Mineralogical and Genetical Aspects of the Doyashiki Kuroko Deposits, Hokuroku Basin, Japan     

Satoshi Kitazono  Hirotomo Ueno 《Resource Geology》2003,53(2):143-153

Abstract. A detail investigation of ore and gangue minerals was performed on the Doyashiki Kuroko deposits, Hokuroku basin, Japan for the first time. Main ore minerals are sphalerite, galena, pyrite, chalcopyrite, tetrahedrite-tennantite and digen-ite. Small amounts of enargite, wittichenite, electrum, covellite, bornite, marcasite and hematite are also observed. Quartz, barite and gypsum are common gangue minerals. Homogenization temperatures and salinities of fluid inclusions in quartz, sphalerite and barite range from 190 to 240C and 3.0 to 5.5 wt% NaCl equivalent, respectively. The FeS contents of sphalerite and Ag contents of electrum were 0.12 to 0.18 mol %, 39.0 to 39.6 atom %, respectively. The chemical composition of digenite as a primary mineral shows high sulfur contents.
These data indicate that ore fluid responsible for digenite and associated ore minerals was characterized by a range of high sulfur fugacity with a moderate formation temperature. This is concordant with the mineral assemblage of bornite-pyrite and chalcopyrite, which shows high sulfur fugacity conditions. It seems that the mineralization closely associated with acidic volcanism has occurred around 13 Ma of Middle Miocene on the seafloor at the depth of about 1500 m.  相似文献   

Iron oxidation state of a 2.45-Byr-old paleosol developed on mafic volcanics     

Satoshi Utsunomiya  Takashi Murakami  Takeshi Kasama 《Geochimica et cosmochimica acta》2003,67(2):213-221

The 2.45-Byr-old weathering profile developed on early Proterozoic mafic volcanics located near Cooper Lake, Ontario, Canada, was examined geochemically and mineralogically for a better understanding of the atmospheric oxygen evolution. Ferrous to ferric ion, Fe(II) and Fe(III), respectively, ratios of the bulk rock samples were analyzed by Mössbauer spectrometry. The total Fe (Fe(T)) and Fe(II) concentrations decrease from 12.0 and 11.2 wt.% to 1.85 and 0.89 wt.%, respectively, from the bottom to the top of the weathering profile. The Fe(T) and Fe(II) concentrations normalized to Ti and Zr, as well as the Fe(II)/Fe(III) ratio of raw data, linearly decrease with depth toward the top, while the Fe(III) concentration remains nearly constant throughout the profile. The linear decrease of Fe(II), accompanied by the nearly constant distribution of Fe(III), is difficult to be explained by the scenario of oxidizing weathering and subsequent reducing hydrothermal alteration. The behaviors of Fe(II) and Fe(III) can be simply explained by anoxic weathering. The anoxic weathering suggests that the 2.45-Ga atmosphere was anoxic. The slight increase of Fe/(Fe+Mg) in the octahedral sites of chlorite toward the top and no Ce anomaly in the REE patterns are also consistent with anoxic weathering.  相似文献   

Gelifluction within a solifluction lobe in the Kärkevagge valley, Swedish Lapland     

Hotaka Matsumoto  & Mamoru Ishikawa 《Geografiska Annaler: Series A, Physical Geography》2002,84(3-4):261-266

Soil displacement, soil temperature, depths of thaw plane and groundwater level were continuously monitored during the period from July 1999 to June 2000 within a solifluction lobe in the Kärkevagge valley, northern Sweden. The strain–probe method was used to measure soil displacement, and we found significant soil displacements in the thawing period 2000. These displacements were the result of gelifluction. The ice content profile showed that gelifluction occurred at the same time as the thaw plane reached the layers with high ice content at shallow soil depths (0–6 and 16–25 cm deep). In contrast, gelifluction did not occur when the thaw plane reached the layers with high ice content at greater depth (46–49 cm deep). These observations indicate that thawing of ice lenses in the near–surface layer triggers gelifluction.  相似文献   

Discovery of a large-scale clumpy structure around the Lynx supercluster at z∼ 1.27     

Fumiaki Nakata  Tadayuki Kodama  Kazuhiro Shimasaku  Mamoru Doi  Hisanori Furusawa  Masaru Hamabe  Masahiko Kimura  Yutaka Komiyama  Satoshi Miyazaki  Sadanori Okamura  Masami Ouchi †  Maki Sekiguchi  Yoshihiro Ueda  Masafumi Yagi  Naoki Yasuda 《Monthly notices of the Royal Astronomical Society》2005,357(4):1357-1362

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Geology of the Gorny Altai subduction–accretion complex, southern Siberia: Tectonic evolution of an Ediacaran–Cambrian intra-oceanic arc-trench system   总被引：1，自引：0，他引：1  

Tsutomu Ota  Atsushi Utsunomiya  Yuko Uchio  Yukio Isozaki  Mikhail M. Buslov  Akira Ishikawa  Shigenori Maruyama  Koki Kitajima  Yoshiyuki Kaneko  Hiroshi Yamamoto  Ikuo Katayama   《Journal of Asian Earth Sciences》2007,30(5-6):666-695

The Gorny Altai region in southern Siberia is one of the key areas in reconstructing the tectonic evolution of the western segment of the Central Asian Orogenic Belt (CAOB). This region features various orogenic elements of Late Neoproterozoic–Early Paleozoic age, such as an accretionary complex (AC), high-P/T metamorphic (HP) rocks, and ophiolite (OP), all formed by ancient subduction–accretion processes. This study investigated the detailed geology of the Upper Neoproterozoic to Lower Paleozoic rocks in a traverse between Gorno-Altaisk city and Lake Teletskoy in the northern part of the region, and in the Kurai to Chagan-Uzun area in the southern part. The tectonic units of the studied areas consist of (1) the Ediacaran (=Vendian)–Early Cambrian AC, (2) ca. 630 Ma HP complex, (3) the Ediacaran–Early Cambrian OP complex, (4) the Cryogenian–Cambrian island arc complex, and (5) the Middle Paleozoic fore-arc sedimentary rocks. The AC consists mostly of paleo-atoll limestone and underlying oceanic island basalt with minor amount of chert and serpentinite. The basaltic lavas show petrochemistry similar to modern oceanic plateau basalt. The 630 Ma HP complex records a maximum peak metamorphism at 660 °C and 2.0 GPa that corresponds to 60 km-deep burial in a subduction zone, and exhumation at ca. 570 Ma. The Cryogenian island arc complex includes boninitic rocks that suggest an incipient stage of arc development. The Upper Neoproterozoic–Lower Paleozoic complexes in the Gorno-Altaisk city to Lake Teletskoy and the Kurai to Chagan-Uzun areas are totally involved in a subhorizontal piled-nappe structure, and overprinted by Late Paleozoic strike-slip faulting. The HP complex occurs as a nappe tectonically sandwiched between the non- to weakly metamorphosed AC and the OP complex. These lithologic assemblages and geologic structure newly documented in the Gorny Altai region are essentially similar to those of the circum-Pacific (Miyashiro-type) orogenic belts, such as the Japan Islands in East Asia and the Cordillera in western North America. The Cryogenian boninite-bearing arc volcanism indicates that the initial stage of arc development occurred in a transient setting from a transform zone to an incipient subduction zone. The less abundant of terrigenous clastics from mature continental crust and thick deep-sea chert in the Ediacaran–Early Cambrian AC may suggest that the southern Gorny Altai region evolved in an intra-oceanic arc-trench setting like the modern Mariana arc, rather than along the continental arc of a major continental margin. Based on geological, petrochemical, and geochronological data, we synthesize the Late Neoproterozoic to Early Paleozoic tectonic history of the Gorny Altai region in the western CAOB.  相似文献   

Level of electrostatic excitation associated with relativistic beam-plasma system and pulsar radiation     

Satoshi Hinata 《Astrophysics and Space Science》1976,44(2):389-395

A class of pulsar models which provide a stationary beam-plasma system as the source of radiation is considered. Since the beam-plasma system is stable near the pulsar where the coherent curvature radiation damps the longitudinal mode, we consider the beam-plasma system away from the star so that the effects of curvature radiation may be neglected. We find that the total wave energy density may attain a significant fraction of the beam energy density provided that the beam and plasma carry away a comparable amount of energy from the star. It should be noted that the attained high wave energy density is peculiar to a relativistic beam-plasma interaction.  相似文献   

Population geography with GIS in Japan     

Y. Ishikawa 《GeoJournal》2000,52(3):189-194

Japanese geography studies are now being greatly affected by the rapid development of geographical information systems (GIS). Unfortunately, there has been little response from Japanese population geographers to this movement. Is GIS a welcome or an unwelcome guest? After discussing the significance of employing GIS, this article introduces some recent papers that used GIS in the field of population geography on such issues as mortality mapping, migration analysis, and household studies. Then, the two promising population-related topics of married one-person households and fertility are discussed. The ability of GIS to greatly facilitate analysis, which previously needed much time and energy, can be an encouraging stimulus of innovation in studies of current population geography. Therefore, GIS is clearly a welcome guest, although it is too wishful to think that its use would lead directly to a revitalization of contemporary population geography studies.  相似文献   

福建沿海铝质A型花岗岩的地球化学及岩石成因   总被引：78，自引：7，他引：71  

邱检生  王德滋  蟹泽聪史 《地球化学》2000,29(4):313-321

以乌山、金刚山和新村三个典型岩体为例,系统研究了福建沿海铝质Ａ型花岗岩的地质和地球化学特征。研究结果表明,铝质Ａ型花岗岩常含有锰铝榴石、富锰白云母等特征的富铝矿物,化学成分上相对富铝,为一套准铝到弱过铝的岩石组成,并具有贫磷、贫钛,氧化指数较低等特征。与碱性花岗岩相比,其Ｎｂ、Ｔａ、Ｚｒ、Ｈｆ、Ｇａ、Ｙ和Ｚｎ等元素的含量及稀土总量和Ｇａ／Ａｌ比值均偏低,但轻、重稀土的分馏程度（尤其是重稀土的分馏程  相似文献   

广域空间尺度上植被净初级生产力的精确推算   总被引：11，自引：0，他引：11  

松下文经  杨翠芬  陈晋  王勤学  龟山哲  田村正行 《地理学报》2004,59(1):80-87

作者介绍了使用遥感、GIS数据和BEPS生态过程模型推算植被净初级生产力 (NPP)的方法。为了准确推算北海道地区NPP,我们改进了BEPS模型,而且使用了高质量GIS数据作为模型的输入数据。通过计算得出1998年北海道NPP的平均值为644 g C/m²,总量为0.078 Gt C。我们还进行了模型输入数据质量对应用生态过程模型推算NPP的精度影响测试。结果表明,高质量的GIS输入数据可以提高NPP推算精度16.6%~39.7%。  相似文献   

Downslope soil detachment–transport on steep slopes via rain splash     

Afshin Ghahramani  Yoshiharu Ishikawa  Takashi Gomi  Shusuke Miyata 《水文研究》2011,25(15):2471-2480

This study developed a one‐dimensional model of downslope rain splash transport based on field experiments and previous studies. The developed model considers soil detachment processes, ground cover, probability densities, and the effect of overland run‐off in preventing detachment. Field monitoring was conducted to observe precipitation run‐off, ground cover, and sediment production on steep hillslopes. Field‐observed data were used to develop the splash detachment rate equation, probability densities for splash transport, and the maximum splash transport distance. Observed and estimated splash transport showed overall agreement, with some differences for small storm events or events with relatively low intensity, probably caused by variation of overland run‐off depth and connectivity as well as differences in soil surface cohesion at various degrees of wetness. Our model can provide insights on the interactions among rainfall intensity, soil surface condition, soil wetness, and splash transport on forested hillslopes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献