Éditeur(s) : EDP Sciences
Résumé : Batch fecundity and relative fecundity of swordfish (Xiphias gladius) in the southwestern Indian Ocean were estimated from seven gravid swordfish females (size range 127-225 cm lower jaw-to-fork length, LJFL) with unovulated, hydrated oocytes collected onboard Reunion-based (France) longline swordfish fishing vessels between December 1999 to January 2001. To investigate the spawning pattern of swordfish, we used data collected through a combination of two at sea sampling regimes. A total of 17 007 geo-located size data of swordfish were recorded during 8 years (1993-2001) and a total of 1727 (size range 75-289 cm, LJFL) swordfish gonads (1107 females and 620 males) were sampled from May 1998 to January 2001. The estimated batch fecundity ranged from 995 000 hydrated oocytes for the smallest ripe female to 4.3 millions for the largest female sampled measuring respectively 127 to 225 cm in curved length (LJFL). The relative fecundity ranged from 25 to 72 hydrated oocytes per gram of body weight. We found that batch fecundity was positively correlated with fish length and that the older/larger females have earlier and longer spawning seasons than younger/smaller females. These findings suggested that older/larger females which are seasonally migrating in this spawning ground seem to play a major role in reproductive success of the species in producing significantly more offspring than younger females during an extended spawning season. Examination of the length-frequency date from the fishery indicated that the young fish are resident around Reunion and around the seamounts off Reunion Island. Our results highlight the important role of the older/larger females in the reproductive capacity of southwestern Indian Ocean stock. We discuss the potential implications of fishing the older/larger females for this stock in terms of reproduction and recruitment.
La fécondité par acte de ponte et la fécondité relative chez l'espadon (Xiphias gladius) dans le sud-ouest de l'océan Indien sont estimées d'après sept femelles de taille comprise entre 127 et 225 cm (de l'extrémité de la mâchoire inférieure à la fourche caudale) ; celles-ci ayant atteint la maturité sexuelle, les ovaires contenant des ovocytes hydratés. Ces femelles ont été pêchées entre décembre 1999 et janvier 2001, par des palangriers ciblant l'espadon et basés à La Réunion. La stratégie de la reproduction chez l'espadon a été étudiée en utilisant des données collectées au cours de deux campagnes d'échantillonnages en mer : soit 17 007 mensurations géo-référencées d'espadons, de 75 à 289 cm, qui ont été enregistrées durant les 8 années d'étude (1993-2001) et 1727 gonades d'espadon (1107 femelles et 620 mâles) prélevées entre mai 1998 et juin 2001.La fécondité par acte de ponte estimée varie de 995 000 ovocytes hydratés, pour la plus petite femelle (127 cm), à 4,3 millions pour la plus grande femelle (225 cm). La fécondité par acte de ponte est corrélée positivement à la taille du poisson. La fécondité relative s'étend de 25 à 72 ovocytes hydratés par gramme de poids de corps. Les femelles les plus âgées/grandes pondent plus tôt et sur une période plus grande que les plus jeunes/petites femelles. Ainsi, les femelles plus âgées/grandes qui migrent de façon saisonnière vers cette aire de ponte, contribueraient plus largement au renouvellement de l'espèce en produisant de façon significative davantage de recrues que les femelles plus jeunes et ceci pendant une saison de ponte plus étendue. Par ailleurs, les jeunes individus semblent séjourner aux abords de l'île de La Réunion et des monts sous-marins situés au large. Nos résultats soulignent l'importance du rôle des femelles âgées/grandes dans la capacité reproductrice du stock d'espadon du sud-ouest de l'océan Indien. Les implications potentielles de la pêche : des femelles âgées et de grandes tailles sont discutées pour ce stock, du point de vue de la reproduction et du recrutement.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2009 , Vol. 22 , N. 1 , P. 59-68

Droits : 2009 EDP Sciences
http://archimer.ifremer.fr/doc/2009/publication-6354.pdf
DOI:10.1051/alr/2009012
http://archimer.ifremer.fr/doc/00000/6354/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Les grands domaines naturels, rattachés aux diverses stations de villégiature, étaient dépositaires des meilleurs lacs à truites, d’immenses territoires de sauvagine, de cerf de Virginie et d’un grand nombre de rivières à saumon. Si le littoral et la montagne ont agi comme attracteurs dans le cas de la villégiature, il en a été autrement pour les clubs de chasse et de pêche, qui sont apparus au milieu du XIXe siècle et se sont multipliés à compter de 1885. En l’occurrence, la mécanique à l’œuvre semble avoir posé la « grande nature » comme visée territoriale et le « coureur des bois » comme figure emblématique du héros romantique. L’argument développé dans cet article va s’employer à montrer que le tourisme et la villégiature ont constitué au Québec des procédures de valorisation positionnelle de nature géoanthropologique. Le « clubage » des Laurentides, au sens large du terme, aura constitué en ce sens le présupposé de leur colonisation intérieure. Qu’il s’agisse du lac Saint-Jean, de la Mauricie ou des Laurentides en général, on retrouve l’efficacité du parcours structural de l’établissement humain développé en géographie structurale : l’occupation utilitaire d’un territoire disponible présuppose non pas d’abord une transformation de la nature, mais une valorisation des positions abstraites par le tourisme et la villégiature. 
The large natural areas, linked to the various resorts, were custodians of the best trout lakes, huge areas of waterfowl, deer of Virginia and a large number of salmon rivers. If the coast and the mountains acted as attractors in the case of the holiday, it was different for the club hunting and fishing, which have emerged in the mid-nineteenth century and have increased from 1885. In this case, the mechanics at work seems to have raised the "great outdoors" as a territorial and "rider of the woods" as emblematic figure of the romantic hero. In this case, the mechanics at work seems to have raised the "great outdoors" as a territorial and "rider of the woods" as emblematic figure of the romantic hero. The argument developed in this article will seek to show that tourism and vacationing were in Quebec recovery procedures such as positional geo-anthropological. The “clubage” Laurentian, in the broadest sense, will be formed in this sense the assumption of internal colonization. Whether Lake Saint-Jean, Mauricie and Laurentides in general, we find the effectiveness of the structural pathways of human settlement geography developed structural: the occupation of territory utility presupposes not available not primarily a transformation of nature but a recovery of vague ... by the tourism and the holiday resort.
Québec

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.3609
http://journals.openedition.org/etudescaribeennes/3609

Éditeur(s) : HAL CCSD
Résumé : Iran covers a large area limited in longitude by the meridians 44°E and 64°E and in latitude by the parallels 25°N and 40°N. Mapping a new gravity field over Iran is the first important data for geodetic, geophysicaland geodynamical considerations. In this thesis, the gravity measurements are used to determine the gravimetric geoid over Iran. This geoid is coupled with the GPS height and altitude (levelling) to realize an operational vertical surface at the territory of Iran. The contribution of the principal geodetic and gravimetric works realized in recent years are the establishment of: 1) the national absolute gravity network of Iran (NAGNI09), 2) the national gravity calibration line of Iran (NGCLI10) and 3) the multi-observations geodetic and gravimetric network of Iran (MPGGNI10). The absolute gravity network consists in 24 stations where the gravity measurement has been realized with the help of gravimeters FG5, with a precision better than 5μ Gal. The repetition of the observations at two stations between 2000 and 2007 makes obvious the inter-annual variations of gravity in relation of the amount of underground water changes and (or) tectonic deformation. The absolute gravity network has served the base stations for the realization of the MPGGNI10 geodetic and gravimetric network with a mesh of 55 km, at which the gravity is measured with the help of relative gravimeters CG-5 and CG-3/M, the GPS height and the altitude with a precision of 0.010 mGal, 0.03 m, and 3mm km respectively. The remove-restore technique coupled with the Helmert's condensation method is chousen to compute a new gravimetric geoid model, IRGeoid10, with a absolute and relative precision of the order of 0.26 m and 2.8 ppm respectively. The gravimetric geoid is adjusted at the GPS/levelling points to define new vertical reference surface over Iran
L'Iran couvre une grande superficie en longitude entre les méridiens 44°E et 64°E et en latitude entre les parallèles 25°N et 40°N. la cartographie de champ de pesanteur sur l'Iran est de premiére importance pour des considérations d'ordre géodésique, géophysique et geodynamique. Dans cette thèse, les mesures de pesanteur sont utilisées pour déterminer le géoïde gravimétrique sur l'Iran. Ce géoïde est couplé à la mesure de hauteur GPS et d'altitude (nivellement) pour réaliser une surface verticale opérationnelle sur le territoire Iranien. La contribution aux principaux travaux géodésiques et gravimétriques réalisés ces dernières années porte sur l'établissement: 1) du réseau national de gravimétrique absolu de l'Iran (NAGNI09), 2) de la ligne nationale d'étalonnage de gravimétrique de l'Iran (NGCLI10), 3) du réseau multi- observations géodésiques et gravimétriques de l'Iran (MPGGNI10). Le réseau gravimétrique absolu, comporte 24 stations où la mesure de la pesanteur a été réalisée à l'aide de gravimètres FG5, avec une précision meilleure que 5μ Gal. La répétition des observations sur deux sites entre 2000 et 2007 met en évidence des variations inter-annuelles de la pesanteur en relation avec l'évolution du contenu en eau du sous-sol et (ou) la déformation tectonique. Le réseau a servi de point d'appui pour la réalisation du réseau géodésique et gravimétrique MPGGNI10 de maille 55 km sur lequel a été mesuré la pesanteur à l'aide des gravimètres relatifs CG5 et CG-3/M, la hauteur de GPS et l'altitude avec une précision respectivement de 0.010 mGal, 0.03 m et 3mm km . La technique de retrait- restoration couplée à la méthode de condensation de Helmert a permis de calculer un nouveau modèle de géoïde gravimétrique, IRGeoid10, avec une précision absolue et relatif respectivement de l'ordre de 0.26m et 2.8 ppm. Ce géoïde est ajusté aux points GPS nivelés pour définir un nouveau référentiel des altitudes sur l'Iran.
https://tel.archives-ouvertes.fr/tel-00627614

tel-00627614
https://tel.archives-ouvertes.fr/tel-00627614
https://tel.archives-ouvertes.fr/tel-00627614/document
https://tel.archives-ouvertes.fr/tel-00627614/file/TheseYaghoubHatamDef.pdf

Résumé : The availability in interesting sites and the zootechnical performances of tropical fish are two impo rt ant assets in favor of the development of fish farming in the Caribbean islands. This repor presents a technical and financial analysis of red drum farming projects in floating cages in Martinique(French West Indies). This project analysis makes it possible to compare the economic feasability of a small-scale production system with that of a semi-industrial one submitted to different technical constraints. The main criteria of the project analysis are the profitability of the funded capital, the financial feasability during the buildup period, the profitability at a steady state and the cost price. Production costs are hi gher in the the small-scale enterprises than in the semi-industrial ones, thanks to better capita] productivity and better labour productivity. An analysis of sensitivity to the variations ofbiological and economical parameters is also contained in the report. The results of these studies indicate that Caribbean fish farming could be profitable, due to the rapid buildup of the facilities and to the short production cycles. Nevertheless, attention should be paid to the risk of storms and hurricanes in this part of the world. Moreover, the analysis of sensitivity highlights the great influence of seed price. [NOT CONTROLLED OCR]
Les bonnes performances zootechniques des poissons tropicaux et la disponibilité en sites propices sont deux atouts majeurs favorables au développement de l'aquaculture de poissons dans les îles des Caraïbes. Ce rapport présente l'adaptation d'un outil de simulation technico- économique à l'éleva ge de l'ombrine en cages flottantes dans le contexte martiniquais. Cet outil permet de disposer d'éléments de comparaison sur la faisabilité de deux systèmes de production, Fun de type artisanal et l'autre de type semi- industriel, soumis à des contraintes techniquesdifférentes : rentabilité du capital investi, faisabilité financière au démarrage, rentabilité en année de routine, prix de revient. Une analyse de sensibilité des résultats aux variations de paramètres biologiques et économiques est également présentée. L'analyse de ces projets fait apparaître une rentabilité satisfaisante de l'activité, liée à la rapidité de mise en route des installations et à la brièveté des cycles de production. Line grande attention doit être cependant portée sur les risques d'accidents climatiques fréquents dans cette région du globe (cyclone, mais aussi tempête...). L'analyse de sensibilité montre la grande influence du prix d'achat de l'alevin, en particulier sur les résultats de la variante artisanale, dont le coût de production de l'ombrine rendue à quai, est plus élevé que celui de la variante semi- industrielle. [OCR NON CONTRÔLE]

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1996/rapport-4019.pdf
http://archimer.ifremer.fr/doc/00000/4019/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : L’art respire et inspire le monde, si bien qu’il ne peut être appréhendé isolément de son contexte, de son époque. La création contemporaine, quant à elle, par son caractère protéiforme et foisonnant, est le reflet singulier d’une planète devenue multipolaire et où, régulièrement, est mise en crise la notion de frontière. Au même moment, cette création est capable d’inventer des formes inédites, qui, à l’instar des utopies du xviiie siècle, ont pour vocation de construire de nouveaux espaces, de nouvelles contrées, sous l’angle d’un idéal mêlant éthique et esthétique. Dès lors, il convient de souligner sa possible faculté à « artialiser » le monde. Les biennales ou triennales, produits de l’industrie culturelle et par conséquent, sujettes aux effets de la mondialisation, ont rendu particulièrement visibles ces œuvres, en façonnant des territoires, des ar-t-chipels, suffisamment attractifs pour drainer, de fait, des flots de touristes en leur direction. Ce migra-r-teur, trouvant là des zones protégées, pourrait y expérimenter une possible façon d’habiter poétiquement un monde perçu comme inhospitalier.
Art feeds on and inspires the world so that it cannot be appreciated neither on its own nor out of its context. As for contemporary art by its protean character and its multiplicity, it is the spitting image of a planet that has become polarized where the notion of frontier is constantly changing. At the same time, contemporary art is capable of inventing original forms which, following the example of the xviiith century utopias, have the purpose of building new spaces, new territories, from the point of view of an ideal where ethics and aesthetics entertwine. Hence it is advisable to highlight its possible capacity to “artialise” the world. The biennial or triennal events, fruits of the cultural industry and consequently prone to the effects of globalisation, have made those pieces of art particularly visible, by shaping territories, ar-t-chipelagoes, attractive enough to draw, henceforth, flows of tourists in their direction. That migr-art-ist finding in those places, protected areas, could experiment there a potential way of living poetically in a world seen as hostile.
El arte respira e inspira al mundo de modo que no puede ser comprendido sin ser vinculado con su contexto, su época. La creación contemporánea por su parte, por su caracter proteiforme y abundante es el singular reflejo de un planeta que se ha vuelto multipolar donde se debate con frecuencia la noción de frontera. En el mismo momento, esta creación es capaz de inventar formar inéditas, que como las utopias del siglo xviii, tienen como vocación construir nuevos espacios, nuevos parajes en términos de un ideal a la vez ético y estético. Desde entonces, cabe subrayar su posible facultad para « artialiser » al mundo. Las bienales o trienales, productos de la industria cultural y por lo tanto sujetas a los efectos de la globalización han hecho visibles estas obras, al crear territorios, unos ar-te-chipielagos, lo suficientemente atractivos como para atraer a miles de turistas. Ese migrante del arte, al encontrar allí unas zonas protegidas podría experimentar una forma posible de ocupar poéticamente un mundo visto como inhóspito.

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.11291
http://journals.openedition.org/etudescaribeennes/11291

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Several studies, both theoretical and experimental, show that sedimentary rocks have a fractal pore-grain interface. In this paper a computer simulated 3-D sedimentary rock structure generated by the Relaxed Ballistic Bidisperse Deposition Model (RBBDM), is investigated to characterize the micro structure of its pores. The pore volume and the rock-pore interface show the same fractal dimension indicating that the pore volume is a fractal. The two point density correlation is computed for the pore space and the results compare favourably with the range reported from experiments. An array of 2-D X-ray tomography micrograph sections of a real sedimentary rock, an oolitic limestone (pure calcite) from the Mondeville formation of Middle Jurassic age (Paris Basin, France), was used to generate a 3-D bitmap. The 3-D real rock sample generated in this manner, was analysed for similar studies as the simulated structure. The results were compared with those obtained from simulation. The simulation results agree qualitatively with the real rock sample. Diffusion through the connected pore space of the simulated structure was studied using a random walk algorithm and the results compared with the similar simulation study done on the 3-D oolitic limestone specimen. In both cases diffusion was found to be anomalous indicating that the sedimentary rock has a fractal geometry. The favourable comparability of results between the simulated and real rock supports the usefulness of the model of sedimentary rock generation which can be applicable to transport phenomena.
ISSN: 0956-540X

hal-00823061
https://hal.archives-ouvertes.fr/hal-00823061
DOI : 10.1093/gji/ggs084

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The Cretaceous paleogeography and the kinematic evolution of the Iberian plate are poorly constrained. Especially problematic is to reconcile Iberian paleomagnetic data with paleomagnetic data of the neighboring plates and with Euler poles derived from seafloor magnetic anomalies. The first limitation arises from the Cretaceous Normal Polarity Superchron where paleogeographic reconstruction using marine magnetic anomalies is handicapped. The second arises from the paucity of reliable paleomagnetic poles with satisfactory statistical criteria and age. In order to address these shortcomings and provide new high quality paleomagnetic poles for Iberia, we conducted a detailed rock magnetic and paleomagnetic study of two Cretaceous magmatic sills, the Paço de Ilhas (PI) and Foz da Fonte (FF) sills, from the Lusitanian Basin, Portugal, recently dated at about 88 and 94 Ma, respectively. Our results show that the magnetic mineralogy of the sills is primary, i.e., acquired during magma cooling, and essentially represented by titanomagnetite. The corresponding paleomagnetic poles match the synthetic APWP from the African plate at 80 and 100 Ma. On the basis of a rigorous selection of Iberian Cretaceous poles, we then calculated mean paleomagnetic poles for different time intervals and found that Iberian paleomagnetic data fit well the global APWP between 70 and 120 Ma, but move far away from the APWP at pre-rift times. Our approach shows that new and better constrained paleomagnetic poles can aide in solving part of the contradiction between Iberian and African APWPs.
ISSN: 0148-0227

hal-00758103
https://hal.archives-ouvertes.fr/hal-00758103
DOI : 10.1029/2011JB009067

Éditeur(s) : HAL CCSD National Institute of Environmental Health Sciences
Résumé : International audience
Background: Glycol ethers (GE) are widely used organic solvents. Despite the potential neurotoxicity of several families of organic solvents, little is known about the impact of GE on the neurodevelopment of infants and children. Objectives: We investigated the relation between urinary concentrations of GE metabolites in pregnant women and neurocognitive abilities in their 6-year-old children in the PELAGIE mother-child cohort. Methods: Five GE metabolites were measured in first morning void urine samples of 204 French pregnant women in early pregnancy (<19 weeks of gestation). Psychologists assessed the neurocognitive abilities of their 6-year-old children with the Wechsler Intelligence Scale for Children IV (WISC) and the Developmental Neuropsychological Assessment (NEPSY). We analyzed the results with linear (WISC) and Poisson regression models (NEPSY), adjusted for potential confounders, including child's stimulation at home. Results: GE metabolites were detected in 90-100% of maternal urine samples. The WISC Verbal Comprehension score was significantly lower for children with the highest tertile of urinary phenoxyacetic acid (PhAA) [beta (third vs. first tertile)=-6.53; 95% CI: -11.44, -1.62]. Similarly, the NEPSY Design Copying subtest score was lower in those with the highest tertile of urinary ethoxyacetic acid (EAA) [beta (third vs. first tertile)=-0.11; 95% CI: -0.21, 0.00]. The other GE metabolites we studied were not significantly associated with WISC or NEPSY scores. Conclusions: Prenatal urine concentrations of two GE metabolites were associated with lower WISC Verbal Comprehension Index scores and NEPSY Design Copying subscale scores, respectively, at age 6 years. PhAA is the primary metabolite of 2-phenoxyethanol (EGPhE), which is commonly found in cosmetics, and precursors of EAA are frequently used in cleaning agents. Additional research is needed to confirm our findings and further explore potential effects of prenatal GE exposures on neurocognitive performance in children.
ISSN: 0091-6765

hal-01519256
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01519256
DOI : 10.1289/EHP39
PUBMED : 27740510

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
We present a 2-D Contact Dynamics discrete element model for simulating initiation and motion of rock avalanches, integrating hillslope geometry, Mohr-Coulomb rock behavior, pore pressure before avalanche triggering, and avalanche trigger. Avalanche motion is modeled as a dense granular flow of dry frictional and cohesive particles. On the basis of granular physics and shear experiments, we review some of the theories for the unexpectedly long runout of rock avalanches. Different causes are evoked, according to the strength (strong or weak) of the slip surface relative to the bulk. "Mechanical fluidization'' and "acoustic fluidization'' theories state that agitation of rock particles reduces frictional strength, increasing runout. Conversely, granular mechanics suggests that, as "shear-strain'' rate increases, granular material becomes more agitated, more dissipative, and more resistant. Another theory states that dynamic fragmentation of clasts creates an isotropic pressure that drives longer runout. In contrast, granular mechanics suggests that fragmentation may induce fluidization and strengthening of the granular material, while particle size reduction (among others) induces weakening of the granular flow and enhances long runout. Runout is also enhanced for column-like rock masses collapsing from steep hillslopes. Long runout may also be linked to thermal weakening mechanisms at the slip surface (e.g., thermal pressurization, and shear melting), which may lower drastically the shear strength. The model is illustrated with a hypothetical example of a rain-triggered avalanche, mobilizing shallowly dipping layers. Several phases are identified, including slope failure, avalanche triggering resulting from slip weakening, and avalanche motion in which rocks are folded and sheared.
ISSN: 0148-0227

hal-00420883
https://hal.archives-ouvertes.fr/hal-00420883
DOI : 10.1029/2008JF001072

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Diffusion parameters for HTO, 36Cl−, and 125I− were determined on Upper Toarcian argillite samples from the Tournemire Underground Research Laboratory (Aveyron, France) using the through diffusion technique. The direction of diffusion was parallel to the bedding plane. The purpose of the present study was 3-fold; it was intended (i) to confirm the I− interaction with Upper Toarcian argillite and to verify the effects of initial I− concentration on this affinity, as previously observed by means of radial diffusion experiments, (ii) to highlight any discrepancy between Cl− and I− diffusivity, and (iii) to investigate the effect of an increase of the ionic strength of the solution on the anionic tracers' diffusive behaviour. The results show that the effective diffusion coefficient (De) and diffusion accessible porosity (εa) values obtained with an ionic strength (I.S.) synthetic pore water of 0.01 eq L−1 are: De = 2.35-2.50 × 10−11 m2 s−1 and εa = 12.0-15.0% for HTO, and De = 14.5-15.5 × 10−13 m2 s−1 and εa = 2.5-2.9% for 36Cl−. Because of anionic exclusion effects, anions diffuse slower and exhibit smaller diffusion accessible porosities than HTO, taken as a water tracer. The associated effective diffusion coefficient (De) and rock capacity factor (α) obtained for 125I are: De = 7.00-8.60 × 10−13 m2 s−1 and α = 4.3-7.2%. Such values make it possible to calculate low 125I distribution ratios (0.0057 < RD < 0.0192 mL g−1) which confirm the trend indicating that the 125I rock capacity factor increases with the decrease of the initial I− concentration. Additional through-diffusion experiments were carried out with a higher ionic strength synthetic pore water (I.S. = 0.11 eq L−1). No evolution of HTO diffusion parameters was observed. The anionic tracers' effective diffusion coefficient increased by a factor of two but no clear evolution of their accessible porosity was observed. Such a paradox could be related to the particularly small mean pore size of the Upper Toarcian argillite of Tournemire. The most significant finding of this study is the large discrepancy (factor of two) between the values of the effective diffusion coefficient for 125I and 36Cl. Whatever the ionic strength of the synthetic solution used, 125I exhibited De values two times lower than those of 36Cl. A detailed explanation for this difference cannot be given at present even if a hypothesis based on ion-pairing or on steric-exclusion cannot be excluded. This makes questionable the assumption usually made for quantifying 125I sorption and postulating that 36Cl and 125I would diffuse in the same porosity. In other terms, at Tournemire, 125I sorption could be more pronounced than previously indicated.
ISSN: 0883-2927

hal-00757749
https://hal.archives-ouvertes.fr/hal-00757749
DOI : 10.1016/j.apgeochem.2011.12.017

Éditeur(s) : HAL CCSD Elsevier
Résumé : We use a triangular representation of the plunges of P, B, and Taxes to compare the different ways tectonic regime is inferred from earthquake focal mechanisms in recent works. We argue that P, B, and Taxes provide a reasonable estimate of principal stress directions when faulting is close to Andersonian conditions, and that this can be estimated from the location on a triangular diagram. We analyze the geometrical relationship between the plunges of P, B, and Taxes on one hand, and the rake of slip and dip of nodal planes on the other hand. We show that the rake and dip level curves correspond to trajectories of the vertical direction along great and small circles with respect to the frame of the P, B. and Taxes. This shows that dip-slip faulting is compatible with vertical P or Taxes, but does not require it, and instead requires horizontal B axes. It also shows that strike-slip faulting does not require vertical B axes, but P and Taxes with equal plunges. This also reveals that focal mechanisms where P, B, and Taxes all have moderate plunge correspond to two very different types of nodal planes: a steeply dipping one with oblique slip and a moderately dipping one with strike-slip. Seismically active and moderately dipping strike-slip faults are to be found among these events.
ISSN: 0040-1951

hal-00486367
https://hal.archives-ouvertes.fr/hal-00486367
DOI : 10.1016/j.tecto.2009.03.006

Éditeur(s) : HAL CCSD Integrated Ocean Drilling Program
Résumé : In this report we present the results of laboratory measurements carried out to explore the electrical properties of gabbroic and troctolitic samples from Integrated Ocean Drilling Program (IODP) Hole U1309D in the Atlantis Massif, an oceanic core complex located at 30°N on the Mid-Atlantic Ridge. Oceanic core complexes are presumably localized in portions of heterogeneous oceanic crust that are relatively rich in igneous rocks and are the locus of significant hydrothermal activity. Electrical properties of igneous rocks are used to discuss the rocks' porosity structure as a function of mineralogy, alteration processes, and deformation. Electrical properties of the gabbroic suites sampled during IODP Expedition 304/305 can contribute to the understanding of these processes in the Atlantis Massif. We present the full suite of electrical data together with density and porosity measurements on the same suite of samples.
ISSN: 1930-1014

hal-00464179
https://hal.archives-ouvertes.fr/hal-00464179
DOI : 10.2204/iodp.proc.304305.204.2009

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Using first principle simulations we calculated the elasticity of chlorite. At a density ρ~ 2.60 g cm−3, the elastic constant tensor reveals significant elastic anisotropy: VP ~27%, VS1 ~56%, and VS2 ~43%. The shear anisotropy is exceptionally large for chlorite and enhances upon compression. Upon compression, the shear elastic constant component C44 and C55 decreases, whereas C66 shear component stiffens. The softening in C44 and C55 is reflected in shear modulus, G, and the shear wave velocity, VS. Our results on elastic anisotropy at conditions relevant to the mantle wedge indicates that a 10-20 km layer of hydrated peridotite with serpentine and chlorite could account for the observed shear polarization anisotropy and associated large delay times of 1-2 s observed in some subduction zone settings. In addition, chlorite could also explain the low VP/VS ratios that have been observed in recent high-resolution seismological studies.
ISSN: 0094-8276

hal-01053707
https://hal.archives-ouvertes.fr/hal-01053707
https://hal.archives-ouvertes.fr/hal-01053707/document
https://hal.archives-ouvertes.fr/hal-01053707/file/Mookherjee_et_al-2014-Geophysical_Research_Letters.pdf
DOI : 10.1002/2014GL059334

Éditeur(s) : HAL CCSD American Association of Petroleum Geologists
Résumé : International audience
We describe the structure, microstructure, and petrophysical properties of fault rocks from two normal fault zones formed in low-porosity turbiditic arkosic sandstones, in deep diagenesis conditions similar to those of deeply buried reservoirs. These fault rocks are characterized by a foliated fabric and quartz-calcite sealed veins, which formation resulted from the combination of the (1) pressure solution of quartz, (2) intense fracturing sealed by quartz and calcite cements, and (3) neoformation of synkinematic white micas derived from the alteration of feldspars and chlorite. Fluid inclusion microthermometry in quartz and calcite cements demonstrates fault activity at temperatures of 195degC to 268degC. Permeability measurements on plugs oriented parallel with the principal axes of the finite strain ellipsoid show that the Y axis (parallel with the foliation and veins) is the direction of highest permeability in the foliated sandstone (10-2 md for Y against 10-3 md for X, Z, and the protolith, measured at a confining pressure of 20 bars). Microstructural observations document the localization of the preferential fluid path between the phyllosilicate particles forming the foliation. Hence, the direction of highest permeability in these fault rocks would be parallel with the fault and subhorizontal, that is, perpendicular to the slickenlines representing the local slip direction on the fault surface. We suggest that a similar relationship between kinematic markers and fault rock permeability anisotropy may be found in other fault zone types (reverse or strike-slip) affecting feldspar-rich lithologies in deep diagenesis conditions.
ISSN: 0149-1423

hal-00903428
https://hal.archives-ouvertes.fr/hal-00903428
DOI : 10.1306/03071312127

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The origin of plate tectonics is one of the most fundamental issues in earth and planetary sciences. Laboratory experiments indicate that the viscosity of silicate rocks is so strongly temperature-dependent that the entire surface of the Earth should be one immobile rigid plate. The rheology of oceanic lithosphere is, however, still poorly understood, and there exist few constraints on the temperature dependency of viscosity on the field scale. Here we report a new kind of observational constraint based on the geoid along oceanic fracture zones. We identify a large number of conspicuous small-scale geoid anomalies, which cannot be explained by the standard evolution model of oceanic lithosphere, and estimate their source density perturbations using a new Bayesian inversion method. Our results suggest that they are caused most likely by small-scale convection involving temperature perturbations of ∼300 K±100 K∼300 K±100 K. Such thermal contrast requires the activation energy of mantle viscosity to be as low as View the MathML source100±50 kJmol−1 in case of diffusion creep, and View the MathML source225±112 kJmol−1 in case of dislocation creep, substantially reducing the thickness of the stiffest part of oceanic lithosphere. Oceanic lithosphere may thus be broken and bent much more easily than previously thought, facilitating the operation of plate tectonics.
ISSN: 0012-821X

hal-01467827
https://hal.archives-ouvertes.fr/hal-01467827
DOI : 10.1016/j.epsl.2016.05.027

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Society's needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate. Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related? The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2011-10 , Vol. 91 , N. 1 , P. 1-33

Droits : 2011 Published by Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00044/15557/15923.pdf
DOI:10.1016/j.pocean.2011.05.001
http://archimer.ifremer.fr/doc/00044/15557/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We performed torsional deformation experiments on pre-hydrated fine-grained olivine aggregates using an innovative experimental assembly to investigate water weakening in mantle rocks at high shear strains. San Carlos olivine powder was cold-pressed and then hot-pressed under hydrous conditions, producing aggregates with average grain sizes of 7 or 15 μm. Deformation experiments were performed in a high-resolution gas-medium apparatus equipped with a torsional actuator, under a confining pressure of 300 MPa, a temperature of 1200 °C, and constant shear strain rates ranging from 8 × 10−5 to 1.4 × 10−4 s−1. Maximum shear stresses range from 150 to 195 MPa. These values are 30% lower relative to those determined in previous torsion experiments on dry, fined-grained dunites under similar conditions. Textures and microstructures of the starting and deformed specimens were characterized by scanning and transmission electron microscopy. All deformed aggregates exhibit a shape-preferred orientation marking a foliation and lineation, as well as a reduction in mean grain size from 15 μm down to 3-4 μm due to dynamic recrystallization. Olivine crystallographic fabrics developed rapidly (γ < 0.1), but their strength, characterized by the J-index, is low compared to naturally deformed peridotites or to polycrystalline olivine deformed at similar finite shear strains under dry conditions. The crystallographic fabrics are consistent with deformation by a dislocation accommodated creep mechanism with activation of multiple {0 k l}[1 0 0] systems, among which the (0 1 0)[1 0 0] slip system is dominant, and minor participation of the (0 1 0)[0 0 1] slip system. Transmission electron microscopy confirmed the occurrence of dislocations with [1 0 0] and [0 0 1] Burgers vectors in most grains. Analysis of unpolarized infrared spectra indicates that hydrogen concentration in the olivine lattice is below the saturation level of 18 ppm wt H2O, which is similar to those typically observed in spinel-bearing peridotite xenoliths, and also provide evidence for water-rich inter-granular material trapped in pores and grain boundaries. Seismic properties computed from the CPO observations correspond to those most commonly observed in naturally deformed mantle peridotites with fast P-wave propagation and S-wave polarization subparallel to the shear direction. These torsion experiments on fine-grained olivine polycrystals under hydrous conditions indicate that water weakening under lithospheric conditions is linked to various defects with hydrogen in the olivine structure, as well as with water-derived species in grain boundaries or pores.
ISSN: 0031-9201

hal-00745170
https://hal.archives-ouvertes.fr/hal-00745170
DOI : 10.1016/j.pepi.2012.05.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In this paper, we determine dislocation core structures and Peierls stresses of wadsleyite, a high-pressure mineral present in the Earth mantle. We use a Peierls-Nabarro model combined with a finite-element method in which we introduce two-dimensional generalized stacking fault energies. Several potential slip planes of wadsleyite are considered. The results show that dislocations in this mineral can exhibit complex dislocation cores with linear or non-collinear dissociation and even three-dimensional dislocation cores. The calculation of the Peierls stresses gives information on the potential activity of slip systems governing the plasticity of wadsleyite. Our study confirms experimental observations that 1/2 < 1 1 1 >{1 0 1} is the easiest slip system in this structure at high-pressure and that [1 0 0](0 1 0) is the second easiest. Both these easily slip systems have dislocations that dissociate into collinear partial dislocations. In contrast [0 1 0] dislocations with very large Burgers vector (11.2 angstrom) are stabilized by complex dissociations involving four partial dislocations.
ISSN: 1359-6454

hal-00475548
https://hal.archives-ouvertes.fr/hal-00475548
DOI : 10.1016/j.actamat.2009.10.047

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
We present new archaeointensity results from three Italian kilns situated at Ascoli Satriano, Vagnari and Fontanetto Po obtained with the Thellier modified by Coe double heating method. These data complement the directional results previously published. All sites are dated on the basis of archaeological information and/or thermoluminescence dating. The results are corrected for the anisotropy of the thermoremanent magnetization and the cooling rate effects. The new data are compared with previously published archaeointensity data from Italy and nearby countries within 900 km radius from Viterbo. An initial data set including archaeointesity data mainly coming from Italy, France, Switzerland, Czech Republic, Slovakia, Hungary, Greece and Bulgaria has been compiled. After the application of strict selection criteria, the most reliable data have been used for the calculation of a preliminary Italian intensity secular variation (SV) curve for the last 3000 yr. The new curve covers the 300 BC-400 AD and 1200-1900 AD periods. It is established by means of sliding windows of 200 yr shifted by 100 yr. The lack of reliable data for the 1000-200 BC and 400-1200 AD time intervals does not permit the calculation of a continuous curve. Clearly, more high-quality archaeointensity data from Italy and Europe are still needed to draw a robust intensity SV curve for the Italian Peninsula that could be used for archaeomagnetic dating in combination with the directional data.
ISSN: 0956-540X

hal-00828691
https://hal.archives-ouvertes.fr/hal-00828691
DOI : 10.1093/gji/ggs120

Éditeur(s) : HAL CCSD Copernicus Publications
Résumé : This workshop report describes plans for scientific drilling in the Samail ophiolite in Oman in the context of past, current, and future research. Long-standing plans to study formation and evolution of the Samail crust and upper mantle, involving igneous and metamorphic processes at an oceanic spreading center, have been augmented by recent interest in ongoing, low temperature processes. These include alteration and weathering, and the associated sub-surface biosphere supported by chemical potential energy due to disequilibrium between mantle peridotite and water near the surface. This interest is motivated in part by the possibility of geological carbon capture and storage via engineered, accelerated mineral carbonation in Oman.
ISSN: 1816-8957

hal-00858243
https://hal.archives-ouvertes.fr/hal-00858243
DOI : 10.2204/iodp.sd.15.10.2013