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1.
The fruticose lichen Cetrariella delisei is among the dominant lichen species in the deglaciated High Arctic areas of Svalbard. As part of a study of carbon cycling in the High Arctic, we aimed to estimate the primary production of lichen in a deglaciated area in Ny-Ålesund, Svalbard (79° N), by examining the effects of abiotic factors on the net photosynthesis ( Pn ) and dark respiration ( R ) rates of C. delisei . Experiments were conducted in the snow-free season of 2000 using an open-flow gas exchange system with an infrared gas analyser. Positive photosynthetic activities were observed on rainy days or soon after rainfall when the thallus water content was high, whereas photosynthetic activities dropped below the detectable limit on clear days because of the low thallus water content. Under a sufficiently high thallus water content and close to light saturation, Pn was nearly constant over a wide temperature range of 4–20 °C, while R increased with increasing temperature. We constructed a model for estimating the net primary production ( NPP ) of lichen based on the relationships between abiotic factors and the CO2 exchange rate. The mean, minimum and maximum NPP values in the snow-free season, estimated using meteorological data obtained from 1995–2003, were 5.1, 1.0 and 8.4 g dry wt. m−2 snow-free season−1 , respectively. These results suggest that NPP is highly variable and the contribution of lichen to carbon input is small compared with that of vascular plants and mosses in the study site. 相似文献
2.
Subsurface Occurrence of Natural Gas Hydrate in the Nankai Trough Area: Implication for Gas Hydrate Concentration 总被引:2,自引:0,他引:2
Abstract. The Nankai Trough runs along the Japanese Islands, where extensive BSRs have been recognized in its forearc basins. High resolution seismic surveys and site-survey wells undertaken by the MITI have revealed the gas hydrate distribution at a depth of about 290 mbsf. The MITI Nankai Trough wells were drilled in late 1999 and early 2000. The highlights were successful retrievals of abundant gas hydrate-bearing cores in a variety of sediments from the main hole and the post survey well-2, keeping the cored gas hydrate stable, and the obtaining of continuous well log data in the gas hydrate-dominant intervals from the main hole, the post survey well-1 and the post survey well-3. Gas-hydrate dominant layers were identified at the depth interval from 205 to 268 mbsf. Pore-space hydrate, very small in size, was recognized mostly filling intergranular pores of sandy sediments. Anomalous chloride contents in extracted pore water, core temperature depression, core observations as well as visible gas hydrates confirmed the presence of pore-space hydrates within moderate to thick sand layers. Gas hydrate-bearing sandy strata typically were 10 cm to a meter thick with porosities of about 40 %. Gas hydrate saturations in most hydrate-dominant layers were quite high, up to 90 % pore saturation.
All the gas hydrate-bearing cores were subjected to X-ray CT imagery measurements for observation of undisturbed sedimentary textures and gas-hydrate occurrences before being subjected to other analyses, such as (1) petrophysical properties, (2) biostratigraphy, (3) geochemistry, (4) microbiology and (5) gas hydrate characteristics. 相似文献
All the gas hydrate-bearing cores were subjected to X-ray CT imagery measurements for observation of undisturbed sedimentary textures and gas-hydrate occurrences before being subjected to other analyses, such as (1) petrophysical properties, (2) biostratigraphy, (3) geochemistry, (4) microbiology and (5) gas hydrate characteristics. 相似文献
3.
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
4.
2500年来艾比湖的环境演变信息 总被引:22,自引:9,他引:22
通过对艾比湖缘1,8m浅孔的沉积相和孢粉组合,结合14C测年资料分析。指出近2500年来艾比湖的沉积环境总体是比较稳定的,但由于气候波动引起艾比湖水位曾发生较明显的变化。约在公元前300~400年,是艾比湖面积缩小时期;约公元前300—公元300年,即东周末至西晋,是艾比湖水位较高时期;约公元300—1400年,即东晋至15世纪初,是艾比湖的高水位时期;约15世纪初至17世纪中是艾比湖的水位下降期,但水位比现代仍然高;约17世纪中至19世纪初的小冰期是艾比湖的水位上升期。研究还提供了历史时期湖泊的盐度变化和湖周发生大火的信息。 相似文献
5.
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
6.
Koji Kakinoki Shiro Imawaki Hiroshi Uchida Hirohiko Nakamura Kaoru Ichikawa Shin-Ichiro Umatani Ayako Nishina Hiroshi Ichikawa Mark Wimbush 《Journal of Oceanography》2008,64(3):373-384
Two inverted echo sounders were maintained on coastal and offshore sides of the Kuroshio south of Japan from October 1993
to July 2004. Applying the gravest empirical mode method, we obtained a time series of geostrophic transport. Estimated transports
generally agree well with geostrophic transports estimated from hydrography. Their agreement with the hydrographic transports
is better than that of transports estimated from satellite altimetry data. The geostrophic transport is expressed as the surface
transport per unit depth multiplied by the equivalent depth. The geostrophic transport varies mostly with the surface transport
and fractionally with the equivalent depth. Seasonal variation of the geostrophic transport has a minimum in March and a maximum
in September, with a range of about one fifth of the total transport. 相似文献
7.
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
8.
Mouradian Z. Soru-Escaut I. Hiei E. McALLISTER A. H. Shibasaki K. Ohyama M. Khan J. I. Uchida Y. 《Solar physics》1998,180(1-2):313-329
The 7 May 1992 filament disappearance in the low corona is analyzed. The cool and hot components of this event are studied, using H, soft X-ray and radio data. We first show the general effect of the disparition brusque (DB) on the life of the filament, which was a quiescent filament in the vicinity of an active region, and then give the history of the development of the 7 May event. The main stages of the event are: (i) the formation of hot arches spanning the cool filament; (ii) rise of the filament, with plasma ejection into the corona, in which we note some spreading of loops from the main body, with two distinct rising velocity phases of the H filament; (iii) formation of X-ray arches below the filament, the foot points of the arcades being two-ribbon H flare patches. The dynamics of H and X-rays features are given. 相似文献
9.
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
10.
The convective boundary layer (CBL) with a wide range of stability is simulated experimentally using a thermally stratified wind tunnel, and numerically by direct numerical simulation (DNS). The turbulence structures and flow characteristics of various CBL flows, capped by a strong temperature inversion and affected by surface shear, are investigated. The various vertical profiles of turbulence statistics similar to those from the observed CBL in the field are successfully simulated in both the wind-tunnel experiment and in DNS. The comparison of the wind-tunnel data and DNS results with those of atmospheric observations and water-tank studies shows the crucial dependence of the turbulence statistics in the upper part of the layer on the strength of the inversion layer, as well as the modification of the CBL turbulence regime by the surface shear. 相似文献