Résultats de la recherche (117 résultats)

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  • The rare earth elements (REE) have been mobilised and fractionated during supracrustal alteration of the Torrongo granodiorite. Compared with the parent granodiorite, incipiently and moderately altered rocks are particularly enriched in the heavy
  • REE, while the extremely altered residual products are especially depleted in the heavy REE. Mobilisation of the REE probably results from PH changes of soil and ground waters as they encounter different chemical environments while fractionation may
  • largely result from mineralogical controls. Submarine and subaerial weathering processes may affect REE similarly, producing intensively weathered materials appreciably depleted in the REE. Spilitisation and hydrothermal alteration processes may affect
  • Geochemical and mineralogical behavior of REE, Th and U in the Akongo lateritic profile (SW Cameroon)
  • The aim of this study is to determine the behavior of REE, U and Th during the weathering of a crystalline rock with common REE-U-Th contents. The Akongo lateritic profile which developed on a syenite has been chosen because 1) this profile
  • This contribution focuses on the interpretation of REE patterns on a regional scale by comparing profiles from varios climatic zones and morphological positions. Under consideration of polyphase and polygenetic weathering processes, present REE
  • distribution patterns are related to different phases of landscape and climatic evolution in SE-Bahia State, Brazil. Finally the use of REE patterns as tools for the reconstruction of landscape evolution and weathering history is discussed.
  • REE geochemistry of modern eolian dust deposits in Harbin city, Heilongjiang province, China : Implications for provenance
  • The REE composition of samples from sand–dust deposit events in Harbin was compared with that of 3 different grain size fractions of sandy soil samples from Horqin Sandy Land and Songnen Sandy Land. The results indicate that the REE distributions
  • of all of the Harbin sand–dust samples are remarkably similar to each other, with distinct negative Eu anomalies and slightly negative Ce anomalies, indicating a stable provenance. Grain size exerts a significant influence on REE compositions
  • A leaching experiment using 5 REE oxides and gravelly, sandy loam soils was conducted and the leaching and binding characteristics of the oxides for the soils were examined. The experiment showed little leaching of the oxides and an enrichment
  • of various size classes of soil particles with the oxides, which reflected the strong binding capability of the REE oxides with the gravelly, sandy loam soils. In this study, the method based on measuring the REE concentrations for 4 particle size groups
  • The aims of this study were : to examine the applicability of the Rare Earth Element (REE) technique for successive storm events for a period of nearly 4 years; to evaluate the relative contribution of each morphological element to sediment yield
  • from the watershed; and to examine the potential sources of error related to using the REE technique for a multi-year of period to study sediment sources.
  • An erosion experiment was conducted using simulated rainfall within a laboratory slope model. Soil was tagged with 10 rare earth element (REE) oxides as sediment tracers and placed in different locations over the slope and at the end
  • of the experiment REE concentrations were measured in samples collected spatially. A new method was developed to quantify the erosion and deposition depths spatially, the relative source contributions to deposited sediment and the sediment transport distances
  • . Particle-size selectivity over an area of net deposition was also investigated, by combining downslope changes in particle-size distributions with changes in sediment REE composition within a flow pathway. Results and discussion about the potential of using
  • REE for quantifying sediment transport processes.