Ore value-tonnage diagrams for resource assessment   总被引：4，自引：0，他引：4  

Tetsuya Shoji  Hiroaki Kaneda 《Natural Resources Research》1998,7(1):25-36

An ore value-tonnage diagram has been proposed for assessing mineral resources. Diagrams of W+Mo, and Pb+Zn deposits show a good linearity between ore value and logarithms of cumulative ore tonnage. Diagrams of the massive sulfide, orthomagmatic, placer, porphyry, replacement, and stratabound types are also linear. It is assumed, therefore, that deposits of each of these commodities and these types belong to a single population. In contrast, the ore value-tonnage relations of all the deposits analyzed here is approximated by the combination of two exponential functions. The same feature is seen for deposits of the Cu+W+Mo, Cu+Pb+Zn, and Au+Ag commodities, and of the vein and unconformity-related types. This suggests that deposits belonging to each of such categories are divided into the high and low value groups. We can expect, accordingly, to find high value deposits of such categories.  相似文献   

Rapid change in nitrate and sulfate concentrations observed in early stage of precipitation and their deposition processes     

Hiroaki Minoura  Yasunobu Iwasaka 《Journal of Atmospheric Chemistry》1996,24(1):39-55

The concentrations of H⁺, nitrate (NO₃ ^-), and sulfate (SO₄ ^2-) in rainwater and their temporal changes were analyzed on the basis of continuous observation from 1 July 1991 to 30 June 1992 at a suburb of Nagoya, Japan. The yearly average for pH was 4.4. In general, an increasing pH with increase in precipitation amount was observed for rain events. Relatively high pH rainwater was sometimes observed at the beginning of rainfall, even though high concentrations of NO₃ ^- and SO₄ ^2- were involved. The high pH values were considered to be caused by the neutralization process with particulate matter containing cations. The yearly averaged ratio of equivalent concentration of nitrate to sulfate (N/S) in rainwater was 0.58. In the early stage of rain, the N/S value was usually more than 1.0 due to the difference of scavenging process between NO₃ ^- and SO₄ ^2-. High values of N/S ranging from 5 to 10 were found under the atmospheric conditions of calm winds and low humidity, during which it is possible that atmospheric particles float for a long time in the air before a rain event. The adsorption of NO₃ ^- in the early stage of rainfall by particulate matter was suggested from the difference in scavenging processes of NO₃ ^- and SO₄ ^2-. A possible scavenging process, called limb cloud scavenging, is presented to explain the interaction of particles and nitrate ions at the early stage of rain. In limb cloud scavenging, the repeated migration of cloud particles or raindrops between the inside and outside of clouds increases the absorption of ions to a highly condensed level, thus increasing the N/S value of rainwater. The influence of global scale seasonal phenomena with large amounts of particulates, such as typhoons or Asian dust storms, was also studied.  相似文献   

Impact of fish net pen culture on the benthic environment of a cove in South Japan     

Hiroaki Tsutsumi 《Estuaries and Coasts》1995,18(1):108-115

Over the past three decades, fish net pen culture has been developed in the coastal waters of Japan. However, serious organic pollution of the surrounding water and sediment followed the development of this new style of fishery. This paper reports a typical example of the environmental disturbance that has occurred due to the organic pollution resulting from fish net pen culture. Since fish cultivation was initiated in 1973, oxygen depletion of the bottom water and extremely reducing conditions within the sediment have occurred during the summer. These environmental disturbances resulted in unusual dynamics of the benthic communities including defaunation in the summer and recolonization of the azoic areas from autumn to the next spring. Significant changes in the benthic fauna were observed between benthic communities before and after organic pollution of the sediment. Molluscs were originally the most dominant benthic fauna. As organic pollution of the bottom sediment progressed, the molluscs were replaced by polychaetes. Likewise, total biomass of the benthic fauna decreased markedly over the past two decades. Prior to contamination, the organic matter deposited on the sediment was decomposed by the action of bacteria, ciliates, meiofauna, and macrofauna. The addition of organic material resulting from fish culture has overwhelmed these decomposition mechanisms, and conditions have worsened as organic matter is continuously added to the sediment. Contamination of marine sediment by the net pen cultivation of fish sets up a vicious cycle: the addition of exogenous sources of organic material increases the need for a more vigorous decomposition process while actually creating conditions that limit the rate of the necessary decomposition activity. The sustainable development of fish net pen culture will require the creation of a new technology that efficiently promotes the decomposition of organic matter deposited below the pen nets.  相似文献   

Inland penetration of the sea breeze over the suburban area of Tokyo     

Hiroshi Yoshikado  Hiroaki Kondo 《Boundary-Layer Meteorology》1989,48(4):389-407

Observational results of the structure of the sea breeze over the urban and suburban areas of Tokyo for four summer days are presented.On two of these days, the inland penetration of the sea breeze front could be clearly traced. In one case, the sea breeze was first observed along the shores of Tokyo Bay around 0900 JST, and propagated in three hours through the Tokyo City area, the width of which is about 20 km. It then advanced inland at a rate of 16 km h^–1. Prior to the arrival of the sea breeze at the suburban site, the mixing height had remained at about 600 m for four hours. With the arrival of the sea breeze front, accompanied by an abrupt change in wind speed and direction, the mixing height increased sharply to 1700 m. It is suggested that this behavior and the structure of the front are intensified due to the urban effect, or the difference in the thermal characteristics between the urban and rural areas.On the days without a sea breeze front, the land breeze system during the early morning was less intense, allowing the sea breeze to develop simultaneously with the inland valley wind and easily form a large-scale local wind system during the morning hours. In both cases, the vertical motion accompanying the local wind system works as a feedback mechanism to control the local winds by modifying the thermal and pressure fields.  相似文献   

新疆北部富蕴县沙尔布拉克玻安岩的地球化学特征及构造意义   总被引：19，自引：1，他引：19  

张海祥  牛贺才  于学元  Hiroaki Sato  Junichi Ito  单强 《地球化学》2003,32(2):155-160

详细的地球化学研究表明，新疆北部富蕴县沙尔布拉克中泥盆统北塔山组的辉石安山岩具有中等的SiO2含量（52.13%-60.45%)；高MgO(3.91%-9.31%)和相容元素（包括Ni、Cr、Co等）含量，以及高Mg^#和Al2O3／TiO2比值；低TiO2含量（0.21%-0.35%)；同时具有U型稀土元素分布模式；并强烈亏损高场强元素。这些特征均与玻安岩的地球化学特征一致，应属于玻安岩，形成于前弧环境。沙尔布拉克玻安岩的存在表明，古亚洲洋在早－中泥盆世向南发生了洋壳俯冲作用。  相似文献   

Assessment of metal concentrations in lake sediments of southwest Japan based on sediment quality guidelines   总被引：1，自引：0，他引：1  

M. Hawa Bibi  Faruque Ahmed  Hiroaki Ishiga 《Environmental Geology》2007,52(4):625-639

Geochemical analysis of the bottom sediments of Lakes Banryoko, Onbe, Hamahara and Kijima in Shimane prefecture of southwest Japan was carried out to determine their metal concentrations, and to assess the potential for ecological harm by comparison with sediment quality guidelines. The work conducted includes water quality measurement, and analyses of trace and major elements and rare earth element (REE) of sediments. Results showed that water quality of the lakes contrasts slightly between their upper and lower parts. Average abundances of As, Pb, Zn, Cu, Ni, and Cr in Banryoko sediments were 27, 33, 90, 27, 25, and 46 ppm, respectively, compared to 31, 52, 175, 44, 44, and 75 ppm at Onbe, 11, 26, 96, 13, 13, and 35 ppm at Hamahara, and 24, 43, 193, 31, 12, and 30 ppm at Kijima. These concentrations exceeded the lowest effect level that has moderate impact on aquatic organisms as proposed by the New York State Department of Environmental conservation. Pb and Cu abundances are comparable to the Coastal Ocean Sediment Database threshold, while As and Zn exceed this value, indicating the concentrations of these metals are potentially toxic. Increases in the abundances of these metals in lake sediments are probably related to the reducing condition of the sediments, anthropogenic sources and surface soil erosion. The REE patterns of sediments in the study areas are broadly comparable to the average upper continental crust, but show some contrast between lakes due to differing source litho type. Significant positive correlations between Fe₂O₃ and As, Pb, Zn, and Cu were found in the sediments, suggesting these metals may be adsorbed on Fe oxides in the lake sediments.  相似文献   

Environmental assessment of Dhaka City (Bangladesh) based on trace metal contents in road dusts   总被引：1，自引：0，他引：1  

Faruque Ahmed  M. Hawa Bibi  Hiroaki Ishiga 《Environmental Geology》2007,51(6):975-985

Geochemical analysis of street dusts was conducted to evaluate the environment of Dhaka City, Bangladesh. Dust samples were collected from different areas (industrial, commercial, and residential) of Dhaka City, and their major, trace and rare earth elements (REE) were determined. Samples from the commercial area had Pb concentrations double those of the industrial and residential areas. Contents of Zn, Cu, Ni, and Cr in the industrial areas were greater than those in the commercial and residential areas. The REE patterns of all dusts in Dhaka are similar and are comparable to the average upper continental crust. The condition of the Dhaka environment was compared to that in Japan and other baseline sediments using Zn–Fe₂O₃ and Pb–Fe₂O₃ diagrams. Zn–Fe₂O₃ trends for the dusts show steep inclination compared to the baseline sediment and the Japanese urban sediment trends. Dhaka lake data show enrichment of Zn over the dusts, suggestive of Zn pollution from poorly controlled industrial sources. In contrast, on the Pb–Fe₂O₃ diagram, Dhaka dusts have greater Pb contents than lake sediments, probably due to the higher traffic density in the commercial area compared to the residential area including the area around the lake. The results suggest that higher levels of Pb and Zn in street dusts in Dhaka can most likely be attributed to the anthropogenic sources like vehicle emissions to the atmosphere and a rapid development.  相似文献   

Notes on non-marine bivalve Trigonioides (Trigonioides?) from the mid-Cretaceous Goshoura Group, Kyushu, Japan     

Toshifumi Komatsu  Chen Jinhua  Hiroaki Ugai  Koji Hirose 《Journal of Asian Earth Sciences》2007,29(5-6):795-802

Trigonioides goshourensis n. sp. and Trigonioides amakusensis Kikuchi and Tashiro occur in the late Albian Eboshi Formation of the Goshoura Group in Kyushu, Japan. These Albian species are characterized by three radial pseudocardinal teeth on the thick and wide hinge plate, and are probably ancestors of Cenomanian species of Trigonioides (Kumamotoa) with four radial pseudocardinal teeth. This chronological relation may be important for the correlation of non-marine Cretaceous strata in East Asia. In addition, the habitat of T. amakusensis is interpreted as estuarine tidal flats under brackish water conditions, although Trigonioides is generally a freshwater bivalve genus.  相似文献   

Experimental study of a low-alkali tholeiite at 1–5 kbar: optimal condition for the crystallization of high-An plagioclase in hydrous arc tholeiite     

Daisuke?Takagi  Hiroaki?SatoEmail author  Mitsuhiro?Nakagawa 《Contributions to Mineralogy and Petrology》2005,149(5):527-540

We conducted melting experiments on a low-alkali tholeiite (SiO₂ ~52 wt%, MgO ~6.5 wt%, CaO/Na₂O~4.4, Al₂O₃/SiO₂ ~0.33) under both H₂O-undersaturated and H₂O-saturated conditions to investigate the effect of H₂O on the Ca–Na partitioning between plagioclase and melt. Experiments were performed in the temperature and pressure ranges of 1,000–1,300°C and 1–5 kbar, respectively, with varying H₂O contents of 0–12wt%. Redox condition was 0–2 log unit above NNO (nickel–nickel oxide) buffer. Temperature-bulk H₂O diagrams for the low-alkali tholeiite are constructed at 1, 2, and 5 kbar, and compositions of near-liquidus plagioclase and coexisting melt are determined. To exclude the effect of melt composition (CaO/Na₂O and Al₂O₃/SiO₂ ratios) on plagioclase composition and to reveal the effect of H₂O on An (=100×Ca/(Ca+Na)) content and (=(Ca/Na)_pl/(Ca/Na)_melt), we focused on the composition of near-liquidus plagioclases which crystallized from melts with nearly constant CaO/Na₂O and Al₂O₃/SiO₂ ratios. Our experimental results show that, at each experimental pressure, An content of the near-liquidus plagioclase and the K_D^Ca-Na almost linearly increases as H₂O content in melt increases. Each of the An content and the variations in a low-alkali tholeiitic system (CaO/Na₂O~4.0–4.5, Al₂O₃/SiO₂ ~0.27–0.33) can be described by one equation using temperature, pressure, and melt H₂O content as parameters. An content and of liquidus plagioclase increases with increasing melt H₂O and with decreasing pressure, elucidating that nearly H₂O-saturated conditions of 2–3 kbar is optimal for the crystallization of the most An-rich plagioclase (>An₈₈). We suggest this pressure condition of 2–3 kbar, corresponding to depth of 7–11 km, plays an important role for the origin of An-rich plagioclase in H₂O-rich low-alkali tholeiite. At pressures more than ca. 4 kbar, crystallization of liquidus Ca-rich clinopyroxene decreases the CaO/Na₂O ratio of liquid, thus prohibiting the crystallization of high-An plagioclase from hydrous tholeiite.  相似文献   

Continuing observation of disturbed reproductive cycle and ovarian spermatogenesis in the giant abalone, Haliotis madaka from an organotin-contaminated site of Japan   总被引：1，自引：0，他引：1  

Horiguchi T  Kojima M  Takiguchi N  Kaya M  Shiraishi H  Morita M 《Marine pollution bulletin》2005,51(8-12):817-822

Histological examination of gonads as well as chemical analysis of organotin compounds in tissues of the giant abalone, Haliotis madaka, was conducted to evaluate continuing endocrine disruption in abalone populations in Japan. Abalone specimens were collected from two different areas, Tsushima as a reference site and Jogashima as a site representative of declining abalone populations where serious organotin contamination had been observed, each month from January 1998 to March 1999. Scores were given to the development stages of reproductive cells in the ovary and testis. The degree of sexual maturation was evaluated by calculating the mean value of a histogram of these scores for the reproductive cells of each abalone. The temporal variations in degree of sexual maturation showed that female and male abalone from Tsushima matured synchronously, while those from Jogashima did not, which were similar to results of the previous study during September 1995–November 1996. Approximately 19% of the female abalone from Jogashima were masculinized with an ovo-testis, which was also similar to the result of the previous study. The masculinization of female abalone is reported to be induced by tributyltin (TBT) and triphenyltin (TPhT) from antifouling paints. Concentrations of the sum of butyltins (TBT, dibutyltin (DBT) and monobutyltin (MBT): ΣBTs) and the sum of phenyltins (TPhT, diphenyltin (DPhT) and monophenyltin (MPhT): ΣPhTs) in the muscle of abalone from Jogashima (n = 73) of 7.8 ± 9.0 ng/g wet wt. and 4.5 ± 6.8 ng/g wet wt., respectively, were significantly higher than those from Tsushima (n = 87) of 4.7 ± 4.9 ng/g wet wt. and 0.8 ± 1.7 ng/g wet wt., respectively (p < 0.05 for ΣBTs; p < 0.001 for ΣPhTs), although concentrations of TBT and TPhT in the muscle of abalone from Jogashima (n = 73) of 2.2 ± 2.5 ng/g wet wt. and 5.8 ± 5.1 ng/g wet wt., respectively, were insignificantly and significantly higher than those from Tsushima (n = 87) of 0.4 ± 0.6 ng/g wet wt. and 0.5 ± 0.9 ng/g wet wt., respectively, (p > 0.05 for TBT; p < 0.001 for TPhT). Thus, endocrine disruption as well as contamination by organotins in the giant abalone from Jogashima is still persisting.  相似文献