Concentrations of the elements Ag,Al, Ca,Cd, Cu,Fe, Mg,Mn, Pb and Zn,and the radionuclides ²¹⁰Pb and ²¹⁰Po in the digestive gland of the squid Nototodarus gouldi     

J. David Smith  Lorraine Plues  Mireille Heyraud  Robin D. Cherry 《Marine environmental research》1984,13(1):55-68

Ag, Al, Ca, Cd, Cu, Fe, Mg, Mn, Pb and Zn concentrations and ²¹⁰Po and ²¹⁰Pb activities were measured in 26 specimens of the squid Nototodarus gouldi taken from the waters of Bass Strait in one jigging operation. All the elements show wide ranges in concentrations in specimens apparently subject to the same environmental conditions. Copper concentration was 27-1 200 μg/g, and ²¹⁰Po activity 4·8–24·2 Bq/g. The animal wet weights, the elements Ag, Al, Cd, Fe and Zn, and the radionuclide ²¹⁰Po have coefficients of variation in the range 40–60%; Ca, Mg and Mn show the smallest variability (CV = < 30%), and Cu the greatest (CV = 12%). Significant correlations (p < 0·001) were found between the following pairs of elements: Cd-Zn, Cd-Cu, Zn-Cu, Mg-Mn, Fe-Mn, Ca-Mg and Fe-²¹⁰Po.  相似文献   

Direct Determination of Lead Isotope Ratios by Laser Ablation-Inductively Coupled Plasma-Quadrupole Mass Spectrometry in Lake Sediment Samples   总被引：1，自引：0，他引：1  

Sébastien Aries  Mikael Motelica-Heino  Rémi Freydier  Thierry Grezes  Mireille Polvé 《Geostandards and Geoanalytical Research》2001,25(2-3):387-398

A direct method for the determination of lead isotopic ratios by laser ablation-inductively coupled plasma-quadrupole mass spectrometry (LA-ICP-QMS) is presented. Samples of lake sediments were ground and pressed as pellets before being analysed. Mass bias was corrected by analysing an external calibration sample manufactured with pure silica doped with NIST SRM 981 solution. The efficiency of the mass bias correction was checked by comparing the ICP-MS data with lead isotopic ratios determined by thermal ionisation mass spectrometry (TIMS). The average long term reproducibilities were 0.40%, 0.40%, 0.20% and 0.30% (RSD) respectively for the ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb ratios. The method was applied to the study of lake sediment samples, in order to determine the amount and origin of historical contamination by lead.  相似文献   

Monitoring alluvial sand suspension by eddy correlation     

Michel Lapointe 《地球表面变化过程与地形》1993,18(2):157-175

Eddy correlation techniques are standard tools in micrometeorology and oceanography to measure momentum and contaminant transport across turbulent boundary layers. They can, in theory, be used to estimate the net vertical suspended sediment flux directly over different areas of an alluvial channel boundary, and thus disclose ongoing erosion/deposition patterns. The basic principles and main problems in applying the technique to alluvial suspension are first introduced. Results from a trial application of the method in a large sand bed river are then presented; the focus of the analysis is on the substantial (and surprising) contributions of multi-minute flow fluctuations to suspension work in the study environment. The data were collected in a 10 m deep channel of the Fraser River near Mission, British Columbia, Canada. Turbulent fluctuations of flow components streamwise and normal to the bed, along with the output of an optical suspended sediment sensor, were monitored over 7 h, 1 m above the bed. Flow velocities averaged 0·9 ms^?1 and mean suspended sediment concentrations 500 mgl^?1, at sensor level above 1–5 dm high dunes. Spectral analysis of the records reveals that approximately 30 per cent of the vertical suspended sand mixing across the sensor level (and roughly as much of the momentum exchange) was linked to gradual flow oscillations with periods between 1 and 13·6 min (underlying briefer, turbulent fluctuations). Extended periods of sediment-rich, slightly upward directed but slower mean flow alternated with periods of sediment-poor, slightly downward and faster mean flow; these slow fluctuations involved 10–20 cms^?1 changes in 5 min average flow speed, 2–4· changes in vertical flow angle and 100 mgl^?1 changes in mean sand concentration. To obtain accurate eddy-correlation estimates of the vertical suspension flux in the study conditions, hour-scale flow and turbidity records that include many of these multi-minute cycles appear to be necessary. The spectra of the Fraser River near-bed signals do not conspicuously differ in overall shape (in terms of low-frequency content and location of peak) from turbulent spectra encountered in some atmospheric boundary layers. Nonetheless, the long period fluctuations observed on the Fraser River may not be turbulent; rather they may reflect slowly evolving perturbations in the near-bed streamlines, caused by bedform translation or gradual fluctuation within the large-scale streamwise cells of the secondary flow.  相似文献   

Gold-bearing iron-formation in a granulite terrane of the Canadian Shield: a possible deep-level expression of an Archean gold-mineralizing system     

B. Lapointe  E. H. Chown 《Mineralium Deposita》1993,28(3):191-197

Gold occurs in metamorphosed iron-formation within a migmatized paragneiss terrane in the Eastern Superior Province of the Canadian Shield. The main gold prospect, which is located 100 m from a tonalite pluton, has undergone skarn-like metamorphism that occurred late during the granulite grade metamorphism. Despite its occurrence in a high-grade metamorphic host-rock, the mineralization shares many of the characteristics of lowergrade Archean greenstone belt gold mineralization, such as: (1) enrichment in Au, As, S, Sb, W, U and FeO; (2) a low base-metal/gold ratio; (3) the inclusion of gold in arsenopyrite; (4) the proximity to a felsic pluton; (5) an iron-rich, fractured host-rock; and (6) a similar mineralization time (around 2650 Ma). This gold occurrence occurs near the metamorphic peak and represents a deep level expression of the widespread crustal-scale mineralizing system documented for the late Archean. The main conclusion of this work is that the principal characteristics of Archean gold mineralization are present in the deep crust, and do not come from the leaching of upper-level rock piles, such as greenstone belts.  相似文献   

Variation of seismic coupling with slab detachment and upper plate structure along the western Hellenic subduction zone     

Mireille Laigle  Maria Sachpazi  Alfred Hirn 《Tectonophysics》2004,391(1-4):85

The western Hellenic subduction zone is characterized by a trenchward velocity of the upper plate. In the Ionian islands segment, complete seismic coupling is achieved, as is predicted by standard plate-tectonic models in which there is no slab pull force because the slab has broken off. The moderate local seismic moment rate relates to a shallow downdip limit for the seismogenic interface. This characteristic may be attributed to the ductility of the lower crust of the upper plate, which allows a décollement between the upper crust of the overriding plate and the subducting plate. Farther south, a deeper downdip limit of the seismogenic interface is indicated by thrust-faulting earthquakes, which persist much deeper in western Crete. A correspondingly larger downdip width of this seismogenic zone is consistent with the suggested larger maximum magnitude of earthquakes here. However, since the seismic moment release rate seems to be moderate in the Peloponnese and western Crete, like in in the Ionian islands, this seismically active interface cannot maintain complete seismic coupling across its larger downdip width. A cause may be the lateral addition of overweight to the part of the slab still attached in Crete, by the free fall of its part that has broken off from the surface further north. This increased slab pull reduces the compressive normal stress across the seismogenic interface and thus causes partial seismic coupling in its shallower part. However, the width of this part may provide an additional area contributing to slip in large earthquakes, which may nucleate deeper on stick-slip parts of the interface. Hints at anomalies in structure and seismicity, which need to be resolved, may relate to the present location of the edge of the tear in the slab.  相似文献   

Geology, Geochemistry and U-Pb SHRIMP Age of the Tacloban Ophiolite Complex, Leyte Island (Central Philippines): Implications for the Existence and Extent of the Proto-Philippine Sea Plate     

Leilanie O. Suerte    Graciano P. Yumul  Jr  Rodolfo A. Tamayo  Jr  Carla B. Dimalanta    Mei-Fu Zhou  René C. Maury    Mireille Polvé  Cesar L. Balce 《Resource Geology》2005,55(3):207-216

Abstract. The oceanic basement of the Central Philippines is exposed in ophiolitic massifs the age and origin of which remain debated. The Tacloban Ophiolite Complex (TOC) outcrops as a NW-SE trending massif in the northeastern portion of Leyte Island, Central Philippines. It is unconformably overlain by sedimentary sequences dated to Late Miocene-Pliocene and Pleistocene volcaniclastic deposits on its eastern and western flanks, respectively. Field, petrographic and trace element data suggest a subduction-related origin for this ophiolite. Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb dating of zircons from a gabbro yielded Early Cretaceous magmatic age for the TOC, which is very much older than a previously reported whole rock K-Ar derived Eocene age. The Early Cretaceous age of the TOC limits its possible progenitor to the proto-Philippine Sea Plate. Correlation with other Cretaceous ophiolites in Central Philippines reveals the possible extent of the proto-Philippine Sea Plate remnants now exposed onland.  相似文献   

Petrogenesis of the Eocene and Mio–Pliocene alkaline basaltic magmatism in Meseta Chile Chico, southern Patagonia, Chile: Evidence for the participation of two slab windows     

Felipe Espinoza  Diego Morata  Ewan Pelleter  Ren  C. Maury  Manuel Su  rez  Yves Lagabrielle  Mireille Polv    Herv  Bellon  Joseph Cotten  Rita De la Cruz  Christelle Guivel 《Lithos》2005,82(3-4):315-343

The Meseta Chile Chico (MCC, 46.4°S) is the westernmost exposure of Eocene (lower basaltic sequence, LBS; 55–40 Ma, K–Ar ages) and Mio–Pliocene (upper basaltic sequence, UBS; 16–4 Ma, K–Ar ages) flood basalt volcanism in Patagonia. The MCC is located south of the Lago General Carrera-Buenos Aires (LGCBA), southeast from the present day Chile Triple Junction (CTJ), east of the actual volcanic gap between Southern South Volcanic Zone and Austral Volcanic Zone (SSVZ and AVZ, respectively) and just above the inferred location of the South Chile Ridge segment subducted at 6 Ma (SCR-1). Erupted products consist of mainly ne-normative olivine basalt with minor hy-normative tholeiites basalt, trachybasalt and basanite. MCC lavas are alkaline (42.7–53.1 wt.% SiO₂, 3–8 wt.% Na₂O+K₂O) and relatively primitive (Ni: 133–360 ppm, Cr: 161–193 ppm, Co: 35–72 ppm, 4–16.5 MgO wt.%). They have a marked OIB-like signature, as shown by their isotopic compositions (⁸⁷Sr/⁸⁶Sr_o=0.70311–0.70414 and εNd=+4.7–+5.1) and their incompatible trace elements ratios (Ba/La=10–20, La/Nb=0.46–1.09, Ce/Pb=15.52–27.5, Sr/La<25), reflecting deep mantle origin. UBS-primitive lavas have characteristics similar to those of the Eocene LBS basalts, while UBS-intermediate lavas show geochemical imprints (La/Nb>1, Sr/La>25, low Ce/Pb, Nb/U) compatible with contamination by arc/slab-derived and/or crustal components. We propose that the genesis and extrusion of magmas is related to the opening of two slab windows due to the subduction of two active ridge segments beneath Patagonia during Eocene and Mio–Pliocene.  相似文献   

Plate Motion of India and Interseismic Strain in the Nepal Himalaya from GPS and DORIS Measurements   总被引：3，自引：0，他引：3  

Pierre Bettinelli  Jean-Philippe Avouac  Mireille Flouzat  François Jouanne  Laurent Bollinger  Pascal Willis  Gyani Raja Chitrakar 《Journal of Geodesy》2006,80(8-11):567-589

We analyse geodetically estimated deformation across the Nepal Himalaya in order to determine the geodetic rate of shortening between Southern Tibet and India, previously proposed to range from 12 to 21 mm yr^?1. The dataset includes spirit-levelling data along a road going from the Indian to the Tibetan border across Central Nepal, data from the DORIS station on Everest, which has been analysed since 1993, GPS campaign measurements from surveys carried on between 1995 and 2001, as well as data from continuous GPS stations along a transect at the logitude of Kathmandu operated continuously since 1997. The GPS data were processed in International Terrestrial Reference Frame 2000 (ITRF2000), together with the data from 20 International GNSS Service (IGS) stations and then combined using quasi- observation combination analysis (QOCA). Finally, spatially complementary velocities at stations in Southern Tibet, initially determined in ITRF97, were expressed in ITRF2000. After analysing previous studies by different authors, we determined the pole of rotation of the Indian tectonic plate to be located in ITRF2000 at 51.409±1.560° N and ?10.915±5.556°E, with an angular velocity of 0.483±0.015°. Myr^?1. Internal deformation of India is found to be small, corresponding to less than about 2 mm yr^?1 of baseline change between Southern India and the Himalayan piedmont. Based on an elastic dislocation model of interseismic strain and taking into account the uncertainty on India plate motion, the mean convergence rate across Central and Eastern Nepal is estimated to 19±2.5 mm yr^?1, (at the 67% confidence level). The main himalayan thrust (MHT) fault was found to be locked from the surface to a depth of about 20 km over a width of about 115 km. In these regions, the model parameters are well constrained, thanks to the long and continuous time-series from the permanent GPS as well as DORIS data. Further west, a convergence rate of 13.4±5 mm yr^?1, as well as a fault zone, locked over 150 km, are proposed. The slight discrepancy between the geologically estimated deformation rate of 21±1.5 mm yr^?1 and the 19±2.5 mm yr^?1 geodetic rate in Central and Eastern Nepal, as well as the lower geodetic rate in Western Nepal compared to Eastern Nepal, places bounds on possible temporal variations of the pattern and rate of strain in the period between large earthquakes in this region.  相似文献   

Isolation and characterization of Aeromonas species from an eutrophic tropical estuary     

Marcel KA  Antoinette AA  Mireille D 《Marine pollution bulletin》2002,44(12):1341-1344

Isolation and characterization of Aeromonas species were undertaken in the Ebrié lagoon (Abidjan, Côte d’Ivoire) over a one year period. Overall 63% of 501 water samples were identified as positive for Aeromonas spp. A. sobria, A. hydrophila and A. caviae represent respectively 49.20%, 20.63% and 30.15% of the positive samples. Thirty nine of the positive samples were recovered from surface water samples; while 24 bottom water samples were positive for Aeromonas. Aeromonas species are most frequently (82.53) present in the Ebrié lagoon urban area during the rainy and flood seasons when the salinity is low and below 10‰. A lower isolation frequency is noticed during the dry season when water salinity is over 10‰. Finally, a higher isolation frequency occurred in samples with highest counts of Escherichia coli.  相似文献   

Mobilization and Co-Transport of Pyrene in the Presence of Pseudomonas aeruginosa UG2 Biosurfactants in Sandy Soil Columns     

Pierre Lafrance  Mireille Lapointe 《Ground Water Monitoring & Remediation》1998,18(4):139-147

Washing technologies are currently applied for the remediation of contaminated soils. The efficiency of biosurfactants produced by Pseudomonas aeruginosa strains to mobilize some hydrocarbons sorbed on soils has already been demonstrated. However, few studies have been made to define optimal procedures for the injection of these rhamnolipids in soil. This study examines (1) the efficiency of the biosurfactants produced by P. aeruginosa UG2 to mobilize pyrene from a contaminated sandy loam as compared to that of sodium dodecyl sulfate (SDS); (2) the injection procedures (surfactant concentration, pore water velocity, continuous or interrupted flow) that might affect the efficiency of pyrene mobilization using UG2 biosurfactants; and (3) the co-transport of UG2 biosurfactants and pyrene. The UG2 biosurfactants were more efficient for pyrene mobilization than SDS and had much less impact on soil. The mobilization of pyrene was approximately proportional to the mass of UG2 biosurfactants injected for both the 0.25% and the 0.50% (w/v) concentrations used. Pyrene mobilization was not greatly dependent on either the pore water velocity—about 5.9 and 10.2 inch/h (15 and 26 cm/h)—or the duration of flow interruption (5 or 15 h), suggesting that mobilization was not rate limited under these conditions. The rhamnolipids appeared to be weakly retained in the soil. Based on the experimental results, it would be advantageous to use a high UG2 biosurfactant concentration, a high pore water velocity, and possibly a flow interruption of more than 15 h in order to reduce the injected volume and the duration of the treatment required. The 0.25% UG2 biosurfactant concentration greatly enhanced pyrene transport and could facilitate contaminant recovery.  相似文献