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1.
The dissolution of opaline silica of diatom tests in sea water 总被引:3,自引:0,他引:3
Two different series of measurements have been made of the solubilities and rates of solution in sea water of acid-washed siliceous tests of the diatomsThalassiosira decipiens andRhizosolenia hebetata. The kinetic approach was carried out on the assumption that the tests behave as identical solid spheres. If the tests were present in considerable excess over that required for saturation of the water with respect to silica, the dissolution obeyed first order reaction kinetics and its rate was proportional to the surface area of the exposed tests. When the tests were not in excess the kinetics of dissolution appeared to be more complex. This was considered to be due to a decrease in specific surface area as dissolution proceeded. An expression developed to allow for the change of surface area as a sphere dissolves offers a partial explanation of the kinetics when the tests are not present in excess. 相似文献
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Yasumasa Ogawa Naotatsu Shikazono Daizo Ishiyama Hinako Sato Toshio Mizuta 《Mineralium Deposita》2005,39(8):813-821
Experimental studies on the interactions between artificial seawater (ASW) and fresh rhyolite, perlite and weakly altered dacitic tuff containing a small amount of smectite suggest changing cation transfer during smectite-forming processes. Initially, dissolution of K from the rocks accompanies incorporation of Mg and Ca from ASW during both earlier (devitrification stage) and later smectite formation, whereas Ca incorporated with early smectite formation redissolves with progressive reaction. Barium mobility increases toward the later smectite-forming reactions. Therefore, the large amounts of barite, anhydrite and gypsum in Kuroko ore deposits are considered to have precipitated from hydrothermal solutions derived from the interaction with previously altered felsic rocks during late smectite formation, rather than by the reaction with fresh felsic rocks.Editorial handling: D. Lentz 相似文献
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Yujiro Ogawa Tetsuzo Seno Hinako Akiyoshi Hidekazu Tokuyama Kantaro Fujioka Hidetsugu Taniguchi 《Tectonophysics》1989,160(1-4):135-150
The Sagami trough is located at the particular plate margin where the Izu forearc is subducted underneath the Honshu forearc. At its southeastern end, the world's only known TTT-type triple junction (Boso triple junction) has developed. Several different kinds of basins occur in different segments along the Sagami trough and at the triple junction. The bathymetric, geologic, and geophysical data obtained during the Kaiko Project and from additional studies are summarized together with our onland studies. We suggest that the right-lateral oblique plate motion formed an eduction margin in the Sagami basin, while a normal subduction margin and an oblique subduction margin have been formed in the Middle Sagami trough basin. These tectonic phenomena resulted from the long-lasting compressional covergence between the Philippine Sea plate and Eurasian plate since the early or middle Miocene. The North basin on the northeasternmost margin of the Philippine Sea plate near the Boso triple junction has developed as a stretched basin due to the westward motion of the Philippine Sea plate with respect to the Eurasian plate. 相似文献
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General absorbing boundary conditions based on Biot's two-phase mixture theory and paraxial approximation is presented for the dynamic analysis of fluid-saturated porous media with isotropic, transverse isotropic, and anisotropic properties. For the last two cases, the equivalent Lame's constants, under conditions of uniqueness, are introduced to facilitate the analytical solutions. The numerical results show that the proposed absorbing boundary can greatly suppress spuriously reflected waves and efficiently model the far field of the system with sufficient accuracy. 相似文献
5.
Ladda Tangwattananukul Daizo Ishiyama Osamu Matsubaya Toshio Mizuta Punya Charusiri Hinako Sato Koichiro Sera 《Resource Geology》2014,64(2):167-181
The Chatree deposit is located in the Loei‐Phetchabun‐Nakhon Nayok volcanic belt that extends from Laos in the north through central and eastern Thailand into Cambodia. Gold‐bearing quartz veins at the Q prospect of the Chatree deposit are hosted within polymictic andesitic breccia and volcanic sedimentary breccia. The orebodies of the Chatree deposit consist of veins, veinlets and stockwork. Gold‐bearing quartz veins are composed mainly of quartz, calcite and illite with small amounts of adularia, chlorite and sulfide minerals. The gold‐bearing quartz veins were divided into five stages based on the cross‐cutting relationship and mineral assemblage. Intense gold mineralization occurred in Stages I and IV. The mineral assemblage of Stages I and IV is characterized by quartz–calcite–illite–laumontite–adularia–chlorite–sulfide minerals and electrum. Quartz textures of Stages I and IV are also characterized by microcrystalline and flamboyant textures, respectively. Coexistence of laumontite, illite and chlorite in the gold‐bearing quartz vein of Stage IV suggests that the gold‐bearing quartz veins were formed at approximately 200°C. The flamboyant and brecciated textures of the gold‐bearing quartz vein of Stage IV suggest that gold precipitated with silica minerals from a hydrothermal solution that was supersaturated by boiling. The δ18O values of quartz in Stages I to V range from +10.4 to +11.6‰ except for the δ18O value of quartz in Stage IV (+15.0‰). The increase in δ18O values of quartz at Stage IV is explained by boiling. PH2O is estimated to be 16 bars at 200°C. The fCO2 value is estimated to be 1 bar based on the presence of calcite in the mineral assemblage of Stage IV. The total pressure of the hydrothermal solution is approximately 20 bars at 200°C, suggesting that the gold‐bearing quartz veins of the Q prospect formed about 200 m below the paleosurface. 相似文献
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满洲里-新巴尔虎右旗斑岩系列矿床石英流体包裹体液相组分的PIXE分析和地质应用 总被引:1,自引:0,他引:1
PIXE(质子感应X射线分析)方法是目前国际上新的流体包裹体成分分析方法。在前人工作的基础上,尝试用PIXE方法分析了满洲里-新巴尔虎右旗斑岩系列多金属矿床石英流体包裹体的液相多元素化学组分,其结果反映了地质矿化规律。该方法对于多金属矿床石英流体包裹体成分研究非常有用。结合其他包裹体研究,提出甲乌拉与直干布拉根矿床流体组分和成矿物理化学条件均不同,初步认为不存在同一矿化中心;还提出了查干布拉根矿床西矿段深部可能存在乌奴格吐山式斑岩型Cu矿床,应引起注意。 相似文献
9.
Which is more important for tropical cyclone (TC) intensity and intensification, sea surface temperature (SST) or tropical cyclone heat potential (TCHP)? Investigations using best-track TC central pressures, TRMM/TMI three-day mean SST data, and an estimated TCHP based on oceanic reanalysis data from 1998 to 2004, show that the central pressure is more closely related to TCHP accumulated from TC formation to its mature stages than to the accumulated SST and its duration. From an oceanic environmental viewpoint, a rapid deepening of TC central pressure occurs when TCHP is relatively high on a basin scale, while composite distributions of TCHP, vertical wind shear, lower tropospheric relative humidity, and wind speed occurring in cases of rapid intensification are different for each TC season. In order to explore the influence of TCHP on TC intensity and intensification, analyses using both oceanic reanalysis data and the results of numerical simulations based on an ocean general circulation model are performed for the cases of Typhoons Chaba (2004) and Songda (2004), which took similar tracks. The decrease in TCHP due to the passage of Chaba led to the suppression of Songda’s intensity at the mature stage, while Songda maintained its intensity for a relatively long time because induced near-inertial currents due to the passage of Chaba reproduced anticyclonic warm eddies appearing on the leftside of Chaba’s track before Songda passed by. This type of intensity-sustenance process caused by the passage of a preceding TC is often found in El Niño years. These results suggest that TCHP, but not SST, plays an important role in TC intensity and its intensification. 相似文献
10.
Seasonal changes in nano/micro-zooplankton grazing on pico-, nano- and micro-size phytoplankton and heterotrophic nano-flagellates
(HNF) feeding on heterotrophic bacteria were quantified by the dilution technique in the surface layer off Cape Esan, southwestern
Hokkaido, Japan. Pico- and nano-size phytoplankton were major components throughout the year except in spring when a diatom
bloom was observed. Although there was little seasonal variation in bacteria and HNF biomass throughout the year, the micro-zooplankton
biomass varied appreciably with a peak in spring. Nano/micro-zooplankton grazing or feeding on pico-size chl-a and bacteria were well balanced throughout the year. However, nano-size and micro-size chl-a growth were much greater than grazing in summer. Nano/micro-zooplankton ingestion of phytoplankton was greater than their
ingestion of bacteria almost throughout the year, which suggests phytoplankton are more important as food sources of nano/micro-zooplankton
in microbial food webs off Cape Esan than bacteria off Cape Esan.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献