Structure et caractérisation des matériaux utilisés dans la construction d'une mosaı̈que romaine de la cité de Volubilis (Maroc)     

Abdelilah Dekayir  Marc Amouric  Juan Olives  Claude Parron  Abdelilah Nadiri  Abdelkader Chergui  M.Abdeljalil El Hajraoui 《Comptes Rendus Geoscience》2004,336(12):1061-1070

In Volubilis, Roman mosaics are very beautiful and reveal, from the bottom to the surface, three layers: (i) ‘hedgehog’ layer, (ii) coarse grain mortar layer (rudus + nucleus) and (iii) tesselatum. Mineralogical analysis of coarse grain mortar sampled in Flavius Germanus mosaic shows that it consisted of quartz and calcite, with some feldspar and probably mica and dolomite. Fine-grained mortar in tesselatum is made from a mixture of calcite and quartz only. Limestone tesserae (white, pink and brown) show petrographic facies that change from micritic to oolithic limestone. Conversely, black and brick red tesserae are respectively made of marble, red sandstone and from fire clay. Other colours as yellow, blue, green and grey are obtained from artificial glass with different chemical compositions. To cite this article: A. Dekayir et al., C. R. Geoscience 336 (2004).  相似文献   

L'hétérogénéité du manteau supérieur à l'aplomb du volcan de Nyos (Cameroun) révélée par les enclaves ultrabasiques     

Robert Temdjim  Pierre Boivin  Gilles Chazot  Claude Robin  Émilie Rouleau 《Comptes Rendus Geoscience》2004,336(14):1239-1244

Volcanic deposits from the lake Nyos (Cameroon) contain ultrabasic xenoliths: lherzolites, harzburgites and websterites, sometimes containing amphibole. Major and trace element compositions of clinopyroxene and amphibole allow the recognition of an old depletion event followed by two episodes of incompatible-element enrichment. One is high in light rare-earth elements, while the other one is low in these elements, but high in U and Th. Their relative chronology is not yet established. To cite this article: R. Temdjim et al., C. R. Geoscience 336 (2004).  相似文献   

MELIMEX,an experimental heavy metal pollution study: Oligochaetes and chironomid larvae in heavy metal loaded and control limno-corrals     

Claude Lang  Barbara Lang-Dobler 《Aquatic Sciences - Research Across Boundaries》1979,41(2):271-276

In two limno-corrals loaded with heavy metals the density of tubificid worms and chironomid larvae was higher than in the control. The better oxygen conditions observed in the heavy metal loaded corrals might explain this discrepancy. The higher oxygen concentration at the sediment-water interface was due to lower organic sedimentation, consequence of the primary production reduced by heavy metals. In all limno-corrals, the tubificid populations consisted ofTubifex tubifex. The size structure of tubificid populations in the heavy metal loaded corrals indicated a delayed reproduction compared to the control.  相似文献   

Stochastic forcing models of climate variability     

Claude Frankignoul 《Dynamics of Atmospheres and Oceans》1979,3(2-4)

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Comments on ‘the bearing of phase-equilibria in simple and complex systems on the origin and evolution of some well-documented garnet websterites’ by C.T. Herzberg     

F. Conquéré  Claude T. Herzberg 《Contributions to Mineralogy and Petrology》1979,70(2):219-228

Currently understood liquidus phase relations in the anhydrous mafic-ultramafic system at high pressures favour polybaric rather than isobaric crystallization models for the origin of the websterites and pyroxenites associated with spinel-lherzolites from Freychinède in the French Pyrénées. Such models call for a thermally perturbed upper mantle which was dynamic rather than static in character. A vertical transport distance of some 60 km in the mantle was recorded by the subsolidus mineral chemistry of garnet-websterite 70–385 and its single-phase subcalcic clinopyroxenite precursor (Kornprobst, 1976; Herzberg, 1978a).  相似文献   

The solubility of olivine in basaltic liquids: an ionic model     

Claude T. Herzberg 《Geochimica et cosmochimica acta》1979,43(8):1241-1251

A simple ionic model which describes the solution of the forsterite component of olivine in silicate liquids is reported. The melting relation is represented: (Mg₂SiO₄)_ol = 2(Mg²⁺)_L + (SiO₄^4?_L and is extended to all silicate liquids by normalizing their compositions to 4 oxygens. At 1 bar, the temperature at which olivine is in equilibrium with any alkali-depleted basaltic composition can be calculated to within ±30°C. This error is increased considerably when applied to terrestrial basalts which contain several weight percent alkalis. Alkalis interfere with the equilibrium by generating strongly repulsive interionic forces which can be crudely modelled in a manner consistent with constraints imposed by regular solution theory.The model quantifies the reduced activity of SiO₄^4? monomers due to increasing SiO₂ concentrations in the melt. This is a consequence of polymerization which does not appear to operate gradually over the entire spectrum of mafic and ultramafic compositions. The coordination of alumina in melts which precipitate olivine only appears to be dominantly octahedral. Titanium acts as a polymerizing agent by interconnecting previously isolated SiO₄^4? monomers. Calcium associated with normative diopside tends to exhibit small but perceptible repulsive forces involving Mg²⁺.  相似文献   

Systematic use of trace element in igneous process     

Claude J. Allègre  Michel Treuil  Jean-François Minster  Bernard Minster  Francis Albarède 《Contributions to Mineralogy and Petrology》1977,60(1):57-75

This paper describes an extended application of the Rayleigh distillation law to trace element behavior in a fractional crystallization sequence. Using a trace element with a very low bulk partition coefficient as a reference (as suggested by Anderson and Greenland, 1969, and extended by Treuil and Varet, 1973), we can derive bulk partition coefficients for other elements and, in turn, the mineralogical composition of the cumulates. Trace elements with large D, such as Ni and Cr, further constrain the system, and we can deduce the initial composition of the magma. An example of this technique is shown for Terceira Island in the Azores.Contribution IPGNS no 229Now at Dept. of Geological Sciences, California Institute of Technology, Pasadena, California, USA  相似文献   

The form of Tsunamis generated in coastal regions     

Claude F. Noiseux 《Dynamics of Atmospheres and Oceans》1985,9(1):39-48

The deep ocean waveform that results from a seismic event localized near a coastline is investigated using a simple model for the near-shore topography and the ground motion. It is found that the variable depth underlying the ground upthrust substantially enhances the distortion of the emerging Tsunami. An appropriate initial-value problem is solved numerically, from which an empirical formula is inferred that provides an approximate assessment of the deep ocean waveshape.  相似文献   

PbSrNd isotopic data of Indian Ocean ridges: new evidence of large-scale mapping of mantle heterogeneities     

Bruno Hamelin  Bernard Dupr  Claude J. Allgre 《Earth and Planetary Science Letters》1986,76(3-4)

A PbSrNd isotope study of South West and East Indian Ridges confirms that the Indian Ocean belongs to a specific regional isotopic domain, as previously suggested by the results from islands of this ocean. The isotopic domain defined by the Indian MORB is indeed different from that of the North Atlantic and East Pacific Oceans. This demonstrates that the convective circulation of the upper mantle does not allow a rapid homogenization from one region to the other.The isotopic data of the Indian ridges can be interpreted by a contamination model, in which the depleted upper mantle (identical to that under the North Atlantic) is contaminated by two different types of contaminant, one corresponding to the source of the “central Indian Ocean” islands (Amsterdam, St. Paul, Marion, Prince Edward, Réunion, Rodriguez, Mauritius), and the other to a source similar to that of Walvis or Ninety East aseismic ridges. These two contaminants would have contributed to the ridge volcanism in different proportions over time.  相似文献   

Origin of carbonatitic magma in the light of the Pb-U-Th isotope system     

Joel R. Lancelot  Claude J. Allegre 《Earth and Planetary Science Letters》1974,22(3):233-238

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