CNRS Matter and Environment Multidisciplinary Research

Noumea, France

CNRS Matter and Environment Multidisciplinary Research

Noumea, France
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Zamora-Munt J.,Polytechnic University of Catalonia | Zamora-Munt J.,Campus University Illes Balears | Garbin B.,CNRS Non-Linear Institute of Nice | Barland S.,CNRS Non-Linear Institute of Nice | And 5 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Rogue waves are devastating extreme events that occur in many natural systems, and a lot of work has focused on predicting and understanding their origin. In optically injected semiconductor lasers rogue waves are rare ultra-high pulses that sporadically occur in the laser chaotic output intensity. Here we show that these optical rogue waves can be predicted with long anticipation time, that they are generated by a crisis-like process, and that noise can be employed to either enhance or suppress their probability of occurrence. By providing a good understanding of the mechanisms triggering and controlling the rogue waves, our results can contribute to improve the performance of injected lasers and can also enable new experiments to test if these mechanisms are also involved in other natural systems where rogue waves have been observed. © 2013 American Physical Society.

Choulet F.,CNRS Earth Sciences Institute of Orléans | Faure M.,CNRS Earth Sciences Institute of Orléans | Cluzel D.,CNRS Matter and Environment Multidisciplinary Research | Chen Y.,CNRS Earth Sciences Institute of Orléans | And 2 more authors.
Gondwana Research | Year: 2012

Along active margins, tectonic features that develop in response to plate convergence are strongly controlled by subduction zone geometry. In West Junggar, a segment of the giant Palaeozoic collage of Central Asia, the West Karamay Unit represents a Carboniferous accretionary complex composed of fore-arc sedimentary rocks and ophiolitic mélanges. The occurrence of quasi-synchronous upright folds and folds with vertical axes suggests that transpression plays a significant role in the tectonic evolution of the West Junggar. Latest Carboniferous (ca. 300. Ma) alkaline plutons postdate this early phase of folding, which was synchronous with accretion of the Carboniferous complex. The Permian Dalabute sinistral fault overprints Carboniferous ductile shearing and split the West Karamay Unit ca. 100. km apart. Oblique convergence may have been provoked by the buckling of the Kazakh orocline and relative rotations between its segments. Depending upon the shape of the convergence zone, either upright folds and fold with vertical axes, or alternatively, strike-slip brittle faults developed in response to strain partitioning. Sinistral brittle faulting may account for the lateral imbrication of units in the West Junggar accretionary complex. © 2011 International Association for Gondwana Research.

Marchand C.,IRD Montpellier | Allenbach M.,CNRS Matter and Environment Multidisciplinary Research | Lallier-Verges E.,CNRS Earth Sciences Institute of Orléans
Geoderma | Year: 2011

Mangroves of New Caledonia act as a buffer between a lagoon of more than 20,000km2 and the Island, which suffers intense processes of erosion resulting from urbanization and natural resources exploitation. This preliminary study aims at determining how heavy metals are distributed in mangrove sediments and pore-waters in relationship with their organic content. To reach our goal, a series of 50-cm deep cores were collected in the mangrove of Conception Bay. The various coring sites are representative of live forests (Avicennia marina, Rhizophora stylosa), dead forest, and intertidal unvegetated area. The ranges of concentrations in sediments were the following (μmolg-1): Cu (0.08 to 0.51), Co (0.01 to 0.38), Ni (0.03 to 3.55), Cr (0.36 to 3.11), Zn (0.68 to 2.36), Mn (1.13 to 5.0) and Fe (22.64 to 721.69). Heavy metals distribution within sediments and pore-water appear to result from diagenetic processes linked to OM decomposition. Beneath the dead Avicennia forest and in the unvegetated sediments, the higher the organic content, the higher the metal concentration in the solid phase. Beneath living mangrove stands, despite a higher organic content, as well as higher sulphur content, heavy metals concentrations were not higher than those measured in the other sampling sites. Beneath these forests, redox conditions were mainly controlled by the length of waterlogging and the activity of root system. We suggest that, because of the specificity of the Avicennia root system and its position in the intertidal zone, heavy metals are more bioavailable and potentially more mobile than beneath Rhizophora stand. © 2010 Elsevier B.V.

Marchand C.,IRD Montpellier | Lallier-Verges E.,CNRS Earth Sciences Institute of Orléans | Allenbach M.,CNRS Matter and Environment Multidisciplinary Research
Journal of Soils and Sediments | Year: 2011

Purpose: The mangroves of New Caledonia, in the south Pacific, act as a buffer between a lagoon of more than 20,000 km2 and the island, which is characterized by ultramafic rocks and lateritic soils that are exploited for their richness in heavy metals. We will provide a better understanding of the redox conditions, and of heavy metal distributions in mangroves receiving shrimp farm effluents. Materials and methods: Samples were collected from four areas defined in terms of vegetation composition: a salt flat, an Avicennia marina forest, in which effluents are released; a Rhizophora stylosa forest, and a dead Rhizophora forest. They were collected during times of maximum effluent release. Some measurements on pore water were also done during a period without effluent. Cores (70 cm deep) were collected at low tide with an Eijkelkamp gouge auger, and pore waters were extracted using soil moisture samplers. Physico-chemical parameters (pH, Eh, salinity) were measured by directly inserting the probes into cores. Total nitrogen and total sulfur were also determined. The sedimentary organic content was studied using a Rock-Eval 6 pyrolysis. Finally, heavy metal concentrations were determined, both in the solid and the dissolved phases, using an HR-ICP-AES. Results and discussion: The distribution of heavy metals in the core collected in the salt flat is mainly controlled, on the one hand, by the sedimentary organic content, and on the other hand, by the elevation of the area, which induced dessication. The release of effluent within the Avicennia stand induced anoxic conditions on the whole depth profile, while these conditions are suboxic without effluent release, probably inducing different metal speciation. The Rhizophora forests, located at 100 m from the release point, do not seem to show any impact from the effluent phase, as indicated by the redox profiles which show similar results with and without effluent release. Beneath these two stands, conditions are mainly anoxic and sulfidic, as a result of the decomposition of high organic matter content. Conclusions: The release of effluent within the Avicennia stand, by modifying the length of waterlogging, clearly modifies the redox conditions. We suggest that the differences in redox conditions between the two periods modify the carrier phase of heavy metals, being mainly associated with sulfides during effluent release. Metals are thus less mobile, and consequently when mangrove receives effluents, they act as a sink for trace metals. © 2011 Springer-Verlag.

Leopold A.,CNRS Matter and Environment Multidisciplinary Research | Leopold A.,IRD Montpellier | Marchand C.,IRD Montpellier | Deborde J.,IRD Montpellier | And 2 more authors.
Geoderma | Year: 2013

Mangroves are the major ecosystems of tropical and subtropical coastlines. They are considered as a sink for atmospheric CO2 because they are characterized both by high net primary production, and by low rates of organic matter decomposition. However, a recent reassessment of the global mangrove budget suggests that organic carbon sinks have been underestimated, notably CO2 efflux from sediments and creek waters, and tidal export of dissolved inorganic carbon. Our objective was to understand the influence of mangrove zonation on the magnitude of CO2 fluxes at the sediment-air interface. Transparent and opaque dynamic closed chamber systems, coupled with an infra-red gas analyzer were used to measure CO2 fluxes. In addition, the physico-chemical properties (salinity, redox potential) of pore waters were determined, as well as the carbon content and the origin of surface sediments (Chlorophyll-a and δ13C). Depending on the type of measurement (in the dark with or without biofilm, in the light with biofilm) and mangrove stand (saltflat, Avicennia sp., or Rhizophora spp.), mean surface sediment CO2 fluxes ranged between 40±56 and 199±95mmol.m-2.d-1. We suggest that these differences mainly result both from the organic content and the redox conditions of the sediments, which are influenced by the physiological activities of the root system, and by the position and the elevation of the stand in the intertidal zone. In addition, the quality and abundance of biofilm, which also vary with the mangrove stand, also appear to strongly affect sediment CO2 fluxes as a result of chemical (metabolism) and also physical (barrier) processes. © 2013 Elsevier B.V.

Ulrich M.,CNRS Matter and Environment Multidisciplinary Research | Ulrich M.,Joseph Fourier University | Picard C.,University of Franche Comte | Guillot S.,Joseph Fourier University | And 3 more authors.
Lithos | Year: 2010

The origin of the New Caledonia ophiolite (South West Pacific), one of the largest in the world, is controversial. This nappe of ultramafic rocks (300 km long, 50 km wide and 2 km thick) is thrust upon a smaller nappe (Poya terrane) composed of basalts from mid-ocean ridges (MORB), back arc basins (BABB) and ocean islands (OIB). This nappe was tectonically accreted from the subducting plate prior and during the obduction of the ultramafic nappe. The bulk of the ophiolite is composed of highly depleted harzburgites (± dunites) with characteristic U-shaped bulk-rock rare-earth element (REE) patterns that are attributed to their formation in a forearc environment. In contrast, the origin of spoon-shaped REE patterns of lherzolites in the northernmost klippes was unclear. Our new major element and REE data on whole rocks, spinel and clinopyroxene establish the abyssal affinity of these lherzolites. Significant LREE enrichment in the lherzolites is best explained by partial melting in a spreading ridge, followed by near in-situ refertilization from deeper mantle melts. Using equilibrium melting equations, we show that melts extracted from these lherzolites are compositionally similar to the MORB of the Poya terrane. This is used to infer that the ultramafic nappe and the mafic Poya terrane represent oceanic lithosphere of a single marginal basin that formed during the late Cretaceous. In contrast, our spinel data highlights the strong forearc affinities of the most depleted harzburgites whose compositions are best modeled by hydrous melting of a source that had previously experienced depletion in a spreading ridge. The New Caledonian boninites probably formed during this second stage of partial melting. The two melting events in the New Caledonia ophiolite record the rapid transition from oceanic accretion to convergence in the South Loyalty Basin during the Late Paleocene, with initiation of a new subduction zone at or near the ridge axis. © 2009 Elsevier B.V.

Butt C.R.M.,CSIRO | Cluzel D.,CNRS Matter and Environment Multidisciplinary Research
Elements | Year: 2013

Nickel laterite ores account for over 60% of global nickel supply. They are the product of intensive deep weathering of serpentinites under humid tropical conditions. Nickel is concentrated to over 1.0 wt% and is hosted in a variety of secondary oxides, hydrous Mg silicates and smectites. The formation, mineralogy and grade of the deposits are controlled by the interplay of lithology, tectonics, climate and geomorphology. Most deposits have a multi-phase development, evolving as their climatic and/or topographic environment change. The richest deposits (>3 wt% Ni) formed where oxide-rich regoliths were uplifted and Ni leached downwards to concentrate in neo-formed silicates in the saprolite.

Maurizot P.,Bureau de Recherches Géologiques et Minières | Cluzel D.,CNRS Matter and Environment Multidisciplinary Research
New Zealand Journal of Geology and Geophysics | Year: 2014

The Bourail Anticline in central New Caledonia has been a target for petroleum exploration since the 1950s. It is a broad structure in which a 4-km-thick pile of Eocene turbidite (Eocene Bourail Flysch) is exposed. The Cadart-1 exploration borehole (1930 m deep) was drilled on the anticlinal axis in 1999, intersecting the Paleogene and underlying Late Cretaceous sedimentary rocks. A sedimentological, stratigraphic and provenance analysis is presented. Volcanic debris appears progressively in the upper part of the flysch, becoming predominant upwards along with the intercalation of upward-thickening and-coarsening debris flow breccia. Clinopyroxene and basalt clasts in the upper part of the flysch were derived from enriched tholeiite (E-MORB) of the Poya Terrane. The Eocene paleogeography can be interpreted as a foreland basin system with a depocentre close to the area of Bourail Anticline, an accretionary complex to the northwest and a forebulge to the southeast. This system migrated southeastward through New Caledonia from the Paleocene to the Late Eocene. © 2014 The Royal Society of New Zealand.

Quiniou T.,CNRS Matter and Environment Multidisciplinary Research | Laperche V.,Bureau de Recherches Géologiques et Minières
Geochemistry: Exploration, Environment, Analysis | Year: 2014

The aim of this work was to determine how in-situportable XRF (pXRF) analysis of ores (in this study, nickel and iron) may be consistent with data obtained from well-prepared samples analysed by conventional XRF methods, and to investigate potential sources of error in field measurements due to different chemical composition, moisture content and particle size. For this study, 201 samples of saprolite and laterite, sieved at 125 μm, were selected for their Ni and Fe contents (from 0.119 to 5.225 % Ni and from 4.7 to 37.2 % Fe for saprolite samples and from 0.38 to 2.94 % Ni and from 21.5 to 55.55 % Fe for laterite samples), compressed to make powder pellets and used to calibrate the pXRF. It is shown that for these two elements, pXRF can correlate extremely well (r2 > 0.98, relative standard error <7 %) with conventional laboratory results when samples are suitably prepared (dried, pulverized and pelletized). Laboratory analysis of a few artificially wetted samples shows that both Ni and Fe estimated concentrations are directly proportional to moisture content. In the field, two experiments were conducted, one on an air-dried drill-core and the second directly on the pit face. The results indicate that because of sample heterogeneity, Ni and Fe contents are better estimated in the laterite layer than in the saprolite layer. Despite the many challenges associated with field conditions, pXRF can provide useful benefits for a number of applications in the mining sector. © 2014 AAG/The Geological Society of London.

Cluzel D.,CNRS Matter and Environment Multidisciplinary Research | Cluzel D.,CNRS Earth Sciences Institute of Orléans | Adams C.J.,Institute of Geological & Nuclear Sciences | Maurizot P.,Bureau de Recherches Géologiques et Minières | Meffre S.,University of Tasmania
Tectonophysics | Year: 2011

The Late Cretaceous clastic coastal sediments of New Caledonia are contemporaneous with the latest stages of the eastern Australian marginal rifting. As such, they record the erosion of basement terranes located on uplifted and tilted blocks and a contemporaneous volcanic activity. Detrital zircon populations contain two major components, the younger of which is Early Cretaceous, and the older Early Paleozoic and Precambrian. Following recent advances in the knowledge of detrital zircon content of basement terranes, and at variance with previous interpretations, that hypothesised a possible direct Australian provenance for Precambrian zircons, the detrital zircon record of these syn-rift sediments allows a local recycled provenance to be established. In consequence, this new evidence confirms that New Caledonia was already isolated from Australia as early as Coniacian time (ca. 89-85. Ma) a fact consistent with the development of faunal and floral endemism at that period. The prominent abundance of Early Cretaceous detrital zircons also establishes the importance of a previously unrecorded Early Cretaceous magmatism in the area. © 2011 Elsevier B.V.

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