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81.
Shigeru Mizugaki Yuichi Onda Taijiro Fukuyama Satoko Koga Hiroki Asai Shinya Hiramatsu 《水文研究》2008,22(23):4519-4531
To analyse suspended sediment sources in unmanaged Japanese cypress plantation watersheds, field measurements and fingerprinting of the suspended sediment was conducted in the Shimanto River basin in southern Japan. For sediment fingerprinting, 137Cs and 210Pbex were detected by means of gamma‐ray spectrometry in the surface soil of the forest floor, stream bank and truck trail and mobilized sediment by interrill erosion. The 137Cs and 210Pbex activities associated with the forest floor materials were considerably higher than those of the stream bank and truck trail. The 137Cs and 210Pbex activities associated with the suspended sediment were found to vary with the sampling period. Evidently, the suspended sediment can comprise materials generated from the forest floor by interrill erosion and those from the truck trail and/or stream bank. The multivariate sediment‐mixing model using 137Cs and 210Pbex showed that the contribution of the forest floor varied periodically, ranging from 23–56% in the Hinoki 156 subwatershed and from 18–85% in the Hinoki 155 subwatershed. The difference in the average contribution of the forest floor between Hinoki 156 (46%) and Hinoki 155 (69%) may relate to the presence of truck trail networks in the watershed. The truck trail network can play roles of sediment source and pathway for sediment from forest floor to stream channel due to the concentrated overland flow on the truck trail during heavy rainfall events. These results indicate that the forest floor should be recognized as a major source of suspended sediment in unmanaged Japanese cypress plantation watersheds. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
82.
A widespread distribution of hydrothermal and hydrogenetic manganese deposits is described in the results of the Hakurei‐Maru cruises conducted in the Bonin Arc areas of the West Pacific from 1984 to 1989. Manganese deposits occur in the active volcano chains, back‐arc basins, remnant back‐arc ridges, and oceanic seamounts. The hydrogenetic iron‐manganese deposits commonly form earthly black crusts and nodules on the topographic highs of inactive ridges and old seamounts, sometimes as thick as 10 cm. They are always composed of the iron‐manganese mineral vernadite. Co and Ni contents are relatively high in the crusts from the seamounts in the open Pacific Ocean (up to 1.1% Co and 1.0% Ni). Two generations of distinct chemistry and texture are typical of these crusts, which can be compared to reported thick crusts from the Central Pacific seamounts. The hydrothermal deposits, characterized by dense, submetallic, and gray appearance, are dominant in the recent and also in past submarine volcanoes of the island‐arc systems. Evidence of past hydrothermal activity was ascertained as fossil hydrothermal manganese deposits inside the hydrogenetic nodules or beneath the hydrogenetic crusts over the Tertiary island arc. Their component minerals are considered to be todorokite and bimessite (stable and contractible upon dehydration), having almost negligible amounts of Fe, Si, Al, Ni, Co, Zn, Pb, Cu, etc. In the small model site, the Kaikata Seamount hydrothermal area, the presumably recent hydrothermal activity has yielded thin slabs of pure manganate deposits growing downward within volcanic and sand layers. Early diagenetic influence is negligible on nodules of this area. 相似文献
83.
84.
Kazuhiro Tsukada Yuki Nakane Koshi Yamamoto Toshiyuki Kurihara Shigeru Otoh Kenji Kashiwagi Minjin Chuluun Sersmaa Gonchigdorj Manchuk Nuramkhaan Masakazu Niwa Tetsuya Tokiwa 《Island Arc》2013,22(2):227-241
We describe the mode of occurrence and geochemical characteristics of basalts, in the Khangai–Khentei belt in Mongolia, overlain by Middle Paleozoic radiolarian chert in an extensive accretionary complex. These basalts are greatly enriched in K, Ti, Fe, P, Rb, Ba, Th, and Nb in comparison to the composition of the mid‐ocean ridge basalts, indicative of within‐plate alkaline type. Ti/Y vs Nb/Y and MnO/TiO2/P2O5 ratios of the basalts also suggest within‐plate affinities. Considering the geochemical characteristics as well as the conformable relationship with the overlying radiolarian chert, the alkaline basalts were clearly not continental but formed a pelagic oceanic island. The mode of occurrence and geochemistry of the basalts show that the alkaline basaltic volcanic activity had taken place to form an oceanic island in the Paleozoic pelagic region sufficiently far from continents to allow radiolarian ooze accumulation. 相似文献
85.
Shigeru Terashima Kohei Sato Masahiro Taniguchi Takashi Okai Noboru Imai 《Geostandards and Geoanalytical Research》2003,27(3):259-271
Two new geochemical reference materials, copper ore JCu-1 and zinc ore JZn-1 have been prepared by the Geological Survey of Japan (GSJ) for the determination of major and minor elements and isotopic compositions. JCu-1 is a sample of Cu-bearing sulfide ore typical of the Kamaishi mine in Iwate Prefecture, Japan, and is composed mainly of hedenbergite, chalcopyrite, quartz and calcite. Pyrrhotite, magnetite and actinolitic amphibole were also commonly found. The Zn-rich ore, JZn-1 is a crude ore from the Kamioka Pb-Zn mine in Gifu Prefecture, Japan. The sample consists of hedenbergite, quartz, calcite, sphalerite and epidote as main crystalline phase. Homogeneity test results showed that all studied constituents including ore elements such as Cu, Pb and Zn can be considered to be homogeneously distributed. Provisional collaborative analyses were carried out in ten laboratories, and the data were evaluated using a robust statistical method using z-scores. Recommended values for a number of major elements including TiO2 , Al2 O3 , MnO, MgO, CaO, Na2 O, K2 O, Fe (total), Zn, Cu and Pb were established. In addition, information values for eighteen major, minor and trace elements are presented to support future collaborative analyses. 相似文献
86.
A new model of back-arc spreading in the Parece Vela Basin, northwest Pacific margin 总被引:1,自引:0,他引:1
Abstract Swath bathymetric data, single-channel seismic reflection profiles, magnetic and gravity anomalies in the northern part of the Parece Vela (West Mariana) Basin were obtained by comprehensive surveys conducted by the Hydrographic Department of Japan. The central zone of the Parece Vela Basin is characterized by the north-south trending chain of depressions in a right-stepping en echelon alignment. The morphology of these depressions is diamond shaped and bordered by steep escarpments of 1000-1500 m relative height. These fault escarpments extend northeastward and southwestward from the depressions into the surrounding basin floor and then gradually fade out. These escarpments have an S-shaped trend, and their geometry seems to be symmetric about the depressions. Minor ridges and troughs trending orthogonal to these escarpments are recognized. It is concluded that these depressions and escarpments are the topographic expression of extinct spreading axes and S-shaped transform faults, respectively. The age of the central depressions seems to be young, although details of tectonic processes forming them remains unsolved. The western province of the basin floor and basement is extremely rugged and characterized by minor ridges and troughs trending in a north-south direction. Although magnetic anomalies of the basin are very weak, magnetic lineations trending parallel to the topographic trend are recognizable in the central and western parts of the basin. Based on updated geomorpholog-ical features and magnetic anomalies revealed by the present survey, together with the previously published data including drilling results, it is proposed that the evolution of Parece Vela Basin took place in four stages of opening and tectonic activity: rifting, east-west spreading, northeast-southwest spreading with counter-clockwise rotation of spreading axes, and post-spreading deformation and volcanism. This proposed spreading model of the Parece Vela Basin is similar to that of the adjacent Shikoku Basin. The spreading axes of both basins were segmented and gradually rotated counter-clockwise in a later phase of the basin evolution, after the cessation of relatively uniform spreading nearly in an east-west direction. 相似文献
87.
Noboru IMAI Shigeru TERASHIMA Shiro ITOH Atsushi ANDO 《Geostandards and Geoanalytical Research》1996,20(2):165-216
Analytical data compiled on nine Geological Survey of Japan (GSJ) reference samples, "Sedimentary rock series" received by February 1996 are reported. After excluding outliers and examining critically the analytical procedures employed, the data were evaluated statistically. Recommended or preferable values for fifteen major and sixty minor and trace elements are proposed. 相似文献
88.
Takahiro Yamamoto Tatsunori Soya Shigeru Suto Kozo Uto Akira Takada Keiichi Sakaguchi Koji Ono 《Bulletin of Volcanology》1991,53(4):301-308
The submarine eruption of a new small knoll, which was named Teishi knoll, off eastern Izu Peninsula behind the Izu-Mariana arc occurred in the evening of 13 July 1989. This is the first historic eruption of the Higashi-Izu monogenetic volcano group. The eruption of 13 July followed an earthquake swarm near Ito city starting on 30 June. There were subsequent volcanic tremors on 11 and 12 July, and the formation of the Teishi knoll on the 100 m deep insular shelf 4 km northeast of Ito city. There were five submarine explosions, which were characterized by intermittent domelike bulges of water and black tephra-jets, which occurred within 10 min on 13 July. Ejecta of the eruption was small in volume and composed of highly crystalline basalt scoria, highly vesiculated pumice, and lithic material. Petrographical features suggest that the pumice was produced by vesiculation of reheated wet felsic tuff of an older formation. The Teishi knoll, before the eruption, was a circular dome, 450 m across and 25 m high, with steep sides and a flat summit. Considerations of submarine topographic change indicate the knoll was raised by sill-like intrusion of 106 m3 of magma beneath a 30 m thick sediment blanket. This shallow intrusion is assumed to have started on 11 July when volcanic tremors were observed for the first time, but there was no indications of violent interaction between wet host sediments and intruding magma. The submarine eruption of 13 July appears to have been Friggered by a major lowering of the magma-column. The basalt scoria, having crystal-contents of more than 60%, is assumed to be derived from the cooled plastic margin of the shallow intrusive body. However, glassy scoria, which would indicate the interaction between hot fluidal magma and external water, was not observed. A scenario for the 1989 submarine eruption is as follows. When rapid subsidence of the hot interior of the intrusive magma occurred, reduced pressure caused the implosion of cooled plastic magma, adjacent pressurized, hot host material, and wet sediment. The mixing of these materials triggered the vigorous vapor explosions. 相似文献
89.
Katsuhiko Matsunaga Kohji Igarashi Kazuo Abe Isao Kudo Shigeru Fukase 《Journal of Oceanography》1983,39(3):115-118
A new type ofin situ filtration sampler is described. The all Teflon sampler is hung on a nylon rope attached to a steel wire (Fig. 3). By dropping a messenger, the sampler piston is pulled down by a released weight of 50 kg, and the sampler is filled with about 400 ml of filtered water. The sample is not contaminated by metals because there is no metal around the sampler. 相似文献
90.
Determinations of Chlorophyll a (Chl a) in eutrophic coastal marine waters were compared using N, N-dimethylformamide (DMF) and 90% acetone techniques. Measured
Chl a concentrations ranged from 0.89 to 10.65 μg l−1 for 90% acetone extracts and from 0.97 to 12.92 μg l−1 for DMF extracts, respectively, for 24 surface water samples from the Harima-nada, Seto Inland Sea, Japan. Chl a concentrations using DMF as a solvent were consistently higher than those found using 90% acetone (p < 0.001, n= 24). Chl a is thus likely to be underestimated (by 13%) when 90% acetone is used for eutrophic waters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献