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91.
Masayuki Hattori 《The Professional geographer》1979,31(3):321-326
A regret frequently expressed at International Geographical Congresses concerns the lack of summary information about the nature of geographic research in the host country. During a discussion of this point with members of the Association of Japanese Geographers, the idea of publishing a series of reports on various aspects of Japanese research surfaced. The concept was later enthusiastically supported by the United States National Committee for the International Geographical Union. This first report, “Historical Geography in Japan,” has been modified for the benefit of the English-speaking readers of THE PROFESSIONAL GEOGRAPHER. Although the reports will be of particular interest to those planning to attend the 1980 IGC in Tokyo, they should prove of general interest as well.—H. Jesse Walker, Member, U.S. National Committee, IGU. 相似文献
92.
Yoshio Takahashi Tomoya Uruga Hajime Tanida Keiko H. Hattori 《Geochimica et cosmochimica acta》2007,71(21):5180-5190
Local atomic structures of Re and radiogenic Os in molybdenite from the Onganja mine, Namibia, were examined using X-ray absorption fine structure (XAFS). Rhenium LIII-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) show that the oxidation state of Re, the interatomic distances between Re and the neighboring atoms, and the coordination number of Re to S are very similar to those of Mo in molybdenite. The results confirm that Re is present as Re(IV) in the Mo site in molybdenite.Measurement of LIII-edge XANES and EXAFS of a minor concentration (8.55 ppm) of radiogenic Os was accomplished in fluorescence mode by removing the interfering X-rays from Re and other elements using a crystal analyzer system. The data indicate that the oxidation state of radiogenic Os is Os(III) and Os(IV) and clearly different from Os(II) in natural sulfide minerals, such as OsS2 (erlichmanite). XANES data also suggest that radiogenic Os does not form a secondary Os phase, such as OsS2 or Os metal, in molybdenite.EXAFS of radiogenic Os was successfully simulated assuming that Os is present in the Mo site in molybdenite. The data are consistent with the XANES data; Os does not form Os phases in molybdenite. The EXAFS simulation showed that the interatomic distance between Os and S is 2.27 Å, which is 0.12 Å smaller than the distances of Re-S and Mo-S (2.39 Å) in molybdenite. Similar valences and ionic sizes of Re and Mo in molybdenite support the fact that large amounts of Re can be incorporated into the Mo site as has been observed in previous studies, whereas the different properties of Os compared to Mo and Re suggested here support much lower abundance of common Os in molybdenite. This makes molybdenite an ideal mineral for the Re-Os geochronometer as shown in many studies. However, the shorter distance between radiogenic Os and S compared to those of Re-S and Mo-S in molybdenite suggests that the radiogenic Os has a smaller ionic size than Re(IV) and Mo(IV). Furthermore, Os may be partly present as Os(III). Smaller and lower charge Os can diffuse faster than larger and higher charge Re in molybdenite at a given set of conditions. Hence, our study provides an atomic-level explanation for the high mobility of Os compared to Re, which has been suggested by earlier workers using laser ablation ICP-MS. 相似文献
93.
We examined As concentration, mineralogical site, and oxidation state in the serpentinites associated with the Tso Morari eclogitic rocks in the Indus suture zone, northwest Himalaya, to examine how highly fluid-soluble elements like As are transferred from slabs to arc magmas in subduction zones. The serpentinite samples represent hydrated peridotites at the base of the mantle wedge beneath Eurasia, and were exhumed from a depth of ∼100 km during subduction of the Indian continental margin. The bulk serpentinite samples contain total As concentrations ranging from 6 to 275 ppm. Arsenic in the samples is most likely present with magnetite and antigorite, since electron probe analysis yielded up to 90 ppm As in these minerals. X-ray absorption near-edge structure spectra indicate that As in serpentinites is mostly As(V) and that the neighboring atoms of As are O, although there are minute grains of sulfides and arsenides. The ratio of As(V) to total As is greater in samples with higher As contents, suggesting that the major source of As was oxidized As(V), introduced to the mantle wedge. Arsenic(V), originally adsorbed on Fe-oxides in slabs and overlying sediments, was most likely liberated during their subduction and incorporated subsequently in the overlying mantle wedge. Our data constrain the introduction of As into the mantle wedge at relatively shallow levels, much shallower than 25 km. Arsenic incorporated in the serpentinites was transported to deeper levels by mantle flow downward along the subduction zone, to be subsequently exhumed together with eclogitic rocks. 相似文献
94.
In order to elucidate high-pressure transformations of high-P clinopyroxene (C2/c) at kinetically low temperature where atoms are not thermally activated, the transformation processes of FeGeO3 clinopyroxene (C2/c) have been investigated at pressures up to 20 GPa and 365 °C by powder X-ray diffraction using a synchrotron radiation source
and TEM observation. With increasing pressure up to 20 GPa at room temperature, FeGeO3 high-P clinopyroxene (C2/c) reversibly transforms into a new high-pressure phase, FeGeO3(II). On increasing the temperature up to 365 °C, this phase rapidly transforms into FeGeO3 ilmenite within about 2 h. Intensity analysis of the X-ray diffraction pattern reveals that the high-pressure phase of FeGeO3(II) has an intermediate structure between clinopyroxene and ilmenite: the cation arrangement is similar to that of clinopyroxene
and the oxygen arrangement is similar to that of ilmenite. The comparison of the crystal structures of these polymorphs suggests
that clinopyroxene to FeGeO3(II) and FeGeO3(II) to ilmenite transformations are performed by the slight deformation of the oxygen packing and the short-range movement
of cations, respectively. It is shown that this high-P clinopyroxene transforms into ilmenite through a low-activation energy
path under the low-temperature condition.
Received: 30 August 2000 / Accepted: 10 February 2001 相似文献
95.
Taku Kitajima Yoji Kobayashi Ryuji Ikeda Yoshihisa Iio Kentaro Omura 《Island Arc》2001,10(3-4):318-325
Abstract Terrestrial heat flow at Hirabayashi in Awaji Island, south-west Japan, was investigated using the deep borehole penetrating through the Nojima Fault, which was activated during the 1995 Hyogo-ken Nanbu earthquake, by measuring the thermal conductivity of basement rocks. Using the temperature logging data, the value of terrestrial heat flow in Hirabayashi was found to be 56.6 ± 5.2 mW/m2 . The relationship between cut-off depth of aftershocks of the Hyogo-ken Nanbu earthquake in Hirabayashi and terrestrial heat flow are discussed. The cut-off depth roughly corresponds to isotherms of 300°C. 相似文献
96.
Reported here are the first 187Os/188Os ratios and abundances of Os and Re for Taklimakan Desert sands and glacial moraines from the Kunlun Mountains. Osmium isotopic data are also reported for river sediments around the Taklimakan Desert, river sediments from the Kunlun and Tianshan Mountains, Tibetan soils and loesses from the Loess Plateau, as well as Sr and Nd isotopic data for these samples. The Taklimakan Desert sands from various regions show surprisingly homogeneous Os isotopic ratios (187Os/188Os = 1.29 ± 0.08) and abundances (Os = 11 ppt), with some variations in Re abundances (Re = 130 to 260 ppt) and 187Re/188Os ratios (60 to 140). The 187Os/188Os ratios for the Taklimakan Desert sands are close to the average for Kunlun moraines, river sediments around the Taklimakan Desert sands, and the Tibetan soils, supporting the idea that the Taklimakan Desert sands are derived from moraines and river sediments around the desert or from Tibetan soils and are homogenized by aeolian activity in the desert. Furthermore, the Os isotopic data for the sediments studied here are compared with those (187Os/188Os = 1.04, Os = 32 ppt, Re = 206 ppt, 187Re/188Os = 35) of loesses from the Loess Plateau reported elsewhere, and it is concluded that the Re-Os data for the loess can be used as proxy for the upper continental crust. 相似文献
97.
Based on the connectivity relations among tetrahedron sites and the NMR spectra, we propose an ordered distribution of aluminum
atoms in the framework of analcime with space groups of Pbcb and Pcaa. The symmetries of the ordered distributions are formally
the same as Pcca. These symmetries are much lower than those reported by others such as Ia3d, I41/acd, Ibca, and I2/a. The lowering of symmetry results apparently from the fact that aluminum atoms in the framework of analcime
were strictly discriminated from silicon atoms. Dependence of the populations of Si(nAl)s upon Al content was estimated from 29Si MAS NMR, and can be successfully simulated by the ordered distributions. In the simulation, a small number of defects in
the Al distribution were introduced into the ordered distribution mainly to adjust the deviation of Al content per unit cell
from the typical composition. Analysis of the powder X-ray diffraction patterns of analcime was carried out, which suggests
that the space groups proposed in the present work offer a better fit than the ones reported previously.
Received: 5 April 1997 / Revised, accepted: 12 March 1998 相似文献
98.
Phosphorus dynamics in Tokyo Bay waters were investigated along with other oceanographic variables. Seasonal variations of dissolved inorganic phosphorus (DIP) and particulate phosphorus (PP) are inversely correlated with each other, and reflect variation in biological activity. A high concentration of PP in summer surface waters is caused by high primary production. The PP settled in the deeper layer is decomposed, and orthophosphate is regenerated within the water column and in sediments. Even during summer stratification period, the regenerated orthophosphate is occasionally advected upward by wind-induced water mixing and contributes to phytoplankton growth in the upper layer. Some dissolved organic phosphorus is producedin situ from PP, but it may be rapidly decomposed in the water column. The ratios of Cchlorophylla and CN in particulate matter suggest that phytoplankton in the summer surface waters of Tokyo Bay are limited neither by nitrogen nor by phosphorus. The PN ratio in particulate matter varies substantially but it is positively correlated with the ambient concentration of DIP. Phytoplankton take up and store phosphorus within their cells when ambient DIP exceeds their demand. An abundance of total phosphorus in the summer water column can be attributed to increased discharge of river waters, although enhanced release of orthophosphate from anoxic sediments cannot be discounted. 相似文献
99.
100.
Takeshi Naganuma Mutsuo Hattori Kazumi Akimoto Jun Hashimoto Hiroyasu Momma & C. Julius Meisel 《Marine Ecology》2001,22(3):267-282
Abstract. Abyssal microfloral succession induced by experimental organic degradation was investigated. Notable changes in amounts and compositions of short-chain (C9-20) sediment fatty acids were observed, which indicated the shift of sediment microflora. Biomarker fatty acids for methanotrophs and sulfate-reducing bacteria dominated. Resultant fatty acid compositions were most closely related to those from a nearby methane seep harboring a dense Calyptogena colony; the clams were also seen in close vicinity of the deployed organic mass. These observations suggest that the organic degradation on the bathyal seafloor stimulates the formation of methanotrophic and thiotrophic microflora, resulting in the formation of a methane-seep-type benthic community. 相似文献