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231.
Franco PIRAJNO Martin J. Van KRANENDONK Long XIAO 《地质科技情报》2008,27(1):1-12
最近美国航空与空间计划署(NASA)开展的卡西尼-惠更斯外空探测计划发现,在直径为500 km的卫星--土卫二上存在水冰和间隙泉的喷发活动.这一现象和在火星上工作的"机遇号"和"勇气号"漫游车所发现的液态水一起,证明了除地球以外的其他星球上过去和现在都存在水,其中的一些星体还有火山活动的证据,这意味着这些星球上可能存在过热液活动地质过程.讨论了火星、木卫二和土卫二可能存在的热液系统类型.这些热液系统类型是根据地球上的构造背景进行相似性研究后得出的,例如海底、火山和裂谷系统.将东非裂谷和贝加尔湖裂谷系统与火星Tharsis高原上巨大的水手大峡谷进行了对比,这些地区都是由地幔柱作用下构造-热液活动导致的地壳抬升、火山和裂谷作用.在火星上,地下冰或低温层会在火山活动和(或)小行星或彗星撞击作用下溶解而形成热液对流. 相似文献
232.
Jingwen Mao Yitian Wang Houmin Li Franco Pirajno Changqing Zhang Ruiting Wang 《Ore Geology Reviews》2008,33(3-4):361-381
The largest gold district in China is the Jiaodong Peninsula, where three types of gold deposits are recognized: quartz vein, fracture-altered and breccia types. The first two developed along a group of NE-trending faults and are hosted by granitic intrusions, dated at 160 to 150 Ma (biotite granite) and 130 to 126 Ma (granodiorite), and by metamorphic rocks of the Precambrian crystalline basement. The breccia-type gold system is mainly located around the northern margin of the Jiaolai Cretaceous basin, where mineralisation is controlled by both detachment fractures and NE-trending faults. This study is based on stable isotope determinations from ten gold deposits, including Linglong, Jiaojia, Sanshandao, Cangshang, Wang'ershan, Dayigezhuang, Denggezhuang, Pengjiakuang, Fayunkuang and Dazhuangzi, as well as the Linglong Jurassic biotite granite, Guojialing Cretaceous granodiorite and Archean gneiss. The stable isotope systematics reflect the style of the three types of gold deposits, but also show that they belong to the same metallogenic system, in which the hydrothermal fluids were derived from a mantle fluid reservoir and mixed with crustal fluids. The ore-forming age is later than both the Jurassic biotite granite and Cretaceous granodiotite, but overlaps with the 121 to 114 Ma ages of lamprophyre and diabase dykes. The hydrothermal fluids that were responsible for both gold mineralisation and the retrograde alteration of the diabase and lamprophyre dykes are similar, and represent a CO2 and potassium-rich system. This fluid system is interpreted to be the consequence of Cretaceous lithospheric thinning, asthenospheric upwelling and mantle degassing in Eastern China. 相似文献
233.
Predicting new snow density in the Italian Alps: A variability analysis based on 10 years of measurements
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Mauro Valt Nicolas Guyennon Franco Salerno Anna B. Petrangeli Rosamaria Salvatori Paola Cianfarra Emanuele Romano 《水文研究》2018,32(20):3174-3187
Despite its strong impact on the time evolution of the snowpack, current estimation of new snow density (ρhn) is usually accomplished either by using local empirical techniques or by assuming a constant snow density. Faced with the lack of an estimation model of ρhn valid for a wide spatial scale and supported by a suitable number of observations, this study aims to develop simple monthly linear regression models at scale of the entire Italian Alpine chain based on 12,112 snowfall observations at 122 stations, using only air temperature as predictor. Moreover, the remaining variance is investigated in both time and space, also considering some qualitative features of the snowfall events. The daily ρhn measurements present a mean value of 115 kg m?3 (105 and 159 kg m?3 for dry and wet conditions, respectively). The mean air temperature of the 24 hr preceding the snowfall event has been found to be the best predictor of the ρhn, within 31% of uncertainty. The analysis of associated residues allows supporting the idea that the adoption of a more local approach than the one analysed here is not able to substantially increase the predictive capabilities of the model. In fact, the main factor explaining the remaining variance over the air temperature is the wind, but in a complex orography, as mountain regions are, supplying realistic local wind fields is particularly challenging. Therefore, we conclude that using only the daily mean temperature as predictor is a good choice for estimating daily new snow density at scale of Italian Alpine chain, as well as at more regional scale. 相似文献
234.
New geomorphological and chronological constraints for glacial deposits in the Rivoli‐Avigliana end‐moraine system and the lower Susa Valley (Western Alps,NW Italy)
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235.
Roberto Battiston Maria Teresa Brunetti Franco Cervelli Cristiano Fidani Mauro Menichelli 《Astrophysics and Space Science》2009,323(4):357-366
We discuss an electromagnetic sampling calorimeter for the detection of very high energy gamma-rays on the Moon, which is
based on the use of scintillating cylinders and plates imbedded in the lunar soil. The use of lunar soil as a calorimeter
radiator reduces the weight of the material to be transported to the Moon and minimises environmental impact. Plastic scintillator
bars inserted into the regolith about 1.5 m are the active elements of this instrument: at the surface, each bar is terminated
by a plastic scintillator plate to veto high energy charge particles. The readout system for the scintillator bars and plates
are based on recently developed single photon solid state detectors (Silicon Photomultiplier, SiPM), extremely compact, sturdy
and sensitive devices suited for detecting small light pulses in a space experiment. The performance of a regolith-scintillator
calorimeter is evaluated and the relevant parameters are optimised using a GEANT4 simulation. 相似文献
236.
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238.
Seoane S Garmendia M Revilla M Borja A Franco J Orive E Valencia V 《Marine pollution bulletin》2011,62(7):1484-1497
Inverted microscopy is widespread employed for the analysis of phytoplankton composition within water quality monitoring networks. However, the analysis at the lowest taxonomical level is not always required for ecological status assessment. In addition, inverted microscopy can underestimate the small phytoplankton, and not always distinguish photoautotrophic from heterotrophic cells. In this study, as alternative tools, epifluorescence microscopy and High Performance Liquid Chromatography (HPLC) were employed to characterize phytoplankton communities within waters of different trophic condition. Epifluorescence microscopy confirmed its effectiveness to count the small phytoplankton. Furthermore, significant correlations between nutrients of anthropogenic origin and nanoplankton abundances were found. However, this technique resulted very time-consuming. HPLC together with the CHEMTAX program was more appropriate than inverted microscopy, in terms of cost-effectiveness. Also, the main variability patterns observed in the phytoplankton community structure by HPLC coincided with previous findings in the study area. Nevertheless, a rapid screening at the inverted microscope is recommended. 相似文献
239.
Di Franco A Graziano M Franzitta G Felline S Chemello R Milazzo M 《Marine pollution bulletin》2011,62(5):926-933
Many human activities add new structures to the marine landscape. Despite the fact that human structures cause some inevitable impacts, surprisingly little information exists on the effects of marina on natural marine assemblages. The aim of this paper is to assess habitat-specific response of benthic sessile organisms of rocky shores in relation to the presence of a small marina. Sampling was carried out at three coastal habitats (midshore, lowshore and subtidal) by means of visual censuses adopting an after-control-impact (ACI) experimental design. It appears that the marina affects the structure and composition of benthic communities of both the midshore and the lowshore. Little effect was evident on shallow subtidal assemblage structure. The results of the present study clearly show habitat-specific responses of coastal benthic assemblages to the presence of infrastructure. 相似文献
240.
This paper presents the analysis of measurements of long waves at the harbor of Marina di Carrara, Italy. Nine pressure gauges
(eight in the inner harbor and one outside the harbor) were used to record continuously the water surface elevation, for about
3 years; incoming short waves were measured using a directional buoy at about 500 m offshore the breakwaters. The analysis
is carried out splitting the energy of the long waves into two bands, i.e., very long waves (VLW; f < 0.003 Hz) and long waves (LW; 0.003 < f < 0.030 Hz); it is found that LW energy is strongly correlated with the energy of the incoming short waves while no correlation
(or very poor) is found for VLW. During energetic sea states, surface elevation spectra of VLW and LW, normalized against
the wave energy of each frequency band, appear to be autosimilar; this suggests that the spectra of the incoming long waves
have a mostly constant shape. Simple numerical computations of harbor resonance, carried out using a mild-slope equation linearized
model, indicate that the amplification of the height of the incoming LW generated by short waves (calculated using empirical
formulae from previous researches by Melito et al. 2007) inside the harbor can be reasonably predicted using such simple approach, assuming that the LW spectra are rectangular.
The shape of the amplification diagram calculated by the numerical model shows reasonable (but not perfect) agreement with
the shape of the normalized measured spectra inside the harbor. 相似文献