Lead-210 in the Japan Sea     

Yoshiyuki Nozaki  Shizuo Tsunogai  Masakichi Nishimura 《Journal of Oceanography》1973,29(6):251-256

This is the first detailed study on the distribution of lead-210 in the Japan Sea water. The content of lead-210 ranged from 9.3±2.1 dph/l in the surface water to 3.4+-0.8 dph/l in the deep water—a quite low content as compared to that in the deep water of the North Pacific. Vertical profiles show that the content of lead-210 abruptly decreases below the seasonal thermocline (10–20 m in depth) and nearly uniform in the deep water. It is suggested that a significant amount of air-borne lead-210 deposited over the Japan Sea is transported along with the Tsushima Current to the open ocean. The budget of lead-210 is calculated by using a simple box-model and the mean residence time of lead-210 in the Japan Sea is estimated to be 15 yr.  相似文献   

Geochemistry of Quaternary lavas from NE Sulawesi: transfer of subduction components into the mantle wedge     

Yoshiyuki Tatsumi  Mitsuhiro Murasaki  Edy M. Arsadi  Susumu Nonda 《Contributions to Mineralogy and Petrology》1991,107(2):137-149

Major and trace element, and Sr-Nd isotope compositions were determined for Quaternary volcanic rocks from NE Sulawesi (the Sangihe are), Indonesia, in order to examine the origin of across-arc variation in lava and magma source chemistry. The arc is formed in an intraoceanic tectonic setting and is not associated with a backarc basin, thereby minimizing possible contributions from non-arc geochemical reservoirs. The geochemistry of these arc lavas is likely to provide essential information about the chemical characteristics of subduction components. All incompatible elements, except Pb, increase away from the volcancic front. Major element data for Mg-rich lavas together with available experimental data, suggest that primary magmas are produced at higher pressured by smaller degrees of partial melting beneath the backarc-side volcanoes. Rb/K and Ba/Pb are higher, and ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd are lower in backarc-side lavas. These variations may be attributed to generation of hydrous fluids in the downdragged hydrous peridotite layer at the base of the mantle wedge through the following reactions: decompositions of pargasitic amphibole to form phlogopite and breakdown of phlogopite to crystallize K-richterite, beneath the volcanic front and the backarc-side volcanoes, respectively.  相似文献   

An absarokite from a phlogopite lherzolite source   总被引：1，自引：0，他引：1  

Yoshiyuki Tatsumi  Takehiro Koyaguchi 《Contributions to Mineralogy and Petrology》1989,102(1):34-40

An absarokite (SiO₂ 47.72 wt %, K₂O 3.41 wt %) occurs in the Katamata volcano, SW Japan. The rock carries phenocrysts of olivine, phlogopite, clinopyroxene, and hornblende. Chemical compositions of bulk rock (FeO^*/ MgO 0.73) and minerals (Mg-rich olivine and phlogopite, Cr-rich chromite) suggest that the absarokite is not differentiated. Melting experiments at high pressures on the Katamata absarokite have been conducted. The completely anhydrous absarokite melt coexists with olivine, orthopyroxene, and clinopyroxene at 1310° C and 1.0 GPa. The melt with 3.29 wt % of H₂O also coexists with the above three phases at 1230° C and 1.4 GPa; phlogopite appears at temperatures more than 80° C below the liquidus. On the other hand, the melt is not saturated with lherzolite minerals in the presence of 5.13 wt % of H₂O and crystallizes olivine and phlogopite as liquidus phases; the stability limit of phlogopite is little affected at least by the present variation of H₂O content in the absarokite melt. It is suggested that the absarokite magma was segregated from the upper mantle at 1170° C and 1.7 GPa leaving a phlogopite lherzolite as a residual material on the basis of the above experimental results and the petrographical observation that olivine and phlogopite crystallize at an earlier stage of crystallization sequence than clinopyroxene. The contribution of phlogopite at the stage of melting processes is also suggested by the geochemical characteristics that the absarokite is more enriched in Rb, K, and Ba and depleted in Ca and Na than a typical alkali olivine basalt from the same volcanic field.  相似文献   

Dissolved Al, In, and Ce in the eastern Indian Ocean and the Southeast Asian Seas in comparison with the radionuclides Pb and Po     

Hajime Obata  Yoshiyuki Nozaki  Yoshiyuki Yamamoto 《Geochimica et cosmochimica acta》2004,68(5):1035-1048

To carry out comparative geochemical investigation of refractory and reactive metals in different oceanic settings covering different θ-S characteristics, productivity, dissolved oxygen profiles, water and sediment discharge, etc., we have determined the vertical profiles of dissolved (<0.04 μm) Al, In and Ce, as well as ²¹⁰Pb and ²¹⁰Po in the eastern Indian Ocean (from 40°S in the Southern Ocean to 8°N in the Bay of Bengal) and the Southeast Asian Seas. In the Antarctic Circumpolar Region, the concentrations of these refractory metals are very low, presumably due to very low the atmospheric input and intensified scavenging. Resemblance in the vertical profiles of these metals is often seen in some other stations. However, there are also significant differences among their distributions, for example, in the magnitude of surface enrichment caused by the external input from eolian and fluvial-coastal sources. Comparison of Al distributions in surface waters with those of atmospherically derived ²¹⁰Pb suggests the relative importance of eolian input over fluvial-coastal sources. Fluvial and coastal input appears to be insignificant for dissolved In, but may be important for Ce. The mean residence time of Al in the surface mixed layer was estimated to be ∼2 years which is similar to that of ²¹⁰Pb.In the intermediate and deep waters, the concentrations of each element vary with depth and location. The range of variation is in the order of Al>Ce>In, depending upon particle reactivity. Although dissolved Al decreases along the water trajectory by particle scavenging, variations of dissolved In and Ce are relatively small which may be due to less scavenging for both elements. Compared with significantly high (>4 pM) dissolved Ce throughout the water column in the Bay of Bengal, dissolved Al concentration remains low, suggesting that it has higher affinity to particles and hence is scavenged by sinking particulate matter. This is consistent with the observation that the dissolved Al in the Antarctic Intermediate Water (AAIW) decreases from 4 to 6 nM in the 30°S Perth Basin to <0.7 nM in the 10°S West Australia Basin along its trajectory. Using the chlorofluorocarbons (CFCs) ventilation age of AAIW (Fine, 1993), the mean residence time of Al in the intermediate and deep waters in the eastern Indian Ocean is estimated to be <17 yr, approximately the same as that of ²¹⁰Pb (10-15 yr). In the semiclosed basins of Southeast Asia, the distributions of Al, In and Ce are also very unique. In the South China Sea, there is a strong sediment source for dissolved In and Ce during the deepwater passage through the Luzon Strait.  相似文献   

Lead-210 in the North Pacific and the transport of terrestrial material through the atmosphere     

Yoshiyuki Nozaki  Shizuo Tsunogai 《Earth and Planetary Science Letters》1973,20(1):88-92

²¹⁰Pb in the surface water of the North Pacific was extensively determined. The results showed that the highest concentrations of²¹⁰Pb of 19 ± 3dpm/100kg were found in the northern mid-latitudes around 30°N, but longitudinal variation across the North Pacific was not observed. The mean residence time of²¹⁰Pb in the surface water up to 100 m in depth is calculated to be 230 days. In the mid-latitudes of the northern hemisphere,²¹⁰Pb may be transported by the prevailing westerly wind of a higher speed than 15 m/sec, likely the jet stream.  相似文献   

Underground storage of carbon dioxide in depleted natural gas reservoirs and in useless aquifers     

Hitoshi Koide  Yoshiyuki Tazaki  Yoshikazu Noguchi  Masaki Iijima  Kazuitsu Ito  Yuji Shindo 《Engineering Geology》1993,34(3-4):175-179

Depleted reservoirs of natural gas and petroleum can provide excellent traps for carbon dioxide. Deep aquifers, which are not used due to high salinity, can host larger amount of the carbon dioxide under their high formation pressure than natural gas and oir reservoirs. Small fraction of aquifers in sedimentary basins in the world are enough to host about 87 gigaton-C of carbon dioxide.

A preliminary technical and economical survey on the carbon dioxide injection system suggests that the energy requirement for carbon dioxide injection into subterranean aquifers is about 269 kWh/ton-C and that the investment and operation costs for system are 79 $/ton-C. By our preliminary cost estimation in Japan, the CO₂-emission-free electricity generation may become possible with a cost increase of 35% for natural-gas-fired power station, and of 60% for coal-fired-power station.  相似文献   

Composition and pressure dependence of lattice thermal conductivity of (Mg,Fe)O solid solutions     

Akira Hasegawa  Kenji Ohta  Takashi Yagi  Kei Hirose  Yoshiyuki Okuda  Tadashi Kondo 《Comptes Rendus Geoscience》2019,351(2-3):229-235

We measured the lattice thermal conductivities of Fe_0.98O wüstite and iron-rich (Mg,Fe)O magnesiowüstite using the pulsed light heating thermoreflectance technique with a diamond anvil cell up to 61 GPa at 300 K. We found that the thermal conductivity of wüstite does not show a monotonic increase as a function of pressure, contrary to that of MgO periclase. Rocksalt (B1) to rhombohedral B1 transition is likely to induce an abnormal pressure response in the conductivity of wüstite. Our results also show that magnesiowüstite has a lower conductivity than that of MgO and FeO endmembers due to a strong iron impurity effect, which is well reproduced by a model considering phonon-impurity scattering in a binary solid solution.  相似文献   

Seismic Wavefields in the Deep Seafloor Area from a Submarine Landslide Source     

Takeshi Nakamura  Hiroshi Takenaka  Taro Okamoto  Yoshiyuki Kaneda 《Pure and Applied Geophysics》2014,171(7):1153-1167

We use the finite difference method to simulate seismic wavefields at broadband land and seafloor stations for a given terrestrial landslide source, where the seafloor stations are located at water depths of 1,900–4,300 m. Our simulation results for the landslide source explain observations well at the seafloor stations for a frequency range of 0.05–0.1 Hz. Assuming the epicenter to be located in the vicinity of a large submarine slump, we also model wavefields at the stations for a submarine landslide source. We detect propagation of the Airy phase with an apparent velocity of 0.7 km/s in association with the seawater layer and an accretionary prism for the vertical component of waveforms at the seafloor stations. This later phase is not detected when the structural model does not consider seawater. For the model incorporating the seawater, the amplitude of the vertical component at seafloor stations can be up to four times that for the model that excludes seawater; we attribute this to the effects of the seawater layer on the wavefields. We also find that the amplification of the waveform depends not only on the presence of the seawater layer but also on the thickness of the accretionary prism, indicating low amplitudes at the land stations and at seafloor stations located near the trough but high amplitudes at other stations, particularly those located above the thick prism off the trough. Ignoring these characteristic structures in the oceanic area and simply calculating the wavefields using the same structural model used for land areas would result in erroneous estimates of the size of the submarine landslide and the mechanisms underlying its generation. Our results highlight the importance of adopting a structural model that incorporates the 3D accretionary prism and seawater layer into the simulation in order to precisely evaluate seismic wavefields in seafloor areas.  相似文献   

Fragility curves for expressway embankments based on damage datasets after recent earthquakes in Japan     

Yoshihisa Maruyama  Fumio Yamazaki  Kiku Mizuno  Yoshiyuki Tsuchiya  Hiroyuki Yogai 《Soil Dynamics and Earthquake Engineering》2010

The seismometer network of the Japanese expressway system was enhanced following the 1995 Kobe earthquake. Based on earthquake information from the instruments of the seismometer network, a traffic control is performed directly after the event because of the potential for damage to expressway structures. Expressways serve as vital trunk lines of transportation and are important for the restoration of damage-stricken areas. Therefore, earthquake-induced damage to expressway structures should be estimated as soon as possible. Expressway embankments were seriously damaged during recent earthquakes, such as the 2004 Niigata Chuetsu earthquake. The present study constructs the fragility curves of expressway embankments in Japan in order to estimate the damage distribution immediately after an earthquake. Damage datasets for expressways are compiled for the 2003 Northern-Miyagi earthquake, the 2003 Tokachi-oki earthquake, the 2004 Niigata Chuetsu earthquake, and the 2007 Niigata Chuetsu-oki earthquake. The spatial distributions of the peak ground velocity (PGV) are estimated for these four earthquakes in order to evaluate the relationship between the damage ratio of expressway embankments and the PGV. Statistical analysis is then conducted in order to draw the fragility curves for expressway embankments. Based on the fragility curves, major damage that disrupts ordinary expressway traffic may occur when the peak ground velocity exceeds approximately 35.0 cm/s. The fragility curves constructed in the present study are helpful for predicting the damage distribution on expressways soon after an earthquake, which enables efficient traffic control and rapid disaster response.  相似文献   

Element transport by dehydration of subducted sediments: Implication for arc and ocean island magmatism   总被引：5，自引：0，他引：5  

Yoshitaka Aizawa  Yoshiyuki Tatsumi  & Hirohisa Yamada 《Island Arc》1999,8(1):38-46

High-pressure experiments on a natural pelite have been conducted at 2–11-GPa pressures in order to evaluate contributions of subducted sediments to arc and ocean island magmatism. Obtained phase relations suggest that, at least in modern subduction zones, subsolidus dehydration of chlorite and phengitic muscovite in the subducted sediments, rather than partial melting, is a predominant process in overprinting sediment components onto the magma source region. Trace element compositions of sediment-derived fluids are estimated based on dehydration experiments at 5.5 GPa and 900/1300°C. Pb is effectively transported by fluids relative to other elements. This results in the Pb enrichment for arc basalts by fluids, generated by the dehydration of subducted sediments, together with altered mid-ocean ridge basalt (MORB), and complementary depletion of Pb in subducted sediments. Inferred arc magma compositions obtained by model calculations based on the present experimental results agree well with a natural primitive arc basalt composition. A large increase in the U/Pb ratio in the subducted sediments at deeper levels than major dehydration depths results in a high Pb isotopic ratio through radioactive decay after long periods of isolation. Combined with other isotopic ratios such as Sr and Nd, it is possible to produce the EM II source, one of the enriched geochemical reservoirs for ocean island basalt magmas, by mixing of a small amount of subducted sediments with depleted or primitive mantle.  相似文献