Structural investigation of the synthetic CaAn(PO4)2 (An = Th and Np) cheralite-like phosphates     

Philippe E. Raison  Regis Jardin  Daniel Bouëxière  Rudy J. M. Konings  Thorsten Geisler  Claudiu C. Pavel  Jean Rebizant  Karin Popa 《Physics and Chemistry of Minerals》2008,35(10):603-609

The crystallographic structures of the synthetic cheralite, CaTh(PO₄)₂, and its homolog CaNp(PO₄)₂ have been investigated by X-ray diffraction at room temperature. Rietveld analyses showed that both compounds crystallize in the monoclinic system and are isostructural to monazite LnPO₄ (Ln = La to Gd). The space group is P2₁/n (I.T. = 14) with Z = 2. The refined lattice parameters of CaTh(PO₄)₂ are a = 6.7085(8) Å, b = 6.9160(6) Å, c = 6.4152(6) Å, and β = 103.71(1)° with best fit parameters R _wp = 4.87%, R _p = 3.69% and R _B = 3.99%. For CaNp(PO₄)₂, we obtained a = 6.6509(5) Å, b = 6.8390(3) Å, c = 6.3537(8) Å, and β = 104.12(6)° and R _wp = 6.74%, R _p = 5.23%, and R _B = 6.05%. The results indicate significant distortions of bond length and angles of the PO₄ tetrahedra in CaTh(PO₄)₂ and to a lesser extent in CaNp(PO₄)₂. The structural distortions were confirmed by Raman spectroscopy of CaTh(PO₄)₂. A comparison with the isostructural compounds LnPO₄ (Ln = Ce and Sm) confirmed that the substitution of the large rare earth trivalent cations with Ca²⁺ and Th⁴⁺ introduces a distortion of the PO₄ tetrahedra.  相似文献   

Improved precision of acoustic surveys of benthopelagic fish by means of a deep-towed transducer     

Kloser  Rudy J. 《ICES Journal of Marine Science》1996,53(2):407-413

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Diagenesis and fracturing of Paleocene–Eocene carbonate turbidite systems in the Ionian Basin: The example of the Kelçyra area (Albania)     

Nadge Vilasi  Rudy Swennen  Franois Roure 《Journal of Geochemical Exploration》2006,89(1-3):409

The Kelçyra area is emplaced in a foreland fold-and-thrust belt (FFTB), characterized by a westward thrusting with the Triassic evaporites as the major décollement level. Several secondary features related with this evolution, like backthrusting, folding, duplex structures, evaporite diapirism are present. During the FFTB evolution, the study area has been subjected to several fracturing events with associated stages of fluid migration. During the pre-deformational stage, complex textures such as crack-and-seal features most likely reflect expulsion of overpressured fluids. These fluids were dominantly host-rock buffered. Within the post-deformational stage, a meteoric fluid caused cementation and development of a karst network during a period of emergence after the thrust emplacement. Subsequently, Mg calcite reprecipitated in the more stable carbonate phase calcite and dolomite, which filled part of the karts network. The latter is finally dedolomitized and locally partially dissolved by a second meteoric fluid flow, which greatly increased the secondary porosity.  相似文献   

Utilization of Shallow Geophysical Sensing at Two Abandoned Municipal/Industrial Waste Landfills on the Missouri River Floodplain     

Richard J. Rudy  John A. Caoile 《Ground Water Monitoring & Remediation》1984,4(4):57-65

In the past 30 to 40 years, floodplain areas of large rivers, such as the Missouri River, have been extensively used for large industrial and municipal landfills. Many of these sites are now causing varying degrees of ground water contamination. Rapid geophysical characterization techniques have proven useful for delineation of anomalous areas indicative of potential contaminant plumes. These methods have also resulted in a cost effective approach to the location and number of monitoring wells.
An effective technique to initially characterize ground water contamination at such landfills along the Missouri River in northwestern Missouri involved a combination of electrical resistivity and electromagnetic conductivity methods. Resistivity was used to obtain soundings of the alluvium by using a modified Wenner array and to corroborate shallow electromagnetic conductivity measurements by using short Wenner array electrode spacings.
Upon confirmation of similar measurements of the upper soils for the two methods, numerous electromagnetic conductivity traverses were made at each landfill site. The data generated from these surveys were graphed and contoured to delineate anomalous areas. Based on the geophysical study, a ground water monitoring well network was then designed for each landfill.
As a result, a minimal number of wells were required to initially characterize the ground water quality at these two sites. In general, analysis of water samples from these wells displayed good correlation with the geophysical results.  相似文献   

Grain-size trends, basin subsidence and sediment supply in the Campanian Castlegate Sandstone and equivalent conglomerates of central Utah   总被引：2，自引：1，他引：1  

Ruth A. J. Robinson  & Rudy L. Slingerl 《Basin Research》1998,10(1):109-127

Reconstructions of grain-size trends in alluvial deposits can be used to understand the dominant controls on stratal architecture in a foreland basin. Different initial values of sediment supply, tectonic subsidence and base-level rise are investigated to constrain their influence on stratal geometry using the observed grain-size trends as a proxy of the goodness of fit of the numerical results to the observed data. Detailed measurements of grain-size trends, palaeocurrent indicators, facies and thickness trends, channel geometries and palynological analyses were compiled for the middle Campanian Castlegate Sandstone of the Book Cliffs and its conglomerate units in the Gunnison and Wasatch plateaus of central Utah. They define the initial conditions for a numerical study of the interactions between large-scale foreland basin and small-scale sediment transport processes. From previous studies, the proximal foreland deposits are interpreted as recording a middle Campanian thrusting event along the Sevier orogenic belt, while the stratal architecture in the Book Cliffs region is interpreted to be controlled by eustatic fluctuation with local tectonic influence. Model results of stratal geometry, using a subsidence curve with a maximum rate of ≈45 m Myr^?1 for the northern Wasatch Plateau region predict the observed grain-size trends through the northern Book Cliffs. A subsidence curve with a maximum rate of ≈30 m Myr^?1 in the Gunnison–Wasatch Plateaus best reproduces the observed grain-size trends in the southern transect through the southern Wasatch Plateau. Eustasy is commonly cited as controlling Castlegate deposition east of the Book Cliffs region. A eustatic rise of 45 m Myr^?1 produces grain-size patterns that are similar to the observed, but a rate of eustatic rise based on Haq et al. (1988) will not produce the observed stratal architecture or grain-size trends. Tectonic subsidence alone, or a combined rate of tectonic subsidence and a Haq et al. (1988) eustatic rise, can explain the stratal and grain-size variations in the proximal and downstream regions.  相似文献   

Crustal thickening and crustal extension as controls on the evolution of the drainage network of the central Swiss Alps between 30  Ma and the present: constraints from the stratigraphy of the North Alpine Foreland Basin and the structural evolution of the Alps     

Fritz Schlunegger  Rudy Slingerl  & Albert Matter 《Basin Research》1998,10(2):197-212

The combined information about sedimentary petrography from the North Alpine Foreland Basin and structural geology from the Alps allows a qualitative reconstruction of the drainage network of the central Swiss Alps between 30 Ma and the present. This study suggests that crustal thickening and crustal thinning significantly controlled the location of the drainage divide. It also reveals the possible controls of crustal thickening/thinning on the change of the orientation of the drainage network from across-strike between 30 and 14 Ma to along-strike thereafter. Initial crustal thickening in the rear of the wedge is considered to have formed the drainage divide between north and south at 30 Ma. Because the location of crustal thickening shifted from east to west between ≈30–20 Ma, the catchment areas of the eastern dispersal systems reached further south than those of the western Alpine palaeorivers for the same time slice. Similarly, the same crustal dynamics appear to have controlled two phases of denudation that are reflected in the Molasse Basin by petrographic trends. Uplift in the rear of the wedge caused the Alpine palaeorivers to expand further southward. This is reflected in the foreland basin by increasing admixture of detritus from structurally higher units. However, tectonic quiescence in the rear of the wedge allowed the Alpine palaeorivers to cut down into the Alpine edifice, resulting in an increase of detritus from structurally lower units. Whereas uplift in the rear of the wedge was responsible for initiation of the Alpine drainage systems, underplating of the external massifs some 50 km further north is thought to have caused along-strike deviation of the major Alpine palaeorivers. Besides crustal thickening, extension in the rear of the wedge appears to have significantly controlled the evolution of the drainage network of the western Swiss Alps. Slip along the Simplon detachment fault exposed the core of the Lepontine dome, and caused a 50-km-northward shift of the drainage divide.  相似文献   

Sedimentary processes and trace metal contaminants in the buccaneer oil/gas field,northwestern gulf of Mexico     

Richard B. Wheeler  John B. Anderson  Rudy R. Schwarzer  Claudia L. Hokanson 《Environmental Geology》1980,3(3):163-175

Sediments are the ultimate sink for contaminants in the marine environment, and physical processes of sedimentation influence the distribution and accumulation of these contaminants. Evaluation of contaminant levels in sediments is one approach to assessing environmental impact; data interpretation depends on consideration of sediment texture and mineralogy, however, which profoundly influence chemical composition. In this study, comparison of potentially contaminated sediments from the production field with control populations was done only within the context of similar (as to texture and organic carbon and carbonate content) sample groups as determined by cluster analysis. Ba, Cd, and Sr are identified as contaminants. Supported by the identification of a well-crystallized expandable clay—possibly bentonite—drilling fluids are a potential source of Ba. Ba and Sr may be unnaturally high because of their abundance in discharged produced formation waters, but may also be naturally controlled by the unique faunal assemblage associated with the structures. Cd is probably derived from corrosion of the structures and assorted debris on the seafloor. In general, contamination is limited to an area within 100 m of the platforms. Furthermore, substantial erosion around platforms has probably effectively removed and dispersed the bulk of the contaminants introduced into the marine environment by the offshore exploration/production operations.  相似文献   

Controlling factors on the morphology and spatial distribution of methane-related tubular concretions – Case study of an Early Eocene seep system     

Eva De Boever  Marijke Huysmans  Philippe Muchez  Lyubomir Dimitrov  Rudy Swennen   《Marine and Petroleum Geology》2009,26(8):1580-1591

Up to 10 m in length and >1 m in diameter tubular, calcite-cemented sandstone concretions are hosted by the faulted Dikilitash unconsolidated sands and sandstones. These structures document shallow subsurface pathways of Early Eocene methane seepage in the Balkan Mountains foreland (NE Bulgaria). Their exceptional exposure allowed a unique study of the factors governing the morphology and spatial distribution of such fossilized fluid conduits. The large dimensions and subvertical, cylindrical shape of the most common tube type primarily reflects the buoyancy-driven, vertical path of an ascending gas-bearing fluid through permeable, mainly unconsolidated sandy host sediments. Tube morphology was also influenced by local stratigraphic anisotropies and might as well document differences in former seepage conditions. Mapping of >800 tubular concretions showed the NNW–NNE elongation and alignment of tube clusters and massive cemented sandstone structures. This suggests that Paleogene fault systems played a major role in directing the movement of fluids. However, within a single tube cluster, tubes are preferentially aligned, over distances up to 50 m along directions at an angle between 10° and 36° with respect to the inferred NNW–NNE, cluster parallel fault traces. In addition, cylindrical tubes of analogue dimensions are aligned over distances >100 m along N15° to N25°-oriented directions. It is hypothesized that this spatial geometry of tubular concretions reflects the complex geometry of deformations structures in fault damage zones along which fluids were preferentially channelled.  相似文献   

Investigation of the potential surface–groundwater relationship using automated base-flow separation techniques and recession curve analysis in Al Zerba region of Aleppo,Syria     

Rudy K. Abo  Broder J. Merkel 《Arabian Journal of Geosciences》2015,8(12):10543-10563

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Sedimentology,three‐dimensional geobody reconstruction and carbon dioxide origin of Pleistocene travertine deposits in the Ballık area (south‐west Turkey)          下载免费PDF全文

Hannes Claes  Jeroen Soete  Koen Van Noten  Hamdy El Desouky  Marcelle Marques Erthal  Frank Vanhaecke  Mehmet Özkul  Rudy Swennen 《Sedimentology》2015,62(5):1408-1445

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