Editorial     

Phil Potts  Mireille Polv 《Geostandards and Geoanalytical Research》2000,24(1):5-5

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Rotation of the Semail ophiolite (Oman): Additional Paleomagnetic data from the volcanic sequence     

Perrin  Mireille  Plenier  Guillaume  Dautria  Jean-Marie  Cocuaud  Emmanuel  Prévot  Michel 《Marine Geophysical Researches》2000,21(3-4):181-194

Thirty-two flows (247 cores) were sampled in the V1 (Geotimes) and V2 (Lasail) volcanic units of the Semail ophiolite, Oman (Aswad, Fizh, Hilti, Sarami, Wuqbah, and Tayin massifs). Paleomagnetic analysis of the samples was complicated by a large overlap of the two components of magnetization carried by the rocks: a crystalline remanent magnetization (CRM) acquired in the present day field, probably during weathering, and an older CRM probably produced by oxidation of the original titanomagnetites during hydrothermal event(s). If the magnetization carried by the V1 samples was acquired during the hydrothermal event related to the emplacement of these lava, e.g., during and/or shortly after cooling, the tectonic unity of the northern domain has to be questioned and a differential rotation considered between the Aswad and Hilti-Sarami massifs but, by the time of emplacement of the V2 series, this northern area seems to behave as one large unit. As only one set of data is available for the southern Tayin-Sumail massif, it is premature but a possible relative rotation on the order of 90° can be suspected between the Hilti-Sarami and Tayin-Sumail massifs, rotation which would have occurred after emplacement of the V2 series.  相似文献   

Lipid biomarkers and bacterial lipase activities as indicators of organic matter and bacterial dynamics in contrasted regimes at the DYFAMED site, NW Mediterranean     

Nicolas Bourguet  Madeleine Goutx  Jean-Franois Ghiglione  Mireille Pujo-Pay  Genevive Mvel  Andr Momzikoff  Laure Mousseau  Catherine Guigue  Nicole Garcia  Patrick Raimbault  Romain Pete  Louise Oriol  Dominique Lefvre 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1454-1469

This study investigated the relationships between dissolved organic matter (DOM) composition and bacterial dynamics on short time scale during spring mesotrophic (March 2003) and summer oligotrophic (June 2003) regimes, in a 0–500 m depth water column with almost no advection, at the DYFAMED site, NW Mediterranean. DOM was characterized by analyzing dissolved organic carbon (DOC), colored dissolved organic matter (CDOM) and lipid class biotracers. Bacterial dynamic was assessed through the measurement of in situ bacterial lipase activity, abundance, production and bacterial community structure. We made the assumption that by coupling the ambient concentration of hydrolysable acyl-lipids with the measurement of their in situ bacterial hydrolysis rates (i.e. the free fatty acids release rate) would provide new insights about bacterial response to change in environmental conditions. The seasonal transition from spring to summer was accompanied by a significant accumulation of excess DOC (+5 μM) (ANOVA, p<0.05, n=8) in the upper layer (0–50 m). In this layer, the free fatty acids release rate to the bacterial carbon demand (BCD) ratio increased from 0.6±0.3 in March to 1.3±1.0 in June (ANOVA, p<0.05, n=8) showing that more uncoupling between the hydrolysis of the acyl-lipids and the BCD occurred during the evolution of the season, and that free fatty acids contributed to the excess DOC. The increase of lipolysis index and CDOM absorbance (from 0.24±0.17 to 0.39±0.13 and from 0.076±0.039 to 0.144±0.068; ANOVA, p<0.05, n=8, respectively), and the higher contribution of triglycerides, wax esters and phospholipids (from <5% to 12–31%) to the lipid pool reflected the change in the DOM quality. In addition to a strong increase of bacterial lipase activity per cell (51.4±29.4–418.3±290.6 Ag C cell⁻¹ h⁻¹), a significant percentage of ribotypes (39%) was different between spring and summer in the deep chlorophyll maximum (DCM) layer in particular, suggesting a shift in the bacterial community structure due to the different trophic conditions. At both seasons, in the chlorophyll layers, diel variations of DOM and bacterial parameters reflected a better bioavailability and/or DOM utilization by bacteria at night (the ratio of free fatty acids release rate to bacterial carbon demand decreased), most likely related to the zooplankton trophic behaviour. In mesotrophic conditions, such day/night pattern was driving changes in the bacterial community structure. In more oligotrophic period, diel variations in bacterial community structure were depth dependent in relation to the strong summer stratification.  相似文献   

Petrography and chemistry of SiO2 filling phases in the amethyst geodes from the Serra Geral Formation deposit,Rio Grande do Sul,Brazil     

Adriane Commin-Fischer  Gilles Berger  Mireille Polvé  Michel Dubois  Paul Sardini  Daniel Beaufort  Milton Formoso 《Journal of South American Earth Sciences》2010,29(3):751-760

The filling process of amethyst-bearing geodes from Serra Geral Formation basalts, Brazil, is investigated by different methods performed on the SiO₂ filling phases. Image analysis of quartz–amethyst deposits suggests a single growing mechanism ruled by geometric selection of randomly oriented crystals. Microthermometry of fluid inclusions reveals formation temperature lower than 100 °C, probably lower than 50 °C, and fluid salinity as high as 3 mass% NaCl eq. Composition in REE and trace-elements measured by ICP-MS on acid-digested or laser-ablated samples indicates a common genesis for amethyst, quartz and chalcedony, as well as the absence of significant variations from one geode to another. ⁸⁷Sr/⁸⁶Sr data on chalcedony shows that both the host basalt or the Botucatu sandstone are possible silica sources. These data, combined with thermo-kinetic considerations, permit us to discuss the filling process. We argue in favor of the contribution of a mineralized fluid of hydrothermal origin producing a regional silica source which decreased with time. The observed mineral sequence is related to the depletion of silica in the solution.  相似文献   

Influence of the Danube River inputs on C and N stable isotope ratios of the Romanian coastal waters and sediment (Black Sea)     

Bănaru D  Harmelin-Vivien M  Gomoiu MT  Onciu TM 《Marine pollution bulletin》2007,54(9):1385-1394

The main aim of this study was to estimate the influence of the seasonal variations of the Danube River particulate organic matter (POM) inputs on the Black Sea surface seawater POM and upper layer of sediments along the Romanian coast. Ratios of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotopes allowed differentiating river and marine organic matter sources. Danube River POM presented significantly lower average values of delta(13)C (-27.52+/-0.88 per thousand) and delta(15)N (4.88+/-1.45 per thousand) than seawater POM (delta(13)C=-24.70+/-2.37 per thousand and delta(15)N=6.75+/-1.96 per thousand), whereas surface sediment presented average values similar to seawater POM (delta(13)C=-24.02+/-2.39 per thousand and delta(15)N=7.29+/-2.16 per thousand). Stable isotope values showed that the Danube River influence on marine ecosystems decreased from the North to the South of the Romanian coast. Strong seasonal variations of C and N isotopic signatures were observed in all compartments studied with generally higher values in spring when the river was flooding.  相似文献   

Editorial     

Phil Potts  Mireille Polv 《Geostandards and Geoanalytical Research》1997,21(1):5-5

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Editorial     

Phil Potts  Mireille Polvé  Edward Williams 《Geostandards and Geoanalytical Research》2007,31(4):297-297

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Revisiting the Jurassic geomagnetic reversal recorded in the Lesotho Basalt (Southern Africa)     

Michel Prévot  Neil Roberts  John Thompson  Liliane Faynot  Mireille Perrin  Pierre Camps 《Geophysical Journal International》2003,155(2):367-378

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The Guenie and Gao chondrites from Burkina Faso: Probably a single shower of stones     

Michle BOUROT-DENISE  Urbain WENMENGA  Mireille CHRISTOPHE 《Meteoritics & planetary science》1998,33(Z4):A181-A182

Abstract— Two H4–5 meteorite showers have been reported to have fallen at one month intervals in the Guenie-Gao area, but eyewitness accounts are imprecise. Though subtle mineralogical differences are found between stones with different ²¹Ne content, these differences are insufficient to confirm that two meteorite falls had occurred.  相似文献   

La matrice noire et blanche de la chondrite de Tieschitz (H3)     

Mireille Christophe Michel-Levy 《Earth and Planetary Science Letters》1976,30(1):143-150

Finely divided products, making a black carbonaceous crust, have coated the chondrules in space. After their agglomeration, a white silica and alumina rich deposit has accumulated between them. Crystalline debris that are found outside the chondrules must not be confounded with the black and white products, which are the only constituents of the low-temperature matrix. These debris are broken chondrules but do not necessarily result from shock effects. Many of them are indeed very fragile, because they are very porous: they contain primary cavities (voids in the crystals, druses) and secondary ones because of selective leaching of part of the glass. The chemical elements leached out of the chondrules may have been reconcentrated in the matrix.  相似文献