Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
Natural disturbances are the dominant form of forest regeneration and dynamics in unmanaged tropical forests. Monitoring the size distribution of treefall gaps is important to better understand and predict the carbon budget in response to land use and other global changes. In this study, we model the size frequency distribution of natural canopy gaps with a discrete power law distribution. We use a Bayesian framework to introduce and test, using Monte Carlo Markov chain and Kuo–Mallick algorithms, the effect of local physical environment on gap size distribution. We apply our methodological framework to an original light detecting and ranging dataset in which natural forest gaps were delineated over 30 000 ha of unmanaged forest. We highlight strong links between gap size distribution and environment, primarily hydrological conditions and topography, with large gaps being more frequent on floodplains and in wind-exposed areas. In the future, we plan to apply our methodological framework on a larger scale using satellite data. Additionally , although gap size distribution variation is clearly under environmental control, variation in gap size distribution in time should be tested against climate variability.
ISSN: 1726-4170

hal-01590729
https://hal-univ-guyane.archives-ouvertes.fr/hal-01590729
https://hal-univ-guyane.archives-ouvertes.fr/hal-01590729/document
https://hal-univ-guyane.archives-ouvertes.fr/hal-01590729/file/bg-14-353-2017.pdf
DOI : 10.5194/bg-14-353-2017

Résumé : Reconnus dans toute la zone intertropicale comme outils d'aménagement incontournables des petites pêches côtières, les DCP (Dispositifs de Concentration de Poissons) ont été implantés autour de La Réunion à partir de 1988 et gérés collectivement par le Comité Régional des Pêches. Ces DCP côtiers, ancrés à quelques milles des ports de pêche ont permis un redéploiement d'une grande partie de l'effort de pêche vers les espèces pélagiques du large, diminuant ainsi la pression exercée sur les espèces récifales côtières. La présente étude a pour objectifs de mettre à jour les connaissances techniques et économiques sur le "système DCP", autour des pêcheurs, de la pêche sur DCP et des DCP eux-mêmes. Une enquête des usages et des perceptions des pêcheurs vis-à-vis des DCP ancrés a été réalisée auprès de plus de la moitié des patrons de la petite pêche réunionnaise. Les principaux types d’usages et de stratégies mettent en évidence la forte polyvalence des pêcheurs, qui pratiquent quasiment tous la pêche sur DCP dont une majorité (51%) montrant un degré de dépendance élevé vis-à-vis de l’outil. Les DCP sont plébiscité par l’ensemble des pêcheurs, au titre de l’aménagement durable de la zone côtière, pour éviter report de la pression de pêche sur les ressources démersales. La pêche plaisance sur DCP est pointée du doigt, comme un facteur important de perturbation du système (conflits sur DCP, non-respect de la règlementation, etc…). Des sorties en mer ont rapporté les activités de pêche de façon détaillée : description des opérations de pêche, variabilité spatiale de la productivité de chaque DCP, apports des DCP ancrés dans la compétitivité économique des entreprises. Mais avec 25 marées seulement et le parc de DCP à moitié en place, seule la méthode et de premiers résultats ont pu être obtenus Ces sorties en mer doivent être poursuivies. L'exploitation des données 2002-2012 du Comité Régional des Pêches de La Réunion sur sa gestion du parc de DCP permet une description précise des évènements et des coûts concernant les DCP : poses, entretiens, pertes, etc. Il en ressort que la durée de vie moyenne des DCP ne dépasse guère 14 mois, avec une grande disparité géographique (durées de vie plus faibles au nord et à l’est), et un délai de repose conséquent de 5 mois1/2 en moyenne. L'analyse des coûts de maintenance et de main d'œuvre met en lumière la nécessité de stabiliser les financements sur un budget de 70 à 80 k€ /an pour permettre un taux optimum de remplissage du parc (> 80 %). Des perspectives d’amélioration technologique des dispositifs sont également présentées, tant sur la ligne de mouillage que sur le choix des flotteurs. Le modèle intermédiaire PLK à chapelet renforcé testé à la Réunion en mai 2012 sur 5 DCP semble être un compromis intéressant pour la Réunion à court et moyen terme pour les DCP ancrés les plus au large. Outre la poursuite des sorties en mer pour le suivi halieutique détaillé il convient maintenant d'engager une réflexion globale sur la gouvernance du "système DCP" à La Réunion (financement, gestion). Les enjeux sont essentiels pour le secteur de la petite pêche artisanale réunionnaise.

Droits : 2012 Ifremer, CRPM La réunion, PARETO Ecoconsult
http://archimer.ifremer.fr/doc/00109/22027/19679.pdf
http://archimer.ifremer.fr/doc/00109/22027/19680.pdf
http://archimer.ifremer.fr/doc/00109/22027/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We report chlorine (Cl) and fluorine (F) abundances in minerals, interstitial glasses, and melt inclusions in 12 andesite-hosted, spinel harzburgite xenoliths and crosscutting pyroxenite veins exhumed from the sub-arc lithospheric mantle beneath Avacha volcano in the Kamchatka Arc (NE Russia). The data are used to calculate equilibrium mineral-melt partition coefficients (Dmineral/meltDmineral/melt) for Cl and F relevant to subduction-zone processes and unravel the history of volatile depletion and enrichment mechanisms in an arc setting.Chlorine is ∼100 times more incompatible in pyroxenes (View the MathML sourceDClmineral/melt = 0.005–0.008 [±0.002–0.003]) than F (View the MathML sourceDFmineral/melt = 0.50–0.57 [±0.21–0.24]), which indicates that partial melting of mantle sources leads to strong depletions in Cl relative to F in the residues. The data set in this study suggests a strong control of melt composition on View the MathML sourceDCl,Fpyroxene/melt, in particular H2O contents and Al/(Al + Si), which is in line with recent experiments. Fluorine is compatible in Ca-amphibole in the ‘wet’ sub-arc mantle (View the MathML sourceDFamphibole/melt = 3.5–3.7 [±1.5]) but not Cl (View the MathML sourceDClamphibole/melt = 0.03–0.05 [±0.01–0.03]), indicating that amphibole may fractionate F from Cl in the mantle wedge. The inter-mineral partition coefficients for Cl and F in this study are consistent amongst different harzburgite samples, whether they contain glass or not. In particular, disseminated amphibole hosts much of the Cl and F bulk rock budgets of spinel harzburgites (View the MathML sourceDClamphibole/pyroxene up to 14 and View the MathML sourceDFamphibole/pyroxene up to 40). Chlorine and fluorine are variably enriched (up to 1500 ppm Cl and 750 ppm F) in the parental arc picrite and boninite melts of primitive pyroxenite veins (and related melt inclusions) crosscutting spinel harzburgites.Based on the data in this study, the main inferences on the behaviour of Cl and F during melting and metasomatic processes in the sub-arc mantle are as follow:(i) Melting models show that most depleted mantle protoliths of intra-oceanic arc sources can have extremely low Cl/F (0.002–0.007) before being overprinted by subduction-derived components.(ii) Chlorine has a higher percolation distance in the mantle than F. Even for small fluid or melt volumes, Cl and F signatures of partial melting are overprinted by those of pervasive percolation, which increases Cl/F in percolating agents and bulk peridotites during chromatographic interaction and/or amphibole-forming metasomatic reactions. These processes ultimately control the bulk Cl and F compositions of the residual mantle lithosphere beneath arcs, and likely in other tectonic settings.(iii) Fluxed melting models suggest that Cl enrichment in arc picrite and boninite melts in this study, and in many arc melt inclusions reported in the literature, could be related to the infiltration of high Cl/F fluids derived from subducted serpentinite or altered crust in mantle wedge sources. However, these high Cl/F signatures should be re-evaluated with new models in light of the possible overprint of pervasive percolation effects in the mantle. The breakdown of amphibole (and/or mica) in the deep metasomatised mantle at higher pressure and temperature conditions than in the slab may explain, at least in part, the positive correlations between F abundances and Cl/F in primitive arc melt inclusions and slab depth.
ISSN: 0016-7037

hal-01553610
https://hal.archives-ouvertes.fr/hal-01553610
DOI : 10.1016/j.gca.2016.10.035

Éditeur(s) : HAL CCSD
Résumé : International audience
The most active deep convection area in the western Mediterranean Sea is located in the Gulf of Lions. Recent studies in this area provides some insights on the complexity of the physical dynamics of convective regions, but very little is known about their impacts on the biogeochemical properties. The CASCADE (CAscading, Surge, Convection, Advection and Downwelling Events) cruise, planed in winter 2011, give us the opportunity to compare vertical profiles of properties sampled either during stratified conditions or after/during a convection event. In the present study, we focus on the distributions of the carbonate system properties (mainly total alkalinity, AT; and total dissolved inorganic carbon, CT) because, in the context of the climate change, deep convection areas are suspected to significantly increase the sequestration of anthropogenic CO2 (CANT). Given its limited size, the impact of the Mediterranean Sea on the global carbon budget is probably minor but this marginal sea can be used as a laboratory to better understand carbon sequestration and its transfer to the basin interior by deep convection processes. Distributions of AT and CT, both measured from bottle samples, and that of CANT (estimated with the TrOCA approach) are first analyzed in the light of other key properties (salinity, temperature, and dissolved oxygen). An objective interpolation procedure is then applied to estimate CT and AT from CTD measured properties. With this procedure, the vertical resolution goes from a maximum of 32 samples per station to one property estimate every meter (more detailed distributions are obtained). Results provide arguments to conclude that CANT is rapidly transferred to the deepest layer due to deep convection events. During deep convection events, the increase of CANT in the water column is positively correlated to that of potential density and oxygen content. The challenge of quantifying the amount of sequestered carbon is however not resolved due to the complexity and the highly dynamical nature of the convective regions. Deep convection in the Gulf of Lions, in parallel with cascading along the continental slope, could thus potentially explain the very high levels of both CANT and acidification estimated in the deep layers of the western Mediterranean Sea.
Deep Sea Research Part I: Oceanographic Research Papers

hal-01336725
https://hal-univ-perp.archives-ouvertes.fr/hal-01336725
DOI : 10.1016/j.dsr.2016.04.003

Résumé : L'IFREMER gère un budget de 993 millions de francs dont l'origine provient en majeure partie de la subvention que lui verse lÉtat et à laquelle s'ajoutent des ressources propres que son statut d'EPIC (établissement public à caractère industriel et commercial) lui permet de développer ; leur évolution constitue chaque année une priorité de l'établissement. Un peu plus de 1 200 ingénieurs, chercheurs, techniciens et administratifs participent aux multiples missions de l'IFREMER. Ces personnels travaillent au siège social à Issy-les-Moulineaux et dans 5 centres (Boulogne-sur- Mer, Brest, Nantes, Toulon, Tahiti), 5 délégations Outre-Mer, 15 stations et plusieurs points isolés répartis le long du littoral français. [OCR NON CONTRÔLE]

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1992/rapport-4812.PDF
http://archimer.ifremer.fr/doc/00000/4812/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We developed a new granular material (MatIV) to study experimentally landscape evolution in active mountain belt piedmonts. Its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation, erosion-transport and sedimentation natural processes. MatIV is a water-saturated composite material made up with 4 granular components (silica powder, glass microbeads, plastic powder and graphite) whose physical, mechanical and erosion-related properties were measured with different laboratory tests. Mechanical measurements were made on a modified Hubbert-type direct shear apparatus. Erosion-related properties were determined using an experimental set-up that allows quantifying the erosion/sedimentation budget from tilted relaxation topographies. For MatIV, we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1D as a function of slope.;Our results indicate that MatIV satisfies most of the defined criteria. It deforms brittlely according to the linear Mohr-Coulomb failure criterion and localizes deformation along discrete faults. Its erosion pattern is characterized by realistic hillslope and channelized processes (slope diffusion, mass wasting, channel incision). During transport, eroded particles are sorted depending on their density and shape, which results in stratified alluvial deposits displaying lateral fades variations. To evaluate the degree of similitude between model and nature, we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes. Results indicate that MatIV succeeded in producing detailed morphological and sedi-mentological features (drainage basin, channel network, terrace, syntectonic alluvial fan). Geometric, kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature. Although scaling is incomplete, it yields particularly informative orders of magnitude. With all these characteristics, MatIV appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics, erosion and sedimentation processes.
ISSN: 0040-1951

hal-00669904
https://hal.archives-ouvertes.fr/hal-00669904
DOI : 10.1016/j.tecto.2011.09.029

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Probabilistic seismic hazard analyses (PSHA) are commonly based on frequency magnitude statistics from 50-100 yearlong earthquake catalogs, assuming that these statistics are representative of the longer-term frequency of large earthquakes. We test an alternative PSHA approach in continental western Canada, including adjacent areas of northwestern U. S. A., using regional strain rates derived from 179 Global Positioning System (GPS) horizontal velocities. GPS strain rates are converted to earthquake statistics, seismic moment rates, and ground shaking probabilities in seismic source zones using a logic-tree method for uncertainty propagation. Median GPS-based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones (Puget Sound and mid-Vancouver Island). In most other zones, median GPS-based moment rates are 6-150 times larger than those derived from earthquake catalogs (shaking estimates 2-5 times larger), although the GPS-based and catalog estimates commonly agree within their 67% uncertainties. This discrepancy may represent an under-sampling of long-term moment rates and shaking by earthquake catalogs in some zones; however a systematic under-sampling is unlikely over our entire study area. Although not demonstrated with a high confidence level, long-term regional aseismic deformation may account for a significant part of the GPS/catalog discrepancy and, in some areas, represent as much as 90% of the total deformation budget. In order to integrate GPS strain rates in PSHA models, seismic versus aseismic partitioning of long-term deformation needs to be quantified and understood in terms of the underlying mechanical processes.
ISSN: 0148-0227

hal-00689004
https://hal.archives-ouvertes.fr/hal-00689004
DOI : 10.1029/2011JB008213

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study investigates if acclimatization to residual pesticide contamination in agricultural soils is reflected in detoxification, antioxidant enzyme activities and energy budget of earthworms. Five fields within a joint agricultural area exhibited different chemical and farming histories from conventional cultivation to organic pasture. Soil multiresidual pesticide analysis revealed up to 9 molecules including atrazine up to 2.4 ng g(-1) dry soil. Exposure history of endogeic Aporrectodea caliginosa and Allolobophora chlorotica modified their responses to pesticides. In the field, activities of soluble glutathione-S-transferases (sGST) and catalase increased with soil pesticide contamination in A. caliginosa. Pesticide stress was reflected in depletion of energy reserves in A. chlorotica. Acute exposure of pre-adapted and naïve A. caliginosa to pesticides (fungicide Opus(®), 0.1 μg active ingredient epoxiconazole g(-1) dry soil, RoundUp Flash(®), 2.5 μg active ingredient glyphosate g(-1) dry soil, and their mixture), revealed that environmental pre-exposure accelerated activation of the detoxification enzyme sGST towards epoxiconazole.
ISSN: 0269-7491

hal-01063923
https://hal.archives-ouvertes.fr/hal-01063923
DOI : 10.1016/j.envpol.2014.05.001
PUBMED : 24874794

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Kimberlites of the Udachnaya-East pipe (Siberia) include a uniquely dry and serpentine-free rock type with anomalously high contents of chlorine (Cl ≤ 6.1 wt%), alkalies (Na2O + K2O ≤ 10 wt%) and sulfur (S ≤ 0.50 wt%), referred to as a “salty” kimberlite. The straightforward interpretation is that the Na-, K-, Cl- and S-rich components originate directly from a carbonate-chloride kimberlitic magma that is anhydrous and alkali-rich. However, because brines and evaporites are present on the Siberian craton, previous studies proposed that the kimberlitic magma was contaminated by the assimilation of salt-rich crustal rocks. To clarify the origin of high Cl, alkalies and S in this unusual kimberlite, here we determine its sulfur speciation and isotopic composition and compare it to that of non-salty kimberlites and kimberlitic breccia from the same pipe, as well as potential contamination sources (hydrothermal sulfides and sulfates, country-rock sediment and brine collected in the area). The average δ34S of sulfides is − 1.4 ± 2.2‰ in the salty kimberlite, 2.1 ± 2.7‰ in the non-salty kimberlites and 14.2 ± 5.8‰ in the breccia. The average δ34S of sulfates in the salty kimberlites is 11.1 ± 1.8‰ and 27.3 ± 1.6‰ in the breccia. In contrast, the δ34S of potential contaminants range from 20 to 42‰ for hydrothermal sulfides, from 16 to 34‰ for hydrothermal sulfates, 34‰ for a country-rock sediment (Chukuck suite) and the regional brine aquifer. Our isotope analyses show that (1) in the salty kimberlites, neither sulfates nor sulfides can be simply explained by brine infiltration, hydrothermal alteration or the assimilation of known salt-rich country rocks and instead, we propose that they are late magmatic phases; (2) in the non-salty kimberlite and breccia, brine infiltration lead to sulfate reduction and the formation of secondary sulfides – this explains the removal of salts, alkali-carbonates and sulfates, as well as the minor olivine serpentinization; (3) hydrothermal sulfur was added to the kimberlitic breccia, but not to the massive kimberlites. In situ measurements of sulfides confirm this scenario, clearly showing the addition of two sulfide populations in the breccia (pyrite-pyrrhotites with average δ34S of 7.9 ± 3.4‰ and chalcopyrites with average δ34S of 38.0 ± 0.4‰) whereas the salty and non-salty kimberlites preserve a unique population of djerfisherites (Cl- and K-rich sulfides) with δ34S values within the mantle range. This study provides the first direct evidence of alkaline igneous rocks in which magmatic sulfate is more abundant than sulfide. Although sulfates have been rarely reported in mantle materials, sulfate-rich melts may be more common in the mantle than previously thought and could balance the sulfur isotope budget of Earth's mantle.
ISSN: 0009-2541

hal-01571982
https://hal.archives-ouvertes.fr/hal-01571982
DOI : 10.1016/j.chemgeo.2016.10.037

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Chromitite pods in the Mayarí-Cristal ophiolitic massif (eastern Cuba) were formed in the Late Cretaceous when island arc tholeiites and MORB-like back-arc basin basalts reacted with residual mantle peridotites and generated chromite-rich bodies enclosed in dunite envelopes. Platinum-group minerals (PGM) in the podiform chromitites exhibit important Os-isotope heterogeneities at the kilometric, hand sample and thin section scales. 187Os/188Os calculated at the time of chromitite crystallization (~90 Ma) ranges between 0.1185 and 0.1295 (γOs = −7.1 to +1.6, relative to enstatite chondrite), and all but one PGM have subchondritic 187Os/188Os. Grains in a single hand sample have initial 187Os/188Os that spans from 0.1185 to 0.1274, and in one thin section it varies between 0.1185 and 0.1232 in two PGM included in chromite which are only several millimeters apart. As the Os budget of a single micrometric grain derives from a mantle region that was at least several m3 in size, the variable Os isotopic composition of PGM in the Mayarí-Cristal chromitites probably reflects the heterogeneity of their mantle sources on the 10-100 m scale. Our results show that this heterogeneity was not erased by pooling and mingling of individual melt batches during chromitite crystallization but was transferred to the ore deposits on mineral scale. The distribution of the Os model ages calculated for PGM shows four main peaks, at ~100, 500, 750 and 1,000 Ma. These variable Os model ages reflect the presence of different depleted domains in the oceanic (Pacific-related) upper mantle of the Greater Antilles paleo-subduction zone. The concordance between the age of crystallization of the Mayarí-Cristal chromitites and the most recent peak of the Os model age distribution in PGM supports that Os in several grains was derived from fertile domains of the upper mantle, whose bulk Os isotopic composition is best approximated by that of enstatite chondrites; on the other hand, most PGM are crystallized by melts that tapped highly refractory mantle sources.
ISSN: 0010-7999

hal-00822742
https://hal.archives-ouvertes.fr/hal-00822742
DOI : 10.1007/s00410-010-0575-2

Éditeur(s) : HAL CCSD
Résumé : National audience
Mass balances are often used to calculate sediment fluxes in sedimentary basins and denudationrates in adjacent topographies on intermediate to long timescales (from a few tens ofthousand to a million years). In this study, we focus on simple Quaternary catchment–alluvial fansystems in the northern Tian Shan Range and its foreland basin to discuss some ideas about sedimentproduction, storage, release, and bypass in relatively short (100 km long) sediment routing systems.Based on a geometrical reconstruction of the fans, we estimated the volumes of sediments exportedout of the range and deposited in its alluvial piedmont during the Middle- Late Pleistocene andthe Holocene. This work shows that the two areas clearly present evidence of a temporary butsignificant storage of sediments during the Pleistocene. These sediments were then excavated anddelivered farther into the foreland basin during the Holocene. The difference between the volumesof materials released from the range and piedmont areas and the volume stored in thecontemporaneous fans downstream indicates that the latter did not trap the whole sediment loadtransported by the rivers. The alluvial fans were bypassed by 27 to 78% of this load toward thedownstream alluvial plain. It implies a major volumetric partitioning of the deposits between thefans and the alluvial plain, with a sedimentation rate about twenty times higher in the fans thanin the plain. However, this volumetric partitioning might only occur during periods with a veryspecific hydrological regime such as the Holocene deglaciation. Eventually, the peculiar sedimentstorage and release pattern within the range and piedmont areas during the Pleistocene and Holocenecomplicates the calculation of mean paleodenudation rates using either sediment budgets or in situproduced cosmogenic nuclides.
Association des Sédimentologistes Français. 15ème congrès français de sédimentologie
Chambéry, France

hal-01252100
https://hal.archives-ouvertes.fr/hal-01252100

Éditeur(s) : [S.n.] (Basse-Terre)
Résumé : Variante(s) de titre : Guadeloupe et dépendances. Service local. Projet de budget des recettes et de dépenses de l'exercice
Périodicité : Annuel
Etat de collection : 1858-
Bibliothèque nationale de France, département Droit, économie, politique, FOL-LK19-170

http://gallica.bnf.fr/ark:/12148/cb34437068j/date

Éditeur(s) : HAL CCSD
Résumé : International audience
Mass balances are often used to calculate sediment fluxes in sedimentary basins and denudationrates in adjacent topographies on intermediate to long timescales (from a few tens ofthousand to a million years). In this study, we focus on simple Quaternary catchment–alluvialfan systems in the northern Tian Shan Range and its foreland basin to discuss some ideasabout sediment production, storage, release, and bypass in relatively short (100 km long) sedimentrouting systems. Based on a geometrical reconstruction of the fans, we estimated thevolumes of sediments exported out of the range and deposited in its alluvial piedmont duringthe Middle-Late Pleistocene and the Holocene. This work shows that the two areas clearlypresent evidence of a temporary but significant storage of sediments during the Pleistocene.These sediments were then excavated and delivered farther into the foreland basin during theHolocene. The difference between the volumes of materials released from the range and piedmontareas and the volume stored in the contemporaneous fans downstream indicates thatthe latter did not trap the whole sediment load transported by the rivers. The alluvial fans werebypassed by 27 to 78% of this load toward the downstream alluvial plain. It implies a majorvolumetric partitioning of the deposits between the fans and the alluvial plain, with a sedimentationrate about twenty times higher in the fans than in the plain. However, this volumetricpartitioning might only occur during periods with a very specific hydrological regime suchas the Holocene deglaciation. Eventually, the peculiar sediment storage and release patternwithin the range and piedmont areas during the Pleistocene and Holocene complicates thecalculation of mean paleodenudation rates using either sediment budgets or in situ producedcosmogenic nuclides.
Source to Sink: a long term perspective of sediment budgets and sources characterization, Abstracts
Rennes, France

insu-01406440
https://hal-insu.archives-ouvertes.fr/insu-01406440

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Recent geochemical work shows that subduction-zone serpentinites are repositories for fluid-mobile elements absorbed during interaction with sediment-derived fluids. Unraveling the geochemical fingerprint of these rocks helps to define timing of tectonic accretion of sediments along the subduction interface and the role of serpentinite in element recycling to volcanic arcs. Here we present the trace element and isotopic composition (B–O–H, Sr, Pb) of high-pressure serpentinites from the Voltri Massif (Ligurian Western Alps, Italy), to discuss their role as incompatible element carriers and their contribution to recycling of sediment-derived components in subduction zones.The serpentinites presented here record metamorphic olivine growth during eclogite-facies metamorphism and show undeformed and mylonitic textures. Field relations show that undeformed rocks are enclosed in deformed ones and that no metasedimentary rocks are present nearby. Undeformed serpentinite has very high δ11BSRM951 (from +26‰ to +30‰), low Sr and Pb isotope ratios (87Sr/86Sr = 0.7053–0.7069; 206Pb/204Pb = 18.131–18.205) and low As and Sb contents (0.1 and 0.01 μg/g, respectively). Oxygen and hydrogen isotope compositions are +4.5‰ and −67‰, respectively. In contrast, mylonitic serpentinite shows lower δ11B (from +22‰ to +17‰), significant enrichment in radiogenic Sr and Pb isotopes (87Sr/86Sr up to 0.7105; 206Pb/204Pb up to 18.725), and enrichment in As and Sb (1.3 and 0.39 μg/g, respectively). δ18O of the mylonitic serpentinites reaches values of +5.9‰, whereas δD is comparable with that of undeformed rocks (approximately −70‰). In mylonitic serpentinites, the B and Sr isotopic values and the fluid-mobile element (FME) concentrations are near those for the Voltri metasedimentary rocks (calc- and mica-schists). Pb systematics also reveal influx of a crust-derived component.Our dataset shows that undeformed serpentinite still preserves an oceanic geochemical fingerprint, whereas mylonitic serpentinite is reset in its concentrations of FME and its B, Sr and Pb isotope compositions, due to interaction with sediment- and crust-derived fluids. The environment of this interaction is either compatible with (i) an outer-rise zone setting, with percolation of seawater-derived fluids enriched in sedimentary components into bending-related fault structures, or with (ii) subduction channel domains, where ascending sediment-derived slab fluids infiltrate slices of former oceanic serpentinite accreted to the plate interface domain. Influx of sediment-derived subduction fluids along major deformation zones in serpentinite modifies the element budget of the rocks, with important implications for element recycling and the tectonic history of serpentinite. The B, Sr and Pb isotopic systematics, coupled with FME concentration in serpentinites are particularly helpful geochemical tracers of interaction between different reservoirs in subduction-interface environments, and are more sensitive than the traditionally applied stable oxygen and hydrogen isotope compositions.
ISSN: 0016-7037

hal-01419940
https://hal.archives-ouvertes.fr/hal-01419940
DOI : 10.1016/j.gca.2016.06.034

Éditeur(s) : Springer
Résumé : While it is well known that the ocean is one of the most important component of the climate system, with a heat capacity 1,100 times greater than the atmosphere, the ocean is also the primary reservoir for freshwater transport to the atmosphere and largest component of the global water cycle. Two new satellite sensors, the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius SAC-D missions, are now providing the first space-borne measurements of the sea surface salinity (SSS). In this paper, we present examples demonstrating how SMOS-derived SSS data are being used to better characterize key land–ocean and atmosphere–ocean interaction processes that occur within the marine hydrological cycle. In particular, SMOS with its ocean mapping capability provides observations across the world’s largest tropical ocean fresh pool regions, and we discuss from intraseasonal to interannual precipitation impacts as well as large-scale river runoff from the Amazon–Orinoco and Congo rivers and its offshore advection. Synergistic multi-satellite analyses of these new surface salinity data sets combined with sea surface temperature, dynamical height and currents from altimetry, surface wind, ocean color, rainfall estimates, and in situ observations are shown to yield new freshwater budget insight. Finally, SSS observations from the SMOS and Aquarius/SAC-D sensors are combined to examine the response of the upper ocean to tropical cyclone passage including the potential role that a freshwater-induced upper ocean barrier layer may play in modulating surface cooling and enthalpy flux in tropical cyclone track regions.
Surveys In Geophysics (0169-3298) (Springer), 2014-05 , Vol. 35 , N. 3 , P. 681-722

Droits : Springer Science+Business Media Dordrecht 2013
http://archimer.ifremer.fr/doc/00152/26334/24430.pdf
DOI:10.1007/s10712-013-9244-0
http://archimer.ifremer.fr/doc/00152/26334/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Spinel lherzolite xenoliths from Mont Briancon, French Massif Central, retain evidence for multiple episodes of melt depletion and melt/fluid infiltration (metasomatism). Evidence for primary melt depletion is still preserved in the co-variation of bulk-rock major elements (MgO 38.7-46.1 wt.%; CaO 0.9-3.6 wt.%), and many samples yield unradiogenic bulk-rock Os isotope ratios (Os-187/Os-188 = 0.11541-0.12626). However, many individual xenoliths contain interstitial glasses and melt inclusions that are not in equilibrium with the major primary minerals. Incompatible trace element mass balance calculations demonstrate that metasomatic components comprise a significant proportion of the bulk-rock budget for these elements in some rocks, ranging to as much as 25%, of Nd and 40% of Sr Critically, for Re-Os geochronology, melt/fluid infiltration is accompanied by the mobilisation of Sulfide. Consequently, bulk-rock isotope measurements, whether using lithophile (e.g. Rb-Sr, Sm-Nd) or siderophile (Re-Os) based isotope systems, may only yield a perturbed and/or homogenised average of these multiple events.;Osmium mass balance calculations demonstrate that bulk-rock Os in peridotite is dominated by contributions from two populations of sulfide grain: (i) interstitial, metasomatic Sulfide with low [Os] and radiogenic Os-187/Os-188, and (ii) primary sulfides with high [Os] and unradiogenic Os-187/Os-188, which have been preserved within host silicate grains and shielded from interaction with transient melts and fluid. The latter can account for >97% of bulk-rock Os and preserve geochronological information of the melt from which they originally precipitated as an immiscible liquid. The Re-depletion model ages of individual primary sulfide grains preserve evidence for melt depletion beneath the Massif Central from at least 1.8 Gyr ago despite the more recent metasomatic event(s). (C) 2009 Elsevier Ltd. All rights reserved.
ISSN: 0016-7037

hal-00454537
https://hal.archives-ouvertes.fr/hal-00454537
DOI : 10.1016/j.gca.2009.09.031

Éditeur(s) : HAL CCSD
Résumé : International audience
In the context of climate change, this study presents the ability of major/trace elements together with strontiumisotopes to trace back water paths at small scale and to deconvolve the geochemical signal of a small watershedsubject to intense flash floods episodes (Peyne, Hérault, France). Two small sub-basins draining distinct lithologiesin their heads (Plio-Villafranchian conglomerate versus Triassic gypsum-rich marls and dolomites) and the sameMiocene lithology downstream are investigated.Major elements and Ca/Na vs. Mg/Na ratios classically applied at large scale to distinguish carbonate from silicateweathering, allow here discriminating the three main lithologies from the two sub-basins. Trace elements Rband Sr coupled to calcium, also allow this lithological discrimination but in addition the Ca/Rb vs. Sr/Rb tracersappear to be much more discriminant for the various hydrological conditions. Thus, in combination with detailedlithological descriptions, they allow identifying the different facies that imprint the water signature through water-rock interaction according to the hydrological conditions.Strontium isotopes and Rb/Sr ratio, discriminate more precisely the drained lithologies of the 2 sub-basins. Firstly,the 87Sr/86Sr ratios allow identifying the nature of the lithologies and their main component(s) contributing to theSr budget in water and thus imprint the isotopic signature. Secondly, Sr isotopes evidenced two distinct Miocenefacies: the detritric faction (sandy marls), and the marine carbonates.The geochemical signatures of the brook samples draining both compartments were compared to the signatureof the Peyne River outlet just before the confluence into the Hérault River. It appears that the signature of thePeyne River, integrating all the water draining the basin, is relatively stable whatever the hydrological conditionsand mainly marked by the Miocene formations. Sr isotopes further highlight that this signature seems to resultfrom the mixing of both Miocene facies present in the lower part of the Peyne watershed, i.e. the sandy marls andthe carbonates. The typical signatures of the Plio-Villafanchian conglomerates and Triassic gypsiferous marls anddolomites of the headwaters of each sub-basin are completely hidden by the Miocene signatures. This should berelated to the large drainage area of the Miocene compared to other lithologies, despite the high solubility of thegypsum formations releasing large quantities of dissolved elements in solution.Understanding water paths at small scale is even more efficient when the geochemical approach is coupled with adetailed geological description. Indeed, the geochemical tracers are extremely dependent on the facies sequences(morphology) and of the soil nature (mineralogical composition), this is particularly sensitive at small scale.In the context of climate change increasing the intensity of rain events in the Mediterranean region, and resultingin catastrophic floods events (flash floods), tracing the origin of water contributing to the runoff is of primaryimportance and this must be investigated at small scale. Geochemical and isotopic fingerprinting thus constituteexcellent tools which can help to define the area of interest to be monitored in the framework of flood forecast andwarning networks
EGU General Assembly 2015
Vienne, Austria

hal-01118622
https://hal-brgm.archives-ouvertes.fr/hal-01118622

Éditeur(s) : Cnexo
Résumé : L'actualité de ces deux derniers mois n'est pas avare d'événements intéressants pour mon commentaire: visite du Président du CNRS au COB, inauguration de la BOM par le Ministre de l'Industrie, inauguration du nouveau bâtiment du CEDRE par le Secrétaire d'État auprès du Ministre de l'Environnement et du Cadre de Vie, décision du gouvernement français de déposer une loi nous mettant sur le même pied que nos concurrents pour accéder à l'exploitation des grands fonds marins, engagement prochain de la campagne PHYCEMED, réduction considérable du budget de la NOAA ... [OCR NON CONTRÔLE]
La Lettre du Cnexo (Cnexo), 1981-02 , N. 5 , P. 1-5

Droits : Cnexo - Ifremer
http://archimer.ifremer.fr/doc/1981/publication-4772.pdf
http://archimer.ifremer.fr/doc/00000/4772/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Scientific interest in urban meteorology has increased because highly populated areas experience high vulnerability to pollution or heavy rain. However, compared to urban air quality or urban heat island (UHI) processes, the urban water vapour cycle is poorly understood because it has been investigated less due to the lack of upper-air measurements and the high sensitivity of surface measurements to local heterogeneities. In this paper, surface measurements of wind, temperature, pressure and humidity, as well as integrated water vapour (IWV) from GPS and MODIS and numerical simulations, have been used to investigate the urban cycle of water vapour in May and June 2004 during the VAPIC field experiment in the Paris area. The surface data show the typical characteristics of an urban area with the absence of water vapour sources and a UHI of about 6 °C at night. The urban IWV distribution differs completely, with an urban IWV excess on average between 1600 and 0600 UTC (with a maximum of about 1.5 kg m−2 at 0600 and 1700 UTC). No IWV difference between the urban and rural areas is found in the middle of the day. The numerical simulations reproduce accurately the urban IWV anomaly. Shallow surface wind convergence associated with the UHI during nighttime provides moisture from the rural areas. Urban areas are therefore under wind convergence for most of the time. The rural water vapour sources and the depth of the convergence control the amplitude of the urban IWV excess. At about 1200 UTC, entrainment at the top of the urban boundary layer is the key process that inhibits the urban IWV excess observed at night
ISSN: 0035-9009

hal-00406370
https://hal.archives-ouvertes.fr/hal-00406370
DOI : 10.1002/qj.446

Éditeur(s) : Elsevier Science Bv
Résumé : There has been growing interest in the development of mud crab aquaculture in New Caledonia. However, for this to become established at a commercial level, a cost-effective formulated feed based on internationally-available ingredients needs to be developed. We have evaluated the optimal dietary protein content for juvenile crabs, Scylla serrata (Forskål, 1775), using a series of diets with a protein content ranging from 27 to 49% and soy protein concentrate (SPC) as the main protein source. For this purpose, 54 individually housed crabs were allocated to five dietary treatments (n = 10 or 11). The crabs were fed ad libitum, for 81 days with the allocated diets. The apparent digestibilities of dry mater, crude protein and energy were high (96.2-97.3%), irrespective of the diet. The voluntary feed intake (VFI) of crabs widely varied from 46 to 220 g kg- 1of fresh initial body weight per week (iBW week- 1) whatever the diet. However, SPC intake and protein intake increased significantly with dietary protein content up to the diet with 40% crude protein, but did not increase further with diets containing 44% and 49% crude protein. The cumulative molts were strongly affected by the VFI levels or energy intake and also, to a lesser extent, by the levels of SPC or protein in diets. Two phases in tissue gain were observed after ecdysis: an initial deposition phase lasting around 30 days followed by a plateau which lasted until the next molt. The daily tissue growth was 16.5% of dry body weight (dry BW) one day after ecdysis and dramatically decreased to 3.6% of dry BW over the first 10 days, then decreased more slowly to the minimum value of 1.3% of dry BW over the next 70 days. During the course of experiment, the best growth (tissue growth and molt frequency) and the best feed efficiency (FCR, PER, retention of proteins and lipids) were obtained with crabs fed on the diet with 40% crude protein. This result was confirmed by a bioenergetic study which showed significantly higher allocation of the energy intake for growth (RE) of crabs fed on diet 40% crude protein. Finally, under our experimental conditions, 1 kg of juvenile crabs required 6.5 ± 1.1 g of protein per day. This level was obtained with the diet SPC-42 that contained 40% of protein of which almost three quarters were derived from SPC. Two hypotheses are proposed to explain the negative effect of high level of SPC or protein on growth and feed efficiency for crabs fed on in diets containing 52% and 60% SPC.
Aquaculture (0044-8486) (Elsevier Science Bv), 2014-10 , Vol. 434 , P. 499-509

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00211/32196/30630.pdf
http://archimer.ifremer.fr/doc/00211/32196/