Éditeur(s) : GFP : Groupe Français des Pesticides
Extrait de : "Protection des cultures et santé environnementale : héritages et conceptions nouvelles" : congrès, le 26 mai 2014. Université des Antilles et de la Guyane
Description : Une méthode d'analyse simple, précise et rapide a été élaborée pour la détermination quantitative des résidus de chlordécone dans des microéchantillons d'eau, de sol et de plantes. La procédure associe un protocole d'échantillonnage simplifiée et une micro-extraction en phase solide (SPME) de 10 minutes, suivie d'une séparation de 40 minutes par chromatographie en phase gazeuse (GC) et une identification par spectrométrie de masse (MS et MS/MS). Les résultats de cette étude montrent que l'utilisation de la SPME associée aux ajouts dosés est une méthode fiable et précise pour la quantification de la chlordécone et ses dérivés dans l'eau, les sols et les plantes. Elle peut être adaptée à d'autres molécules, d'autres matrices et combinée avec d'autres techniques d'échantillonnage et d'extraction en phase solide.
Siècle(s) traité(s) : 21
Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V14249
V14249

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The aim of this study was to establish a new QuEChERS (quick, easy, cheap, effective, rugged and safe) method coupled to gas chromatography-mass spectrometry (GC-MS) detection for the evaluation of the pesticide biodistribution in specific maternal and fetal tissues. This method was validated for the quantification of pesticides such as chlorotriazines (atrazine, simazine and propazine), their chlorinated metabolites (DIA, DEA and DACT). This new QuEChERS method was developed to facilitate extraction from small tissues such as fetal tissues (mean value: 200mg). The limits of detection, quantification, recovery, precision and accuracy were evaluated for different tissues (liver and brain) and blood. LOD and LOQ ranged between 0.34 and 3.27 ng/g and 1.04 to 9.91 ng/g, respectively. Recovery exceeded 80% for all pesticides, except DACT, with an associated RSD<15%. Precision and accuracy satisfied the criteria usually applied in the validation of bioanalytical methods. The results obtained indicate that this technique is suitable for use in studies of the biodistribution of pesticides in fetal tissues and can be used to evaluate the risk of exposure to pesticides during gestation.
ISSN: 0731-7085

hal-01122837
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122837
PUBMED : 25497890
DOI : 10.1016/j.jpba.2014.10.035

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Metasedimentary rocks in the transition zone between the Pernambuco-Alagoas Domain and the Sergipano Belt (southern Borborema Province, NE Brazil) were studied in order to place constraints on the geological evolution of this portion of West Gondwana. High-grade metamorphic conditions are recorded by the garnet-sillimanite assemblage and common anatexis in pelitic paragneisses. Two samples dated by LA-ICP-MS in the north yielded a predominance of early Neoproterozoic detrital zircons, with age peaks between 990 Ma and 827 Ma, with the youngest grain suggesting deposition after 670 Ma. Low Th/U zircons (Th/U < 0.1) in these samples display a significant spread in ages, from 691 to 568 Ma. One sample in the south is dominated by a homogenous population of Paleoproterozoic grains, with a 2200 Ma peak. The southernmost sample also contains Paleoproterozoic zircons but the most abundant population is Neoproterozoic, and characterized by age peaks at c. 670, 647 and 623 Ma. These results show that deposition of sediments in the southern PEAL Domain and in the northern Sergipano Belt occurred in the Late Neoproterozoic. The differing age spectra between samples are correlated with potential source rocks in the study area or in its proximity, reflecting variable input from local sources. The data are interpreted to indicate that during the course of an extensional event at c. 673-647 Ma, Tonian granitic intrusions and synextensional metamorphic rocks were unroofed and eroded to provide zircons for sediments deposited in the north, whereas Paleoproterozoic and synextensional magmatic rocks were the main sources for sediments in the south. Peak metamorphic conditions and contractional deformation are constrained to c. 630-600 Ma.
ISSN: 0895-9811

hal-01468011
https://hal.archives-ouvertes.fr/hal-01468011
DOI : 10.1016/j.jsames.2016.09.010

Éditeur(s) : Gauthier-Villars
Résumé : The analysis of humic compounds by elemental analysis, PY-GC-MS and HPLC techniques permitted determination of the origin of organic inputs, essentially terrestrial, and the effects of environmental conditions in the deposits along a north-south transect through the Rhone delta, from the river mouth to the open sea. In the prodelta the sedimentation of fine particles enriches the sediments in organic matter. The humic compound contents were relatively low in sediments, perhaps due to a rapid burying of organic matter which leads to anoxic conditions. In sediments fulvic acids are more abundant than humic acids. Elemental analysis indicated that fulvic acids were enriched in hydrogen and nitrogen as compared to humic acids. Furthermore, H/C and N/C ratios increased in the fulvic and humic acids towards the open sea, related to a more marine character. Pyrolysis analysis showed some differences between the chemical composition of fulvic acids which correspond to low molecular weights enriched in carbohydrates, and that of humic acids, high molecular weight compounds which are enriched in phenols and aromatic hydrocarbons. The pyrolysis-derived phenols were abundant near the river mouth, decreasing towards the open sea as nitrogen-containing-compounds increased. Near the river mouth, the abundance of phenolic aldehydes demonstrated by HPLC emphasized the existence of fresh organic matter. On the other hand, off the mouth, an increase in phenolic acids could indicate a more degraded organic material. The fractionation of humic acids in various classes of molecular weight species using ultrafiltration (Amicon membranes) and their analysis showed that, close to the river mouth, the large proportion of the high molecular weight humic compounds observed was enriched in phenols and carbohydrates, probably inherited from the terrestrial ligno-cellulosic complex. This process seemed to be superimposed on the increase of molecular weights which is usually observed as the environment becomes purely marine. These humic compounds would derived either from organic matter from terrestrial soils swept along by the river flow, after deposition on its bed or, more probably, from high molecular weight compounds which, associated with the mineral phase, flocculated when reaching the fluvio-marine front. Generally, the low molecular weight fractions were enriched in hydrogen and nitrogen. Near the river mouth, nitrogen-containing compounds were concentrated in the low molecular weight classes which correspond to organic molecules regarded as humic precursors. Off the mouth, they were incorporated into the high molecular weight complexes, certainly of marine origin.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1992 , Vol. 15 , N. 1 , P. 61-74

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00101/21187/18804.pdf
http://archimer.ifremer.fr/doc/00101/21187/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Major and trace element signatures and Sr-Nd-Pb isotope data for muscovite (Ms)-bearing amphibolite blocks and associated muscovite-bearing trondhjemite and quartz-muscovite rocks from the Sierra del Convento melange (eastern Cuba) indicate that Proto-Caribbean oceanic crust underwent wet partial melting processes during Mesozoic subduction and after accretion to the upper plate. Trace element normalized patterns of Ms-bearing amphibolites are enriched in light rare earth elements (LREE) and large-ion lithophile elements (LILE) and evidence variable trace element transfer from the Proto-Caribbean subducting slab to the mantle wedge. Ms-bearing trondhjemites show LREE enrichment and HREE depletion and have geochemical features similar to adakites, including SiO2>56 wt.%, high Na2O contents (5.5-9.0 wt.%) and high Sr/Y (16-644). We consider that the trondhjemites represent primary and natural melts formed by deep partial melting of the subducting slab which did not significantly react with the mantle wedge before intrusion in the subduction channel. The Ms-bearing trondhjemites show different geochemical and petrological signatures compared with the Ms-free tonalites-trondhjemites from Sierra del Convent, that are interpreted as primary slab melts. These differences support the idea that partial melting processes in the Sierra del Convento subduction channel were triggered by the infiltration of fluids derived from three distinct subducted sources: sediments, altered mid-ocean ridge basalts (MORB), and serpentinites. In this scenario, the pegmatitic quartz-muscovite rocks, which are highly enriched in LILE, probably represent the crystallization products of fluids derived by differentiation of the trondhjemitic melts.
ISSN: 0024-4937

hal-00669881
https://hal.archives-ouvertes.fr/hal-00669881
DOI : 10.1016/j.lithos.2011.07.011

Éditeur(s) : Gauthier-Villars
Résumé : Samples of recent sediments and marine organisms from seven coastal lagoons along the Mexican coast of the Gulf of Mexico were analyzed by gas chromatography and GC-MS coupled system to determine the present levels of fossil hydrocarbons. Results show that the highest concentrations of fossil hydrocarbons are present in organisms and sediments located near petrochemical plants and oil refineries, indicating that petroleum hydrocarbons are being released into the coastal lagoons. Stable carbon isotope ratios (12C/13C) of sedimentary organic carbon in sediment and organism samples were also determined. For most of the lagoons, the delta 13C ratios for sediments ranged from -19.0 to -23.9%, anomalous ratios ranging from -26.8 to -29.3% were shown for sediments and organisms (oysters) of two of the studied areas, probably because of the presence of organic carbon from anthropogenic terrestrial sources.
Oceanologica Acta, Special issue (0399-1784) (Gauthier-Villars), 1982

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00246/35713/34222.pdf
http://archimer.ifremer.fr/doc/00246/35713/

Éditeur(s) : HAL CCSD Elsevier
Résumé : LA-ICP-MS and SIMS U–Pb analyses have been performed on detrital zircon grains from four heavy mineral rich metasediments collected at different levels of the Nathorst Land Group (Eleonore Bay Supergroup, Greenland). Zircons from high-grade samples collected in the sillimanite and migmatite zones exhibit modifications to their structure, which are lacking in grains from a low-grade sample (0.3 GPa and 350–400 °C). In the sillimanite zone (0.5 GPa, 650 °C), thin discontinuous rims (<20 μm) plating detrital zircon grains document a metamorphic overgrowth during the Caledonian event dated at 428 ± 25 Ma (2σ). In the migmatite zone (0.4 GPa, 700 °C), zircons underwent severe recrystallisation processes but no new zircon growth. Ilmenite, which constitutes over 50% of the heavy mineral layers, underwent recrystallisation in both high-grade samples and is likely to represent the main source of Zr available for growth of zircon rims in the sillimanite zone. However, in the migmatite zone sample, the metamorphic conditions allowed titanite overgrowth around ilmenite, which acted as a sink for Zr and inhibited new zircon growth. 207Pb/206Pb ages for 152 detrital zircons broadly range between 2800 and 990 Ma. The detrital zircon age signature is characterized by the large predominance of late Paleoproterozoic (1.85–1.60 Ga) grains in all analysed samples and by lesser amounts of Archean (2.7–2.8 Ga) and Mesoproterozoic (1.2–1.0 Ga) zircons. The overall age range indicates that detritus can be sourced from the Labradorian and Makkovikian provinces of northeastern Laurentia. The youngest grain analysed (987 ± 18 Ma) indicates that deposition took place during the Neoproterozoic, in a post-Grenvillian sedimentary environment and was likely coeval with the Mid-Neoproterozoic episode of aborted rifting that affected the eastern margin of Laurentia. The lack of detritus originating from Amazonia or Baltica, placed adjacent to Laurentia during the early stages of Rodinia fragmentation, suggests that these two continental landmasses did not constitute a topographic high during the Neoproterozoic or that the Mid-Neoproterozoic rifting opened toward an open ocean to the north of a combined Laurentia/Baltica, thus resulting in a general south to north direction of transport of the sediments.
ISSN: 0301-9268

hal-00407204
https://hal.archives-ouvertes.fr/hal-00407204
DOI : 10.1016/j.precamres.2007.01.002

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
People are exposed to multiple pollutants, especially indoors, in particular through ingestion of indoor settled dust. In the perspective of a cumulative risk assessment, a multi-residue analytical method based on pressurized liquid extraction (PLE) and gas chromatography/tandem mass spectrometry (GC/MS/MS) was developed for the simultaneous analysis in indoor dust of several classes of semi-volatile organic compounds (SVOCs) of health concern, from trace to highly concentrated compounds, including musk fragrances, organochlorines (OCs), organophosphates (OPs), polycyclic aromatic hydrocarbons (PAHs), polybromodiphenylethers (PBDEs), polychlorobiphenyls (PCBs), phthalates and pyrethroids. The method was validated in terms of limits of quantification (LOQ), and accuracy and precision via spiking experiments on an inert material (Celite(®) 545) and replicate analysis of the standard reference material SRM 2585 supplied by the National Institute of Standards and Technology (NIST). Method LOQs for 200 mg samples of sieved dust were 26 ng g(-1) for PCBs and some OCs, 65 ng g(-1) for musks, OPs, PAHs, PBDEs, pyrethroids, other OCs and some phthalates, 132 ng g(-1) for butylbenzylphthalate (BBP), 197 ng g(-1) for tributylphosphate and 1579 ng g(-1) for other phthalates. Quadratic calibration curves were established for each compound by analyzing at least five calibration solutions and exhibited determination coefficients higher than 0.999. The method was successfully applied to the SRM 2585 and seven real indoor dust samples. The results obtained on SRM 2585 demonstrate both excellent reproducibility and agreement with the indicative, reference or certified values and provide, for the first time, indicative concentrations for chlorpyrifos, diazinon, diisononylphthalate (DiNP) and tetramethrin. The results obtained on real dust samples illustrate the ability of the proposed method to quantify a wide range of SVOCs in a single analysis, making it appropriate for environmental monitoring programs or large-scale studies with a large number of samples.
ISSN: 0021-9673

hal-00994493
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00994493
DOI : 10.1016/j.chroma.2014.02.004
PUBMED : 24598454

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Ibituruna quartz-syenite was emplaced as a sill in the Ribeira-Aracuai Neoproterozoic belt (Southeastern Brazil) during the last stages of the Gondwana supercontinent amalgamation. We have measured the Anisotropy of Magnetic Susceptibility (AMS) in samples from the Ibituruna sill to unravel its magnetic fabric that is regarded as a proxy for its magmatic fabric. A large magnetic anisotropy, dominantly due to magnetite, and a consistent magnetic fabric have been determined over the entire Ibituruna massif. The magmatic foliation and lineation are strikingly parallel to the solid-state mylonitic foliation and lineation measured in the country-rock. Altogether, these observations suggest that the Ibituruna sill was emplaced during the high temperature (similar to 750 degrees C) regional deformation and was deformed before full solidification coherently with its country-rock. Unexpectedly, geochronological data suggest a rather different conclusion. LA-ICP-MS and SHRIMP ages of zircons from the Ibituruna quartz-syenite are in the range 530-535 Ma and LA-ICP-MS ages of zircons and monazites from synkinematic leucocratic veins in the country-rocks suggest a crystallization at similar to 570-580 Ma, i.e., an HT deformation >35My older than the emplacement of the Ibituruna quartz-syenite. Conclusions from the structural and the geochronological studies are therefore conflicting. A possible explanation arises from Ar-40-Ar-39 thermochronology. We have dated amphiboles from the quartz-syenite, and amphiboles and biotites from the country-rock. Together with the ages of monazites and zircons in the country-rock, Ar-40-Ar-39 mineral ages suggest a very low cooling rate: <3 degrees C/My between 570 and similar to 500 Ma and similar to 5 degrees C/My between 500 and 460 Ma. Assuming a protracted regional deformation consistent over tens of My, under such stable thermal conditions the fabric and microstructure of deformed rocks may remain almost unchanged even if they underwent and recorded strain pulses separated by long periods of time. This may be a characteristic of slow cooling "hot orogens" that rocks deformed at significantly different periods during the orogeny, but under roughly unchanged temperature conditions, may display almost indiscernible microstructure and fabric.
ISSN: 0040-1951

hal-00445262
https://hal.archives-ouvertes.fr/hal-00445262
DOI : 10.1016/j.tecto.2009.02.039

Éditeur(s) : HAL CCSD
Résumé : International audience
Tsavorite is exclusively hosted in the Neoproterozoic Metamorphic Mozambique Belt (NMMB). The gemstone mines, widespread between Kalalani (Tanzania) and Mgama Ridge (Kenya), define a continuous corridor over a hundred kilometers in length. The tsavorite is hosted by a metasedimentary sequence defined as the Kurase tsavorite-bearing metasediments (Kurase-TB metasediments) that also hosts rubies. These metasediments underwent amphibolite-facies metamorphism and are surrounded by granulitic gneisses that are also of sedimentary origin (the Kurase high-temperature gneisses). All these rocks lie below the Kasigau Group, a unit dominated by granulite-facies metamagmatic rocks.To constrain the timing of events that led to this peculiar occurrence of tsavorite, we have performed geochronological analyses of thin sections and of separated grains of zircon, monazite, and rutile using LA-ICP-MS and ID-TIMS, as well as 40Ar/39Ar of muscovite and phlogopite from various lithologies. The results show that the different terranes were metamorphosed synchronously between 620–580 Ma but under different P-T strain conditions. The Kurase-HT gneisses and the rocks from the Kasigau Group are highly strained and underwent granulite-facies metamorphism with abundant partial melting and emplacement of felsic melts between 620 and 600 Ma. Textural observations also underlined a late regional water flux controlling the occurrence of V-free muscovite and monazite mineralizations at 585 Ma. The latter event can be related to the activity of the Galana shear zone, in the east. The Kurase-TB metasediments escaped strain and partial melting. They record amphibolite-facies conditions with static heating, since initial sedimentary structures were locally preserved. The age of the tsavorite mineralization was inferred at 600 Ma from metamorphic zircon rims and monazite from the closest host-rocks, sampled in the mines. Hence, tsavorite crystallization occurred statically at the end of the metamorphic event, probably when the temperature and the amount of volatiles were at maximum levels.Conversely, the ruby formed by local metasomatism of felsic dikes and isolated ultramafic bodies. The rubies are older and zircons and monazites from a ruby-bearing felsic dike (plumasite) were dated at 615 Ma. Finally, data from rutile and micas indicate a global cooling below 430 °C of the whole region between 510 and 500 Ma.
The Canadian Mineralogist

hal-01616037
https://hal.archives-ouvertes.fr/hal-01616037
https://hal.archives-ouvertes.fr/hal-01616037/document
https://hal.archives-ouvertes.fr/hal-01616037/file/JEM.pdf
DOI : 10.3749/canmin.1700019

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The natural river water certified reference material SLRS-5 (NRC-CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made using ICP-MS. Because no certified values are assigned by NRC-CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given. Le matériau de référence certifié d'eau de rivière naturelle SLRS-5 (NRC-CNRC) est analysé régulièrement comme contrôle qualité par dix laboratoires français étudiant les éléments majeurs et en trace dans les solutions naturelles. La plupart des mesures sont réalisées par ICP-MS. Le silicium et 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y et Zr) ne sont pas certifiés par NRC-CNRC. Aucun rapport isotopique n'est disponible. Nous proposons, pour ces éléments, des valeurs moyennes et leurs incertitudes associées obtenues par les différents laboratoires participants. Le rapport isotopique de Sr est aussi mesuré.
ISSN: 1639-4488

hal-00906166
https://hal.archives-ouvertes.fr/hal-00906166
DOI : 10.1111/j.1751-908X.2013.00232.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During the treatment process of drinking water, disinfectants (chlorine, ozone, chlorine dioxide) react on water containing organic matter and bromide to produce disinfection by-products at trace levels. Among them, five of the nine existing halo-acetic acids (HAAs) are commonly found in drinking water (monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), monobromoacetic acid (MBAA), dibromoacetic acid (DBAA), and Trichloroacetic acid (TCAA)), including four classified in the 2B IARC group of potential carcinogens (BCAA, DBAA, DCAA, TCAA). With respect to drinking water quality, guidelines are proposed by WHO (2006) and water quality standards are imposed in many countries such as less than 100 μg/L for the sum of the five HAAs by US EPA (1998) and Canadian Health Department (2008). For this purpose, two analytical methods are commonly used, GC/MS with derivatization and LC/MS, UV or conductivity. A new method, based on two-dimensional ion chromatography (IC 2D) with suppressed conductivity is proposed. This method presents the main advantage of offering a quick implementation compared to GC or LC methods: direct injection, slight maintenance, lower cost of investment, by leading to good performances (specificity and sensitivity). The use of two different selectivity columns, and the fractionation on the first dimension canceling interferences, improves the specificity. The sensitivity is enabled by interfacing a preconcentration column between the two different internal diameter columns. The analytical conditions are optimized for the analysis of nine HAAs. The performances of the method are evaluated. The optimized method applied to natural water samples demonstrates its ability to quantify HAAs at trace levels in drinking water.
Microchemical Journal

hal-00877151
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00877151
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00877151/document
DOI : 10.1016/j.microc.2013.07.012

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The active collision zone around Taiwan orogen receives a variety of sedimentary inputs, including terrigenous flux from Taiwan and Chinese rivers, oceanic currents and atmospheric dust. In order to determine the present-day respective contributions of these different sources, we analysed the Pb and Sr isotopic compositions of late Quaternary sediments accumulated offshore east Taiwan. Samples from the Taiwan Coastal Range (andesites, sandstones, conglomerate and Peinan River terraces and suspended loads) have also been analysed to constrain the mean Taiwan isotopic signature. Mixing lines between the different sources of material indicate that the core located in the Okinawa Trough represents a mixture of about 60% of Taiwan, 30% of Chinese Loess and 10% of Yangtze River contributions. The southernmost core, located close to Luzon Are, is influenced by Taiwan (60%) and volcanic material (40%). The Sr and Pb isotopic compositions of samples cored in the Manila Trench and in the Huatung Basin are strongly influenced by the Taiwan signature, while the Ryukyu Trench core samples point to significant but variable contributions of Chinese Loess and Yangtze River. This work also reports Zn isotopic variations in the silicate fraction of these marine core samples. The overall variation in Zn isotopic compositions (expressed as 666 Zn) is greater than 0.3 per mil (parts per thousand) for an analytical precision of +/- 0.05 parts per thousand. The Zn isotopic signal for most of the marine core samples is similar to the literature data measured on sedimentary material, except for the Manila Trench core samples and the older sample from the Huatung Basin: they present values heavier by 0.2-0.3 parts per thousand, close to those obtained on all Taiwan rocks and Peinan River particulates. These results show: 1- the particular characteristics of Taiwan Zn isotopic compositions on a large scale; and: 2- the possible use of Zn isotopes as a tracer of material sources.
ISSN: 0009-2541

hal-00412214
https://hal.archives-ouvertes.fr/hal-00412214
DOI : 10.1016/j.chemgeo.2007.10.024

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
The Kekem shoshonitic gabbro-norite association is part of the high-K calc-alkaline (HKCA) post-collisional magmatism, a major feature of the Pan-African Belt in Cameroon. LA-ICP-MS U-Pb zircon analyses provide an age of 576 ± 4 Ma for the Kekem complex. This age is interpreted as dating the emplacement of the massif during the waning stage of the Pan-African orogeny. The latter is related to dextral movements along the Central Cameroon Shear Zone (CCSZ). The REE patterns display enriched LREE (LaN/YbN = 14.2-23.5) while HREE present a nearly flat profile (DyN/YbN = 1.3-1.7), and the La/Sm and Sm/Yb ratios led to propose that the Kekem gabbro-norites have been derived from the partial melting of a garnet-spinel lherzolite mantle source. The negative Nb-Ta and Ti anomalies and the positive Pb anomalies indicate that this mantle source was modified by contribution of a subduction-related material. The low Ce/Pb (2.6-10.4) and Th/Yb ratios associated to high Ba/La ratios, indicate that source enrichment could be related to slab derived fluids. As a whole, the Kekem geochemical features suggest that primary gabbro-noritic magmas derived from a subduction-modified mantle source (metasomatised lithospheric mantle). Moderately high 86Sr/87Sr initial ratios (0.7068-0.7082), low εNd (−5 to −9) and old Nd TDM model ages (1.6-1.8 Ga) are interpreted to result from contamination of Neoproterozoic mantle by the Paleoproterozoic crust. The ca. 576 Ma movements along the CCSZ are related to a Neoproterozoic metacratonization of the northern margin of the Congo craton during the Pan-African orogeny. This metacratonization led to vertical planar lithospheric delamination along lithospheric transcurrent faults, asthenospheric uprise and partial melting of the Paleoproterozoic lithospheric mantle.
ISSN: 0899-5362

hal-00903665
https://hal.archives-ouvertes.fr/hal-00903665
DOI : 10.1016/j.jafrearsci.2013.03.010

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Terrane accretion and intraplate deformation are both common processes occurring during the assembly of large continental masses. The relative roles of these mechanisms are at the heart of a debate concerning the tectonic evolution of the Borborema Province, northeastern Brazil. In the Central subprovince, four terranes or domains have been proposed. In the Alto Moxotó domain, paragneiss of the Sertânia Complex were considered to record a distinct structural and geochronological evolution compared to those in the adjacent Rio Capibaribe domain, in the East. Here, we report the results of a geological study conducted in the type area of the Sertânia Complex. Kinematic criteria and metamorphic mineral assemblages indicate that the main foliation record top-to-the-W tectonic transport under upper amphibolite facies conditions (650–700 °C). The main foliation was affected by overturned folds and upright to inclined folds; the latter two formed coevally with the development of transcurrent shear zones. Samples of mafic orthogneiss and paragneiss tectonically intercalated in the same outcrop were dated by LA-ICP-MS. The orthogneiss sample yields a crystallization age of 1978 ± 8 Ma. Detrital zircons in the paragneiss sample show a multimodal pattern with a well-defined age peak at c. 700 Ma, showing that the paragneiss is younger than 700 Ma and so the main foliation is also younger than this age. In turn, these findings suggest that the occurrence of exclusively Paleoproterozoic zircons in three other dated samples of paragneiss cannot be used to accurately define the deposition age of the detritus. The structural and geochronological characteristics of the Sertânia Complex are similar to those of the Surubim Complex in the Rio Capibaribe domain. Together with previous results showing that the basement of the Alto Moxotó and Rio Capibaribe domains is also similar, we interpret these sequences as having been deposited on a once contiguous tract of continental crust. An accretionary terrane model is thus not required to account for the tectonic evolution of this portion of the Borborema Province. Instead, a model of intracontinental deformation of a preexistent continent is fully supported by the data and also by the lack of evidence for oceanic subduction.
ISSN: 0301-9268

hal-01622825
https://hal.archives-ouvertes.fr/hal-01622825
DOI : 10.1016/j.precamres.2017.07.006

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
People are exposed to multiple pollutants, especially indoors. In the perspective of a cumulative risk assessment, a multi-residue analytical method was developed to assess the contamination of indoor suspended particulate matter by 55 semi-volatile organic compounds (SVOCs) including musk fragrances, organochlorines (OCs), organophosphates (OPs), polycyclic aromatic hydrocarbons (PAHs), polybromodiphenylethers (PBDEs), polychlorobiphenyls (PCBs), phthalates and pyrethroids. It is based on thermal desorption (TD) coupled with gas chromatography/mass spectrometry (GC/MS). Once the thermal desorption conditions were optimized, the method was validated in terms of quantification limits and accuracy using a standard reference material (SRM 2585). Instrumental quantification limits were 10pg (some OCs, some pyrethroids, musk fragrances, OPs, PAHs, PBDEs and PCBs), 100pg (phthalates and other OCs) and 1000pg (other pyrethroids) corresponding respectively to method quantification limits of 1, 10, and 100pg/m(3) for a sampled air volume of 20m(3). Calibration quadratic curves for ranges of 10-1000, 100-10,000, and 1000-100,000pg, depending on the substance, exhibit determination coefficients above 0.999. Recoveries were between 61 and 96% for chlorinated pesticides, PAHs, PBDEs and PCBs present in the SRM 2585. A test of the method on indoor particulate matter samples (PM(10)) collected on quartz fiber filters in French dwellings demonstrated its ability to quantify SVOCs from a small amount of PM.
ISSN: 0021-9673

hal-00732133
https://hal.archives-ouvertes.fr/hal-00732133
DOI : 10.1016/j.chroma.2012.07.025
PUBMED : 22840824

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The N-S oriented Raghane shear zone (8 degrees 30') delineates the western boundary of the Saharan metacraton and is, with the 4 degrees 50' shear zone, the most important shear zone in the Tuareg shield. It can be followed on 1000 km in the basement from southern Air, Niger to NE Hoggar, Algeria. Large subhorizontal movements have occurred during the Pan-African orogeny and several groups of granitoids intruded during the Neoproterozoic. We report U-Pb zircon datings (laser ICP-MS) showing that three magmatic suites of granitoids emplaced close to the Raghane shear zone at c. 790 Ma, c. 590 and c. 550 Ma. A comprehensive and detailed (158 sites, more than 1000 cores) magnetic fabric study was performed on 8 plutons belonging to the three magmatic suites and distributed on 200 km along the Raghane shear zone. The main minerals in all the target plutons do not show visible preferential magmatic orientation except in narrow shear zones. The AMS study shows that all plutons have a magnetic lineation and foliation compatible with the deformed zones that are zones deformed lately in post-solidus conditions. These structures are related to the nearby mega-shear zones, the Raghane shear zone for most of them. The old c. 793 Ma Touffok granite preserved locally its original structures. The magnetic structures of the c. 593 Ma Ohergehem pluton, intruded in the Aouzegueur terrane, are related to thrust structures generated by the Raghane shear zone while it is not the case of the contemporaneous plutons in the Assode-Issalane terrane whose structures are only related to the subvertical shear zones. Finally, the c. 550 Ma granite group has magnetic structure related to the N-S oriented Raghane shear zone and its associated NNE-SSW structures when close to them, but NW-SE oriented when further. These NW-SE oriented structures appear to be characteristic of the late Neoproterozoic evolution of the Saharan metacraton and are in relation to the convergence with the Murzuq craton. This evolution reflects the rheological contrast existing along the Raghane shear zone marking the western boundary of the Saharan metacraton.
ISSN: 0040-1951

hal-00429354
https://hal.archives-ouvertes.fr/hal-00429354
DOI : 10.1016/j.tecto.2009.04.022

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In many orogens, high-pressure (HP) metamorphic rocks such as eclogite occur as lenses in quartzofeldspathic gneiss that equilibrated at much lower pressures. The pressure–temperature–time (P–T–t) history of eclogite relative to host gneiss provides information about mechanisms and timescales of exhumation of orogenic crust. The Montagne Noire of the southern Massif Central, France, is an eclogite–bearing gneiss (migmatite) dome located at the orogen-foreland transition of the Variscan belt. Results of our study show that it contains the youngest eclogite in the orogen, similar in age to migmatite and granite that crystallized under low-pressure conditions. P–T conditions for an exceptionally unaltered eclogite from the central Montagne Noire were estimated using a pseudosection supplemented by garnet–clinopyroxene and Zr-in-rutile thermometry. Results indicate peak P∼1.4 GPaP∼1.4 GPa and View the MathML sourceT∼725°C for Mg-rich garnet rim (50 mol% pyrope) + omphacite (36 mol% jadeite) + rutile + quartz. U–Pb geochronology (LA-ICP-MS) of 16 zoned zircon grains yielded ∼360 Ma (4 cores) and ∼315 Ma (12 rims and cores). Rare earth element abundances determined by LA-ICP-MS for dated zircon are consistent with crystallization of ∼315 Ma zircon under garnet-stable, plagioclase-unstable conditions that we interpret to indicate high pressure; in contrast, the ∼360 Ma zircon core corresponds to crystallization under lower pressure plagioclase-stable conditions. Based on garnet zoning and inclusion suites, rutile textures and Zr zoning, P–T results, and zircon petrochronology, we interpret the ∼315 Ma date as the age of eclogite-facies metamorphism that only slightly preceded dome formation and crystallization at 315–300 Ma. This age relation indicates that eclogite formation at high pressure and migmatite dome emplacement at low pressure were closely spaced in time. We propose that collapse-driven material transfer from the hot orogen to the cool foreland resulted in thickening of the orogen edge, leading to eclogite facies metamorphism of the deep crust. Soon after, the low-viscosity partially molten crust flowed from the plateau toward the foreland, incorporating and exhuming eclogite. The P–T–t history of the Montagne Noire eclogite shows that some dome material ascended from >40 km depth to shallow crustal levels, likely in a single decompression event, and that migmatite domes are therefore very efficient at exhuming the deep crust.
ISSN: 0012-821X

hal-01243499
https://hal.archives-ouvertes.fr/hal-01243499
DOI : 10.1016/j.epsl.2015.08.026