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Maurizot P.,Bureau de Recherches Geologiques et Minieres | 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.

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.

Marchand C.,IRD Montpellier | Allenbach M.,CNRS Matter and Environment Multidisciplinary Research | Lallier-Verges E.,CNRS Earth Sciences Institute of Orleans
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 Orleans | 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.

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.

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