Surface wave higher-mode phase velocity measurements using a roller-coaster-type algorithm     

Éric Beucler  Éléonore Stutzmann  Jean-Paul Montagner 《Geophysical Journal International》2003,155(1):289-307

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The Lac Cornu retrograded eclogites (Aiguilles Rouges massif,Western Alps,France): evidence of crustal origin and metasomatic alteration     

Jean-Paul Liégeois  Jean-Clair Duchesne 《Lithos》1981,14(1):35-48

Metabasic rocks interbedded in amphibolite facies supracrustal gneisses outcrop around Lac Carnu in the Aiguilles Rouges massif (Western Alps). The cores of the thickest boudinaged lenses are made up of eclogitic amphibolites grading outwards into amphibolites. The common assemblage is unzoned garnet + symplectitic clinopyroxebe + hornblende + plagioclase. In a slightly amphibolitized sample, minimum P and T conditions of equilibrium between garnet and omphacite inclusions are 780°C and 11 Kb. A polymetamorphic pre-Alpine evolution of the massif is thus demonstrated. Eclogitic amphibolites show variations in major element composition similar to the Skaergaard evolution in the Al₂O₃ ? FeO + Fe₂O₃ ? MgO triangle. Variation diagrams in which Zr is taken as differentiation index also indicate magmatic trends for Mn, Ti, P, Ni, Co, Y, V and Cr, Ca, K, Na, Sr, Rb and Si were mobile during the evolution of the rocks. The igneous trend can be described by a quantitative model of fractional crystallization in which a noritic assemblage separated in the initial stage. This provides evidence of crustal P, T conditions of differentiation for the original materoal and in situ evolution for the eclogites. A second group of amphibolites shows banded structure and transitional terms with the surrounding gneisses. A volcano-sedimentary origin is suggested though the process cannot be modelled. The rocks may result from complex interactions of magnetic, metasomatic and sedimentary processes. It is concluded that Lac Cornu metabasites were originally continental tholeiites, though several geochemical criteria tend to indicate an oceanic origin. This casts some doubt on the validity of these criteria, when applied to metamorphic rocks.  相似文献   

Les rhyolites hyperalcalines (pantellérites) du lac Tchad. Composition et signification tectonomagmatiqueThe peralkaline rhyolites (pantellerites) of the Lake Chad. Composition and tectonomagmatic significance     

Jean-Paul Vicat  André Pouclet  Yves Bellion  Jean-Claude Doumnang 《Comptes Rendus Geoscience》2002,334(12):885-891

Remnants of rhyolite lava-dome and of alkaline microgranite extrusions emerge, as inselbergs, in the alluvial plain, south of Lake Chad. The peralkaline, arfvedsonite- and acmite-bearing rhyolites are determined as pantellerites. They can be related to a tectonomagmatic stage, dated of the Late Cretaceous, of the western central Africa rift system. They may constitute the NNE extension of a N50° to 30° elongated succession of small alkaline complexes, from the Gulf of Guinea to the North-Cameroon, which initiated the magmatic activity of the Cameroon Line. To cite this article: J.-P. Vicat et al., C. R. Geoscience 334 (2002) 885–891.  相似文献   

Signification du signal isotopique (δ18O, δ13C) des carbonates néritiques : composante diagénétique et composante originelle (Jurassique supérieur de l'Est du bassin de Paris,France)     

Benoı̂t Vincent  Laurent Emmanuel  Jean-Paul Loreau 《Comptes Rendus Geoscience》2004,336(1):29-39

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Effets de la vitesse d'écoulement sur le transport et la cinétique de dépôt de particules en suspension en milieu poreux saturé     

Ahmed Benamar  HuaQing Wang  Nasre-dine Ahfir  Abdellah Alem  Nicolas Masséi  Jean-Paul Dupont 《Comptes Rendus Geoscience》2005,337(5):497-504

We study in this paper the transport and deposition of suspended particles in saturated porous media. Some chromatographic short-pulse tests were performed in a laboratory column with a tracer and two types of suspended particles. A mathematical model was used to determine the hydrodispersive parameters and deposition rates from the breakthrough curves. The results show that the fitted parameters obtained vary with the flow rate and the characteristics of the suspended particles. We also observe, at high flow rates, that particles have a migration velocity higher than that of the conservative tracer. To cite this article: A. Benamar et al., C. R. Geoscience 337 (2005).  相似文献   

Ash layers in deep-sea sediments as tracers of arc volcanic activity: Japan and Central America as case studies     

Herve  Cambray Jean-Paul  Cadet André  Pouclet 《Island Arc》1993,2(2):72-86

Abstract Arc volcanic activity on opposite sides of the Pacific Ocean (Japan and Central America) has been investigated by examining the number of volcanic ash layers recorded in Neogene and Quaternary deep-sea sediments. The data suggest that ash layers counted in deep-sea sediments may provide a reliable record of arc volcanism. The study is based on a quantitative analysis of arc volcanic activity using cores collected on DSDP (Deep-Sea Drilling Project) and ODP (Ocean Drilling Program) legs. Five distinct parameters which might affect ash distribution in marine sediments were reviewed: nature of the eruption, wind influence, settling conditions, diagenesis, and plate motion. Of these five, past atmospheric circulation was the most significant. The main constraint on the analysis is that temporal scattering of ash is not directly related to wind pattern variations. Results of this analysis are correlated with dating of terrestrial volcanic sequences. Although marine tephra records for individual regions reveal minor differences in the episodes of volcanic activity, a general correlation exists between activity of arc volcanism in Japan and in Central America. Two important pulses of arc volcanism occurred during Middle Miocene times (18–13 Ma) and Plio-Quaternary times (5–0 Ma). These episodes of intense volcanism are separated by a well recorded quiescent period during Late Miocene times. These correlating episodes of the volcanic record indicate a direct link between arc volcanism and the global tectonic evolution of the Pacific ocean margins.  相似文献   

Variation in chlorophylla concentrations and Margalef’s index of pigment diversity in two solar salt ponds,Aveiro, Portugal     

N. Vieira  F. Amat 《International Journal of Salt Lake Research》1993,2(1):41-45

Variations of chlorophylla and Margalef's pigment diversity index were studied in two solar salt ponds at Aveiro (Esmolas and Tanoeiras). Portugal. In the Esmolas ponds, mean chlorophyll a values varied between 2.49 and 13.33 mg m⁻³ in the non-growing season, and between 5.43 and 40.55 mg m⁻³ in the growing season. In the Tanoeiras ponds, mean chlorophylla values were between 8.12 and 14.85 mg m⁻³ in the non-growing season, and 8.65 and 21.19 mg m⁻³ in the growing season. Fluctuations of Margalef's pigment diversity index were more irregular.  相似文献   

Radiative surface temperature and convective flux calculation over crop canopies     

Jean-Paul Lhomme  Nader Katerji  Alain Perrier  Jean-Michel Bertolini 《Boundary-Layer Meteorology》1988,43(4):383-392

The analysis presented in this paper aims at a better understanding of the potential role of radiative temperature, as measured by a radiometer over crops, in sensible heat flux calculation. Defining radiative temperature as the mean temperature of the surfaces viewed by the radiometer (leaves and soil surface) and assuming that an Ohm's law type formula can be used to express sensible heat flux as a function of the difference between air temperature and radiative temperature, the aerodynamic resistance which divides this temperature difference has been analytically defined. The parameters which appear in the resistance expression depend essentially on wind velocity and canopy structure but also on the inclination angle of the radiometer. Finally an experimental verification is presented with data obtained over a potato crop.  相似文献   

Preface to the Proceedings of ENS''93 Conference     

Michael Elliott  Jean-Paul Ducrotoy 《Marine pollution bulletin》1994,29(6-12):253-254

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The 3100 BP eruption of the Soufrière of Guadeloupe     

Pascale Besson  Jean-Paul Poirier 《Bulletin of Volcanology》1994,56(3):184-192

Fragments of unaltered andesite found at all levels in the deposits of the catastrophic flank-failure, directed-blast eruption of the Soufrière of Guadeloupe in 3100 bp are thought to be remnants of the cryptodome. They were observed in analytical transmission electron microscopy for clues to the evolution of the intrusion prior to the eruption. Several features that could potentially be used as temperature markers were identified, among which the angle between microexsolutions of magnetite in augite phenocrysts was used to find an upper boundary of the temperature of the intrusion before the eruption: 600–700°C. Calculation of the time a dyke or sphere-shaped intrusion may have taken to cool from the emplacement temperature down to the temperature of exsolution of the magnetite leads to an estimate of the time between emplacement of the intrusion and the eruption, which could not have been less than a few tens of years. It therefore seems probable that the emplacement of the magmatic intrusion was not the immediate cause of the flank destabilization and catastrophic eruption of the Soufrière in 3100 bp.  相似文献