Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
An analytical solution in the Laplace domain is derived for modeling anomalous pressure diffusion during pumping tests in aquifer displaying hierarchical fractal fracture networks. The proposed solution generalizes all of the analytical models for fractal flow published previously by combining multifractal diffusion and nested multiporosity with transient exchanges, interface skin effects, and well storage effect. Solutions are derived for fracture-delimited blocks with planar, cylindrical, and spherical shapes, as well as with any fractional dimensional shapes. Any combinations of these shapes can be defined in order to model a large range of situations. Within each permeability level, the fractal properties of the fracture network can be specified and the fractal dimension can be distinct from the shape dimension of the block.
ISSN: 0043-1397

hal-00411549
https://hal.archives-ouvertes.fr/hal-00411549
DOI : 10.1029/2008WR007125

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Despite many studies, our understanding of silica precipitation from natural waters remains limited, in particular for geothermal waters. Here we present a detailed study on the kinetics of silica polymerization as a function of fluid temperature and pH using high-temperature (250-260 °C) seawater-derived geothermal fluids as those discharged from the Bouillante geothermal site.We monitored the on-site decrease in monomeric silica concentration(initial SiO2 concentration of about 600 mg/l)with time using the molybdenum blue spectrophotometric method on samples of separated water collected from the high-pressure separator at 167 °C and cooled to 25, 50, 75, and 90 °C and for pH values ranging from 5 to 8. During all these experiments, only silica polymerization was observed, with the formation of colloidal particles in suspension in the solutions. No scaling of amorphous silica was formed. The collected data were after modeled in order to determine the useful kinetic parameters for predicting and preventing amorphous silica precipitation in the production wells during fluid exploitation in the specific context of Bouillante. Results under the investigated experimental conditions show that the kinetics of silica precipitation is affected more strongly by pH than by temperature change. The reaction in the acidic Bouillante solution begins with a transition period that significantly decreases the kinetics of silica polymerization. Modeling the experimental data indicates that the silica polymerization up to the state of equilibrium is characterized by a 2nd-order kinetic law relative to dissolved silica; this could indicate that the polymerization is controlled mainly by the formation of dimers. However, the first hour of the experiments is better characterized by a 4th-order kinetic law, suggesting more complex polymerization reactions in the initial stage with the formation of nanocolloidal particles containing 3 to 4 monomers. In both cases, the corresponding kinetics rate constant k is linearly dependent on pH for pH between 5 and 7. The activation energy Ea for the overall reaction, calculated using the Arrhenius equation under the considered pH and temperature conditions, ranges between 41±9.8 and 54±9.6 kJ/mol. To complete this work, the colloid particles formed at the end of the kinetics experiments were extracted and analyzed by SEM and TEM microscopy, X-ray Diffraction and the BET method. Results show that the size of the colloids increase and their specific surface decrease with increasing pH and are thus dependent on pH. Globally, our work provides a reliable database for understanding silica polymerization kinetics in natural geothermal brines or geologic waters characterized by a near neutral pH and moderate dissolved silica concentrations.
ISSN: 0009-2541

hal-01403092
https://hal-brgm.archives-ouvertes.fr/hal-01403092
DOI : 10.1016/j.chemgeo.2016.08.031

Résumé : Les mutualismes, interactions interspécifiques où chaque partenaire retire un bénéfice net de leur association, sont centraux dans l’origine et l’organisation de la biodiversité. Bien que globalement bénéfiques pour chacun des partenaires, ces interactions n’enlèvent rien à l’égoïsme inhérent de chaque espèce pour sa survie et sa reproduction, générant des conflits d’intérêts entre les espèces. Ainsi, comprendre les processus écologiques et évolutifs qui maintiennent le caractère mutualiste d’interactions entre plusieurs espèces est primordial dans la compréhension du maintien de la biodiversité. Néanmoins, le corpus scientifique s’est jusqu'à présent surtout concentré sur des paires d’espèces en interaction. Or, ces avancées scientifiques restent partielles car la plupart de ces interactions s’englobent dans un contexte communautaire. C’est dans ce cadre conceptuel que se place mon travail de thèse. Alors que la diversité structurelle des mutualismes de protection entre plantes et fourmis en ont fait un modèle d’étude clé dans la compréhension des mutualismes, j’ai concentré mes recherches sur l’intégration d’un troisième partenaire fongique pour comprendre ses conséquences sur les résultantes écologiques et évolutives de ces mutualismes tripartites. Je me suis tout d’abord intéressé à définir la relation qui lie de façon mutualiste le champignon aux deux autres partenaires et à établir les conflits d’intérêts émanant de ces différentes interactions pour comprendre quels facteurs permettaient de les réguler. Ainsi, la relation qui lie le champignon aux fourmis peut être qualifiée d’agriculture. Les fourmis protègent, nourrissent et disséminent le champignon et celui-ci, via ses propriétés structurales, permet l’élaboration de galeries servant de piège pour capturer des proies. Ce phénomène crée cependant un conflit d’allocation de la force ouvrière des fourmis et nuit directement aux bénéfices de la plante par une diminution de l’intensité des patrouilles sur ses feuilles, diminuant consécutivement sa protection et sa fitness. Néanmoins, le rôle du champignon dans les transferts de nutriments entre les fourmis et la plante, ainsi que certaines réponses évolutives de la plante permettent de réguler ces conflits, stabilisant les bénéfices nets de chaque partenaire dans ce mutualisme tripartite. Puis, je me suis concentré à comprendre comment certains facteurs évolutifs pouvaient moduler cette résultante écologique. La prise en compte du caractère multipartite d’un mutualisme change radicalement la vision de l’évolution des mutualismes jusqu’alors étudiée entre paires d’espèces. Alors que le corpus scientifique s’accorde à dire que la spécialisation entre espèce par coévolution renforce la stabilité et les bénéfices perçus par chaque partenaire, le contexte multipartite semble altérer ces prédictions. Au contraire la spécialisation multipartite peut être dans certains cas un moteur d’instabilité et de baisse des bénéfices. Enfin cette thèse permet de faire le lien entre deux concepts qui s’opposent : la coévolution diffuse et la coévolution par paire. Je montre ainsi que la coévolution peut intervenir sur plus de deux espèces à la fois, mais qu’elle peut quand même entrainer une spécialisation multispécifique. Finalement, au contraire des prédictions de la coévolution diffuse, cette thèse montre que plusieurs pressions de sélection contrastées émanant de différentes espèces envers un seul trait d’une troisième espèce peuvent promouvoir la spécialisation multi-spécifique.
Mutualisms, defined as interspecific interactions where each partner receives net benefices from their interactions, are central to the organization of earth biodiversity. Although globally beneficial for each partner, such interactions do not modify the inherent selfishness of species for their survival and reproduction, generating conflicts of interests between species. Thus understanding the ecological and the evolutionary processes maintaining positive outcomes in mutualisms is fundamental to understand how mutualisms shape earth biodiversity. However, scientific research on mutualisms has most of the time focused on interaction between pairs of species. Such knowledge is thus partial as mutualisms are embraced in a community context. My doctoral thesis takes place in this conceptual framework. I focused my research on the integration of a third fungal partner in protective interactions between ants and plants to evaluate its consequences on the ecological and evolutionary outcomes of such mutualisms, taken as multispecies interactions. I first focused my researches in defining the mutualistic interaction linking the fungal partner with its two other associates and in revealing any conflict of interests and their regulation that may emerge from such tripartite interactions. The interactions between the ants and the fungi can be qualified as a case of non-food fungiculture. The ants protect, provide food and disseminate the fungus, and the latter, thanks to its structural properties, allows the elaboration of galleries used that are then used as trap to capture preys. This phenomenon creates a conflict of interest in the allocation of the worker force, altering host plant benefits through a decrease of worker patrolling activity and consequently leaves protection and thus fitness. However, the role of the fungus in the nutrient transfers between ants and plants added to evolutionary responses from the plant allows regulating this conflict, stabilizing the net benefits towards the plant. Then I have concentrated my researches in understanding how evolutionary factors would modulate the ecological outcomes of such interactions. Taking into account the multispecific character of mutualisms changes radically the vision on the evolution of mutualisms when pair of species are considered. While it is widely accepted that specialization of mutualist species through coevolution reinforce the stability of the interaction and the net benefit of each partner, the multispecific context seems to deviate these predictions. Conversely, I show that specialization between three mutualistic partners can drive instability and decrease of benefits. Finally, the results of this thesis join the gap between two previously opposed concepts: diffuse coevolution and pairwise coevolution. I show that coevolution can happen between more than two species simultaneously and that it can drive mutlispecific specialization. Opposed to the diffuse coevolution, I show that contrasting selective pressures on a same trait from different partner can promote specialization of species.

http://www.theses.fr/2013AGUY0622/document

Éditeur(s) : HAL CCSD
Résumé : The mantle deformation processes that control the thinning and break-up of continental lithosphere remain poorly understood. Our knowledge is restricted to either lithospheric scale thermo-mechanical models --that use experimentally derived flow laws--, geophysical imaging and/or rare xenoliths from active continental rifts, such as the East African Rift System. The originality of this work relies on the study of the two largest outcrops of diamond facies subcontinental lithospheric mantle in the world: the Beni Bousera and Ronda peridotite massifs in N Morocco and S Spain, respectively. The structures and petrologic and metamorphic zoning preserved in these massifs --implying a polybaric and polythermal evolution-- provides a unique opportunity to investigate the thermo-mechanical evolution of thick subcontinental lithospheric mantle in extensional settings. In this thesis we studied the deformation mechanisms in both peridotites and pyroxenites to constrain the modes of exhumation of subcontinental lithospheric mantle from garnet-, to spinel-, and finally, to plagioclase lherzolite facies conditions. We combined field mapping of tectonometamorphic domains and structural mapping of ductile structures, microstructural analysis, crystal preferred orientations (CPO) measurements and conventional thermobarometric calculations and thermodynamic modeling (Perple_X) to unravel the pressure and temperature conditions of deformation. We showed that exhumation from garnet- to spinel lherzolite facies conditions was accommodated by fast shearing --in thermal disequilibrium--along a lithospheric scale transtensional shear zone. In this context, the petrological zoning and the large temperature gradient (ca. 100ºC/km) preserved in the Beni Bousera massif represent the mechanical juxtaposition of progressively deeper and hotter lithospheric levels at depths of ca. 60 km in the latest Oligocene (ca. 25 Ma). Final exhumation from spinel- to plagioclase facies lherzolite and emplacement into the crust is best recorded in the Ronda massif where it occurred by inversion and lithospheric scale folding of the highly attenuated continental lithosphere in a back-arc region, probably in relation with southward slab rollback and subsequent collision with the palaeo-Maghrebien passive margin in the early Miocene (21-23 Ma).
Les processus de déformation contrôlant l'amincissement de la lithosphère continentale sont encore mal contraints. Nos connaissances sont principalement basées sur la modélisation thermomécanique d'extension à l'échelle de la lithosphère--utilisant des lois rhéologiques derivées expérimentalement, l'imagerie géophysique et l'analyse de xénolithes provenant de rift continentaux actifs à ce jour, tels que le Rift Est-Africain. L'originalité de ce travail reside dans l'étude des deux plus grands massifs de péridotites sous-continentales ayant enregistrées des conditions primaires du facies à diamant: les massifs de Beni Bousera au nord du Maroc et de Ronda au sud de l'Espagne, respectivement. Les structures et la zonation petrologique et métamorphique --impliquant une évolution polybarique et polythermique-- préservéees dans ces massifs offrent une opportunité unique pour étudier l'évolution thermo-mécanique du manteau sous-continental dans un contexte extensif. Dans ce travail, nous avons étudié les mécanismes de déformation des péridotites et des pyroxénites afin de contraindre les modes d'exhumation du manteau lithosphérique sous-continental, depuis des conditions du facies des lherzolites à grenat, jusqu'au facies à spinelle et enfin à plagioclase. Nous avons combiné la cartographie des faciès tectono-métamorphiques et des structures ductiles de déformation, l'analyse des microstructures, la mesure d'orientations préférentielles de réseau (OPR), et la géothermobarométrie conventionelle couplée à la modélisation thermodynamique (PerpleX) afin de contraindre les conditions de pression et température de la déformation. Nous avons montré que l'exhumation précoce du facies à grenat au facies à spinelle était accomodée par une faille transtensive affectant le manteau lithosphérique. Dans ce contexte, la zonation tectono-métamorphique et le gradient thermique important (ca. 100ºC/km) préservés à Beni Bousera résultent de la juxtaposition mécanique de domaines lithosphériques initialement équilibrés à différentes pressions et températures, fossilisée à une profondeur de ca. 60 km durant l'Oligocène supérieur (ca. 25 Ma). L'exhumation finale du facies de lherzolite à spinelle au facies à plagioclase et l'emplacement final dans la croûte, mieux enregistrés dans Ronda, se sont produits par inversion et plissement de la section lithosphérique fortement amincie dans un contexte arrière-arc, probablement lors du retrait vers le sud de la lithosphère subduite et la collision de l'arc avec les paléo-marges maghrébines au Miocène inférieur (21-23 Ma).
https://tel.archives-ouvertes.fr/tel-00767700

tel-00767700
https://tel.archives-ouvertes.fr/tel-00767700
https://tel.archives-ouvertes.fr/tel-00767700/document
https://tel.archives-ouvertes.fr/tel-00767700/file/THESE_Frets.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We have analyzed the microstructures and crystal preferred orientations (CPO), and calculated the seismic properties of 53 mantle xenoliths from four localities within the North Tanzanian Divergence of the East African rift: two within the rift axis and two in the transverse volcanic belt. Olivine OH concentrations were measured in 15 xenoliths.Most samples have harzburgitic to dunitic compositions and high olivine Mg#. Microstructures and olivine CPO patterns vary strongly depending on the location. In-axis peridotites display mylonitic to porphyroclastic microstructures, which record recent deformation by dislocation creep. Highly stretched orthopyroxenes in mylonites indicate that the deformation was initiated under high stress and probably low temperature. Orthopyroxene replacement by olivine in mylonitic and porphyroclastic peridotites suggest syn-kinematic melt–rock reactions and further deformation under near-solidus conditions. Exsolutions in orthopyroxene imply significant cooling between melt-assisted deformation and xenolith extraction. Late metasomatism is evidenced by the occurrence of veins crosscutting the microstructure and interstitial clinopyroxene and phlogopite. Axial-[100] olivine CPOs predominate, suggesting activation of the high temperature, low pressure [100] {0kl} slip systems and, probably, transtensional deformation. In the volcanic belt, Lashaine peridotites display very coarse-granular textures, indicating deformation by dislocation creep under low deviatoric stress conditions followed by annealing. Axial-[010] olivine CPOs are consistent with transpressional deformation or simultaneous activation of the [100](010) and [001](010) slip systems. Intermediate microstructures and CPOs in Olmani suggests heterogeneous deformation within the volcanic belt. Olivine OH concentrations range between 2 and 12 ppm wt. H2O. No systematic variations are observed between in- and off-axis samples. Maximum P wave azimuthal anisotropy (AVp) ranges between 3.3 and 18.4%, and the maximum S wave polarization anisotropy (AVs) between 2.3 and 13.2%. Comparison between seismic properties of in-axis peridotites and SKS splitting data suggests transtensional deformation in the lithospheric mantle beneath the rift.
ISSN: 0040-1951

hal-01121552
https://hal.archives-ouvertes.fr/hal-01121552
DOI : 10.1016/j.tecto.2014.11.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Volumetrically minor microsyenites, alkali microgranite and related trachytic dykes intrude early Pliocene OIB-like alkali basaltic and basanitic flows of the Meseta del Lago Buenos Aires in Central Patagonia (47 degrees S-71 degrees 30'W), and occur together with scarce trachytic lava flows. Whole-rock K-Ar ages between 3.98 and 3.08 Ma indicate that the emplacement of these felsic rocks occurred more or less synchronously with that of the post-plateau basaltic sequence that they intrude, during a bimodal mafic-felsic magmatic episode devoid of intermediate compositions. Chemically, these rocks have A(1)-type granitoid affinities and are characterized by high silica and alkali contents (60-68 wt.% SiO2; 8.7-10.8 wt.% Na2O+K2O), major and trace elements patterns evidencing evolution by low-pressure fractional crystallization, and Sr and Nd isotopic signatures similar to those of coeval basalts ((Sr-87/Sr-86)o=0.70488-0.70571; (Nd-143/Nd-144)(o)=0.512603-0.512645). Nevertheless, some of them have the most radiogenic Sr values ever reported for a magmatic rock in the Meseta and even in the whole Neogene Patagonian Plateau Lavas province ((Sr-17/Sr-86)(o)= 0.70556-0.70571; (Nd-143/Nd-144)(o)=0.512603-0.512608). In addition, very high contents of strongly incompatible elements in the most evolved rocks, together with Sr isotopic ratios higher than those of coeval basalts, suggest the occurrence of open-system magmatic processes. Continuous fractional crystallization from a primitive basaltic source, similar to post-plateau coeval basalts, towards alkali granites combined with small rates of assimilation of host Jurassic tuffs (AFC) in a shallow magmatic reservoir, best explains the geochemical and petrographic features of the felsic rocks. Therefore, A(1)-type magmatic rocks can be generated by open-system crystallization of deep asthenospheric melts in back-are tectonic settings. In Central Patagonia, these similar to 3-4 Ma old alkaline intrusions occur aligned along a similar to N160-170 trending lineament, the Zeballos Fault Zone, stacking the morphotectonic front of one segment of the Patagonian Cordillera. Intrusion along this fault zone
ISSN: 0024-4937

hal-00412030
https://hal.archives-ouvertes.fr/hal-00412030
DOI : 10.1016/j.lithos.2007.07.002

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
The nine countries sharing the Amazon forest accounted for 89% of all malaria cases reported in the Americas in 2008. Remote sensing can help identify the environmental determinants of malaria transmission and their temporo-spatial evolution. Seventeen studies characterizing land cover or land use features, and relating them to malaria in the Amazon subregion, were identified. These were reviewed in order to improve the understanding of the land cover/use class roles in malaria transmission. The indicators affecting the transmission risk were summarized in terms of temporal components, landscape fragmentation and anthropic pressure. This review helps to define a framework for future studies aiming to characterize and monitor malaria.
ISSN: 1475-2875

inserm-00834790
http://www.hal.inserm.fr/inserm-00834790
http://www.hal.inserm.fr/inserm-00834790/document
http://www.hal.inserm.fr/inserm-00834790/file/1475-2875-12-192.pdf
DOI : 10.1186/1475-2875-12-192

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Coral reefs are among the most species-rich and threatened ecosystems on Earth, yet the extent to which human stressors determine species occurrences, compared with biogeography or environmental conditions, remains largely unknown. With ever-increasing human-mediated disturbances on these ecosystems, an important question is not only how many species can inhabit local communities, but also which biological traits determine species that can persist (or not) above particular disturbance thresholds. Here we show that human pressure and seasonal climate variability are disproportionately and negatively associated with the occurrence of large-bodied and geographically small-ranging fishes within local coral reef communities. These species are 67% less likely to occur where human impact and temperature seasonality exceed critical thresholds, such as in the marine biodiversity hotspot: the Coral Triangle. Our results identify the most sensitive species and critical thresholds of human and climatic stressors, providing opportunity for targeted conservation intervention to prevent local extinctions.
ISSN: 2041-1723

hal-01282870
https://hal-univ-perp.archives-ouvertes.fr/hal-01282870
https://hal-univ-perp.archives-ouvertes.fr/hal-01282870/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01282870/file/ncomms10491.pdf
DOI : 10.1038/ncomms10491

Éditeur(s) : HAL CCSD
Résumé : International audience
The Kazdağ Massif exposes a metamorphic dome in the Biga Peninsula of northwest Turkey. An extensional origin has been proposed for the dome, limited on both flanks by detachments and/or shear zones. The northern flank is bounded by the extensional Alakeçi Shear Zone (ASZ), whose P-T-t path is still poorly known. We therefore focus on its metamorphic conditions and related temporal history to precise its tectono-metamorphic evolution. The local tectonostratigraphy in structurally ascending order comprises: (i) the high-grade metamorphic core rocks of the Kazdaǧ Massif (gneisses and micaschists intercalated with amphibolites and marbles); (ii) the two kilometer-thick ASZ; (iii) the overlaying unmetamorphosed pre-Cenomanian accretionary Çetmi mélange; and (iv) Neogene sedimentary and volcanic cover rocks. ASZ mylonites were derived from both the core rocks and the mélange lithologies. From the north to the south the mylonitic fabrics in the ASZ depict a top-to-the N-NNE shearing, parallel to the NNE-plunging stretching lineation and NNW-dipping mylonitic foliation. This geometry implies normal sense movement i.e. north-side down-dip extensional displacement along this flank of the Kazdaǧ Massif. The northward transition from ductile to brittle-ductile regime through the ASZ shows that the deformation occurred at decreasing temperatures and degree of metamorphism. The paragenesis in equilibrium within the mylonitic gneisses and schists contains Qtz + Fs + Ms + Bt + Grt ± St ± Sill, with late retrogressive chlorite after biotite and garnet. Four samples of ASZ rocks yielded pressures between 6.9-5.7 kbar and temperatures between 706-587°C. Three samples from the mylonitic rocks supplied in situ isochron 36Ar/40Ar mica ages between 31.2-24.2 Ma, which we interpret to date the cooling of the mylonites following the P-T decrease across the ASZ. The metamorphic and structural results support the extensional character of the ASZ, and sketch transition from sillimanite core gneisses in the deeper structural levels to chlorite schists towards the top of the shear zone. These new data allow to precise the peak P-T conditions and the temporal evolution in the northern flank of the Kazdaǧ Massif, where Late Oligocene extensional exhumation was assisted by NNE-directed ductile-brittle ASZ, which had operated from amphibolite to greenschist facies. At the regional scale, this tectono-metamorphic pattern is similar to those observed on other places of the north Aegean domain.
IOP Conference Series
Austin, TE, United States

hal-00642725
https://hal-brgm.archives-ouvertes.fr/hal-00642725
DOI : 10.1088/1755-1307/2/1/012012

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Orogenic wedges locally present chaotic tectonostratigraphic units that contain exotic blocks of various size, origin, age and lithology, embedded in a sedimentary matrix. The occurrence of ophiolitic blocks, sometimes huge, in such “mélanges” raises questions on (i) the mechanisms responsible for the incorporation of oceanic basement rocks into an accretionary wedge and (ii) the mechanisms allowing exhumation and redeposition of these exotic elements in “mélanges” during wedge growth.To address these questions, we present the results of a series of analogue experiments performed to characterize the processes and parameters responsible for accretion, exhumation and tectonosedimentary reworking of oceanic basement lithospheric fragments in an accretionary wedge.The experimental setup is designed to simulate the interaction between tectonics, erosion and sedimentation. Different configurations are applied to study the impact of various parameters, such as irregular oceanic floor due to structural inheritance, or the presence of layers with contrasted rheology that can affect deformation partitioning in the wedge (frontal accretion vs basal accretion) influencing its growth. Image correlation technique allows extracting instantaneous velocity field, and tracking of passive particles. By retrieving the particle paths determined from models, the pressure-temperature path of mélange units or elementary blocks can be discussed. The experimental results are then compared with observations from ophiolite-bearing mélanges in Taiwan (Lichi and Kenting mélanges) and Raman spectroscopy of carbonaceous material (RSCM) Thermometry data on rocks from the northern Apennines (Casanova mélange). A geological scenario is proposed following basic observations. The tectonic evolution of the retroside of doubly vergent accretionary wedges is mainly controlled by backthrusting and backfolding. The retro wedge is characterized by steep slopes that are prone to gravitational instabilities. It triggers submarine landslides inducing huge mass transfers. This erosion combined with backthrusting could favour exhumation of the ophiolitic fragments formerly accreted at the base of the wedge along the rough seafloor-sediments interface. Such an exhumed material can be reworked and deposited as debris- flows in proximal basins located at the foot of the retrowedge slope forming a tectono-sedimentary mélange. These syntectonic basins are continuously deformed and involved in prograding backthrusting-induced deformation.
ISSN: 0264-3707

hal-01395127
https://hal.archives-ouvertes.fr/hal-01395127
DOI : 10.1016/j.jog.2016.05.008

Éditeur(s) : HAL CCSD Advisory Council on Underwater Archaeology
Résumé : International audience
On 18 December 1809 under the pressure of an English fleet, two Napoleonic Period store-ships, corvettes de charge,were sunk in Anse à la Barque on the west coast of Guadeloupe (FWI), south of the town of Bouillante. Underwaterarchaeological excavations, took place between 2001 and 2008. these investigationsrevealed that, in addition to those two shipwrecks, hulls of four different ships were also present on the seafloor. Twoof them have been identified as the French vessels Seine and Loire by comparing archival data to the archaeologicalrecord. The presence of so many shipwrecks in a secondary mooring of the west coast of Guadeloupe is explained by itstopographical characteristics and its proximity to Basse-Terre.
ACUA Underwater Archaeology Proceedings 2010

hal-01443280
https://hal.archives-ouvertes.fr/hal-01443280
https://hal.archives-ouvertes.fr/hal-01443280/document
https://hal.archives-ouvertes.fr/hal-01443280/file/ACUA%20Proceedings%202010%20JS%20Guibert.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We have inferred the deformation mechanisms of antigorite by high-resolution EBSD mapping of samples from Cerro del Almirez ultramafic massif (Betic Cordillera, SE Spain). Textural relations and phase diagram calculations constrain the foliation development conditions to the subduction prograde path at up to 600-630 °C and 1.6-1.9 GPa. Deformation was followed by static annealing of antigorite at ca. 680 °C. The Crystal Preferred Orientation (CPO) of antigorite is characterised by a strong alignment of (001) poles normal to the foliation plane and a weaker, but clear, parallelism between [100] axes and the macroscopic lineation defined by the elongation of magnetite aggregates. Analysis of misorientations across subgrains shows predominance of [010] rotation axis, consistent with activation of the [100](001) slip system. However, tilt subgrain boundaries subparallel to (100), probably formed by edge dislocations of this system, are subsidiary. Most subgrain boundaries are subparallel to (001) planes. They are interpreted as (001) twins wherein continuing viscoplastic deformation resulted in a slight increase of the misorientation between the twins. Modelling of the evolution of the antigorite CPO using a lower bound approach and considering different deformation regimes and sets of basal and non-basal slip systems has shown that intensities of [100] and [010] maxima reflect the relative strength of the antigorite [100](001) and [010](001) systems. Activation of other basal or non-basal slip systems does not change significantly the CPO patterns, but results in less concentrated CPO. 3D transpression models better reproduce the CPO of natural antigorite serpentinites. We propose that the widespread occurrence of strong CPO in high-pressure antigorite serpentinite is consistent with deformation by dislocation creep with dominant glide on [hk0](001), together with the activation of twinning, implying that a power law rheology would better account for the mechanical behaviour of antigorite serpentinite deep in the subduction channel and mantle wedge.
ISSN: 0012-821X

hal-00795511
https://hal.archives-ouvertes.fr/hal-00795511
DOI : 10.1016/j.epsl.2012.06.049

Résumé : La gestion du foncier martiniquais est un sujet complexe, sensible et à forte densité politique. La superficie de la Martinique est de 1 100km2, soit l’une des plus petites régions françaises, avec la plus forte densité de population, soumise à de multirisques (cyclonique, sismique, volcanique, technologique, inondation, pollution de l’air, des sols et de l’eau, tsunami…).La triangulation urbanistique composée d’une multiplicité d’acteurs, de textes et de réglementations et d’un millefeuille institutionnel (6 niveaux d’administration : commune, intercommunalité, département, région, Etat, Europe) annihile toute responsabilité et obère un développement endogène de ce micro territoire.Un juste équilibre entre développement économique, social, culturel et environnemental doit être trouvé en conciliant les objectifs économiques et sociaux liés au développement insulaire.La remarquable biodiversité de la Martinique constitue un atout touristique indéniable, menacé par de fortes pressions anthropiques foncières.Cette recherche démontre la pertinence de la réglementation applicable au foncier à la Martinique et l’influence du développement durable sur cette réglementation. La thèse propose des solutions pérennes à mettre en œuvre pour pallier les incohérences juridiques révélées par l’étude.
Management of land in Martinique is a complex, sensitive and highly political topic.The total area of the island is 1 100 km2 (square meters), e.g, one of the smallest French areas, with the highest concentration of population, submitted to multirisk desasters (cyclonic, seismic, volcanic, technological, flood, air, ground and water pollutions, tsunami…).The urban triangulation made up of a multiplicity of actors, texts and regulations, as well as a multi-level institutional cream cake (6 levels of administration: the city, the intercity, the Department, the Regional Council, the State and Europe), destroys all kind of responsibility and obstruct an endogenous development of this micro territory.A fair balance between economic, social, cultural and environmental development is necessary, by reconciling with the economic and social goals related to the insular development.The astonishing biodiversity of the island of Martinique represents an obvious tourist asset, threatened by strong land anthropic pressures.This research study highlights the relevance of the regulation applicable to the land in Martinique as well as the influence of sustainable development on this regulation. This thesis suggests perennial solutions to implement, in order to mitigate the legal inconsistencies pointed out by the study.

http://www.theses.fr/2011AGUY0503/document

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
A San Carlos olivine polycrystal has been deformed under uppermost mantle conditions, by compression at 900 °C, at a strain rate of 1.1 × 10−5 s−1, under a confining pressure of 300 MPa, using the Paterson press. Transmission electron tomography of dislocations has been performed by scanning transmission electron microscopy, by conventional transmission electron microscopy using the weak-beam dark-field technique, associated with precession or not, in order to determine the glide planes of [001] screw dislocations. This recent technique is the most suitable one since most [001] dislocations exhibit straight screw segments due to the high lattice friction on this character at low temperature. We find that [001] dislocations glide in (100), (010) and {110} as already reported, but also more unexpectedly in {120} and {130}. We show that at 900 °C, [001] {110} glide is dominant in polycrystals. We have, however, noted and characterized numerous cross-slip events in the specimen.
ISSN: 0342-1791

hal-01054330
https://hal.archives-ouvertes.fr/hal-01054330
DOI : 10.1007/s00269-014-0665-1

Éditeur(s) : HAL CCSD Elsevier
Résumé : Over-exploitation and fragmentation are serious problems for tropical forests. Most sustainable forest management practices avoid clear-cuts and apply selective logging systems focused on a few commercial species. We applied a simulation model to estimate the impact of such selective logging scenarios on the genetic diversity and demography of four tropical tree species from French Guiana. The simulations used data on genetic and demographic composition, growth, phenology and pollen and seed dispersal obtained for Dicorynia guianensis, Sextonia rubra, Symphonia globulifera and Vouacapoua americana at the experimental site in Paracou. Whereas Symphonia globulifera serves as a model for a species with low logging pressure, the other three species represent the most exploited tree species in French Guiana. In simulations with moderate logging, typical for French Guiana, with large cutting diameter (>60 cm diameter) and long cutting cycles (65 years), the two species V. americana and Sextonia rubra were not able to recover their initial stock at the end of the rotation period, with a large decrease in the number of individuals and in basal area. Under a more intensive logging system (cutting diameter >45 cm diameter, cutting cycles of 30 years) that is common practice in the Brazilian Amazon, only Symphonia globulifera showed no negative impact. Generally, the differences between the genetic parameters in the control scenarios without logging and the logging scenarios were surprisingly small. The main reasons for this were the overlapping of generations and the effective dispersal ability of gene vectors in all species, which guarantee relative homogeneity of the genetic structure in different age classes. Nevertheless, decreasing the population size by logging reduced the number of genotypes and caused higher genetic distances between the original population and the population at the end of the logging cycles. Sensitivity analysis showed that genetic changes in the logging scenarios were principally determined by the growth, densities and cutting diameter of each species, and only to a very small extent by the reproductive system including factors such as pollen and seed dispersal and flowering phenology
ISSN: 0006-3207

hal-01032050
https://hal.archives-ouvertes.fr/hal-01032050
DOI : 10.1016/j.biocon.2006.02.014

Éditeur(s) : CM. 1982/K : 8
Résumé : Since 1978, the habits of the french fishermen working with bottom trawl in the Irish Sea and in the Celtic Sea were altered (CHARUAU et M0RIZUR, 198l) under the pressure of the new mesh regulation. Two facts are pointed out: - the shifting, stabilized during 1980 and 198l, of a part of the effort of the vessels fishing for gadoids, from the area VIIa to the areaVIIf - a tendancy inside the area VIIg of a part of the effort of the Nephrops trawlers to be transferred on benthic fishes when the yield of Nephrops is low.
Cette communication décrit l'évolution des habitudes des pêcheurs français travaillant au chalut de fond en Mer d'Irlande (division CIEM VIIfa) et sur le Plateau Celtique (divisions CIEM VIIf et g) sous la pression des nouvelles réglementations de irai liage. Elle fait suite à la communication de CHARUAU et M0RIZUR(198l) sur le même sujet. Deux phénomènes simultanés se sont produits depuis 1978 : - un repli qui semble s'être stabilisé entre 1980 et 198l, d'une partie de la flottille des bateaux spécialisés dans la pêche du poisson, de la division VIIa vers la division VIIf, - un report, à l'intérieur de la division VIIg, d'une partie de l'effort des langoustiniers vers le poisson. Ce changement qui s'explique surtout par des raisons socio-économiques n'est pas analysé. Seules les tendances par rapport a 1980 sont constatées.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1982/acte-2342.pdf
http://archimer.ifremer.fr/doc/00000/2342/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Melting phase relations of model carbonated peridotite in the system CaO-MgO-Al2O3-SiO2-CO2 from 2 to 3 GPa are reported. Experimentally produced melts, which are model carbonatites, with approximately 36-40 wt % CaO, 12-17 wt % MgO, 0.2-1.5 wt % Al2O3, 1-4 wt % SiO2, and 40-42 wt % CO2 (carbon dioxide) are present at all pressures investigated. At 2.8 and 3 GPa, carbonatitic melts are seen experimentally at temperatures that are very close to the vapor-free (CO2) peridotite solidus and are found in equilibrium with forsterite, orthopyroxene, clinopyroxene, and garnet. Solidus phase relations with isobaric and pressure-temperature invariant points, defining the so-called carbonated peridotite solidus ledge, are also reported from 2.1 to 3 GPa. A divariant region exists from 2 to 2.6 GPa wherein two, compositionally different melts are present. In this region, these two melts, carbonatitic and silicate in composition, coexist with crystalline phase assemblage and free vapor. The silicate liquid has approximately 30-48 wt % SiO2 and approximately 6 to 20 wt % of dissolved CO2. The presence of carbonatitic and silicate liquids is interpreted to be due to liquid immiscibility. On the basis of melting phase relations reported here, we conclude that (a) the ledge is a feature along which model carbonatitic liquids are produced by reaction of silicates and CO2 vapor and (b) alkali-free carbonatites and silicate melts can form through melt unmixing at depths of ~60-80 km in the Earth's mantle.
ISSN: 0148-0227

hal-01053913
https://hal.archives-ouvertes.fr/hal-01053913
DOI : 10.1002/2013JB010913

Éditeur(s) : Elsevier
Résumé : A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-resolution reflection seismic data in the Danube deep-sea fan, associated with acoustic features indicating free gas. Our study provides evidence that this pattern is developed in relation with the architecture of distinct channel-levee systems of the Danube fan. Channel-levee systems hosting multiple BSRs act as relatively sealed gas-bearing systems whose top is situated above the base of the gas hydrate stability zone (BGHSZ). Inside these systems, free gas accumulates below the BGHSZ under a combined lithological, structural and stratigraphical control. The uppermost BSR marks the current equilibrium BGHSZ, for a gas composition of more than 99% methane. Model-derived depths of the BGHSZ for different gas compositions and pressure-temperature conditions show that multiple BSRs would correspond to the BGHSZ either for (1) layers of gas hydrates with high contents of heavy hydrocarbons or hydrogen sulphide, or (2) stable climatic episodes with temperatures between glacial values and the present-day conditions. As the gas hydrate compositions required by hypothesis (I) are in sharp contradiction with the general background of the gas composition in the study area, we suggest that multiple BSRs are most probably relics of former positions of the BGHSZ, corresponding to successive steps of climate warming. In this case, they can provide sea-bottom paleotemperature values for these episodes, and hence they are potential new proxies for deciphering past climate conditions.
Marine Geology (0025-3227) (Elsevier), 2006-03 , Vol. 227 , N. 3-4 , P. 163-176

Droits : 2006 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/2006/publication-1210.pdf
DOI:10.1016/j.margeo.2005.12.006
http://archimer.ifremer.fr/doc/00000/1210/

Éditeur(s) : Marine Biological Laboratory
Résumé : Hydrothermal vent tubeworms, Riftia pachyptila Jones, were maintained alive and studied on board ship using flow-through pressure aquaria. Simultaneous measurements of O2, SIGMA-CO2, SIGMA-H2S fluxes showed that the intact symbioses reach maximum rates of uptake of SIGMA-CO2 (>2 mu-mole g-1 h-1) at about 90 mu-M SIGMA-H2S. Measurements were made of hemolymph and coelomic fluid SIGMA-CO2, SIGMA-H2S, thiosulfate, pH, and hemoglobin concentrations in worms kept under various conditions of O2 and SIGMA-H2S. Normal hemolymph pH appears to be about 7.5 and is not affected by SIGMA-H2S and SIGMA-CO2 concentrations within the ranges observed. We conclude that Riftia is specialized to provide sulfide to its symbionts with minimal interaction of sulfide with the animal metabolism. The uptake of sulfide is apparently by diffusion into the hemolymph, facilitated by the sulfide-binding properties of the hemoglobins. Both SIGMA-CO2 and P(CO2) are elevated in the hemolymph above their levels in the medium, although they are reduced under autotrophic conditions. Thus inorganic carbon is apparently concentrated from the medium into the hemolymph by an unknown mechanism.
Biological Bulletin (0006-3185) (Marine Biological Laboratory), 1991-02 , Vol. 180 , N. 1 , P. 135-153

Droits : 1991 Marine Biological Laboratory
http://archimer.ifremer.fr/doc/00178/28970/27392.pdf
DOI:10.2307/1542437
http://archimer.ifremer.fr/doc/00178/28970/

Éditeur(s) : HAL CCSD Geological Society
Résumé : International audience
We constrain the slip and cooling history of the Mykonos detachment footwall using thermochronometry. A U-Pb zircon age of 13.5 +/- 0.3 Ma dates intrusion of the Mykonos monzogranite. Ar-40/ Ar-39 homblende and biotite ages from the monzogranite are 12.7 +/- 0.6 Ma and 10.9 +/- 0.6 Ma, whereas zircon and apatite fission-track ages range from 13 +/- 0.8 Ma to 10.7 +/- 0.8 Ma and 12.5 +/- 2.2 Ma to 10.5 +/- 1.8 Ma. (U-Th)/He ages range from 13.6 +/- 0.6 Ma to 9.0 +/- 0.7 Ma for zircon and 11. +/- 10.5 Ma to 8.9 +/- 0.4 Ma for apatite. The ages in part overlap within 2 sigma errors and together with the long apatite fission-track lengths (>14 mu m) support rapid cooling at rates > 100 degrees C Ma(-1). The low-temperature thermochronometric ages decrease east-northeastwards in the direction of hanging-wall transport on the Mykonos detachment. Age-distance relationships show that the Mykonos detachment slipped at an average rate of 6.0 + 9.2/-2.4 km Ma(-1) c. 30 km of offset and c. 12 km of exhumation. This result indicates that Miocene low-angle normal faulting was not important for the exhumation of the Cycladic blueschist unit. The opening of the Aegean Sea basin in the Miocene was controlled by a few large-magnitude low-angle normal faults.
ISSN: 0016-7649

hal-00412177
https://hal.archives-ouvertes.fr/hal-00412177
DOI : 10.1144/0016-76492006-145