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The Iwami epithermal silver deposit consists of Ag-Cu veins in a dacitic intrusive body at the deep portion of the Eikyu area, and veinlets with disseminated Ag mineralization in dacitic tuff breccia at a shallow portion of the Fukuishi area. Hydrothermal alteration associated with the silver mineralization is characterized by intense potassium metasomatism with oxidizing conditions. An illite zone occurs around the pathways of uprising fluids in both the Eikyu and Fukuishi areas. It grades laterally into the illite/smectite zone, which is surrounded by a broad smectite zone. Because of boiling, abundant adularia associated with silver mineralization overlaps on the altered tuff breccia in the Fukuishi area. The alteration zoning suggests that the western Eikyu area and the eastern Fukuishi area belong to a single hydrothermal system. The data of fluid inclusion microthermometry indicate that the temperatures range 220–270°C, and salinities range 5–7 wt percent NaCl equivalent for the silver mineralization at the upper portion in the Eikyu area and the lower portion in the Fukuishi area. Radiometric ages for volcanic rocks in the area range from 2.19 to 1.64 Ma, and the dacitic intrusion formed at approximately 1.6 Ma. The silver-dominant mineralizing hydrothermal fluids system was active around 1.44 to 1.07 Ma, which formed the Eikyu Ag-Cu veins at depth, and the Fukuishi Ag ores at the shallower portion. 相似文献
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Marc H. Hanke J. David Lambert Kelly J. Smith 《International journal of geographical information science》2014,28(8):1642-1657
A critical component of maintaining biodiversity in fragmented habitats is maintaining connectivity among the usable fragments. Least cost path (LCP) analysis is a tool that can be used for predicting the ability of an organism to move from one habitat patch to another, based on geographical features of the landscape and life history traits of the organism. While this analysis has been utilized for terrestrial habitats, it is rarely applied to aquatic environments. Aquatic hypoxic conditions occur when dissolved oxygen falls below 2 mg/L. These conditions can create barriers in the water column that can either force fish to leave a habitat, or avoid that habitat altogether. Using the lower St. Johns River (LSJR) estuary in Florida, USA, as a study system, the ability of an adult silver perch, Bairdiella chrysoura, to escape a large-scale hypoxic event was modeled using a multicriteria LCP approach. Criteria-specific cost grids were constructed based upon current speed, risk of predation, and whether oxygen levels in the habitat area were normoxic (>5.5 mg/L), or hypoxic (<2.0–1.5 mg/L) as a function of water depth for the LSJR. The criteria cost grids were combined using relative weighting to produce the multicriteria cost grid used to implement the LCP analysis. Three origin and destination point locations within the LSJR study area were selected for modeling whether or not a silver perch would be able to escape a hypoxic zone. Since the LCP model will always determine a LCP from the specified origin point location, ecologically relevant swimming capacities for silver perch under normoxic and hypoxic conditions were then applied to assess the model, and to determine whether the fish would be able to reach areas unimpacted by hypoxia. The LCP model and the swimming capacity results for this study predict that under normoxic conditions, fish movement was unimpeded. During the rapidly developing hypoxic event that was modeled, the results from the LCP model indicate that the fish could move outside the hypoxic zone, but when swimming capacities were applied to the model, the silver perch could not escape. Ecologically, the results of this study suggest that silver perch would experience high mortality under a rapidly developing hypoxic event. Additionally, the results of this study indicate that a LCP model can be applied to an aquatic habitat, as long as the cost grids incorporate relevant abiotic and biotic factors. 相似文献
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GAO Can HU Yaoqiang ZHANG Huifang YE Xiushen LI Quan LIU Haining WU Zhijian 《《地质学报》英文版》2014,88(Z1):313-314
正Iodine and iodine compounds are widely applied in medicaments,dyes,energy materials,food additives etc.The development and utilization of iodine resources have attracted much attention.A large amount of iodide is 相似文献
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Microcystis bloom, one of the most objectionable characteristics of eutrophication in tropical and subtropical waters, occurred in Donghu Lake (East lake) of Wuhan every summer from the 1970s up to 1984, but from 1985 up to now failed to occur there. The cause of its disappearance rema-ined in obscurity until recently. In situ enclosure experiments in the lake for three years showed that the stocking of the filter-feeding silver carp ( Hypophthalmichthys molitrix ) and big-head carp (Aristichthys nobilis ) played a decisive role in eliminating Microcystis bloom from the lake; but that recurrence of the bloom is possible under certain conditions. This paper presents the details and the results of enclosure ex-periments. The authors‘ analysis of fish biomass data obtained by echo-sounding and the fishery produc-tion of the lake over the years, revealed that the recurrence of Microcystis bloom can be prevented so long as the combined biomnss of silver carp and big-head carp remains at or exceeds 50 g per cubic meter of lakewater, as was the case in the lake‘s 1985 fish yield of 1015 t. 相似文献
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Study of the feeding capacity of silver carp and bighead carp by means of experimental ecologyshowed that the filtering frequency of silver carp was slightly greater than that of bighead carp,but thatthe latter's suction volume was much greater than the former's so the filtering rate(filtering frequency mul-tiplied by the suction volume)of silver carp was smaller than that of bighead carp.The filtering efficien-cy of silver carp for phytoplankton was greater than that of bighead carp for them.The removal ratesof silver carp for phytoplankton were greater than those of bighead carp,but for zooplankton the formerwere smaller than the latter.For food particles about 70 μm both removal rates were almost equal.The feeding habits of the two species in natural waters is also discussed in the paper. 相似文献