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排序方式: 共有291条查询结果,搜索用时 328 毫秒
281.
Johann Tuduri Alain Chauvet Aomar Ennaciri Luc Barbanson 《Comptes Rendus Geoscience》2006,338(4):253-261
Based on a combined geometrical and mineralogical analysis, a three-stage model of formation of the mineralized veins of the giant Imiter silver deposit (Anti-Atlas, Morocco) is herein proposed. A first episode is characterized by the development of quartz, pink dolomite and Ag-rich minerals veins formed during a dextral transpressive event. The second episode is associated with a normal left-lateral motion that re-opens previous structures, filled by pink dolomite gangue. Alteration stages contribute to a local Ag enrichment. To cite this article: J. Tuduri et al., C. R. Geoscience 338 (2005). 相似文献
282.
A construct of internal multiples from surface data only: the concept of virtual seismic events 总被引:1,自引:0,他引:1
Luc T. Ikelle 《Geophysical Journal International》2006,164(2):383-393
283.
WANG Bo CLUZEL Dominique JAHN Bor-ming SHU Liangshu CHEN Yan BRANQUET Yannick BARBANSON Luc 《《地质学报》英文版》2013,87(Z1):316-316
284.
Florian Perez Claude Mügler Philippe Jean-Baptiste Jean Luc Charlou 《Computational Geosciences》2013,17(2):217-237
We present a new numerical tool developed in the Cast3M software framework to model hydrothermal circulation. Thermodynamic properties of one-phase pure water are calculated from the International Association for the Properties of Water and Steam formulation. This new numerical tool is validated on several test cases of convection in closed-top and open-top boxes. Simulations of hydrothermal circulation in a homogeneous-permeability porous medium also give results in good agreement with already published simulations. This new numerical tool is used to construct a geometric and physical conceptual model of the Rainbow vent site at 36°14′N on the Mid-Atlantic Ridge. Several configurations are discussed, showing that high temperatures and high mass fluxes measured at the Rainbow site cannot be modeled with hydrothermal circulation in a homogeneous-permeability porous medium. These high values require the presence of a fault or a preferential pathway right below the venting site. We propose and discuss a two-dimensional single-pass model that allows us to simulate both high temperatures and high mass fluxes. This modeling of the hydrothermal circulation at the Rainbow site constitutes the first but necessary step to understand the origin of high concentrations of hydrogen issued from this ultramafic-hosted vent field. 相似文献
285.
Cabral Victor Carvalho Reis Fábio Augusto Gomes Vieira D’Affonseca Fernando Mazo Lucía Ana dos Santos Corrêa Claudia Vanessa Veloso Vinicius Gramani Marcelo Fischer Ogura Agostinho Tadashi Lazaretti Andrea Fregolente Vemado Felipe Pereira Filho Augusto José dos Santos Claudia Cristina Lopes Eymar Silva Sampaio Rabaco Lis Maria Reoni do Carmo Giordano Lucilia Zarfl Christiane 《Natural Hazards》2021,108(3):3021-3043
Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,... 相似文献
286.
Probabilistic climate data have become available for the first time through the UK Climate Projections 2009, so that the risk of change in tree growth can be quantified. We assessed the drought risk spatially and temporally using drought probabilities calculated from the weather generator data and tree species vulnerabilities using Ecological Site Classification model across Britain. We evaluated the drought impact on the potential yield class of three major tree species (Picea sitchensis, Pinus sylvestris, and Quercus robur), which cover around 59 % (400,700 ha) of state-managed forests, across the lowlands and uplands. We show that drought impacts result mostly in reduced tree growth over the next 80 years when using B1, A1B, and A1FI IPCC emissions scenarios, but varied spatially. We found a maximum reduction of 94 % but also a maximum increase of 56 % in potential stand yield class in the 2080s from the baseline climate (1961–1990). Furthermore, potential production over the state-managed forests for all three species in the 2080s is estimated to decrease due to drought by 42 % in the lowlands and by 32 % in the uplands in comparison to the baseline climate. Our results reveal that potential tree growth and forest production on the state-managed forests in Britain is likely to reduce, and indicate where and when adaptation measures are required. Moreover, this paper demonstrates the value of probabilistic climate projections for an important economic and environmental sector. 相似文献
287.
Agnès Bouchez Noémie Pascault Cècile Chardon Marc Bouvy Philippe Cecchi Luc Lambs Mélanie Herteman François Fromard Patrice Got Christophe Leboulanger 《Marine pollution bulletin》2013,66(1-2):39-46
Mangroves are threatened ecosystems that provide numerous ecosystem services, especially through their wide biodiversity, and their bioremediation capacity is a challenging question in tropical areas. In a mangrove in Mayotte, we studied the potential role of microbial biofilm communities in removing nutrient loads from pre-treated wastewater. Microbial community samples were collected from tree roots, sediments, water, and from a colonization device, and their structure and dynamics were compared in two areas: one exposed to sewage and the other not. The samples from the colonization devices accurately reflected the natural communities in terms of diversity. Communities in the zone exposed to sewage were characterized by more green algae and diatoms, higher bacteria densities, as well as different compositions. In the area exposed to sewage, the higher cell densities associated with specific diversity patterns highlighted adapted communities that may play a significant role in the fate of nutrients. 相似文献
288.
Carolina Bernal Frédéric Christophoul Jean-Claude Soula José Darrozes Luc Bourrel Alain Laraque José Burgos Séverine Bès de Berc Patrice Baby 《International Journal of Earth Sciences》2012,101(7):1913-1928
The successive courses of the Rio Pastaza in the upper Amazonian Puyo plateau (Ecuador) during the past century have been followed using historical maps, aerial photographs, satellite imagery, topographic and river long profiles, and field studies. The abrupt change in direction of the Rio Pastaza from transverse to longitudinal was a result of two avulsions occurred between 1906 and 1976 at the braided-meandering transition of the former alluvial plain. These avulsions are related to aggradation at the toe of a braided piedmont fan prograding on to a hinterland-dipping topographic slope formed by ongoing tectonic backtilting. The main avulsion proceeded by annexation of a south-dipping depression created in front of the cordillera by backtilting of the plateau. A partial and gradual avulsion having occurred upstream of the former site between 1976 and 2008 is marked by the progressive predominance of a newly formed inner branch. Tectonic backtilting enhanced aggradation upstream of the initial site while it offered the newly avulsed channel a still more favorable way along the cordillera by creating a westward lateral slope. The correlation between ENSO events and the occurrence of the 1976–2008 avulsions strongly suggests that the triggers of the avulsions were the floods caused by the high water and sediment discharges associated with ENSO (La Ni?a) events contrasting with the regular monthly discharge and the lack of actual ‘normal’ floods during the inter-ENSO periods. 相似文献
289.
YANG Ming-yu VAN COILLIE Frieke HENS Luc DE WULF Robert OU Xiao-kun ZHANG Zhi-ming 《山地科学学报》2014,11(1):142-155
Development of appropriate tourism infrastructure is important for protected areas that allow public access for tourism use.This is meant to avoid or minimize unfavourable impacts on natural resources through guiding tourists for proper use.In this paper,a GIS-based method,the least-cost path(LCP) modelling,is explored for planning tourist tracks in a World Heritage site in Northwest Yunnan(China),where tourism is increasing rapidly while appropriate infrastructure is almost absent.The modelling process contains three steps:1) selection of evaluation criteria(physical,biological and landscape scenic) that are relevant to track decision; 2) translation of evluation criteria into spatially explicit cost surfaces with GIS,and 3) use of Dijkstra's algorithm to determine the least-cost tracks.Four tracks that link main entrances and scenic spots of the study area are proposed after optimizing all evaluation criteria.These tracks feature lowenvironmental impacts and high landscape qualities,which represent a reasonable solution to balance tourist use and nature conservation in the study area.In addtion,the study proves that the LCP modelling can not only offer a structured framwork for track planning but also allow for different stakeholders to participate in the planning process.It therefore enhances the effectivenss of tourism planning and managemnt in protected areas. 相似文献
290.
Measured groundwater temperatures in the surficial zone are dependent on the properties of porous media and vertical flow velocity. Sensitivity analyses, collinear diagnostics and an inverse numerical solution to the one-dimensional heat-transport equation are used to determine which parameters can be estimated from temperature measurements in the surficial zone. This is done for heat transport in the saturated zone considering a constant vertical flow velocity. The use of temperature profiles, temperature time-series and temperature envelopes are considered. There is an important difference between a conduction and a convection dominated system. Sensitivity analysis shows that temperature measurements are sensitive to effective thermal conductivity and heat capacity and are insensitive to effective porosity and thermal dispersivity. In a conduction dominated system, temperature is also insensitive for vertical velocity. Collinear diagnostics show that in a conduction dominated system, only the combination of heat capacity and effective thermal conductivity, the thermal diffusivity, can be derived. In a convection dominated system, both the vertical velocity and the effective thermal conductivity can, theoretically, be derived. 相似文献