High temperature X-ray study of single crystal stishovite synthesized with Li2WO4 as flux     

S. Endo  T. Akai  Y. Akahama  M. Wakatsuki  T. Nakamura  Y. Tomii  K. Koto  Y. Ito  M. Tokonami 《Physics and Chemistry of Minerals》1986,13(3):146-151

Single crystal stishovite with a square prismatic habit and maximum length 0.8 mm was grown from α-quartz at 120 kbar and ～1,300° C. Li₂WO₄, chosen as a result of a previous experiment in growing coesite, was also successful as flux for stishovite. Single crystal X-ray structure analysis of the crystals thus obtained has been carried out at high temperatures under ambient pressure. Lattice constant measurements give a larger thermal expansion coefficient along the a-axis than along the c-axis. The bond distances and bond angles show a decreasing distortion of the SiO₆ octahedron with increasing temperature. The increasing amplitude of thermal vibrations of oxygen atoms with increasing temperature results in increasing O-O repulsion in the basal plane, which explains the observed crystallographic changes.  相似文献   

Resource Evaluation and Some Genetic Aspects of Indium in the Japanese Ore Deposits   总被引：7，自引：1，他引：7  

Shunso Ishihara    Kenichi Hoshino  Hiroyasu Murakami  Yuji Endo 《Resource Geology》2006,56(3):347-364

Abstract. There have been two primary sources for industrial indium; one from massive sulfides, while the other is dissemination-veins and skarns, related to felsic igneous rocks. The latter group of the In-bearing deposits is abundant in the Japanese Islands. Indium occurs as In-minerals such as sakuraiite, roquesite, laforetite and many unidentified minerals, but the majority is contained as an impurity in sphalerite, and tin and copper sulfides. Average grades of the ores from which indium has been extracted vary from a few ppm (e.g., Kosaka mine) to more than 300 ppm (Toyoha mine). The amount of indium in all the major basemetal deposits is estimated by analyzing representative samples. The main indium deposits are subvolcanic and tin-poly-metallic vein types. The largest one is Toyoha mine (4,700 tons hi) and the Ashio mine (ca. 1,200 tons In) was found to be the second largest. Many small occurrences, were recognized in the Miocene magnetite-series belt, besides the classic occurrences in the ilmenite-series granitic terrains of SW Japan, including the Ikuno and Akenobe tin(-tungsten) polymetallic veins, located in the northern margin of the late Cretaceous Sanyo ilmenite-series province. Magnetite-series magmas with deep source are necessary to concentrate sulfur in the magma chamber but sedimentary source rocks and their reducing agents are needed to collect and to precipitate indium. The Japanese islands are essentially accretionary terrains intruded by various deep oxidized magmas; thus forming magnetite/ilmenite-series paired belts, which are sometimes mixed. This unique geologic setting may be the most fundamental reason why indium is rich in vein-type deposits of the Japanese Island arcs.  相似文献   

Relationship Between Solidification Depth of Granitic Rocks and Formation of Hydrothermal Ore Deposits   总被引：14，自引：0，他引：14  

Etsuo Uchida    Sho Endo  Mitsutoshi Makino 《Resource Geology》2007,57(1):47-56

Chemical analysis of biotite in representative granitic rocks in Japan shows that the total Al (^TAl) content changes with the metal type of the accompanying hydrothermal ore deposits and increases in the following order: Pb‐Zn and Mo deposits < Cu‐Fe and Sn deposits < W deposits < non‐mineralized granitic rocks. The ^TAl content of biotite in granitic rocks may be a useful indicator for distinguishing between mineralized and non‐mineralized granitic rocks. A good positive correlation is seen between the ^TAl content of biotite and the solidification pressure of the granitic rocks estimated by sphalerite and hornblende geobarometers and the mineral assemblages of the surrounding rocks. These facts suggest that the ^TAl content of biotite can be used to estimate the solidification pressure (P) of the granitic rocks. The following empirical equation was obtained: where ^TAl designates the total Al content in biotite on the basis O = 22. According to the obtained biotite geobarometer, it is estimated that Pb‐Zn and Mo deposits were formed at pressures below 1 kb, Cu‐Fe and Sn deposits at 1–2 kb, W deposits at 2–3 kb and non‐mineralized granitic rocks were solidified at pressures above 3 kb.  相似文献   

洪湖沉积物的磁性特征及其环境意义   总被引：9，自引：0，他引：9  

曹希强  郑祥民  周立旻  杜耘  远藤邦彦 《湖泊科学》2004,16(3):227-232

以洪湖沉积物为研究对象,通过对Hh01-2(B)孔岩芯磁参数的测量发现在岩芯所代表的时间段内洪湖沉积物磁化率呈现了明显的四个主阶段变化;频率磁化率变化与磁化率变化具有较好的相关性,亚铁磁性矿物的变化主导了沉积物磁化率的变化.同时结合年代、孢粉分析以及参考相关历史记载资料,发现磁化率高值段对应湖水动力强、湖面较宽、气候较湿润,而磁化率低值段对应湖水动力弱、湖面较小、气候偏干旱.从而得出了洪湖沉积物磁参数曲线波峰和波谷分别对应洪湖在历史上曾经历了扩张和收缩、气候温湿和冷干的旋回.  相似文献   

Volcanic history and tectonics of the Southwest Japan Arc   总被引：1，自引：0，他引：1  

Hiroki Kamata and  Kazuto Kodama 《Island Arc》1999,8(3):393-403

Abstract Remarkable changes in volcanism and tectonism have occurred in a synchronous manner since 1.5–2 Ma at the junction of the Southwest Japan Arc and the Ryukyu Arc. Although extensive volcanism occurred in Kyushu before 2 Ma, the subduction-related volcanism started at ca 1.5 Ma, forming a NE–SW trend volcanic front, preceded by significant changes in whole-rock chemistry and mode of eruptions at ca 2 Ma. The Median Tectonic Line has intensified dextral motion since 2 Ma, with a northward shift of its active trace of as much as 10 km, accompanied by the formation of rhomboidal basins in Central Kyushu. Crustal rotation and incipient rifting has also occurred in South Kyushu and the northern Okinawa Trough over the past 2 million years. We emphasize that the commencement age of these events coincides with that of the transition to the westward convergence of the Philippine Sea plate, which we interpret as a primary cause of these synchronous episodes. We assume that the shift in subduction direction led to an increase of fluid component contamination from subducted oceanic slab, which then produced island-arc type volcanism along the volcanic front. Accelerated trench retreat along the Ryukyu Trench may have caused rifting and crustal rotation in the northern Ryukyu Arc.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987112000643   总被引：2，自引：1，他引：1  

Takahiro Endo  Toshiaki Tsunogae  M.Santosh  E.Shaji 《地学前缘(英文版)》2012,3(6):801-811

Incipient charnockites represent granulite formation on a mesoscopic scale and have received considerable attention in understanding fluid processes in the deep crust.Here we report new petrological data from an incipient charnockite locality at Rajapalaiyam in the Madurai Block,southern India,and discuss the petrogenesis based on mineral phase equilibrium modeling and pseudosection analysis. Rajapalaiyam is a key locality in southern India from where diagnostic mineral assemblages for ultrahigh-temperature（UHT） metamorphism have been reported.Proximal to the UHT rocks are patches and lenses of charnockite（Kfs + Qtz + Pl + Bt + Opx + Grt + Ilm） occurring within Opx-free Grt-Bt gneiss（Kfs + Pl + Qtz + Bt + Grt + Ilm + Mt） which we report in this study.The application of mineral equilibrium modeling on the charnockitic assemblage in NCKFMASHTO system yields a p-T range of～820℃and～9 kbar.Modeling of the charnockite assemblage in the MnNCKFMASHTO system indicates a slight shift of the equilibrium condition toward lower p and T（～760℃and～7.5 kbar）. which is consistent with the results obtained from geothermobarometry（710—760℃,6.7—7.5 kbar）. but significantly lower than the peak temperatures（>1000℃） recorded from the UHT rocks in this locality,suggesting that charnockitization is a post-peak event.The modeling of T versus molar H₂O content in the rock（M（H₂O）） demonstrates that the Opx-bearing assemblage in charnockite and Opxfree assemblage in Grt-Bt gneiss are both stable at M（H₂O） = 0.3 mol%-0.6 mol%.and there is no significant difference in water activity between the two domains.Our finding is in contrast to the previous petrogenetic model of incipient charnockite formation which envisages lowering of water activity and stabilization of orthopyroxene through breakdown of biotite by dehydration caused by the infiltration of CO₂-rich fluid.T-X_Fe³⁺（= Fe₂O₃/（FeO + Fe₂O₃） in mole） pseudosections suggest that the oxidation condition of the rocks played a major role on the stability of orthopyroxene:Opx is stable at X_Fe³⁺ <0.03 in charnockite.while Opx-free assemblage in Grt-Bt gneiss is stabilized at X_Fe³⁺ >0.12.Such low oxygen fugacity conditions of X_Fe³⁺ <0.03 in the charnockite compared to Grt-Bt gneiss might be related to the infiltration of a reduced fluid（e.g.,H₂O + CH₄） during the retrograde stage.  相似文献   

Cellular model for sand dunes with saltation,avalanche and strong erosion: collisional simulation of barchans     

Atsunari Katsuki  Macoto Kikuchi  Hiraku Nishimori  Noritaka Endo  Keisuke Taniguchi 《地球表面变化过程与地形》2011,36(3):372-382

  相似文献   

Carbon storage in desertified lands: A case study from North China     

Feng Qi  Cheng Guodong  Endo Kunihiko 《GeoJournal》2000,51(3):181-189

Based on the organic and carbonate carbon levels of the top 1 m of soil from desertified soils of Northern People's Republic of China, climatic and vegetative cover zones have been derived for some 334000 km² of desertification-prone lands. Regional accumulations of pedogenic carbonates were examined relative to precipitation, altitude, and temperature. The largest accumulations of pedogenic carbonates were found in Calcic soils in warm, arid areas. Accumulated organic carbon predominated in soils under Betula platyphylla. In the naturally desertified lands of China, for example, the top 1.0-m soil layer contains some 7.84 Pg of organic carbon and 14.9 Pg of carbonate carbon. Total stored carbon, including carbonate carbon, is 1.8-fold more than organic carbon alone. The carbon released through land desertification in China may be an important factor affecting changes in concentrations of greenhouse gases worldwide.  相似文献   

Effects of oil spill on seawater infiltration and macrobenthic community in tidal flats   总被引：1，自引：0，他引：1  

Chung IY  Cho KJ  Hiraoka K  Mukai T  Nishijima W  Takimoto K  Okada M 《Marine pollution bulletin》2004,49(11-12):959-963

Tidal flat ecosystem simulators are used to clarify the effects of stranded fuel oil on tidal flat ecosystems. Results show that oil spills increase the periphyton on sediment by decreasing the predation stress caused by deposit feeders. About a month after an oil spill, the total population density of the macrobenthos recovered. The oxidation-reduction potential in the surface sediment drops to a negative value after the oil spill, and the anaerobic condition throughout the sediment seems to be responsible for the decrease in the population density of the macrobenthos. The infiltration volume of seawater into the oil-stranded sediment decreases to a third of that without the oil spill. The recovery of infiltration volume after about a month coincides with the recovery of the population density of the macrobenthos. This result suggests that the macrobenthic population is highly dependent on the infiltration of seawater.  相似文献   

Oceanic plateau accretion inferred from Late Paleozoic greenstones in the Jurassic Tamba accretionary complex, southwest Japan   总被引：3，自引：0，他引：3  

Kazuto  Koizumi Akira  Ishiwatari 《Island Arc》2006,15(1):58-83

Abstract The Jurassic Tamba accretionary complex is divided into two tectono‐stratigraphic suites (Type I and II nappe groups), which are further divided into six complexes (nappes) each of which is characterized by a rock sequence of Late Paleozoic greenstone/limestone, Permian to Jurassic chert and Jurassic terrigenous clastic rocks. The mode of occurrence of the greenstone is divided into two types. The major basal type occurs as a large coherent slab associated with Permian chert and limestone, constituting the basal part of each complex, and the minor mixed type occurs as fragmented allochthonous greenstone blocks and lenses mixed with chert, limestone and sandstone in the Jurassic mudstone matrix. Most of the basal greenstones have uniform geochemical characteristics, which indicate enriched‐mid‐oceanic ridge basalt (MORB) affinity. Their geochemical compositions are akin to the reported Permo‐Carboniferous and Triassic oceanic plateau basalts. Mixed greenstones are divided into two petrochemical types: (i) tholeiitic basalt with normal‐MORB affinity, which is predominant in the uppermost complex of the Type II suite (upper nappe group); and (ii) tholeiitic and alkalic basalts of oceanic island or seamount origin, which are common in all complexes of the Tamba Belt. Geochemical characteristics of the greenstones thus vary in accordance with their occurrences and the structural units to which they belong. This relationship reflects the difference in topographic relief and crustal thickness of the accreted oceanic edifices – the remnants of thick oceanic plateau crust tended to accrete to the continental margin as a large basal greenstone body, whereas thin normal oceanic crust with small seamounts or oceanic islands accreted as mixed greenstones because of their mechanical weakness. The Type II suite (upper nappe group) contains the basal and mixed greenstones, whereas the Type I suite (lower nappe group) includes only mixed greenstones. This distinction may reflect the temporal change of subducting edifices from a thick oceanic plateau to a thin normal oceanic crust, and suggests that the accretion of a large oceanic plateau may be responsible for building accretionary complexes with thick basal greenstones slabs.  相似文献