全球生态地质环境遥感调查研究     

夏乐  李应真  邱罗  厉贤葵 《国土资源导刊(湖南)》2015,(2):85-89

全球生态地质环境是世界共同关注的一项热点问题,我国在国内已经开展了大量生态地质环境的相关研究,但是从宏观上去分析研究整个生态地质环境系统为数不多。本文从全球的角度出发,将植被、冰川、沙漠化和碳酸盐岩等4类确定为生态地质环境因子,通过卫星遥感技术,提取大量相关信息,并选择性开展生态地质环境与全球气候变化关系的研究。  相似文献   

Reply to the comment by M. Bouabdellah et al. on the paper “A late Triassic age for the El Hammam high-REE fluorite deposit (Morocco): mineralization related to the central Atlantic magmatic Province?”     

Alain Cheilletz  Dominique Gasquet  Douglas A. Archibald 《Mineralium Deposita》2010,45(7):733-733

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Glaciation and deglaciation of the Libyan Desert: The Late Ordovician record     

D.P. Le Heron  H.A. Armstrong  C. Wilson  J.P. Howard  L. Gindre 《Sedimentary Geology》2010,223(1-2):100-125

Detailed outcrop studies at the flanks of Al Kufrah Basin, Libya, reveal the nature of glacially-related sedimentation and post-depositional deformation styles produced in association with the Late Ordovician glaciation, during which ice sheets expanded northward over North Africa to deposit the Mamuniyat Formation. At the SE basin flank (Jabal Azbah), the Mamuniyat Formation is sand-dominated, and incises interfingering braidplain and shallow marine deposits of the Hawaz Formation. The glacially-related sediments include intercalations of mud-chip bearing tabular sandstones and intraformational conglomerates, which are interpreted as turbidite and debrite facies respectively. These record aggradation of an extensive sediment wedge in front of a stable former ice margin. An increase in mudstone content northward is accompanied by the occurrence of more evolved turbidites. A widespread surface, bearing streamlined NW–SE striking ridges and grooves, punctuates this succession. The structures on the surface are interpreted to have formed during a regional north-westward ice advance. Above, siltstones bearing Arthrophycus burrows, and Orthocone-bearing sandstones beneath tidal bars testify to glaciomarine conditions for deposition of the underflow deposits beneath. By contrast, the northern basin margin (Jabal az-Zalmah) is appreciably different in recording shallower water/paralic sedimentation styles and major glaciotectonic deformation features, although facies analysis also reveals northward deepening. Here, a siltstone wedging from 8 to 50 m toward the north was deposited (lower delta plain), succeeded by climbing ripple cross-laminated sandstones up to 60 m in thickness (distal through proximal delta mouth bar deposits) with occasional diamictite interbeds. These rocks are deformed by thrusts and > 50 m amplitude fault-propagation folds, the deformation locally sealed by a diamictite then overlain by conglomeratic lag during ultimate deglaciation. Integrating observations from both basin margins, a model of fluvial-dominated delta systems feeding a pulsed debrite and turbidite fan system in a shallow proglacial shelf is proposed.  相似文献   

Sediment entrainment under fully developed waves as a function of water depth,boundary layer thickness,bottom slope and roughness     

J.P. Le Roux 《Sedimentary Geology》2010,223(1-2):143-149

Many sediment entrainment equations for oscillatory waves are based on the linear (Airy) theory for deep water, but at the depth where such waves begin to transport sediments they commonly have trochoidal or cnoidal (non-linear) forms. These changes in the wave profile, together with the fact that it is displaced upward with respect to the still water level (SWL), have a profound influence on the hydrodynamics. A method is presented to determine the thickness of the boundary layer from the wave profile, which can be used to calculate the boundary velocity under the wave crest and trough, respectively, in any water depth. The critical boundary velocity can be determined from a published procedure based on laboratory experiments that takes account of the sediment and water properties as well as the wave period. An adjustment is made for the bottom slope and roughness, so that differential land- or seaward sediment entrainment can be predicted for any defined wave cycle. The results explain why sediments are normally transported landward under fair weather conditions and seaward during storms.  相似文献   

Zn/Fe systematics in mafic and ultramafic systems: Implications for detecting major element heterogeneities in the Earth’s mantle     

V. Le Roux 《Geochimica et cosmochimica acta》2010,74(9):2779-17643

Oceanic basalts, such as mid-ocean ridge basalts (MORB) and ocean island basalts (OIB), are characterized by large isotopic and trace element variability that is hard to reconcile with partial melting of a peridotitic mantle alone. Their variability has been attributed to the presence of heterogeneities within the mantle, such as recycled crust, metasomatized material or outer core contribution. There have been few attempts to constrain the major element composition of those heterogeneities, most studies focusing on incompatible trace elements and radiogenic isotopes. Here, we report Zn, Mn and Fe systematics in mafic and ultramafic systems (whole-rocks and minerals) and we explore their use for detecting lithological heterogeneities that deviate from peridotitic mantle dominated by olivine and orthopyroxene. We suggest that Zn/Fe ratio is a particularly promising proxy. Zn/Fe fractionates equally between olivine, orthopyroxene and melt (e.g. the inter-mineral exchange coefficients  ∼  is ∼0.9-1), and the distribution of Zn/Fe between minerals appears to be temperature-independent within error. In contrast, clinopyroxene and garnet are characterized by low Zn/Fe ratios compared to co-existing melt, olivine and orthopyroxene, that is, and are both <<1. These partitioning behaviors imply that Zn/Fe ratios are minimally fractionated during partial melting of peridotite and differentiation of primitive basalts, if differentiation is dominated by olivine control. Thus, the Zn/Fe ratios of primitive basalts preserve the Zn/Fe ratio of the primary parental magma, providing insight into the signature of the mantle source region. We also infer that Zn/Fe ratios in melts are unlikely to be fractionated by modal variations in peridotitic material but are highly fractionated if garnet and/or clinopyroxene are the main phases in the source during melting. Similar Zn/Fe ratios between MORB and average upper mantle confirm the lack of fractionation during peridotite melting. However, high Zn/Fe ratios of some OIB cannot be explained by peridotite melting alone, but instead require the presence of high Zn/Fe lithologies or lithologies that have bulk exchange coefficients  < 1. All garnet-bearing or clinopyroxene-bearing lithologies, such as eclogites and garnet pyroxenites, fit the latter requirement.  相似文献   

General database for ground water site information   总被引：3，自引：0，他引：3  

de Dreuzy JR  Bodin J  Le Grand H  Davy P  Boulanger D  Battais A  Bour O  Gouze P  Porel G 《Ground water》2006,44(5):743-748

In most cases, analysis and modeling of flow and transport dynamics in ground water systems require long-term, high-quality, and multisource data sets. This paper discusses the structure of a multisite database (the H+ database) developed within the scope of the ERO program (French Environmental Research Observatory, http://www.ore.fr). The database provides an interface between field experimentalists and modelers, which can be used on a daily basis. The database structure enables the storage of a large number of data and data types collected from a given site or multiple-site network. The database is well suited to the integration, backup, and retrieval of data for flow and transport modeling in heterogeneous aquifers. It relies on the definition of standards and uses a templated structure, such that any type of geolocalized data obtained from wells, hydrological stations, and meteorological stations can be handled. New types of platforms other than wells, hydrological stations, and meteorological stations, and new types of experiments and/or parameters could easily be added without modifying the database structure. Thus, we propose that the database structure could be used as a template for designing databases for complex sites. An example application is the H+ database, which gathers data collected from a network of hydrogeological sites associated with the French Environmental Research Observatory.  相似文献   

Effect of water on the heat capacity of polymerized aluminosilicate glasses and melts     

M. Ali Bouhifd  Alan Whittington  Jacques Roux 《Geochimica et cosmochimica acta》2006,70(3):711-722

The effect of water on heat capacity has been determined for four series of hydrated synthetic aluminosilicate glasses and supercooled liquids close to albite, phonolite, trachyte, and leucogranite compositions. Heat capacities were measured at atmospheric pressure by differential scanning calorimetry for water contents between 0 and 4.9 wt % from 300 K to about 100 K above the glass transition temperature (T_g). The partial molar heat capacity of water in polymerized aluminosilicate glasses, which can be considered as independent of composition, is (J/mol K). In liquids containing at least 1 wt % H₂O, the partial molar heat capacity of water is about 85 J/mol K. From speciation data, the effects of water as hydroxyl groups and as molecular water have tentatively been estimated, with partial molar heat capacities of 153 ± 18 and 41 ± 14 J/mol K, respectively. In all cases, water strongly increases the configurational heat capacity at T_g and exerts a marked depressing effect on T_g, in close agreement with the results of viscosity experiments on the same series of glasses. Consistent with the Adam and Gibbs theory of relaxation processes, the departure of the viscosity of hydrous melts from Arrhenian variations correlates with the magnitude of configurational heat capacities.  相似文献   

Simulations of accidental coal immersion     

Jaffrennou C  Giamarchi P  Cabon JY  Stephan L  Burel-Deschamps L  Bautin F  Thomas A  Dumont J  Le Floch S 《Marine pollution bulletin》2007,54(12):1932-1939

Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups – a laboratory seawater canal called “polludrome” is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L⁻¹), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 μg L⁻¹. Fortunately, the results show that the environmental impact of this type of accident would remain limited.  相似文献   

Influence of Magnetic Clouds on Variations of Cosmic Rays in November 2004     

Xiao Xia Yu  Hong Lu  Gui Ming Le  Feng Shi 《Solar physics》2010,263(1-2):223-237

We investigate the effects of two magnetic clouds on hourly cosmic-ray intensity profiles in the Forbush decrease events in November 2004 observed by 47 ground-based neutron-monitor stations. By using a wavelet decomposition, the start time of the main phase in a Forbush decrease event can be defined, and then clearer definitions of initial phase, main phase, and recovery phase are proposed. Our analyses suggest that the main phase of this Fd event precedes the arrival time of the first magnetic cloud by about three hours, and the Fds observed at the majority (39/47) of the stations were found to originate from the sheath region as indicated by large fluctuations in magnetic field vectors at 19:00 UT on 7 November 2004, regardless of the station location. In addition, about 45% of the onset times of the recovery phase in the Forbush decreases took place at 04:00 UT on 10 November, independent of the station position. The results presented here support the hypothesis that the sheath region between the shock and the magnetic cloud, especially the enhanced turbulent magnetic field, results in the scattering of cosmic-ray particles, and causes the following Forbush decreases. Analysis of variation profiles from different neutron monitors reveals the global simultaneity of this Forbush decrease event. Moreover, we infer that the interplanetary disturbance was asymmetric when it reached the Earth, inclined to the southern hemisphere. These results provide several observational constraints for more detailed simulations of the Forbush decrease events with time-dependent cosmic-ray modulation models.  相似文献   

A 3-D coastal tidal rectification process: observations, theory and experiments     

Denis Aelbrecht  Gabriel Chabert d'Hires  Dominique Renouard 《Continental Shelf Research》1999,19(15-16)

In homogeneous rotating fluid, when there is an oscillating forcing in the interior fluid with a period long enough for an Ekman layer to develop, there is an interaction between the oscillatory Ekman layer and the vertical wall, since the latter imposes an alternating adjustment flow confined near the wall. As a result, this coastal rectification process leads to a Lagrangian transport along the coast. The Ekman number, the Rossby number and the temporal Rossby number of the forcing flow are the governing parameters of that mechanism which can be described by a simplified analytical model taking into account both the vertical time-dependent structure of the current and the presence of the wall. The model shows that the residual (rectified) current flowing with the coast to its right results from the strong nonlinear interaction between along- and cross-shore tidal currents leading to asymmetrical momentum exchanges between the Ekman bottom layer and the coastal boundary layer. The model provides simple scaling laws for the maximum intensity and width of the residual current. The latter is significantly larger than the friction (Stokes) lateral boundary layer of the forcing flow. A comprehensive set of experiments is performed in the 13 m diameter rotating tank by oscillating an 8 m×2 m horizontal plate and vertical wall in a homogeneous fluid at rest in solid-body rotation and measuring the two horizontal components of the current at several locations and depths above the central part of the plate. The predicted and experimentally measured maximum intensity and width of the residual current are in very good agreement, within the range of validity of the model, i.e. when the Ekman number is sufficiently small. However experiments also show that the residual current still occurs when the Ekman layer thickness is of the same order as the fluid depth, but it is then confined to a narrower band along the vertical wall. The flow structure found experimentally is also correctly described by a numerical model developed by Zhang et al. (1994). Current measurements in the Eastern part of the English Channel near the French coast reveal a significant coastal residual current flowing Northward and the coastal rectification process described here may account for part of it.  相似文献