Evolution paragénétique de la minéralisation uranifère de Chaméane (Puy-de-Dôme), France: chaméanite,geffroyite et giraudite,trois séléniures nouveaux de Cu,Fe, Ag et As

Résumé Trois séléniures nouveaux ont été découverts dans la minéralisation unranifère à séléniures et sulfures de Chaméane, France. Geffroyite, (Cu, Fe, Ag)₉(Se, S)₈, cubique,Fm3m,a=10.889 ,Z=4; structure type pentlandite. Densité calculée 5.39 g/cm³. Les raies les plus intenses du diagramme de poudre sont: 9 3.282 (311); 9 3.145 (222); 6 2.094 (511;333); 10 1.925 (440); 5 1.660 (533); 6 1.112 (844). Microdureté Vickers 70 kg/mm². Brun crème en lumière réfléchie, réflectances: 19.0 (420), 27.5 (500), 30.1 (540), 33.6 (600), 35.8 (660), 36.9 (700 nm). Chaméanite. Les analyses à la microsonde correspondent à (Cu_3.46Fe_0.52)_3.98 (As_0.94 Sb_0.02)_0.96(Se_3.72S_0.34)_4.06, formule idéale (Cu, Fe)₄As(Se, S)₄. Le rapport Cu/Fe varie de 6 à 13. Cubique,I---,a=11.039 ,Z=8, densité calculée 6.17 g/cm³. Raies les plus intenses du diagramme de poudre: 10 3.187 (222); 9 1.951 (440); 8 1.665 (622); 4 1.381 (800); 6 1.266 (662); 7 1.127 (844); 5 1.062 (10.2.2; 666). Microdureté Vickers 265 kg/mm². Gris foncé en section polie, plages à zonage complexe dû à des variations de Cu/Fe. Réflectances maximales: 27.1 (420), 26.6 (500), 27.1 (540), 27.7 (600), 28.2 (660); 28.7 (700 nm). Giraudite, (Cu, Zn, Ag)₁₂(As, Sb)₄(Se, S)₁₃. Cubique ,a=10.578 ,Z=2; structure type tétraédrite. Analogue arsénié de la hakite. Densité calculée 5.75 g/cm³. Raies les plus intenses du diagramme de poudre: 10 3.050 (222); 5 2.497 (411; 330); 6 1.932 (521); 9 1.868 (440); 7 1.593 (622). Microdureté Vickers 293 kg/mm². Gris clair, réflectances: 32.2 (420), 31.6 (500), 31.7 (540), 31.7 (600), 31.5 (660), 30.8 (700 nm).Trois épisodes minéralisants, séparés par des mouvements tectoniques, forment la paragenèse de Chaméane, comportant: barytine, pechblende, hématite, löllingite, mispickel, pyrite, chalcopyrite, clausthalite, tétraédrite, tennantite, bukovite, athabascaïte, umangite, berzelianite, klockmannite, eucaïrite, geffroyite, chaméanite, giraudite, eskebornite.

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Paragenetic evolution of the uranium mineralization rich in selenides at chaméane (Puy-de Dôme), France: Chaméanite, geffroyite and giraudite, three new selenides of Cu, Fe, Ag and As

Summary Three new selenides occur in the uranium mineralization rich in selenides and sulphides at Chaméane, France. Geffroyite, (Cu, Fe, Ag)₉(Se, S)₈, cubic,Fm3m,a=10.889 ,Z=4; pentlandite-like structure. Calculated density 5.39 g/cm³. The strongest lines in the X-ray powder pattern are: 9 3.282 (311); 9 3.145 (222); 6 2.094 (511; 333); 10 1.925 (440); 5 1.660 (533); 6 1.112 (844). Vickers microhardness 70 kg/mm². In reflected light, it has a brown colour with a cream tint. Reflectances: 19.0 (420), 27.5 (500), 30.1 (540), 33.6 (600), 35.8 (660), 36.9 (700 nm). Chaméanite. Microprobe analyses gave (Cu_3.46Fe_0.52)_3.98(As_0.94Sb_0.02)_0.96(Se_3.72S_0.34)_4.06; ideal formula is (Cu, Fe)₄As(Se, S)₄. The Cu/Fe ratio varies from 6 to 13. CubicI---,a=11.039 ,Z=8, calculated density 6.17 g/cm³. Strongest lines in the powder pattern: 10 3.187 (222); 9 1.951 (440); 8 1.665 (622); 4 1.381 (800); 6 1.266 (622); 7 1.127 (844); 5 1.062 (10.2.2; 666). Vickers microhardness 265 kg/mm². Dark grey in reflected light. Some grains exhibit irregular zoning due to variations of Cu/Fe ratio. Maximum reflectances: 27.1 (420), 26.6 (500), 27.1 (540); 27.7 (600), 28.2 (660), 28.7 (700 nm). Giraudite, (Cu, Zn, Ag)₁₂(As, Sb)₄(Se, S)₁₃. Cubic, ,a=10.578 ,Z=2; member of tetrahedrite series. Arsenian analogue of hakite. Calculated density 5.75 g/cm³. Strongest lines in the powder pattern: 10 3.050 (222); 5 2.497 (411; 330); 6 1.932 (521); 9 1.868 (440); 7 1.593 (622). Vickers microhardness 293 kg/mm². Light grey in reflected light, reflectances: 32.2 (420), 31.6 (500), 31.7 (540), 31.7 (600), 31.5 (660), 30.8 (700 nm). The mineralization of the Chaméane deposit consists of three cycles separated by tectonic movements. The minerals found are: barite, pitchblende, hematite, löllingite, arsenopyrite, pyrite, chalcopyrite, clausthalite, tetrahedrite, tennanite, bukovite, athabascaite, umangite, berzelianite, klockmannite, eucairite, geffroyite, chaméanite, giraudite and eskebornite.

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Avec 5 Figures     

Comparisons of internal solitary wave and surface wave actions on marine structures and their responses

In this paper, a time-domain numerical model is established for computing the action of internal solitary wave on marine structures and structure motion responses. For a cylindrical structure, its side and bottom are discretized by pole and surface elements, respectively. The drag and inertial forces in the perpendicular direction of the structure are computed by the Morison equation from the pole elements, and the Froude–Krylov force in the axial direction of the structure due to internal wave motion is computed by integration of the dynamic pressure over the surface elements. The catenary theory is used to analyze the reaction force due to mooring lines, and the motion equation of the marine structure is solved by the fourth-order Runge–Kutta method in the time domain. The model is used to calculate the interaction of the internal solitary wave with a Spar platform with mooring system, and the surface wave action with the platform has also been computed by a frequency-domain boundary element method for comparison. Through the comparison based on a practical internal wave and surface wave states, it can be concluded that the internal wave force on the structure is only 9% of the one due to surface waves. However, the motion response due to the internal wave is much greater than the one due to the surface waves. It shows that the low-frequency effect of internal solitary waves is a great threat to the safety of marine structures.     

Budget and Fluxes of Particulate Organic Carbon and Nitrogen According to the Data on Their Vertical Distribution in the Deep Part of the Black Sea

On the basis of the analysis of the many-year data on the vertical distributions of particulate organic carbon and nitrogen, we compute their annual average amounts for three typical layers of water in the deep part of the Black Sea: for a layer located above the oxycline and characterized by the formation of new portions of particulate organic matter in the course of photosynthesis, inside the oxycline, where the major part of oxygen is consumed and the major part of the flux of particulate organic matter is oxidized, and for the upper part of the anoxic zone characterized by the most active microbiological processes of oxidation of the organic substances and production of sulfides. The available literature data on sedimentation traps are used to study the downward annual average fluxes of particulate organic matter from the euphotic zone into the oxycline and into the anaerobic zone. The seasonal variability of the amounts and fluxes of particulate carbon and nitrogen is revealed.     

Seasonal and long-term dynamics of the chlorophyll concentration in the Black Sea according to satellite observations

The spatial and temporal variability of the chlorophyll (Chl) concentration in the surface water layer of the Black Sea in 1998–2008 has been analyzed using the data obtained by the SeaWiFS satellite sensor. In the deep-sea areas, the seasonal pattern of the Chl concentration is represented by a U-shape curve. The maximal concentrations are observed in the winter-spring and autumn periods, while the minimal, in the summertime. In the northwestern Black Sea, the maximal concentrations are registered in mostly the summer and autumn periods. Pronounced interannual variability is found for the summer concentrations of Chl observed for an 11-year period. After a cold winter, the concentration of Chl in the spring period is 3–5 times higher compared to the mild-winter years. In December–March, a negative correlation between the water temperature and the average Chl concentration is registered.     

Detection of the bottom facies characteristics at El Zeit Bay,Red Sea,by using a single-beam acoustic sound

El Zeit Bay is a semi-closed area with a rectangular shape which south side is connected witu northwestern side of Red Sea. The study was done to detect the characteristics of the bottom facies at El Zeit Bay. Single-beam seabed echoes combined with diving survey and sediments analyses were used to detect sea bed characteristics. The seabed floor of the study area is characterized by three physiographical distinct bottom facies; sand facies: floral facies and coral patches facies. Sand facies lies at very shallow water it extended from shore line to depth about 2 m. It has very fine sand size intercalated by mud sediments. It is characterized by very poor benthos. Floral bottom facies has medium sand which characterized by rich floral vegetation this flora appear in scattered and irregular forms. It is observed at an average depth from 4 m to 6 m. Coral patches facies is characterized by the presence of coarse sediments. The coral reef covers about 40% of the study area (29.5% hard corals and 10.5% is soft ones) while the rest of the area (60%) is characterized by different benthos. In communities general, his area characterized by high biodiversity.     

Features of the distributions of the transparency and particulate matter content in the surface water layer in the northwestern part of the Black Sea in the autumn period

Using the data of long-term simultaneous optical, biological, and hydrological observations (1980–1993), particular features of the horizontal distribution of the transparency and the total particulate matter content and the contents of its organic components (organic carbon and nitrogen and chlorophyll a) and their variability in the surface water layer (0–5m) over the northwestern shelf and the adjacent abyssal part of the Black Sea in the autumn season are considered. The detritus/phytoplankton ratio in the particulate organic matter and their relative contents in the total particulate matter are calculated. The distributions of the transparency and particulate matter content were found to be in good agreement and both depend on the water dynamics. It was established that, during the period of the abrupt growth in the Black Sea water turbidity (in the early 1990s), a significant decrease in the transparency and an increase in the particulate matter content caused by the production-destruction processes were observed only in the central and southern regions of the sea.     

Distribution of metal concentrations in sediments of the coastal zone of the Gulf of Riga and open part of the Baltic Sea

The comparison of spatial and temporal distribution of Hg, Cd, Pb, Cu, Ni, Zn, Mn and Fe concentrations in sediments from the Gulf of Riga and open Baltic Sea along the coastal zone is presented for the first time. There were considerable differences in Pb, Zn, Mn and Fe levels in sediment at various stations of the Gulf of Riga. A significant difference of Cd, Pb, Cu, Ni, Zn levels was found in sediments of various stations in the open Baltic coast. The amount of Cd, Pb, Cu, Ni, Zn and Fe levels also differed significantly in the sediments of the Gulf of Riga in different years. A considerable yearly difference in amount of Hg, Cd, Pb, Cu, Ni and Mn levels was found in sediments in the open Baltic coast. The essential highest values of Pb and Zn in coastal sediments of the open Baltic Sea are stated in comparison with the Gulf of Riga. The concentrations of other metals have only a tendency to be higher in coastal sediments of the open Baltic Sea in comparison with the Gulf of Riga. Natural and anthropogenic factors were proved to play an important role in determining resultant metals concentrations in the regions.     

Trophic Status of the South-Eastern Baltic Sea: A Comparison of Coastal and Open Areas

Primary production, nutrient concentrations, phytoplankton biomass (incl. chlorophyll a) and water transparency (Secchi depth), are important indicators of eutrophication. Earlier basin-wide primary production estimates for the Baltic Sea, a shallow shelf sea, were based mainly on open-sea data, neglecting the fundamentally different conditions in the large river plumes, which might have substantially higher production. Mean values of the period 1993–1997 of nutrient concentrations (phosphate, nitrate, ammonium and silicate), phytoplankton biomass, chlorophyll a (chl a) concentration, turbidity and primary production were calculated in the plumes of the rivers Oder, Vistula and Daugava and Klaipeda Strait as well as the open waters of the Arkona Sea, Bornholm Sea, eastern Gotland Sea and the Gulf of Riga. In the plumes, these values, except for primary production, were significantly higher than in the open waters. N:P ratios in the plumes were >16 (with some exceptions in summer and autumn), indicating potential P-limitation of phytoplankton growth, whereas they were <16 in the open Baltic Proper, indicating potential N-limitation. On the basis of in situ phytoplankton primary production, phytoplankton biomass and nutrient concentrations, the large river plumes and the Gulf of Riga could be characterized as eutrophic and the outer parts of the coastal waters and the open sea as mesotrophic. Using salinity to define the border of the plumes, their mean extension was calculated by means of a circulation model. Taking into account the contribution of coastal waters, the primary production in the Baltic Proper and the Gulf of Riga was 42·6 and 4·3×10⁶ t C yr⁻¹, respectively. Hence, an annual phytoplankton primary production in the whole Baltic Sea was estimated at 62×10⁶ t C yr⁻¹. The separate consideration of the plumes had only a minor effect on the estimation of total primary production in comparison with an estimate based on open sea data only. There is evidence for a doubling of primary production in the last two decades. Moreover, a replacement of diatoms by dinoflagellates during the spring bloom was noticed in the open sea but not in the coastal waters. A scheme for trophic classification of the Baltic Sea, based on phytoplankton primary production and biomass, chl a and nutrient concentrations, is proposed.