Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy B - Oxford Open Option A Oxford University Press (OUP)
Résumé : International audience
Peridotite xenoliths exhumed by Quaternary alkaline magmatism in the Tahalgha district, southern Hoggar, represent fragments of the subcontinental lithospheric mantle beneath the boundary between the two major structural domains of the Tuareg Shield: the ‘Polycyclic Central Hoggar’ to the east and the ‘Western Hoggar’, or ‘Pharusian Belt’, to the west. Samples were collected from volcanic centres located on both sides of a major lithospheric shear zone at 4°35' separating these two domains. Although showing substantial variations in their deformation microstructures, equilibrium temperatures and modal and chemical compositions, the studied samples do not display any systematic changes of these features across the 4°35' fault. The observed variations rather record small-scale heterogeneities distributed throughout the study area and reflecting the widespread occurrence of vein conduits and metasomatized wall-rocks related to trans-lithospheric melt circulation during the Cenozoic. These features include partial annealing of pre-existing deformation microstructures, post-deformation metasomatic reactions, and trace-element enrichment, coupled with heating from 750–900°C (low-temperature lherzolites) to 900–1150°C (intermediate-T lherzolites and high-T harzburgites and wehrlites). Trace-element modelling confirms that the range of rare earth element (REE) variations observed in the Tahalgha clinopyroxenes may be accounted for by reactive porous flow involving a single stage of basaltic melt infiltration into a light REE (LREE)-depleted protolith. Whole-rock compositions record the final entrapment of disequilibrium metasomatic melts upon thermal relaxation of the veins–wall-rock system. The striking correlations between equilibrium temperatures and trace-element enrichment favor a scenario in which the high-temperature peridotites record advective heat transport along melt conduits, whereas the intermediate- and low-temperature lherzolites reflect conductive heating of the host Mechanical Boundary Layer. This indicates that the lithosphere did not reach thermal equilibrium, suggesting that the inferred heating event was transient and was rapidly erased by thermal relaxation down to the relatively low-temperature present-day geotherm. The low-T (<900°C) deformed lherzolites (porphyroclastic to equigranular) are characterized by only incipient annealing and LREE-depleted clinopyroxene compositions. They were only weakly affected by the Cenozoic events and could represent relatively well-preserved samples from rejuvenated Pan-African lithosphere. Extensive lithospheric rejuvenation occurred either regionally during the Pan-African orogeny, as a result of lithospheric delamination or thermomechanical erosion after thickening, or more locally along the meridional shear zones. The low-T Tahalgha lherzolites are comparable with lherzolites from Etang de Lherz, southern France, interpreted as lithospheric mantle rejuvenated by melt-induced refertilization during a late stage of the Variscan orogeny.
ISSN: 0022-3530

hal-01107410
https://hal.archives-ouvertes.fr/hal-01107410
DOI : 10.1093/petrology/egu056

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
IODP Site U1309 was drilled at Atlantis Massif, an oceanic core complex, at 30 degrees N on the Mid-Atlantic Ridge (MAR). We present the results of a bulk rock geochemical study (major and trace elements) carried out on 228 samples representative of the different lithologies sampled at this location. Over 96% of Hole U1309D is made up of gabbroic rocks. Diabases and basalts cross-cut the upper part of the section; they have depleted MORB compositions similar to basalts sampled at MAR 30 degrees N. Relics of mantle were recovered at shallow depth. Mantle peridotites show petrographic and geochemical evidence of extensive melt-rock interactions. Gabbroic rocks comprise: olivine-rich troctolites (>70% modal olivine) and troctolites having high Mg# (82-89), high Ni (up to 2300 ppm) and depleted trace element compositions (Yb 0.06-0.8 ppm); olivine gabbros and gabbros (including gabbronorites) with Mg# of 60-86 and low trace element contents (Yb 0.125-2.5 ppm); and oxide gabbros and leucocratic dykes with low Mg# (<50), low Ni (similar to 65 ppm) and high trace element contents (Yb up to 26 ppm). Troctolites and gabbros are amongst the most primitive and depleted oceanic gabbroic rocks. The main geochemical characteristics of Site U1309 gabbroic rocks are consistent with a formation as a cumulate sequence after a common parental MORB melt, although (lack of systematic) downhole variations indicate that the gabbroic series were built by multiple magma injections. In detail, textural and geochemical variations in olivine-rich troctolites and gabbronorites suggest chemical interaction (assimilation?) between the parental melt and the intruded lithosphere. Site U1309 gabbroic rocks do not represent the complementary magmatic product of 30 degrees N volcanics, although they sample the same mantle source. The bulk trace element composition of Site U1309 gabbroic rocks is similar to primitive MORB melt compositions; this implies that there was no large scale removal of melts from this gabbro section. The occurrence of such a large magmatic sequence implies that a high magmatic activity is associated with the formation of Atlantis Massif. Our results suggest that almost all melts feeding this magmatic system stays trapped into the intruded lithosphere.
ISSN: 0012-821X

hal-00413562
https://hal.archives-ouvertes.fr/hal-00413562
DOI : 10.1016/j.epsl.2008.12.034

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Various bagasse fibre/cement composites have been prepared, the fibres having a random distribution in the composites. The influence of different parameters on the setting of the composite material has been studied: (1) botanical components of the fibre, (2) thermal or chemical treatment of the fibre, (3) bagasse fibre content and (4) added water percentage. This study shows a retarding effect of lignin on the setting of the composite, for small amount of heat-treated bagasse (200 °C) the behaviour of the composite is closely the same as the classical cement or cellulose/cement composite.
ISSN: 0958-9465

hal-00809715
https://hal.univ-antilles.fr/hal-00809715
DOI : 10.1016/S0958-9465(02)00003-3

Éditeur(s) : HAL CCSD Elsevier
Résumé : Understanding chemical element mobility during high-pressure metamorphism is paramount to the knowledge of the transformations occurring during the course of eclogite-facies metamorphism. In particular, the role of deformation and fluid circulation appear essential. In order to better decipher this role, we investigated two eclogite-facies samples from the Lindas Nappe in the Bergen arcs (Norwegian Caledonides), which are related to a fluid/deformation metamorphic event. This study, based on detailed microtextural investigations, coupled with major and trace element analyses, either in situ EMPA and LA-ICP-MS or by conventional ICP-MS nebulisation on mineral fractions, illustrates the complexity of chemical reactions accompanying the eclogite- and amphibolite-facies metamorphism. A single eclogite-facies mineral species two eclogite-facies (i.e. phengite and epidote) depicts various chemical features depending on its textural location at thin-section scale. The correlation with the mineralogical reaction occurring in each textural site demonstrates that the compositional variations are inherited from the precursor minerals. Thus, the composition of eclogite-facies minerals is locally controlled by the composition of few hundred-micron domains. On the contrary, alteration phases of the amphibolite facies (symplectite and calcic amphibole) display clear enrichment in LILE, Pb, Sr and LREE compared to their precursor minerals (omphacite and garnet). This supports that the transport of elements at hand-sample scale was enhanced during the retrogression and elements were efficiently delocalised from one textural site to another. The contrasting behaviour of element mobility between peak eclogite-facies metamorphism and retrogression can be explained in terms of rate processes and fluid/deformation activity. During eclogitisation,deformation allows the formation of textural and mineralogical microdomains. Contemporaneously the fluid circulation favours the development of heterogeneities by transport of elements in excess towards areas protected from deformation where phengite-bearing quartz lenses crystallise. This, together with the very fast recrystallisation of eclogite-facies minerals, results in a heterogeneous redistribution of elements at sample scale and in a chemical disequilibrium between different microdomains of hundred-micron size. During retrogression in the amphibolite facies, coeval with long-term ductile deformation, the fluids act as an efficient vector to redistribute the elements from a given textural site to another and, thus, allow to reach, at hand-sample scale, a new chemical equilibrium between the different crystallising phases.
ISSN: 0024-4937

hal-00404602
https://hal.archives-ouvertes.fr/hal-00404602
DOI : 10.1016/j.lithos.2006.10.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We report new data on the geochemical evolution, metasomatic and deformation processes in the lower layers of cratonic lithospheric mantle based on a detailed study of extraordinarily fresh and large deformed peridotite xenoliths from the Udachnaya kimberlite pipe, Siberia. Based on our T-P estimates, the deformed peridotites are localized in a depth range of 170 to 220 km near the base of cratonic mantle. The degree of deformation is not correlated with the depth and equilibration temperatures of the xenoliths. The deformed peridotites are depleted in magmaphile major elements indicating their residual nature, but are enriched in incompatible trace elements, Fe and K. The deformed peridotites experienced a complex evolution, i.e., they were formed initially as high-degree melt extraction residues and later were subjected to three main stages of metasomatic modification. (1) An old, mostly cryptic metasomatism by melt/fluid of carbonatitic composition, which formed garnets with sinusoidal REE patterns (Smn/Ern > 1). (2) Silicate metasomatism, which led to the most significant changes in mineralogical and chemical composition of the deformed peridotites. (3) Fe and Ti metasomatism just before the entrainment of the deformed rocks into kimberlite magma. Enrichment of the peridotites in large-ion lithophile elements (K, Rb, Ba) is related to the formation of kelyphitic rims around garnet. The nature of the metasomatic agent of silicate metasomatism was evaluated from mass-balance of measured and calculated whole-rock compositions, ratios of highly incompatible elements (D < 0.1) and fractional crystallization modeling. All this evidence indicates that the agent of silicate metasomatism had a composition intermediate between that of kimberlites and HIMU OIB. The metasomatic processes responsible for the formation of deformed peridotites and precipitation of megacryst suites cannot be widespread at the base of the cratonic mantle. Rather, they are local features only existing in the cratonic mantle below kimberlite fields and localized along the metasomatic vein system.
ISSN: 0024-4937

hal-00941010
https://hal.archives-ouvertes.fr/hal-00941010
DOI : 10.1016/j.lithos.2012.11.014

Éditeur(s) : HAL CCSD E Schweizerbart Science Publishers
Résumé : International audience
Mass balance calculations have been performed through a comparison of published graphical and statistical approaches applied to two contrasted geological settings: (i) the development of a greenschist-facies ductile shear-zone that recorded a weak volume change but significant mass transfers, and (ii) the formation of exoskarns in metacarbonate xenoliths that recorded a large volume decrease related to huge mass transfers. The comparison of the four mass-balance approaches shows that, if uncertainties are ignored, (1) they yield similar results concerning the mobile vs immobile behaviour of many components; (2) they yield similar mass-change values on bulk rock and on individual chemical elements (bulk-rock mass-change values differ by a maximum of ca. 15 % between graphical and statistical treatments of the metacarbonate xenolith evolution). The main difference concerns the uncertainties on mass changes (for bulk rocks and individual elements), which are much larger with the graphical than with the statistical approaches when uncertainties on chemical elements are taken into account, as they should be.The main advantage of the graphical methods is their rapid implementation and the clarity of the diagrams. Their main disadvantages are that uncertainties on each chemical element and bulk compositions are not taken into account and the difficulty in choosing an accurate immobility field to precisely define errors. Graphical methods need to be completed by a statistical treatment that gives absolute mass transfer results. The statistical approaches have the advantage of taking into account the chemical heterogeneities of the compared populations, in conjunction to a precise data treatment. The statistical treatment is an important and necessary step to decipher and to be pertinent in interpreting mobility/immobility of chemical elements, and, thus, in the absolute quantification of mass and volume changes.
ISSN: 0935-1221

hal-01260258
https://hal.archives-ouvertes.fr/hal-01260258
DOI : 10.1127/ejm/2015/0027-2475

Éditeur(s) : HAL CCSD Lavoisier
Résumé : International audience
Afin de réduire la consommation d'énergie électrique liée à l'utilisation intense de la climatisation dans les logements des régions tropicales de la Caraïbe, des matériaux composites fibres végétales/ciment ont été préparés en vue d'être utilisés dans le domaine de la construction. Les fibres de dictame (Maranta arundinacée), résidus de l'extraction de la farine de dictame, sont étudiées. Dans cet article, une première partie sera consacrée à la détermination des dimensions des particules et de la composition chimique des fibres de dictame brutes, à l'étude des évolutions structurales et de texture des fibres après leur pyrolyse (200 - 700°C). Puis le travail sur la prise des composites fibres de dictame/ciment sera mené. En particulier, l'influence de paramètres tels que la teneur en fibres, la teneur en eau et la température de pyrolyse des fibres de dictame sera abordée. Par ailleurs les chaleurs dégagées lors de la dégradation thermique des composites sont également déterminées.
ISSN: 1169-7954

hal-00809828
https://hal.univ-antilles.fr/hal-00809828
DOI : 10.3166/rcma.17.327-350

Éditeur(s) : Gauthier-Villars
Résumé : Cyprideis torosa (Crustacea, Ostracoda), which is well known for its ability to live in a wide range of salinity and for the variability of its ornamentation, was sampled in the paralic environment. in the Camargue (France) and in the area of Santa-Pola (south-east Spain), in ambient waters whose salinity varies from 1 to 120 g/l. The collected valves. which are smooth, punctuated, reticulated or have nodes on their surface, were analyzed by means of spark-source mass spectrometry. We detected twenty-six chemical elements, and found a clear relationship between the chemical composition, the ornamentation of the valves and the environmental parameters. In the oligohaline environment, the carapaces are thick, reticulated or node-bearing ; they are enriched in Si, Al, Fe, Mn and Ba which are terrigenous elements introduced by fresh water. In an open hypersaline environment, the carapaces are reticulated or punctuated ; they are chemically characterized by P, Sr and Li, typical for concentrated seawater. Finally, in a closed hypersaline environment. the collected individuals are smooth, and their carapaces are very thin ; their content S is related to the abundant organic matter provided by the development of algal and cyanobacterial mats. Salinity and confinement, which are the main parameters characteristic of the studied ecosystems, are also the two factors that control the ornamentation of the valves. The chemical analysis and the field observations reveal that the granulometric characteristics of the microhabitats must be considered because they control the exchanges at the water-sediment interface. The anthropic influences on the chemical composition of the carapace must be emphasized: it is possible to detect industrial and domestic wastes. But the ornamentation of the carapace is not related to these pollutants - chiefly heavy metals (Pb, Ni Sn) - and depends mainly on the open or closed character of the ambient environment. The present method highlights, on the basis of the chemical composition, a relationship between ornamentation and environmental parameters. It is particularly efficient in the interpretation of the morphology of the valves in relation to the palaeoenvironment.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 5 , P. 505-514

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00103/21378/18978.pdf
http://archimer.ifremer.fr/doc/00103/21378/

Éditeur(s) : Wiley-blackwell
Résumé : Aim The aims of this study were: (1) to identify global communities of tuna and billfish species through quantitative statistical analyses of global fisheries data; (2) to describe the spatial distribution, main environmental drivers and species composition of each community detected; and (3) to determine whether the spatial distribution of each community could be linked to the environmental conditions that affect lower trophic levels by comparing the partitions identified in this study with Longhursts biogeochemical provinces. Location The global ocean from 60 degrees S to 65 degrees N. Methods We implemented a new numerical procedure based on a hierarchical clustering method and a nonparametric probabilistic test to divide the oceanic biosphere into biomes and ecoregions. This procedure was applied to a database that comprised standardized data on commercial longline catches for 15 different species of tuna and billfish over a period of more than 50 years (i.e. 1953-2007). For each ecoregion identified (i.e. characteristic tuna and billfish community), we analysed the relationships between species composition and environmental factors. Finally, we compared the biogeochemical provinces of Longhurst with the ecoregions that we identified. Results Tuna and billfish species form nine well-defined communities across the global ocean. Each community occurs in regions with specific environmental conditions and shows a distinctive species composition. High similarity (68.8% homogeneity) between the spatial distribution of the communities of tuna and billfish and the biogeochemical provinces suggests a strong relationship between these species and the physical and chemical characteristics of the global ocean. Main conclusions Despite their high tolerance for a wide range of environmental conditions, these highly migratory species are partitioned into clear geographical communities in the ocean at a global scale. The similarity between biogeochemical and biotic divisions in the ocean suggests that the global ocean is a mosaic of large biogeographical ecosystems, each characterized by specific environmental conditions that have a strong effect on the composition of the trophic web.
Journal Of Biogeography (0305-0270) (Wiley-blackwell), 2012-01 , Vol. 39 , N. 1 , P. 114-129

Droits : 2011 Blackwell Publishing Ltd
http://archimer.ifremer.fr/doc/00060/17141/14716.pdf
DOI:10.1111/j.1365-2699.2011.02582.x
http://archimer.ifremer.fr/doc/00060/17141/

Éditeur(s) : HAL CCSD Elsevier
Résumé : This contribution reports our preliminary work to determine Cu isotope ratios for various granite rocks and examine the Cu isotope systematics within granite suites. A chemical procedure, modified from Marechal [Marechal, C.N., Telouk, R and Albarede, F., 1999. Precise analysis of copper and zinc isotopic compositions by plasma-source mass spectrometry. Chemical Geology, 156(1-4): 251-273.], Was used to separate Cu from rock matrix. Quantitative recovery (100.6 +/- 1.6%), with a low total procedural blank (2.65 +/- 0.66 ng) for Cu, has been achieved, allowing Cu isotopic measurements on samples with as little as 10 ppm Cu. The Cu isotope ratios (delta Cu-65 relative to NIST SRM 976) of 32 rock samples, ranging from mafic to felsic compositions, from 3 batholiths (2 I-type, 1 S-type) from the Lachlan Fold Belt in southeastern Australia. vary from -0.46 parts per thousand to 1.51 parts per thousand. Most of them cluster around zero, With mean values for the I-type and S-type granites of 0.03 +/- 0.15 parts per thousand and - 0.03 +/- 0.42 parts per thousand (2 sigma) respectively. These data, together with Cu isotope ratios of two loess samples, provide preliminary evidence that the baseline Cu isotopic composition of the crystalline part of upper continental crust is close to zero. The tight clustering of Cu isotope ratios of rocks from the I-type suites Suggests that high-temperature magmatic processes do not produce significant Cu isotope fractionation. However, two granites with abnormally heavy Cu isotope signatures (up to 1.51 parts per thousand) appears to be the result of localized hydrothermal alteration. Measurable variation in Cu isotopic composition of the S-type granite may reflect isotopic heterogeneity in the sedimentary Source region as a result of redox processes or may be due to hydrothermal overprinting. Thus, Cu isotope geochemistry may be a useful tracer for studying hydrothermal alteration and Source heterogeneity of granitic rocks.
ISSN: 0009-2541

hal-00413130
https://hal.archives-ouvertes.fr/hal-00413130
DOI : 10.1016/j.chemgeo.2008.06.047

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The ultramafic rocks of the Collo region in northeastern Algeria crop out as “stratified” masses that cut across older metamorphic formations of the Petite Kabylie basement. Based on petrological compositions and mineralogical observations, these rocks are mainly peridotites and serpentinites. The peridotites are identified as lherzolites, but dunites may occur rarely. The lherzolites are composed of olivine, orthopyroxene, clinopyroxene and chromian spinel. Their chemical composition shows high MgO (34.4–37.5 wt%), Cr (0.14–0.27 wt%), Ni (0.14–0.26 wt%) and Co (34–133 ppm) contents and low CaO and Al2O3 concentrations (0.02–2.2 wt% and 0.5 to 2.8 wt%, respectively). The chromite, which represents approximately 1–3% of the rock, is ubiquitous and shows two different generations: primary millimetric euhedral crystals and secondary fine xenomorphic grains and interstitial aggregates. The primary chromites are alumino-ferro-magnesian crystals that show high Al2O3 (25.77%–27.36%) and MgO (10.70%–13.36%). Cr# (100 × Cr/(Al + Cr)) ranges from 45 to 48, and Mg# (100 × Mg/(Mg + Fe2+)) from 49 to 59. The secondary interstitial grains are iron-rich chromites. They show low Al2O3 (4.67%–9.54%) and MgO (4.60%–4.65%). Cr# is relatively high (77–88), whereas Mg# shows relatively low values, ranging from 22 to 25. Primary chromite and whole-rock chemistry show that the Collo ultramafic rocks belong to Alpine-type peridotites that were emplaced within an orogenic setting. The oxygen isotopic composition of both peridotites and chromites is consistent with their derivation from a mantle source (δ18O ranges from +3.0 to +5.9‰). Low δ18O values (<+4.4‰) are recorded in serpentinites and are attributed to the effect of serpentinization processes through high-temperature metasomatic fluids. Magnesite-bearing serpentinites show the lowest δ18O values. These are interpreted as the result of surface water input.
ISSN: 0899-5362

hal-01468003
https://hal.archives-ouvertes.fr/hal-01468003
DOI : 10.1016/j.jafrearsci.2016.10.012

Éditeur(s) : HAL CCSD Elsevier
Résumé : The Erro-Tobbio peridotites (Voltri Massif, Ligurian Alps) represent subcontinental lithospheric mantle tectonically exhumed during Permo-Mesozoic extension of the Europe-Adria lithosphere. Previous studies have shown that exhumation started during Permian times, and occurred along kilometer-scale lithospheric shear zones which enhanced progressive deformation and recrystallization from spinel- to plagioclase-facies conditions. Ongoing field and petrologic investigations have revealed that the peridotites experienced, during uplift, a composite history of diffuse melt migration and multiple episodes of ultramafic-mafic intrusions. In this paper we present the results of field, structural and petrologic-geochemical investigations into a sector of the Erro-Tobbio peridotite unit that preserves well this multiple intrusion history. Melt impregnation in the peridotites is evidenced by significant plagioclase enrichment and crystallization of unstrained orthopyroxene replacing kinked mantle olivine and clinopyroxene; impregnating melts were thus opx-saturated. Melt-rock interaction caused chemical changes in mantle minerals (e.g. Al decrease and REE increase in cpx; Ti and Cr# enrichment in spinel). Nevertheless, clinopyroxenes still exhibit LREE depletion (Ce;N;/Sm;N; = 0.006-0.011), indicating a depleted signature for the percolating melts. Melt impregnation was thus related to diffuse porous flow migration of depleted MORB-type melt fractions that modified their compositions towards opx saturation by mantle-melt interaction during ascent. The impregnated peridotites are intruded by a hectometer-scale stratified cumulate body, mostly consisting of troctolites and plagioclase wehrlites, showing gradational, interfingered contacts with the host mantle rocks. Subsequent intrusion events are revealed by the occurrence of olivine gabbros as decameter-wide lenses, variably thick (centimeter- to meter-scale) dykes and thin dykelets, which crosscut both the peridotite foliation and the magmatic layering in the cumulates. Overall, major and trace element compositions of minerals in the intrusives indicate that they represent variably differentiated cumulus products crystallized from rather primitive N-MORB-type aggregated melts. Slightly more evolved compositions are shown by olivine gabbros, relative to the troctolites and plagioclase wehrlites of the cumulate body. Mineral chemistry features (e.g. the Fo-An correlation and high Na, Ti, Mg# in cpx) indicate that the studied intrusive rocks crystallized at moderate pressure conditions (3-5 kbar, i.e. 9-15 km depth). Our study thus points to a progressive transition from porous flow melt migration to emplacement of magmas in fractures, presumably related to progressive change of lithospheric mantle rheology during extension-related uplift and cooling.
ISSN: 0024-4937

hal-00407669
https://hal.archives-ouvertes.fr/hal-00407669
DOI : 10.1016/j.lithos.2006.06.014

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A reactive percolation experiment was conducted by injecting seawater into a permeable olivine aggregate at 190 °C and 19 MPa to explore the relationships between hydration reactions and hydrodynamic properties during the onset of serpentinization in the ultramafic lithosphere exposed at mid-ocean ridges. The experiment was stopped after 23 days when the sample became impermeable. The initial flow rate was 0.2 mL/h and then was decreased down to 0.06 mL/h after 8 days. Permeability decreased continuously throughout the experiment. The analyses of fluid chemistry time series and of the mineralogy and structure of the reacted sample showed olivine dissolution and precipitation of proto-serpentine, brucite and Fe-oxides. These reactions are controlled by coupled hydrodynamic and chemical processes interacting at different time and spatial scales. Their first characteristic is the production of silica rich outlet fluids in disequilibrium with the observed reacted mineral assemblages. These compositions are interpreted as resulting from a suite of coupled dissolution-precipitation reactions, controlled at the pore scale by surface kinetic processes, that rapidly reaches steady-state (constant fluid composition independent of fluid flux). Hence, the effective rate of serpentinization was controlled, to the first order, by the transport of reactants during the experiment. Mass balance calculations show that the rate of olivine conversion was fast (0.2-0.5 wt%/day), yet only ∼8 wt% of the olivine sample reacted, because the permeability drop limited fluid circulation. Porosity varied little during the experiment compared to permeability changes: the decrease of permeability was explained by the structure of the newly formed serpentine favouring the clogging of fluid paths. The rate at which permeability decreased was the fastest at low flux conditions. This suggests that permeability changes were not controlled simply by the kinetics of the serpentinization reactions, but mainly reflected the development of low Peclet pore scale zones forming micro-environments that control the serpentinization reaction-paths. These results outline the need to take into account the coupling of hydrodynamic and chemical processes when modelling the effects of reactive transport within the hydrating oceanic lithosphere.
ISSN: 0012-821X

hal-00855043
https://hal.archives-ouvertes.fr/hal-00855043
DOI : 10.1016/j.epsl.2013.03.052

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Jacupiranga Complex is one of several Meso-Cenozoic alkaline intrusive complexes along the margins of the intracratonic Paraná Basin in southern Brazil. The complex encompasses a wide range of rock-types, including dunites, wehrlites, clinopyroxenites, melteigites-ijolites, feldspar-bearing rocks (diorites, syenites, and monzonites), lamprophyres and apatite-rich carbonatites. While carbonatites have been extensively investigated over the last decades, little attention has been paid to the silicate rocks. This study presents new geochonological and geochemical data on the Jacupiranga Complex, with particular emphasis on the silicate lithotypes. 40Ar/39Ar ages for different lithotypes range from 133.7 ± 0.5 Ma to 131.4 ± 0.5 Ma, while monzonite zircon analyzed by SHRIMP yields a U-Pb concordia age of 134.9 ± 1.3 Ma. These ages indicate a narrow time frame for the Jacupiranga Complex emplacement, contemporaneous with the Paraná Magmatic Province. Most of the Jacupiranga rocks are SiO2-undersaturated, except for a quartz-normative monzonite. Based on geochemical compositions, the Jacupiranga silicate lithotypes may be separated into two magma-evolution trends: (1) a strongly silica-undersaturated series, comprising part of the clinopyroxenites and the ijolitic rocks, probably related to nephelinite melts and (2) a mildly silica-undersaturated series, related to basanite parental magmas and comprising the feldspar-bearing rocks, phonolites, lamprophyres, and part of the clinopyroxenites. Dunites and wehrlites are characterized by olivine compositionally restricted to the Fo83-84 interval and concentrations of CaO (0.13–0.54 wt%) and NiO (0.19–0.33 wt%) consistent with derivation by fractional crystallization, although it is not clear whether these rocks belong to the nephelinite or basanite series. Lamprophyre dikes within the complex are considered as good representatives of the basanite parental magma. Compositions of calculated melts in equilibrium with diopside cores from clinopyroxenites are quite similar to those of the lamprophyres, suggesting that at least a part of the clinopyroxenites is related to the basanite series. Some feldspar-bearing rocks (i.e. meladiorite and monzonite) show petrographic features and geochemical and isotope compositions indicative of crustal assimilation, although this may be relegated to a local process. Relatively high CaO/Al2O3 and La/Zr and low Ti/Eu ratios from the lamprophyres and calculated melts in equilibrium with cumulus clinopyroxene point to a lithospheric mantle metasomatized by CO2-rich fluids, suggesting vein-plus-wall-rock melting mechanisms. The chemical differences among those liquids are thought to reflect both variable contributions of melting resulting from veins and variable clinopyroxene/garnet proportions of the source.
ISSN: 0895-9811

hal-01583547
https://hal.archives-ouvertes.fr/hal-01583547
DOI : 10.1016/j.jsames.2017.05.009

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
This paper presents the effects of chemical and thermal treatments on the strength of vegetable fibers that were being considered as reinforcements in cementitious matrix composites for affordable housing. These include vegetable fibers extracted from banana trunks and sugar cane residues. The results suggested that pyrolysis increased the fiber strength, at least by a factor three. Acid attack generally degraded the strengths, while alkali attack had only a limited effect. Pyrolyzed banana leaves, coconut coir, and coconut sheaths fibers were also tested. The implications of the results were discussed for the development of strong cementitious matrix composites.
ISSN: 1042-6914

hal-00809827
https://hal.univ-antilles.fr/hal-00809827
DOI : 10.1080/10426910601063386

Éditeur(s) : HAL CCSD
Résumé : The bacterial microbiota of ants (Hymenoptera: Formicidae) is known to have a defensive role in social insects, particularly for leaf-cutting ants (Formicidae: Attini) due to the use of antimicrobial molecules produced by cuticular actinobacteria. In this thesis, we studied the bacterial microbiota of ants in French Guyana using different approaches based on natural products chemistry and molecular ecology. The first chapter describes the isolation, identification, culture and biological evaluations of 43 cuticular actinobacteria. Antagonism bioassays of isolated strains and antibiotic activities of the culture extracts against human pathogens are presented as well as the identification of an antimicrobial cyclic dipeptide (Cyclo (LPro-LPhe)) isolated from a strain close to Streptomyces thioluteus. Moreover, the implementation of molecular networks applied to UPLC/MS/MS analysis of actinobacterial cocultures allowed us to explore the diversity of metabolites produced under these conditions. The second chapter presents a methodological study to evaluate the capacity of four DNA extraction methods, in terms of richness and composition of the cuticular bacterial microbiota, in high-throughput sequencing from Atta cephalotes and Pseudomyrmex penetrator. The results of metabarcoding highlight two methods of extraction and reveal inter- and intraspecific differences in the composition of cuticular bacterial communities. Finally, chapter three describes the composition of the cuticular bacterial microbiota of Camponotus femoratus and Crematogaster levior in ant garden and the results reveal the acquisition in the environment of a part of the microbiota. In parallel, metabolomic analyses of ant’s cuticle show, on the contrary, a greater specificity related to the ant species. Future researches focusing on statistical analysis strategies combining metabarcoding and metabolomics data are discussed.
Le microbiote bactérien cuticulaire des fourmis (Hymenoptera : Formicidae) est connu pour avoir un rôle défensif chez ces insectes sociaux, notamment chez les fourmis attines (Formicidae : Attini) grâce l’utilisation de molécules antimicrobiennes produites par des actinobactéries cuticulaires. Dans le cadre de cette thèse, nous avons étudié le microbiote bactérien des fourmis de Guyane en utilisant différentes approches en chimie des produits naturels et en écologie moléculaire. Le premier chapitre décrit l’isolement, l’identification, la culture et l’évaluation biologique de 43 actinobactéries cuticulaires de fourmis de Guyane. Les tests d’antagonismes des souches isolées et l’activité antibiotique des extraits de culture contre des micro-organismes pathogènes humains sont présentés ainsi que l’identification d’un dipeptide cyclique (Cyclo(LPro-LPhe)) antimicrobien qui a été isolé à partir d’une souche proche de Streptomyces thioluteus. Par ailleurs, la mise en œuvre de réseaux moléculaires appliqués à une analyse par UPLC/MS/MS de cocultures d’actinobactéries a permis d’explorer la diversité des métabolites produits dans ces conditions. Le deuxième chapitre présente une étude méthodologique pour comparer quatre méthodes d’extraction d’ADN, en termes de richesse et de composition du microbiote bactérien cuticulaire, par séquençage haut débit à partir des espèces Atta cephalotes et Pseudomyrmex penetrator. Les résultats du métabarcoding ADN mettent en lumière deux méthodes d’extraction et révèlent des différences inter- et intraspécifiques dans la composition des communautés bactériennes cuticulaires. Enfin, le chapitre trois décrit la composition du microbiote bactérien cuticulaire des espèces Camponotus femoratus et Crematogaster levior dans les jardins de fourmis. Les résultats soulignent l’acquisition d’une partie du microbiote dans l’environnement. En parallèle l’analyse métabolomique des cuticules montre à contrario une plus grande spécificité liée à l’espèce de fourmi. Les recherches futures axées sur les stratégies d’analyses statistiques combinant le métabarcoding et la métabolomique sont discutées.
https://tel.archives-ouvertes.fr/tel-01537793

NNT : 2017YANE0003
tel-01537793
https://tel.archives-ouvertes.fr/tel-01537793
https://tel.archives-ouvertes.fr/tel-01537793/document
https://tel.archives-ouvertes.fr/tel-01537793/file/thesecarolinebirer.pdf

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : Ants have evolved venoms rich in peptides and proteins used for predation, defense, and communication. However, they remain extremely understudied due to the minimal amount of venom secreted by each ant. The present study investigated the differences in the proteome and peptidome of the venom from the bullet ant, Paraponera clavata. Venom samples were collected from a single colony either by manual venom gland dissection or by electrical stimulation and were compared using proteomic methods. Venom proteins were separated by 2D-PAGE and identified by nanoLC-ESI-QTOF MS/MS. Venom peptides were initially separated using C18 reversed-phase high-performance liquid chromatography, then analyzed by MALDI-TOF MS. The proteomic analysis revealed numerous proteins that could be assigned a biological function (total 94), mainly as toxins, or roles in cell regulation and transport. This investigation found that ca. 73% of the proteins were common to venoms collected by the two methods. The peptidomic analysis revealed a large number of peptides (total 309) but with <20% shared by the two collection methods. There was also a marked difference between venoms obtained by venom gland dissection from different ant colonies. These findings demonstrate the rich composition and variability of P. clavata venom.
ISSN: 1535-3893

hal-01603415
https://hal.archives-ouvertes.fr/hal-01603415
DOI : 10.1021/acs.jproteome.6b00948
PRODINRA : 406775
PUBMED : 28118015

Éditeur(s) : HAL CCSD
Résumé : 38 pages
Rapport
The Chicxulub impact crater, México, is unique. It is the only known terrestrial impact structure that has been directly linked to a mass extinction event and the only terrestrial impact with a global ejecta layer. Of the three largest impact structures on Earth, Chicxulub is the best preserved. Chicxulub is also the only known terrestrial impact structure with an intact, unequivocal topographic peak ring. Chicxulub’s role in the Cretaceous/Paleogene (K-Pg) mass extinction and its exceptional state of preservation make it an important natural laboratory for the study of both large impact crater formation on Earth and other planets and the effects of large impacts on the Earth’s environment and ecology. Our understanding of the impact process is far from complete, and despite more than 30 years of intense debate, we are still striving to answer the question as to why this impact was so catastrophic.During International Ocean Discovery Program (IODP) Expedition 364, Paleogene sediments and lithologies that make up the Chicxulub peak ring were cored to investigate (1) the nature and formational mechanism of peak rings, (2) how rocks are weakened during large impacts, (3) the nature and extent of post-impact hydrothermal circulation, (4) the deep biosphere and habitability of the peak ring, and (5) the recovery of life in a sterile zone. Other key targets included sampling the transition through a rare midlatitude section that might include Eocene and Paleocene hyperthermals and/or the Paleocene/Eocene Thermal Maximum (PETM); the composition and character of the impact breccias, melt rocks, and peak-ring rocks; the sedimentology and stratigraphy of the Paleocene–Eocene Chicxulub impact basin infill; the chronology of the peak-ring rocks; and any observations from the core that may help us constrain the volume of dust and climatically active gases released into the stratosphere by this impact. Petrophysical property measurements on the core and wireline logs acquired during Expedition 364 will be used to calibrate geophysical models, including seismic reflection and potential field data, and the integration of all the data will calibrate impact crater models for crater formation and environmental effects. The proposed drilling directly contributes to IODP Science Plan goals:Climate and Ocean Change: How resilient is the ocean to chemical perturbations? The Chicxulub impact represents an external forcing event that caused a 75% level mass extinction. The impact basin may also record key hyperthermals within the Paleogene.Biosphere Frontiers: What are the origin, composition, and global significance of subseafloor communities? What are the limits of life in the subseafloor? How sensitive are ecosystems and biodiversity to environmental change? Impact craters can create habitats for subsurface life, and Chicxulub may provide information on potential habitats for life, including extremophiles, on the early Earth and other planetary bodies. Paleontological and geochemical studies at ground zero will document how large impacts affect ecosystems and effects on biodiversity.Earth Connections/Earth in Motion: What are the composition, structure and dynamics of Earth’s upper mantle? What mechanisms control the occurrence of destructive earthquakes, landslides, and tsunami? Mantle uplift in response to impacts provides insight into dynamics that differ between Earth and other rocky planets. Impacts generate earthquakes, landslides, and tsunami, and scales that generally exceed plate tectonic processes yield insight into effects, the geologic record, and potential hazards.IODP Expedition 364 was a Mission Specific Platform expedition to obtain subseabed samples and downhole logging measurements from the sedimentary cover sequence and peak ring of the Chicxulub impact crater. A single borehole was drilled into the Chicxulub impact crater on the Yucatán continental shelf, recovering core from 505.7 to 1334.73 m below seafloor with ~99% core recovery and acquiring downhole logs for the entire depth.
International Ocean Discovery Program

hal-01639520
https://hal.archives-ouvertes.fr/hal-01639520
DOI : 10.14379/iodp.pr.364.2017

Éditeur(s) : Ofioliti
Résumé : Serpentinisation of mantle rocks, leading to natural venting of hydrogen and methane, has been reported to occur at the global scale, wherever fluids percolate in ultramafic formations. Here we compare gas composition from two on-land, low-temperature, and hyper-alkaline springs hosted on ultramafic rocks in the ophiolite massifs of the Sultanate of Oman and the Ligurian Alps (Voltri Group, Genoa region, Northern Italy). These two settings exhibit similar chemical and mineralogical features but show diverse styles of gas venting. Commonly to all hyper-alkaline springs, gases are characterised by relatively high N-2, very low O-2 and CO2 concentrations, and a strong enrichment in H-2 and CH4. The comparison between Oman and Liguria highlights a high variability of the H-2/CH4 ratios whereby the gas phase of the Oman Ophiolite is enriched in H-2 whereas being CH4 enriched in the Voltri Ophiolite. These results combined with literature data define three groups that may reflect different stages of serpentinisation producing fluids from hydrogen-dominated to methane-dominated. The origin of these distinct groups might lie in the difference of the mineralogical composition of the rocks within which the fluids circulate, on the degree of alteration of the rocks and finally on the geological/metamorphic history of the ophiolite.
Ofioliti (0391-2612) (Ofioliti), 2013-12 , Vol. 38 , N. 2 , P. 143-156

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00175/28634/27059.pdf
DOI:10.4454/ofioliti.v38i2.423
http://archimer.ifremer.fr/doc/00175/28634/

Éditeur(s) : Université de Pau et des Pays de l'Adour
Résumé : In a context of decline of European eel (Anguilla anguilla L.) and search for biological markers of habitat use and quality, a multidisciplinary approach was engaged on the Adour estuary and its associated wetlands. Two axes were developed. The first axe aimed at highlighting the successive presence of the species in different ecosystems based on the otolith elemental composition. The second aimed at the evaluation of the chemical pressure underwent by eels based on the contaminant bioconcentration in soft tissues and the early molecular response to the chemical stress. With a view to the analyses of otolith elemental composition taking into account the 3D structure, the low elemental concentration in the matrix and keeping the finest spatial resolution, four micro sampling strategies and multi elemental analyses using femtosecond laser ablation ICP-MS were tested (crater, 1D scan, 2D scan, flash ablation). The strategy showing the best compromise according to the objectives (continuous recording, multi elemental approach) was applied on otolith of yellow eels from the Adour. The simultaneous use of Sr and Ba profiles, after validation, represents a new tool, easy, fast and reliable for the reconstruction of freshwater and brackish ecosystems use by eel avoiding misinterpretation due to vaterite inclusions. Three major behaviors were highlighted on the Adour: a residency in brackish water, a residency in freshwater and nomad behavior. The last one is illustrated by a shift to brackish water after three to four years spent in freshwater. Simultaneously, the study of inorganic and organic contamination of eel soft tissues showed that sampled wetlands are moderately contaminated. These results were confirmed by the first estimation, in wild conditions, of the early response to the chemical stress using the hepatic expression of CYP1A1 gene measured by real time RT-PCR. Conversely, in the downstream part of the Adour estuary, Hg loads in eels, especially methyl mercury, and PCBs analyses indicate values that need further investigations considering the European norms of consumption. The comparison of the different markers used (heavy metal and organochlorinated compounds contamination of soft tissues, condition index) support a lower quality of the estuary despite higher eel growth rate on this site. This study supports the use of numerous markers in integrated studies in order to understand and specify the relationships between eels and their continental growth zones.
Dans un contexte de déclin de l'anguille européenne (Anguilla anguilla L.) et de recherche de marqueurs biologiques retraçant la fréquentation des divers habitats et renseignant sur la qualité de ceux-ci, une approche pluridisciplinaire a été mise en place sur l'estuaire de l'Adour et ses zones humides. Deux axes ont été privilégiés. Le premier cherchait à visualiser la présence successive de l'espèce dans différents écosystèmes en se basant sur la composition élémentaire des otolithes. Le deuxième avait pour but d'évaluer la pression chimique inorganique et organique subie par l'anguille dans les zones d'études en s'appuyant sur la bioconcentration des contaminants dans les tissus mous et la réponse moléculaire précoce au stress chimique. En vue des analyses de la composition élémentaire des otolithes et pour répondre au mieux à la structure en trois dimensions, à la faible concentration des éléments dans la matrice tout en conservant une résolution spatiale la plus fine possible, quatre stratégies de micro-échantillonnage et d'analyses multiélémentaires par ablation laser femtoseconde ICP-MS ont été testées (cratère, scan 1D, scan 2D, ablation flash). La méthodologie présentant le meilleur compromis par rapport aux objectifs fixés (enregistrement continu, approche multiélémentaire) a ensuite été appliquée sur les otolithes d'anguilles jaunes du Bas-Adour. L'utilisation simultanée des profils continus de Sr et de Ba, après validation, constitue un outil facile d'utilisation, rapide et fiable pour reconstruire les historiques de fréquentation des différents écosystèmes estuariens et dulçaquicoles par l'anguille tout en s'affranchissant des problèmes potentiels liés aux inclusions de vatérite, un polymorphe du carbonate de calcium. Trois grands types de comportement ont pu être mis en évidence sur l'Adour : résidence en eau saumâtre, résidence en eau douce et nomadisme. Ce dernier est plus particulièrement illustré par un mouvement marqué vers l'eau saumâtre pour des individus ayant passé de trois à quatre ans dans l'eau douce. Parallèlement, l'étude de la contamination organique et inorganique des tissus mous de l'anguille a permis de déduire à la faible contamination des zones humides échantillonnées. La première estimation en condition naturelle de la réponse précoce au stress chimique par évaluation de l'expression hépatique du gène CYP1A1 par RT-PCR en temps réel confirme ces résultats. En revanche, dans la partie estuarienne aval de l'Adour, les niveaux en Hg, présent en majorité sous sa forme méthylée dans les anguilles, et l'analyse des PCBs indiquent des valeurs qui suscitent un examen plus approfondi au regard des normes européennes en vigueur. La confrontation des différents descripteurs (contamination des tissus mous par les métaux lourds et organochlorés, indice de condition) utilisés conforte la qualité moindre de la zone estuarienne malgré des performances de croissance de l'anguille favorisées sur ces sites. Ainsi, cette étude supporte l'intérêt de la mise en oeuvre de descripteurs multiples utilisés (niveaux de métaux lourds et organochlorés dans les tissus mous, réponse moléculaire au stress chimique, microchimie de l'otolithe, indice de condition, taux de croissance) dans des approches intégrées pour comprendre et préciser les relations existantes entre l'anguille et ses zones de croissance continentales.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2009/these-7381.pdf
http://archimer.ifremer.fr/doc/00000/7381/