wave observations with abyssal ocean-bottom seismometers can improve the detection of small earthquakes and help our understanding of the seismotectonics of remote oceanic areas. 相似文献
87.
Kota Katsuki Yasushi Miyamoto Kazuyoshi Yamada Hiroyuki Takata Keiko Yamaguchi Daisuke Nakayama Hugo Coops Hidenobu Kunii Ritsuo Nomura Boo-Keun Khim 《Journal of Paleolimnology》2008,40(4):1115-1125
Lake Nakaumi, southwest Japan, is an enclosed lagoon characterized by polyhaline and halocline conditions. Since the last
century, its ecological state has been altered by eutrophication. We used a paleolimnological approach and studied multiple
proxies, including chemical compounds, diatoms, foraminifera and molluscs, to infer the eutrophication history of the ecosystem.
Eutrophication in Lake Nakaumi was associated with several factors, including increased nutrient loading, input of herbicides,
and dike building since the 1920s. The ecological condition of this lake was divided into several stages that reflect the
eutrophication process after the 1940s. A catastrophic “regime shift” from a clear state with aquatic vegetation to a turbid
one with phytoplankton occurred in the early 1950s. Environmental degradation in the Honjo area, a part of Lake Nakaumi, was
attributed primarily to physical changes caused by the construction of an enclosing dike. Eutrophication occurred almost simultaneously
with the physical changes to the Honjo area in the 1970s. Until recently, no regime shift was observed in this area, though
the core-top sediments show possible symptoms of incipient change. 相似文献
88.
Contributions of slab fluid and sediment melt components to magmatism in the Mariana Arc–Trough system: Evidence from geochemical compositions and Sr,Nd, and noble gas isotope systematics
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Yasuo Ikeda Keisuke Nagao Teruaki Ishii Daisuke Matsumoto Robert J. Stern Hiroo Kagami Makoto Arima Sherman H. Bloomer 《Island Arc》2016,25(4):253-273
This study presents new major and trace element, mineral, and Sr, Nd, and noble gas isotope geochemical analyses of basalts, gabbro, and clinopyroxenite from the Mariana Arc (Central Islands and Southern Seamount provinces) including the forearc, and the Mariana Trough (Central Graben and Spreading Ridge). Mantle source compositions beneath the Mariana Arc and the Mariana Trough indicate a mantle source that is depleted in high field strength elements relative to MORB (mid‐oceanic ridge basalt). Samples from the Mariana Arc, characterized by high ratios of Ba/Th, U/Th, 84Kr/4He and 132Xe/4He, are explained by addition of fluid from the subducted slab to the mantle wedge. Correlations of noble gas data, as well as large ion lithophile elements, indicate that heavy noble gases (Ar, Kr, and Xe) provide evidence for fluid fluxing into the mantle wedge. On the other hand, major elements and Sr, Nd, He, and Ne isotopic data of basalts from the Mariana Trough are geochemically indistinguishable from MORB. Correlations of 3He/4He and 40Ar/36Ar in the Mariana Trough samples are explained by mixing between MORB and atmosphere. One sample from the Central Graben indicates extreme enrichment in 20Ne/22Ne and 21Ne/22Ne, suggesting incorporation of solar‐type Ne in the magma source. Excess 129Xe is also observed in this sample suggesting primordial noble gases in the mantle source. The Mariana Trough basalts indicate that both fluid and sediment components contributed to the basalts, with slab‐derived fluids dominating beneath the Spreading Ridge, and that sediment melts, characterized by high La/Sm and relatively low U/Th and Zr/Nb, dominate in the source region of basalts from the Central Graben. 相似文献
89.
Tuite has been suggested as a potential reservoir for trace elements in the deep mantle,but no evidence confirms this supposition.By using a natural apatite as starting material,the trace-element-bearing tuite large crystals were obtained under highpressure and high-temperature conditions(15 GPa and 1800 K).X-ray diffraction pattern and Micro-Raman spectrum of the run product confirm that tuite was synthesized.The concentrations of trace elements in tuite crystals were analyzed by laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS).The rare earth element patterns of tuite show enrichment of light rare earth elements relative to heavy rare earth elements.Tuite shows high concentrations of Th and Sr,and negative anomalies of Rb,Nb,and Hf.The results show that tuite can accommodate a large amount of trace elements.Tuite might be an important host to accommodate trace elements if there is much apatite subducted into the deep mantle. 相似文献
90.
Laboratory measurements of ‘porosity‐free’ intrinsic Vp and Vs in an olivine gabbro of the Oman ophiolite: Implication for interpretation of the seismic structure of lower oceanic crust
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In order to determine ‘porosity‐free’ intrinsic ultrasonic compressional (Vp) and shear wave (Vs) velocities and Vp/Vs of an olivine gabbro from the Oman ophiolite, we developed a new experimental system using a piston‐cylinder type high‐pressure apparatus. The new system allowed us to measure velocities at pressures ranging from 0.20 to 1.00 GPa and at temperatures up to 300°C for Vp and 400°C for Vs. At room temperature, the Vp and Vp/Vs increase rapidly with pressure up to 0.40 GPa, while between 0.45 and 1.00 GPa the increase is more gradual. The change in increasing rate is attributed to closure of porosity at pressures above 0.45 GPa. Based on the linear regression of data obtained at higher pressures (0.45–1.00 GPa) and extrapolation to the lower pressures, combined with temperature derivatives of velocities of the sample measured at 1.00 GPa, we determined the intrinsic Vp and Vs of the sample as a function of pressure (P, in GPa) and temperature (T, in °C). The intrinsic velocities can be expressed as Vp (km/s) = 7.004 + 0.096 × P ? 0.00015 × T, and Vs (km/s) = 3.827 + 0.007 × P ? 0.00008 × T. We evaluated the intrinsic Vp and Vs of the olivine gabbro at oceanic crustal conditions and compared them with a velocity depth‐profile of the borehole seismic observatory WP‐2 area in the northwestern Pacific Basin. Although the intrinsic Vp (~7.0 km/s) and Vs (~3.8 km/s) for the olivine gabbro studied are comparable to those of seismic layer 3 in the WP‐2 area, the estimated vertical gradients of intrinsic velocities are significantly smaller than those reported from layer 3. These results suggest that velocity profiles of layer 3 in the WP‐2 area may reflect the presence of a minor porosity in lower oceanic crust, which closes with increasing depth and/or continuous changes in mineralogy of layer 3 rocks. 相似文献