A Comparison of Methods for Calculating the Matrix Block Source Term in a Double Porosity Model for Contaminant Transport     

Clarisse Alboin  Jérôme Jaffré  Patrick Joly  Jean E. Roberts  Christophe Serres 《Computational Geosciences》2002,6(3-4):523-543

Contaminant transport in a fractured porous medium can be modeled, under appropriate conditions, with a double porosity model. Such a model consists of a parabolic equation with a coupling term describing contaminant exchange between the fractures, which have high permeability, and the matrix block, which has low permeability. A locally conservative method based on mixed finite elements is used to solve the parabolic problem, and the calculation of the coupling term, which involves the solution of diffusion equations in the matrix blocks, is based on an analytic expression. Numerical experiments show that this semi-analytic method for the coupling term is accurate and faster than several other methods but at a small expense of computer memory.  相似文献   

Évolution thermique des séries sédimentaires de la Marge ardéchoise : étude pétrographique de la matière organique et des argilesThermal evolution of the sedimentary series of the Ardèche Margin: petrological studies of organic matter and clays     

Luis Martinez  Joëlle Duplay  Isabel Suarez-Ruiz  Jean Robert Disnar  Geneviève Farjanel  Philippe Larqué  Nicole Liewig 《Comptes Rendus Geoscience》2002,334(14):1021-1028

Two wells, Balazuc (BA1) and Morte-Mérie (MM1), located in a confined area (1200 m apart) and separated by the Uzer fault (a Liassic structure with a dip fault of 1300 m) were analysed using conventional methodologies and techniques (PRV, TAI, XRD, STEM) in order to compare the diagenetic evolution of clays and organic matter. The thermal convective process allows the circulation of hot fluids and the oxidation of organic matter. The conductive process allows the maturation of the organic matter, the expulsion of hydrocarbons and the deposit of pyrobitumes in the migration channels. To cite this article: L. Martinez et al., C. R. Geoscience 334 (2002) 1021–1028.  相似文献   

Accreted fragments of the Late Cretaceous Caribbean–Colombian Plateau in Ecuador     

Marc Mamberti  Henriette Lapierre  Delphine Bosch  Etienne Jaillard  Raynald Ethien  Jean Hernandez  Mireille Polv 《Lithos》2003,66(3-4):173-199

The eastern part of the Western Cordillera of Ecuador includes fragments of an Early Cretaceous (≈123 Ma) oceanic plateau accreted around 85–80 Ma (San Juan–unit). West of this unit and in fault contact with it, another oceanic plateau sequence (Guaranda unit) is marked by the occurrence of picrites, ankaramites, basalts, dolerites and shallow level gabbros. A comparable unit is also exposed in northwestern coastal Ecuador (Pedernales unit).

Picrites have LREE-depleted patterns, high Nd_i and very low Pb isotopic ratios, suggesting that they were derived from an extremely depleted source. In contrast, the ankaramites and Mg-rich basalts are LREE-enriched and have radiogenic Pb isotopic compositions similar to the Galápagos HIMU component; their Nd_i are slightly lower than those of the picrites. Basalts, dolerites and gabbros differ from the picrites and ankaramites by flat rare earth element (REE) patterns and lower Nd; their Pb isotopic compositions are intermediate between those of the picrites and ankaramites. The ankaramites, Mg-rich basalts, and picrites differ from the lavas from the San Juan–Multitud Unit by higher Pb ratios and lower Nd_i.

The Ecuadorian and Gorgona 88–86 Ma picrites are geochemically similar. The Ecuadorian ankaramites and Mg-rich basalts share with the 92–86 Ma Mg-rich basalts of the Caribbean–Colombian Oceanic Plateau (CCOP) similar trace element and Nd and Pb isotopic chemistry. This suggests that the Pedernales and Guaranda units belong to the Late Cretaceous CCOP. The geochemical diversity of the Guaranda and Pedernales rocks illustrates the heterogeneity of the CCOP plume source and suggests a multi-stage model for the emplacement of these rocks. Stratigraphic and geological relations strongly suggest that the Guaranda unit was accreted in the late Maastrichtian (≈68–65 Ma).  相似文献   

Guest Editorial - "Geoanalysis 2003"     

Jean S. Kane  Heikki Niskavaara  Lea Hmlinen  Harry Sandstrom  Michael H. Ramsey 《Geostandards and Geoanalytical Research》2004,28(1):7-7

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Determination of Platinum-Group Elements in Geological Reference Materials by High Resolution-ICP-MS after Nickel Sulfide Fire-Assay Collection and Te Co-Precipitation     

Claudia P.R. Morcelli  Ana Maria G. Figueiredo  Jacinta Enzweiler  Jorge E.S. Sarkis  Alexandre P.S. Jorge  Maurício Kakazu 《Geostandards and Geoanalytical Research》2004,28(2):305-310

Inductively coupled plasma-mass spectrometry (ICP-MS) after NiS fire assay-Te co-precipitation was employed in the determination of Ru, Rh, Pd, Os, Ir and Pt at ng g^-1 levels in six platinum-group element (PGE) geological reference materials. In general, the average of several results was in good agreement with the certified values taking into account respective uncertainties. High relative standard deviations were observed for the reference materials GPt-3 and GPt-4. Problems associated with the NiS fire assay procedure and PGE determination at the sub-10 ng g^-1 level are reviewed and discussed.  相似文献   

How reliable are growth strata in interpreting short-term (10 s to 100 s ka) growth structures kinematics?     

Sébastien Castelltort  Stéphane Pochat  Jean Van den Driessche 《Comptes Rendus Geoscience》2004,336(2):151-158

High-frequency stratigraphic cycles (10 s to 100 s ka) often show, at a specific location, an alternation of ‘dynamic’ (proximal-energetic), and ‘non-dynamic’ (distal-pelagic) processes with time. When sedimentation is syn-deformation, these processes tend respectively to fill-up tectonically-induced topography or to drape it. As a consequence, growth strata are alternatively thickened and isopach across the growth structure. High-resolution kinematic studies of growth structures (folds and faults), which assume that sedimentation always fills up topographies (‘fill-to-the-top’ model), may therefore mistake sedimentary cyclicity for tectonic cyclicity. We address this problem with one example of growth anticline in the Spanish Pyrenees, and we discuss the fill-to-the-top model. To cite this article: S. Castelltort et al., C. R. Geoscience 336 (2004).  相似文献   

Les sillons plissés du Burundien supérieur dans la chaı̂ne Kibarienne d'Afrique centrale     

Michel Villeneuve  Jean Chorowicz 《Comptes Rendus Geoscience》2004,336(9):807-814

The Kibaran belt that extends all over the central Africa, from the Katanga to the southern Uganda, straddles the African great lakes area. The Kibaran stratigraphy is one of the most debated questions. Some geologists favoured two different systems: the Ruzizian system (1800–2000 Ma) and the Burundian or Kibaran system (1600–960 Ma). Some others favoured a single Burundian system with large areas granitised and metamorphosed during several Burundian tectonic events and with a lot of sedimentary fold belts of the Burundian age. Recent geological data and new remote sensing interpretations allow us to favour the second hypothesis but with a major disconformity within the Burundian system which is separating the Upper and the Lower Burundian. To cite this article: M. Villeneuve, J. Chorowicz, C. R. Geoscience 336 (2004).  相似文献   

Reply to the comment by A. Cherchi and R. Schroeder on an article by J. Guex, Eclogae geol. Helv. 94 (2001) 321–328.     

Jean Guex 《Eclogae Geologicae Helvetiae》2004,97(3):445

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华南陡山沱期古地理环境及"雪球地球"研究新进展   总被引：4，自引：1，他引：4  

孙知明杨振宇  裴军令Jean BESSE　Melina MACOUIN　Stuart GILDER　Magali ADER 《地质通报》2004,23(8):728-731

华南地块陡山沱组的古地磁和C同位素研究揭示了其形成于赤道附近的古地理环境。对冰期后的盖帽白云岩的C同位素研究表明，δ^13C从-5‰开始有缓慢升高的趋势，与世界上Marinoan冰期其他剖面的c同位素变化相一致。陡山沱期大气中CO2含量的升高可能与kodinia超大陆的裂解及火山活动等密切相关。  相似文献   

L'érosion des chaînes de montagnes : influence de la sédimentation de piedmont     

Julien Babault  Jean Van Den Driessche   《Comptes Rendus Geoscience》2005,337(16):1431

The applanation of mountain belts that results in peneplain is generally considered to be caused by the long-term activity of erosion. Peneplanation has been previously defined as the lowering of an elevated topography and the concomitant subduing of its relief. We propose a model following which piedmont sedimentation induces the base level rise, allowing applanation to develop at high elevation and resulting in an elevated ‘peneplain’. This model is illustrated by the morphological evolution of the southern flank of the Pyrenees during the Cainozoic. To cite this article: J. Babault, J. Van Den Driessche, C. R. Geoscience 337 (2005).  相似文献