Systematic use of trace element in igneous process     

Claude J. Allègre  Michel Treuil  Jean-François Minster  Bernard Minster  Francis Albarède 《Contributions to Mineralogy and Petrology》1977,60(1):57-75

This paper describes an extended application of the Rayleigh distillation law to trace element behavior in a fractional crystallization sequence. Using a trace element with a very low bulk partition coefficient as a reference (as suggested by Anderson and Greenland, 1969, and extended by Treuil and Varet, 1973), we can derive bulk partition coefficients for other elements and, in turn, the mineralogical composition of the cumulates. Trace elements with large D, such as Ni and Cr, further constrain the system, and we can deduce the initial composition of the magma. An example of this technique is shown for Terceira Island in the Azores.Contribution IPGNS no 229Now at Dept. of Geological Sciences, California Institute of Technology, Pasadena, California, USA  相似文献   

Multibeam bathymetry and sidescan imaging of the Rivera Transform–Moctezuma Spreading Segment junction, northern East Pacific Rise: New constraints on Rivera–Pacific relative plate motion     

William L. Bandy  Franois Michaud  Jrme Dyment  Carlos A. Mortera-Gutirrez  Jacques Bourgois  Thierry Calmus  Marc Sosson  Jose Ortega-Ramirez  Jean-Yves Royer  Bernard Pontoise  Bertrand Sichler 《Tectonophysics》2008,454(1-4):70-85

To better understand the recent motion of the Pacific plate relative to the Rivera plate and to better define the limitations of the existing Rivera–Pacific plate motion models for accurately predicting this motion, total-field magnetic data, multibeam bathymetric data and sidescan sonar images were collected during the BART and FAMEX campaigns of the N/O L'Atalante conducted in April and May 2002 in the area surrounding the Moctezuma Spreading Segment of the East Pacific Rise, located offshore of Manzanillo, Mexico, at 106°16′W, between 17.8°N and 18.5°N. Among the main results are: (1) the principle transform displacement zone of the Rivera Transform is narrow and well defined east of 107o15′W and these azimuths should be used preferentially when deriving new plate motion models, and (2) spreading rates along the Moctezuma Spreading Segment should not be used in plate motion studies as either seafloor spreading has been accommodated at more than one location since the initiation of seafloor spreading in the area of the Moctezuma Spreading Segment, or this spreading center is not a Rivera–Pacific plate boundary as has been previously assumed. Comparison of observed transform azimuths with those predicted by the best-fit poles of six previous models of Rivera–Pacific relative motion indicate that, in the study area, a significant systematic bias is present in the predictions of Rivera–Pacific motion. Although the exact source of this bias remains unclear, this bias indicates the need to derive a new Rivera–Pacific relative plate motion model.  相似文献   

A new amber deposit from the Cretaceous (uppermost Albian-lowermost Cenomanian) of southwestern France   总被引：1，自引：0，他引：1  

Didier Nraudeau  Vincent Perrichot  Jean-Paul Colin  Vincent Girard  Bernard Gomez  Franois Guillocheau  Edwige Masure  Daniel Peyrot  Florent Tostain  Blaise Videt  Romain Vullo 《Cretaceous Research》2008,29(5-6):925

A Cretaceous amber deposit has recently been discovered in a quarry of Charente-Maritime (southwestern France), at Cadeuil. This paper presents the sedimentary and palaeoenvironmental settings of the uppermost Albian-lowermost Cenomanian series including the amber deposit. A preliminary analysis of the amber samples reveals diverse fossil arthropods (a few mites and at least 20 insect families within 9 orders), as well as numerous micro-organisms, mainly algae and mycelia. A myceloid colony of bacteria, a flagellate algae and four especially well preserved insects are illustrated (Diptera Dolichopodidae, Diptera Chironomidae, Hymenoptera Parasitica, and Heteroptera Tingidae). The abundance of the limnic micro-organisms is discussed in terms of bloom events. Their relative scarcity in almost all the amber pieces containing fossil arthropods is attributed to differences in the origin of resin: production along trunk and branches for amber with arthropods; production by aquatic roots for amber rich in algae. The absence of pollen and spores in amber is attributed to differences in the respective periods of resin and palynomorph production, which may be related to a seasonal climate during the Albian-Cenomanian transition in Western Europe.  相似文献   

Long term mobilisation of chemical elements in tephra-rich peat (NE Iceland)   总被引：1，自引：0，他引：1  

Franois De Vleeschouwer  Brigitte Van Vliët Lano  Nathalie Fagel 《Applied Geochemistry》2008,23(12):3819-3839

This paper presents geochemical profiles of a tephra-bearing minerotrophic peat column from NE-Iceland obtained using various elemental analyses of the solid phase and the pore water. The influence of tephra grain size, thickness and composition of each tephra on the peat geochemistry was investigated. Interpretations are supported by a statistical approach, in particular by autocorrelation, and by microscopy observations. Minerotrophic peat geochemistry may be strongly dependent upon post-depositional mobilization and possible leaching of elements as demonstrated by Fe and trace metal concentration profiles. Chemical elements, and more specifically potentially harmful metals, can be slowly leached out of volcanic falls during their weathering and re-accumulate downwards. It is emphasised that a tephra deposit can act as an active geochemical barrier, blocking downward elemental movements and leading to the formation of enriched layers. In this study, the formation of poorly amorphous Fe phases above the Hekla 3 tephra is shown. These poorly crystalline Fe phases scavenged Ni.  相似文献   

Interactions between Volatile Reduced Sulfur Compounds and Metals in the Seine Estuary (France)     

Amandine Cozic  Eric Viollier  Jean-François Chiffoleau  Joël Knoery  Emmanuelle Rozuel 《Estuaries and Coasts》2008,31(6):1063-1071

Concentrations of volatile hydrogen sulfide (H₂S), carbonyl sulfide (OCS), methane thiol (MeSH), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) in the Seine estuary (France) were investigated in spring 2005 using samples collected from the first meter beneath the surface. Levels of dissolved metals (Ag, Cd, Cu, Zn, Ni, Co, Pb), suspended particulate matter, and particular organic carbon were also assessed. Maximum concentrations were 0.80 nM for H₂S, 0.64 nM for OCS, 3.06 nM for MeSH, 11.06 nM for DMS, and 1.18 nM for DMDS, and different features were observed for the five volatile reduced sulfur compounds (VRSCs). Experiments were conducted to determine silver–VRSC conditional stability constants. Major interactions were observed between H₂S and Ag, which may partially account for the absence of volatile H₂S at the lowest salinities. OCS, MeSH, and DMS did not interact with Ag, as revealed by their insignificant K′ values. Variations in concentrations along the salinity gradient may be explained by the influence of phytoplanktonic compounds.  相似文献   

Multivariate analysis as a tool to infer hydrologic response types and controlling variables in a humid temperate catchment     

Genevive A. Ali  Andr G. Roy  Marie‐Claude Turmel  Franois Courchesne 《水文研究》2010,24(20):2912-2923

We assess the ability of multivariate statistical analyses applied to event hydrographs parameters, to characterize a catchment hydrological behaviour. Motivation for such an approach lies in the fact that streamflow records have yet to be exploited to their full potential towards hydrological interpretation and can be used to infer a catchment state of connectivity from a qualitative standpoint. We have therefore processed 96 event hydrographs from a small headwater temperate humid forested catchment using principal component analysis, variation partitioning and classification tree analysis. These techniques prove to be promising in discriminating contrasted types of hydrologic responses (e.g. low‐ vs high‐magnitude events, slow vs quick timing events), identifying the main hydro‐meteorological variables that control these responses and determining thresholds values of the hydro‐meteorological variables leading to a switch between catchment response types. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Correcting wind‐induced bias in solid precipitation measurements in case of limited and uncertain data     

Vincent Fortin  Charles Therrien  François Anctil 《水文研究》2008,22(17):3393-3402

Automatic precipitation gauges tend to underestimate solid precipitation in the presence of wind. Loss as a function of wind speed is typically evaluated by comparing the gauge with a more accurate measurement made using a double‐fence intercomparison reference gauge (DFIR). For small precipitation events, small errors in the observations can induce large errors in the ‘catch’ ratio, i.e. the ratio of the automatic gauge measurement to the DFIR observation. For this reason, precipitation events of less than 3 mm are typically discarded before performing the regression analysis. This can mean discarding more than 90% of the observations. This paper shows how the method of weighted least squares can be used to perform a regression analysis that can take into account the whole sample to provide a more accurate estimation of the relationship between the catch ratio and the wind speed. This methodology is then used to obtain an adjustment curve for a shielded Geonor T‐200B precipitation gauge in Northern Québec. Copyright © 2008 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada.  相似文献   

Small-scale variability of the current in the Strait of Bonifacio   总被引：1，自引：1，他引：0  

Olivia Gérigny  Sylvain Coudray  Chiara Lapucci  Corinne Tomasino  Paul-Antoine Bisgambiglia  François Galgani 《Ocean Dynamics》2015,65(8):1165-1182

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Assimilating along-track SLA data using the EnOI in an eddy resolving model of the Agulhas system   总被引：1，自引：1，他引：0  

Björn C. Backeberg  François Counillon  Johnny A. Johannessen  Marie–Isabelle Pujol 《Ocean Dynamics》2014,64(8):1121-1136

The greater Agulhas Current is one of the most energetic current systems in the global ocean. It plays a fundamental role in determining the mean state and variability of the regional marine environment, affecting its resources and ecosystem, the regional weather and the global climate on a broad range of temporal and spatial scales. In the absence of a coherent in-situ and satellite-based observing system in the region, modelling and data assimilation techniques play a crucial role in both furthering the quantitative understanding and providing better forecasts of this complicated western boundary current system. In this study, we use a regional implementation of the Hybrid Coordinate Ocean Model and assimilate along-track satellite sea level anomaly (SLA) data using the Ensemble Optimal Interpolation (EnOI) data assimilation scheme. This study lays the foundation towards the development of a regional prediction system for the greater Agulhas Current system. Comparisons to independent in-situ drifter observations show that data assimilation reduces the error compared to a free model run over a 2-year period. Mesoscale features are placed in more consistent agreement with the drifter trajectories and surface velocity errors are reduced. While the model-based forecasts of surface velocities are not as accurate as persistence forecasts derived from satellite altimeter observations, the error calculated from the drifter measurements for eddy kinetic energy is significantly lower in the assimilation system compared to the persistence forecast. While the assimilation of along-track SLA data introduces a small bias in sea surface temperatures, the representation of water mass properties and deep current velocities in the Agulhas system is improved.  相似文献   

Multi-scale analysis of water alteration on the rockslope stability framework     

Sandra Dochez  Farid Laouafa  Christian Franck  Sylvine Guedon  François Martineau  Julie D’Amato  Albane Saintenoy 《Acta Geophysica》2014,62(5):1025-1048

Water is an important weathering factor on rock discontinuities and in rock mass mechanical behaviour because of its chemical features such as temperature, pH or salinity which make it a “good” candidate to rock degradation. Furthermore the increase of rainfall frequency or intensity highlights some problems on the rock slope stability analysis. This study aims to evaluate the effect of water flow on the rock slope stability and it is performed at two space scales: in situ scale and laboratory (micro scale and macro scale). It shows how water induces degradation at multi-scale (surface roughness and matrix) and thus may decrease the stability of the discontinuous rock mass. It has two main components: the effect of water-solid chemical mechanisms and the analysis of the mechanical response of the discontinuity modified by the water alteration.  相似文献