1972 values for international geochemical reference samples

Best values for constituents determined in a rock analysis and for trace elements are collected for samples prepared by the Centre de Recherches Petrographiqueset Geochimiques, France, the Canadian Standard Reference Materials Project (formerly SSC), the Geological Survey of Japan, the National Institute for Metallurgy, South Africa, the U.S. Geological Survey and the Zentrales Geologisches Institut, D.D.R.     

青藏高原西部喀喇昆仑断裂活动构造研究进展综述（英文）

喀喇昆仑断裂系(KF)位于青藏高原西缘,具有右旋走滑性质,从帕米尔高原至尼泊尔西部延绵1 000多km。长期以来,对于喀喇昆仑断裂活动的起始时间、总位移量、在不同时间尺度上的滑移速率以及断层两端的精确位置等问题,都存在较大争议。为了更好的了解喀喇昆仑断裂现今的运动学特征及其与喜马拉雅—青藏高原陆内碰撞造山带的关系,确定喀喇昆仑断裂的滑移速率历史以及它随时间和/或空间的变化规律是极其重要的。目前研究表明,从现今的大地测量学尺度到几个百万年的地质学尺度,喀喇昆仑断裂走滑速率的变化范围为3～10 mm/yr。本论文对断裂各段的分布情况进行了详细描述,阐述了获得晚第四纪以来走滑速率的方法,回顾了喀喇昆仑断裂在大地测量学、晚第四纪以及地质学等不同时间尺度的走滑速率,并重点讨论了晚第四纪以来断裂的走滑速率。然后,确定了喀喇昆仑断裂北端的精确位置、讨论了其运动学意义和地震灾害效应。鉴于喀喇昆仑断裂具有长期的活动历史、规模巨大、运动速率较高,我们认为即使板块内部小尺度的似连续变形非常发育,板块模型依然可以很好的解释由于印度-亚洲板块碰撞造成的喜马拉雅北部的岩石圈变形。喀喇昆仑断裂、阿尔金断裂、昆仑断裂及龙木错—郭扎错断裂等青藏高原周缘的主要走滑断裂对青藏高原向东的挤出起着重要的调节作用。     

Delayed-Neutron Activation Determination Of Uranium in Thirteen French Rock Reference Samples

The uranium contents of thirteen rock reference samples from the Centre de Recherches Pétrographiques et Géochimiques, Nancy, France, were determined by delayed-neutron activation analysis. Four others from the same laboratory were found to have uranium concentrations below our limit of detection. Meaningful comparison of our data with other workers is presently not possible (i) because of the paucity of uranium data and (ii) because of the disparity of uranium data on the samples for which uranium data exist.     

Multielemental Neutron Activation Analysis of Chinese Geochemical Reference Samples

The concentrations of 36 elements in geochemical reference samples issued by the Ministry of Geology and Mineral Resources of China were determined by neutron activation analysis. Three main variants of the technique, instrumental, epithermal, and nreirradiation separation neutron activation analysis (INAA, ENAA, PNAA), were employed in a systematic study of the samples by three laboratories: the Institute of Atomic Energy of the Academia Sinica (INAA, ENAA), the Institute of High Energy Physics of the Academia Sinica (INAA), and the Institute of Geophysical and Geochemical Prosnecting of the Ministry of Geology and Mineral resources (INAA,PNAA). Both long and short irradiations and both Ge(Li) and HPGe detectors were used. A supplementary software nackage for data processing was developed. About 81% of the data determined by neutron activation agreed with recomended values with in 15%.     

A probabilistic model for the prediction of meteorological droughts in Venezuela

Droughts occur when rainfalls diminish or cease for several days, months or years. In the last five years several meteorological droughts have occurred in Venezuela, impacting negatively water supply, hydro-power and agriculture sectors. In order to provide institutions with tools to manage the water resources, a probabilistic model has been developed and validated to predict in advance the occurrence of meteorological droughts in the country using monthly series of 632 rainfall stations. The standardized precipitation index (SPI) was used to identify dry events of each rainfall series. A principal component analysis associated to a geographic information system was used to define geographically continuous homogeneous sub-regions (HS) for the values of SPI. For each HS a representative station was selected (reference station, RS). A lagged correlation analysis was applied to the SPI series of the RS and the corresponding series of anomaly indices of 10 macroclimatic variables (MV). The four MV with higher correlation in each RS were organized into three levels (-1, 0 and +1), using the quartiles Q₂ and Q₄ as values of truncation. The SPI series are expressed in four ranges: non-dry, moderately dry, severely dry and extremely dry. The conditional probability of occurrence of the four ranges of SPI was determined in every combination that can occur in the four VM best correlated. The resulting model in each RS was validated using the SPI series from 20 meteorological stations operated by the Servicio de Meteorología de la Fuerza Aérea Venezolana (Meteorological Service of the Venezuelan Air Force) which were not used in the development of the models. Results indicate that models detected the occurrence of ES with an accuracy ranging from 85.19 to 100%; the success is directly proportional to the length of records used in the development of the model. This methodology could be applied in any country that has long, continuous and homogeneous rainfall series.     

DETERMINATION OF TWELVE TRACE ELEMENTS IN TWENTY-SEVEN AND TEN MAJOR ELEMENTS IN TWENTY-THREE GEOCHEMICAL REFERENCE SAMPLES BY X-RAY FLUORESCENCE SPECTROMETRY

This study reports the results of twelve trace elements in twenty-seven International geochemical reference samples (IGRS) (15 from Japan, 7 from South Africa, 4 from France and 1 from U.S.A.). Similarly, ten major elements were also determined in twenty-three GRS (15 from Japan, 5 from South Africa, 2 from France and 1 from U.S.A.). Whenever possible, the results are compared with literature values for these GRS.     

Geochemical behaviour and relative mobility of metals (Mn, Cd, Zn and Pb) in recent sediments of a retention pond along the A-71 motorway in Sologne, France

 Retention ponds have been dug along some of the motorways in France to minimize environmental pollution by keeping pollutants from spreading over the surrounding area. In the current work, eight core samples were collected from the bottom of a retention pond located along the A-71 motorway in Sologne to study the pollution of sediment by heavy metals and their diagenetic behaviour. The vertical concentration profiles of metals (Pb, Zn, Cd, Fe and Mn) in sediment as well as in interstitial water were determined. Especially in the case of the sediment, a sequential extraction method was employed to investigate how the movement of each metal is associated with the other metals and with other solid phases such as organic matter. In addition, to investigate the relative mobility of the metals, the distribution coefficients (K_D) were also determined. The concentrations of the metals were always found to be highest in the topmost layer of sediment. This so-called surface enrichment is caused by a substantial increase of the non-detrital fraction of these metals at the sediment surface. For instance, the accumulation of Pb and Zn is associated with the increase in the "fraction II" in the sequential extraction. The accumulation of Cd at the surface (0–2 cm) is partly due to the liberation of Cd from the particles during early diagenesis. However, the major factor contributing to the accumulation of Cd at the sediment surface is attributed to the dissolution of Cd from polluted roadside soil during the periods of rainstorms and its subsequent redeposition on the sediment surface after being carried to the retention pond. K_D values for Zn and Cd were found to decrease with depth, while K_D values for Pb increased. Based on the K_D values, the relative mobilities of the studied metals were determined to be as follows: Mn>Zn>Cd>Pb, for the upper layer, and Mn>Cd>Zn>Pb, for the layers below. Received: 28 October 1996 / Accepted: 21 November 1996     

Using ion and isotope characterization to design a frame of protection of a wetland system (Massif Central,France)

The bio-diversity (vegetation and fauna) of peatlands, like all wetland ecosystems, is very fragile as it requires specific wet conditions. Over the past 20 years, increasing efforts have been made to restore degraded wetlands, to re-create new wetlands where they were lost, and to sustainably manage for multiple benefits. However, actions to restore and preserve wetlands require an in-depth knowledge of the water cycle in the system. We used chemical and multi-isotopic approaches, combined with hydrological tools (measuring potentiometric levels and spring discharge), for tracing the water and dissolved-element fluxes in the Narces de la Sauvetat peatland (Central France) and for better understanding of water budget components involved in this ecosystem. This multi-pronged approach clearly demonstrated its effectiveness for improving our understanding of the hydrological functioning of this wetland ecosystem. The two main results are that: (1) The water volume flowing out of the peatland through the Fouragettes stream is often negligible; and (2) At least three strong groundwater fluxes with distinct chemical and isotopic signatures supply water to the peatland. This new understanding will help decision makers maintain the water balance of the peatland, which is essential for the preservation of this fragile ecosystem.     

Dual-energy computerized tomography in compacted soil

This paper describes an alternative nondestructive technique for bulk density and water content determination in soils using dual-energy computerized tomography. A first generation tomographic system (STAC-1) was used in the analysis of the specimens. The system used ¹³⁷Cs (662 keV), ¹⁹²Ir (316 keV) and ²⁴¹Am (60 keV) as radiation sources and a Sodium Iodine crystal (NaI(Tl)) with photomultiplier tube as the detector. The specimens of soil tested were from different regions, one from São Paulo, and the other from Rio de Janeiro. The bulk density and the water content were determined point by point, in a transverse section of the soil specimens, using a computational algorithm that generated images of bulk density and water content. By utilizing the average pixel values of linear attenuation coefficient in these images, for each specimen, a characteristic curve could be built for each soil. The linear attenuation coefficient values agreed with the expected data. The compaction curves presented good agreement between the tomographic technique and the standard geotechnical method.     

Modelling ion composition in seepage water from a column experiment with an open cut coal mine sediment

Secondary reactions occurring in pyrite-containing sediments from open cut coal mines are complex and not fully understood. In this study, the changes in seepage water composition in a column experiment with a sediment containing pyrite (5.6 g kg⁻¹) were evaluated using a chemical equilibrium model. A column experiment with artificial irrigation (730 mm water yr⁻¹) was carried out for 2 yr with a sediment from the open pit mine Garzweiler, Germany, at the Institute of Applied Geology. Tracer (LiCl) was added to the sediment. Seepage water composition at 52 cm depth was sampled weekly. Redox potential and the water potential were also recorded weekly. Sulphate and Fe(II) were the dominant ions in the seepage water with concentration maxima of 500 and 350 mmol l⁻¹ after 50 days (0.7 pore volumes (PV)). Minimum pH values were around 0.8 after 100 days (1.4 PV), but increased subsequently and reached 2.4 after 700 days (9.5 PV). Ion activity product calculations indicated the intermediate formation of gypsum (19th–480th day of the experiment). Solutions were undersaturated with respect to alunite, jarosite, jurbanite, schwertmannite, melanterite, gibbsite and goethite during the whole experiment. The model of coupled equilibria which included inorganic complexation, precipitation/dissolution of gypsum and multiple cation exchange was tested. Pyrite oxidation and pH-dependent silicate weathering were considered using simple input functions. Transport was modelled using a field capacity cascade submodel. Model results showed satisfactory agreement with measured values for pH and concentrations of SO₄, Fe, Mg, Ca and Al. Correlation coefficients lay between 0.7 and 0.9 and linear regression coefficients (modelled against measured) were 1.5 (Ca), 1.0 (Fe, SO₄), 0.8 (Mg), 0.7 (pH) and 0.6 (Al). The results showed that the protons produced during pyrite oxidation (94 mmol_c H⁺ kg⁻¹) were mainly released into seepage water (as HSO₄⁻ and H⁺). Cation exchange reactions buffered 20 mmol_c of H⁺ kg⁻¹ sediment, and Al released by silicate weathering accounted for 3.6 mmol_c H⁺ kg⁻¹. Modelling was useful to further understand the significance of different pH buffer reactions.     

Concretions de Bioxyde de Manganese sur des affleurements granitiques dans une zone de balancement des marees. (Anse de Belmont,France)-l-Analyse et mineralogie des encroutements

Résumé Des encroûtements de bioxyde de manganèse d'une épaisseur de quelques millimètres recouvrent les rochers granitiques de l'Anse de Belmont (Loire-Atlantique, France). Ils sont découverts à marée basse. Ils sont constitués de bioxyde hydraté amorphe, todorokite, ranciéite et cryptomélane qui sont agencés selon l'édifice des micas. Leur teneur en fer est très faible; ils sont enrichis en cobalt et uranium. Des eaux douces riches en manganèse et pauvres en fer se jettent dans la mer au niveau de ces dépôts qui se forment par réaction de précipitation du manganèse au moment du mélange des eaux douces avec l'eau de mer. Les observations sur place indiquent que ces dépôts sont récents, et que leur croissance est rapide.Manganese dioxide concretions, a few millimeters thick, are covering granite outcrops in the intertidal area of the cove of Belmont (Loire-Atlantique, France). The concretions are constituted by an association of several manganese dioxide minerals (amorphous hydrated dioxide, todorokite, ranciéite and cryptomelane) which are epitaxially growing on the mica minerals of the granite. The concretions have a very low iron content, and are enriched in cobalt and uranium. A fresh water spring, with high manganese and low iron concentration, is flowing out at the level of the MnO₂ concentrations. The mixing of sea water and fresh waters leads to MnO₂ precipitation. Field observations show that the concretions are recent and that they grow rapidly.     

The hydrologic function and behavior of the Houzhai underground river basin, Guizhou Province, southwestern China

The genesis of the Houzhai karstic water system of the Guanling Formation, southwestern China, dates back to the Middle Triassic. Due to differences in the geomorphology and the extent of the underground river system with highly developed conduits, the hydrologic function appears to be complex. The hydrologic function and behavior of the karst system were analyzed by spring hydrograph (Mangin 1975) and by groundwater hydrochemical methods. The result obtained from the former shows that the Houzhai karstic water system behaves in a non-karstic way, with slow infiltration and a large regulation power. This study shows that Mangin’s karst classification is not applicable in the karstic water systems of southwest China. The hydrodynamic parameters obtained from Mangin’s spring hydrograph and the hydrochemical parameters obtained from the analysis of the bicarbonate relative frequency were combined to characterize the hydrologic function and behavior of the Houzhai karstic water system. The synthesized result shows that the distortion degree of the precipitation input is lower upstream, due to the different surface landform and the degree of karst heterogeneity. Mangin A (1975) Contribution à l’étude hydrodynamique des aquifères karstiqus (Contribution to the hydrodynamic study of karst aquifers). Thèse, Université of Dijon, France (Annales de Spéléologie 29(3), 283–332; 29(4), 495–601; 30(1), 21–124).     

Dynamic scheme of water circulation in karstic aquifers as constrained by Sr and Pb isotopes. Application to the Hérault watershed,Southern France

This paper focuses on the relationship between the karst aquifers and the Hérault River (southern France) as a function of hydrologic conditions. The combination of major and trace element, and Sr and Pb isotopes determined on dissolved load in karstic springs makes it possible to identify a dynamic scheme of the hydrology of the karstic area.In the headwaters part of this area, the Sourcettes Spring is fed by an interrupted stream that infiltrates at the basement-sedimentary cover contact. Internal geochemical processes are also pointed out: (1) water–rock interactions during underground circulation, and (2) water originating from different layers of the aquifer may show different chemistry depending on the hydrological conditions. The Vernède Spring, is fed by a second water supply during high flows (previously considered as unconnected). Finally, the Cent-Fonts Springs have been confirmed to be fed by the Buège interrupted stream.Pb isotopes on the dissolved and particulate loads of the river samples make it possible to discriminate the natural (local rocks) versus anthropogenic (mining district and road traffic) Pb sources. The Pb isotope investigations on karstic water make it possible to differentiate between neighboring springs presenting identical Sr isotope and element ratios, and to point out different underground circulation.

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Resumen Este artículo trata de la relación río-acuífero kárstico en la cuenca de Hérault (Francia), en función de las condiciones hidrológicas. La combinación de elementos principales, elementos traza, e isótopos de estroncio y plomo en muestras de manantiales kársticos permite construir un esquema dinámico de la zona.El manantial de Sourcettes, en la parte alta de la región, está alimentado por una corriente interrumpida que se infiltra a través la cubierta sedimentaria del lecho. También, se apunta a los procesos internos geoquímicos: (1) interacciones roca-acuífero, (2) aguas procedentes de capas diferentes del acuífero, dependiendo de las condiciones hidrológicas. El manantial de Vernède, en el sector oriental de la cuenca, se nutre de una segunda fuente de agua en períodos de aguas altas, que anteriormente se consideraba desconenctada. Finalmente, se ha confirmado que los manantiales de Cent-Fonts captan las aguas del curso interrumpido del Buège.Los isótopos de plomo, tanto en fase disuelta como en suspensión de muestras de río, permiten discriminar entre orígenes naturales (rocas naturales) y antrópicos (minería y tráfico) de este elemento. Las investigaciones en aguas kársticas llevan a diferenciar entre manantiales vecinos que tienen relaciones de isótopos de estroncio idénticas, así como a proponer circulaciones distintas en el acuífero por drenaje o por mineralización no diseminada del plomo.

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Résumé Cet article s'intéresse à la relation entre le karst et une rivière dans le bassin de l'Hérault (France), en fonction des conditions hydrologiques. La combinaison des éléments majeurs, des traces et des isotopes de Sr et Pb déterminés dans la charge dissoute de sources karstiques permet de construire un schéma dynamique de la région karstique.Dans la partie la plus haute de cette région, la source des Sourcettes est alimentée par un cours d'eau qui s'infiltre au contact de la série sédimentaire sur le socle. Des processus géochimiques sont également mis en évidence: (1) des interactions eau-roche au cours du trajet souterrain, (2) de l'eau provenant de différents niveaux de l'aquifère en fonction des conditions hydrologiques. Dans la partie orientale du bassin, la source Vernède reçoit une seconde alimentation lors des fortes crues, précédemment considérée comme n'étant pas connectée. Finalement, on confirme que la source des Cent-Fonts est alimentée par les pertes de la rivière de la Buèges.Les isotopes du Pb dans les charges dissoute et solide des échantillons de rivières ont conduit à faire la distinction entre les sources naturelle (roches locales) et anthropique (mines et trafic routier). Les études sur les isotopes du Pb dans les eaux karstiques permettent de différencier les sources voisines présentant des rapports d'éléments et de signatures isotopiques du Sr identiques, et à distinguer différentes circulations souterraines drainant ou non des minéralisations disséminées de Pb.

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In situ and laboratory investigations of fluid flow through an argillaceous formation at different scales of space and time, Tournemire tunnel, southern France

In the context of a research and development program on waste disposal, an experimental site (Tournemire tunnel, Aveyron, France) was selected by the French Institute for Nuclear Protection and Safety (IPSN) in order to undertake studies on potential fluid flow at different scales of space and time within a 250-m-thick argillaceous formation. The argillite has a low natural water content (~3–5%) and very low radii access porosity. Diffusion (tritiated water) coefficients (1×10^–12 to 2×10^–11 m²/s) and hydraulic conductivities derived from different types of laboratory tests (10^–14 to 10^–13 m/s) are characteristics of a very low-permeable rock. In situ hydraulic tests (including long-term hydraulic-head measurements) were used to obtain values for hydraulic head and hydraulic conductivity at a scale of 1–10 m (10^–13 to 10^–11 m/s). Despite uncertainties on these data (due to a scale factor, presence of fissures, and possible artefacts due to hydro-chemo-mechanical coupling), it is expected that fluid flow is essentially governed by diffusion processes. Identification of possible natural flows at larger scales of time and space was investigated using natural isotopic tracers from interstitial fluids. Modelling, based on the deuterium profile along the clay formation and assuming pure diffusion processes, provides estimations of possible flow times. However, lack of knowledge concerning the past geological evolution of the site and the possible role of a fracture network do not permit reduction of uncertainties on these estimations at this stage. Electronic Publication     

Speleothem evidence of warm episodes in northeast France during Marine Oxygen Isotope Stage 3 and implications for permafrost distribution in northern Europe

U-Th ages have been obtained by TIMS on the growth periods of a stalagmite from the “Grotte des Puits de Pierre-la-Treiche” (northeastern France), during the middle part of the “Weichselian glaciation” (Marine Isotope Stage 3), between 55.36 ± 0.95 and 53.34 ± 0.49 ka and around 45.85 ± 0.49 ka. These episodes are contemporaneous with abrupt climatic variations recorded in Greenland ice cores (Greenland interstadials 12, 14 and 15) that have been previously recognized in European speleothems. They also coincide with two interstadials, known as “Goulotte” and “Pile” in the Grande Pile pollen sequence (eastern France), which have been correlated with the Moershoofd complex in the Netherlands. Such evidence of speleothem deposition related to temperate episodes gives a strong indication of the absence of continuous shallow permafrost during the middle part of MIS 3 in northeastern France.     

Estimated Recharge Rates From Groundwater Temperatures In The Nara Basin,Japan

Groundwater recharge rates to the sandy aquifer in the Nara basin, Japan, were determined by using a theory that describes the simultaneous transfer of heat and water in a porous medium. Seasonal changes in temperatue-depth profiles were used to estimate the recharge rates in a relatively shallow aquifer. Estimations of the recharge rates were done by fitting a dimensionless parameter to the type curves developed by Taniguchi (1993) after the amplitudes of annual variations of groundwater temperatures were measured at several depths. Annual recharge rate estimated by fitting observed temperatures to the type curves was 459 mm in the Nara basin. This value agrees well with values calculated from water-balance methods and values reported in the literature. Résumé: Les taux de recharge d'un aquifère sableux dans le bassin de Nara (Japon) ont été déterminés au moyen d'un modèle qui décrit le transfert simultané de la chaleur et de l'eau en milieu poreux. Les variations saisonnières le long de profils verticaux de température sont utilisées pour estimer les taux de recharge dan un aquifère relativement superficiel. Les estimations de ces taux de recharge ont été réalisées par l'ajustement d'un paramètre sans dimension aux courbes types proposées par Taniguchi (1993) d'après les amplitudes des variations annuelles de la température de l'eau souterraine mesurée à différentes profondeurs. La recharge annuelle estimée par l'ajustement des températures observées aux courbes types est 459 mm dans le bassin de Nara. Cette valeur est en bon accord avec celles caculées à partir du bilan hydrologique et avec celles de littérature. Resumen: Las velocidades de recarga en el acuífero arenoso de la cuenca del Nara, Japón, se determinaron por medio de una teoría que describe la transferencia simultánea de calor y agua en un medio poroso. Los cambios estacionales en los perfiles temperatura-profundidad permitieron estimar las velocidades de recarga en una acuífero relativamente somero. Las estimaciones de la velocidad de recarga se hicieron por ajuste de un parámetro adimensional a las curvas-tipo desarrolladas por Taniguchi (1993). Para ello se utilizaron las amplitudes de las variaciones anuales de las temperaturas del agua a distintas profundidades. La recarga anual en la cuenca del Nara, estimada mediante este método de ajuste de curvas, fue de 459 mm. Este valor es semejante a la recarga calculada a partir de métodos de balance y a la obtenida de la bibliografía.     

The lithostratigraphy of the Les Echets basin, France: tentative correlation between cores

Two new long sediment cores (EC1 and EC3), recovered from different locations within the infilled basin at Les Echets, France, provide a new high-resolution record of terrestrial and lacustrine responses to climatic changes during Marine Isotope Stages (MIS) 3 and 2. The lithologies of the cores are described in detail and correlated with each other by stratigraphic marker horizons, fluctuations in organic matter and AMS radiocarbon ages. The tentative correlation of the new cores to those described and analysed by de Beaulieu et al. (1980) and de Beaulieu & Reille (1984a) provides a preliminary chronostratigraphic framework. Sedimentation during MIS3 started with accumulation of sands and silts and was followed by alternating gyttja and clayey gyttja silts. Exceptionally high sedimentation rates during MIS2 led to the infilling of the basin. Alternating organic-rich and minerogenic-rich sediments appear to coincide with changes in pollen assemblages (de Beaulieu & Reille 1984a) and suggest that millennial-scale climatic changes controlled lake productivity and catchment stability during most of MIS3.     

Redox and pH conditions in the water column and in the sediments of an acidic mining lake

Physico-chemical parameters of the acidic mining lake (ML) 111 in the Lusatian region (Germany) were determined in April and August 1997 using a multiparameter probe for the water column and punch-in pH and Eh electrodes for the sediment, respectively. Samples of the sediment profile were taken by a gravity corer. Besides determination of the physico-chemical parameters, grain size and water contents were determined after sediment slicing.Differences in the redox state of the water body, deduced from oxygen saturation between April and August, could not be inferred. However, a shift in pH to lower values was apparent. Data support the conclusion that the enhanced oxygen content was consumed for oxidation of ferrous iron to ferric iron (oxides/hydroxides) coupled with the release of protons.In the sediment, different buffer systems of iron compounds could be detected within separate zones with values below and above pH 3. At higher pH values, the redox conditions are controlled and stabilized by the presence of Fe-oxide-hydroxides and possibly Fe-sulfates.     

Diffusion And Flow In Gravel,Soil, And Whole Rock

Transport parameters (diffusion coefficients, D(/), hydraulic conductivities, K(/), and retardation factors, R_f were experimentally determined in unsaturated soil, gravel, bentonite, and whole rock over a wide range of water contents, fixed at desired levels using the Unsaturated Flow Apparatus (UFA^TM). Effective diffusion coefficients in all media were found primarily to be a function of volumeric water cintent (/) and not material characteristics, except where the characteristics affect or determine water content. At high water contents, D(/) gradually declines as water content decreases, from 10^-5cm²/s at a / of about 50% to 10^-7cm²/s at a / of about 5%, followed by a sharp decline as surface films become thin and discontinuous, and pendular water elements become very small, from 10^-7cm²/s at a / of about 5% to 10^-10cm²/s at a / of about 0,5%. The several whole rock cores studied behaved similary. In aggregate material such as gravel and soil where the particles themselves have significant porosity, only the surface water content, not the internal water of the particles, contributes to the diffusion coefficient and hydraulic conductivity under unsaturated conditions, although the internal water is very important in retardation and other chemical effects. Experimentally determined K(/) compares favorably to van Genuchten/Mualem relationships calculated from laboratory-determined water retention versus matric potential data obtained on the same soils. Experimentally determined K(/) for whole rock appears to validate capillary bundle theory. Résumé. Diffusion et écoulement dans les graviers, les sols et les roches. Les paramètres de flux (coefficient de diffusion, D(‹), conductivité hydraulique, K(‹), et facteur de retard, R_f) ont été déterminés expérimentalement dans des formations non saturées (sol, gravier, benthonite et roche consolidée) pour une large gamme de tenneurs en eau (‹); ces teneurs en eau ont été ajustées aux valeurs désirées grâce à un dispositif spécial fournissant un écoulement non saturé (UFATM). Les résultats montrent que les coefficients de diffusion efficace de tous ces milieux sont d'abord fonction de la teneur volumique en eau et non des caractéristiques du matéeriau, sauf lorsque ces caractéristiques affectent ou déterminent la teneur en eau. Pour les fortes teneurs en eau, D(‹) décroit progressivement avec la teneur en eau, de 10 ^ч cm²/s pour un ‹ de 50% jusqu'à 10^щ cm²/s pour environ 5%. Lorsque les films d'eau deviennent minces et discontinus et lorsque la fraction d'eau gravitaire devient trop faible, D(‹) diminue très brutalement de 10^щ cm²/s pour un ‹ de 5% à 10^⪞ cm²/s pour un ‹ de 0,5%. Plusieurs roches consolidées, testées sur carottes, se comportent de la même façon. Dans les agrégats, comme les graviers et les sols, où les particules possèdent une porosité propre, seule la teneur en eau intergranulaire, et non l'eau de l'intérieur des particules, contribue à la valeur du coefficient de diffusion et à la conductivité hydraulique, dans des conditions non saturées, bien que l'eau intragranulaire joue un rôle très important quant au retard et aux autres effets chimiques. Les Valeurs de K(‹) déterminées expérimentalement montrent un bon accord avec les relations de van Genuchten/Mualem calculées à partir des teneurs en eau de rétention, déterminées au laboratoire en fonction du potentiel matriciel obtenu sur les mêmes sols. Les valeurs expérimentales de K(‹) pour des roches consolidées semblent valider la théorie du faisceau capillaire.     

Les associations paragenetiques dans la metallogenie varisque du massif armoricain

Résumé Cette note est un essai de classification des différentes associations paragénétiques varisques du Massif Armoricain (France). Après une présentation de la structure d'ensemble de cette région naturelle, en termes de tectonique des plaques (lère partie), 13 groupes paragénétiques sont successivement décrits (2ème partie). Leur répartition spatiale permet de souligner l'importance des accidents linéamentaires, souvent granitisés, dans la localisation et la nature des gisements (3ème partie).

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An attempt is made to classify the different variscan paragenetic units of the Armorican Massif (France). After a presentation of the general structure of this country, in terms of plate tectonics (1st part), 13 paragenetic units are successively described (2nd part). Their spacial distribution allows to emphasize the importance of the lineaments, often granitized, in the localization and nature of ore deposits (3rd part).