Influence du gypse sur la mesure de la teneur en eau et de la densite des marnes du keuper de lorraine     

Alain Thomas 《Engineering Geology》1971,5(4):313-329

Can we justifiably use a special drying process for measuring water content and dry density on marls containing gypsum so as to avoid errors due to the thermal dehydration of gypsum? In order to give an answer to this question, the author studied the variation of the systematic errors in the measures with measurable parameters such as temperature, length of drying time, gypsum content and water content. He also examined the incertitude due to the non-numerical parameters of dispersion, such as the nature of the tested marls and the size of the gypsum inclusions.

These investigations allowed the author, within the numerical parameters studied, to determine the regions where the precision of the corrections possible justifies the use of special methods of testing. He also shows that the usual way of desiccation below 55°C, is reliable only within a very limited range of water content.  相似文献   

Interpreting catch per unit effort data to assess the status of individual stocks and communities   总被引：3，自引：0，他引：3  

Maunder  Mark N.; Sibert  John R.; Fonteneau  Alain; Hampton  John; Kleiber  Pierre; Harley  Shelton J. 《ICES Journal of Marine Science》2006,63(8):1373-1385

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Modelling discard ogives from Irish demersal fisheries     

Borges  Lisa; Zuur  Alain F.; Rogan  Emer; Officer  Rick 《ICES Journal of Marine Science》2006,63(6):1086-1095

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Long-term fish and macro-crustacean community variation in a Mediterranean lagoon     

Gilles Poizat  Elizabeth Rosecchi  Philippe Chauvelon  Pascal Contournet  Alain J. Crivelli 《Estuarine, Coastal and Shelf Science》2004,59(4):615-624

The fish and macro-crustacean community of the Vaccarès lagoon (Rhône River delta, South France) was sampled monthly from 1993 to 2002. The lagoon salinity shifted from 15 in 1993 to 5 in 1994–1997 and went back to 15 in 1999–2002. Connections with the sea also varied during the study period with larger openings in 1996–1997. During the study period, the community changed to revert in 2002 to a state similar to 1993. These changes consisted of a sequence of increased and decreased patterns of freshwater species and some marine species. Typical lagoon species tended to resist to salinity changes. Freshwater species colonised the lagoon when the salinity was low. Marine species may have varied both in relation to connections with the sea and to indirect effects of freshwater outflow. This study shows that community changes following environmental variations can be delayed in time, and emphasises the need for long-term studies.  相似文献   

Modelling the monthly sea surface f_CO2 fields in the Indian Ocean     

Ferial Louanchi  Nicolas Metzl  Alain Poisson 《Marine Chemistry》1996,55(3-4)

In order to construct monthly fields of sea surface fugacity of carbon dioxide (f_CO2) on a large scale in the Indian Ocean, we use a one-dimensional model which takes into account the main physical and biogeochemical processes controlling f_CO2 variations in the ocean. Physical and biogeochemical processes are constrained by the monthly variations of sea surface temperature, salinity, chlorophyll concentration, wind speed and mixed-layer depth. The model is applied to four locations in the Indian Ocean and it well predicts observed temporal variations in f_CO2 at these locations. Regarding to monthly f_CO2 observations, the model also well simulates the f_CO2 distribution and its temporal variations along a track located between 20 ° and 50 °S with a maximal error of + 10 μatm. The model is also used to predict f_CO2 for 2 ° × 2 ° grids over the entire Indian Ocean and simulates seasonal cycles that are consistent with observations. The monthly f_CO2 fields derived from the model are used to estimate a global air-sea CO₂ flux over the Indian Ocean basin. We estimate a net sink of 0.5 Gt/yr C for the Indian Ocean (20 °N-50 °S), with the main sink located between 20 ° and 50 °S.  相似文献   

Quantitative mapping of active mud volcanism at the western Mediterranean Ridge-backstop contact     

Alain Rabaute  Nicolas Chamot-Rooke 《Marine Geophysical Researches》2007,28(3):271-295

Based on a new quantitative analysis of sidescan sonar data combined with coring, we propose a revised model for the origin for Mediterranean Ridge mud volcanism. Image analysis techniques are used to produce a synthetic and objective map of recent mud flows covering a 640 × 700 km² area, which represents more than half of the entire Mediterranean Ridge mud belt. We identify 215 mud flows, extruded during the last 37,000–60,000 years. This time period corresponds to the limit of penetration of the sonar, that we evaluate through geoacoustic modeling of the backscattered signal returned by the mud breccia-hemipelagites contact, and calibrate by coring. We show that during this period, at least 96% of the mud volume has been extruded at the Mediterranean Ridge-Hellenic backstop contact, the remaining being scattered over the prism. We suggest that the source is a Messinian (5–6 Ma) mud reservoir that remained close to the backstop contact, at variance with the classical transport-through-the-wedge model. A revised mud budget indicates that steady-state input is not needed. We propose that the source layer was deposited in deep and narrow pre-Messinian basins, sealed by Messinian evaporites, and finally inverted in post-Messinian times. Onset of motion of the Anatolia-Aegea microplate in the Pliocene resulted in change from slow to fast convergence, triggering shear partitioning at the edges of the backstop and basin inversion. Mud volcanism initiation is probably coeval with the latest events of this kinematic re-organization, i.e. opening of the Corinth Gulf and activation of the Kephalonia fault around 1–2 Ma.  相似文献   

Mineralogical and geochemical evolution of the 1982–1983 Galunggung eruption (Indonesia)     

Marie-Christine Gerbe  Alain Gourgaud  Olgeir Sigmarsson  Russell S Harmon  Jean-Louis Joron  Ariel Provost 《Bulletin of Volcanology》1992,54(4):284-298

Pyroclastic deposits from the 1982–1983 eruption of Galunggung volcano (Java, Indonesia) reflect preeruptive magmatic evolution which is of interest because of: (1) its duration of nine months, compared to a few hours or days for most historical eruptions; (2) the diversity of eruptive styles, from ash and scoria flows to phreatomagmatic explosions, and to the strombolian activity that marked the end of the eruption; and (3) the progressive variation in chemical composition with time, from andesite (58 wt.% SiO₂) to high-Mg basalt (47 wt.% SiO₂). The 1982–1983 Galunggung basalts are rather primitive: 10 to 12 wt% MgO, 180 to 200 ppm Ni and 550 to 700 ppm Cr. Despite the presence of about 40% phenocrysts, they may represent the most primitive basalts recognized in western Java. Basalts contain phenocrysts of olivine (Fo_90-80), diopside-salite, and plagioclase (An_95-75). Andesites contain plagioclase (An_80–60), augite, hypersthene (En_67-64), and titanomagnetite. The distribution of mineral compositions in each petrographic type is nearly unimodal, although scarce plagioclase and olivine xenocrysts have been observed. Abundance of gabbroic cumulates associated with the pyroclastic flows and evolution of mineral compositions from high-Mg basalts to andesites support crystal fractionation as the main differentiation mechanism, although magma mixing of basaltic andesite and andesite cannot be excluded. Major and trace element trends, which display rough decreases of MgO, CaO, Ni, Cr with increasing degree of differentiation and also linear positive correlations of hygromagmaphile elements, are compatible with both processes. However, some discrepancies are observed between major and trace element modelling, which may be explained to some extent by the influence of in situ crystallization and/or magma mixing. The constancy of ¹⁴³Nd/¹⁴⁴Nd (0.51286±3), ²³⁰Th/²³²Th (0.65±0.02), Th/U (4.08±0.07) ratios, and to a lesser extent ¹⁸O values (+5.8 to +6.4 % SMOW) and ⁸⁷Sr/⁸⁶Sr ratios (0.70440 to 0.70468) is compatible with a magmatic evolution through fractional crystallization without significant crustal contamination. Nevertheless low-¹⁸O and high ⁸⁷Sr/⁸⁶Sr values in basaltic andesites may be due to the introduction of meteoric fluids into the Galunggung magma.  相似文献   

Results from microseismic monitoring,conventional instrumentation,and tomography surveys in the creation and thinning of a burst-prone sill pillar     

Richard McCreary  John McGaughey  Yves Potvin  Dave Ecobichon  Marty Hudyma  Harald Kanduth  Alain Coulombe 《Pure and Applied Geophysics》1992,139(3-4):349-373

Located in northern Québec, the Lac Shortt Mine was a small gold mine consisting of a thin subvertical orebody which was mined in three main phases. High stress and rockbursting conditions were experienced when ore was extracted in the upper zone between the surface and a depth of 500 metres during the first two phases of mining. Severe rockbursts were experienced in late 1989 near the shaft and in the footwall development following a deepening of the mine shaft to a depth of 830 m and partial development of footwall drift access for the third phase of mining (the mining of the lower zone starting at a depth of 830 m moving upward toward a depth of 500 m). A 16-channel Electrolab MP250 microseismic system, with a Queen's University Full-Waveform piggy-back system, was installed underground at the site due to these problems.It was expected that the thinning sill would be subjected to an ever-increasing load as the thickness of the 500 m sill pillar decreased in the face of the mining excavation from below. A monitoring program consisting of the microseismic monitoring system, a range of conventional geomechanics monitoring tools as well as the undertaking of periodic seismic tomography surveys to assess the ongoing state of stress and rock mass condition within the sill was therefore warranted.The anomalously high-magnitude stress field and the brittle rockmass created a situation in which rockmass failure was common and violent. In the creation and thinning of the sill pillar, the location of banded microseismic activity was crucial in tracing rockmass failure and the associated ground control problems. Reliable source-location determination enabled the identification of areas of stress increase. The movement of the rockmass failure front could be followed, and was responsible for stope dilution, footwall and orebody development deterioration, and caving.Source-mechanism analyses gave accurate double-couple solutions for approximately forty percent of these events having at least ten recognizable polarities. Results suggested movement along vertical north-south striking or vertical east-west striking features. Underground observation of damaged access points showed that vertical north-south striking joints were experiencing failure.The microseismic activity, which was consistently concentrated close to the southwest and northeast corners of current production stopes, could be explained by a stress field oriented obliquely to the strike of the orebody, as measured prior to shrinkage of the sill pillar byin situ stress measurements and observed borehole overbreaks. The orientations of theP andT axes for the microseismic activity further confirmed that the stress field oriented obliquely to strike.While an increase in compressional-wave velocity of 2.3 percent, corresponding to a measured stress increase of approximately 10 MPa could be measured by repeated tomographic surveys, it was relatively small and only a factor of two or so above the velocity measured uncertainty. The relative insensitivity of thein situ rock mass modulus to the applied stress is believed to be largely due to the rockmass discontinuities being relatively closed prior to stress increase, as substantiated by the small deformations seen by the extensometer and borehole camera. This situation existed because of the very high pre-mining stress level.The experimental demonstration that the rock could not absorb substantially increased load through the mechanism of discontinuity closure or tightening (which would be reflected in the modulus) may be evidence in itself of potentially burst-prone ground, such as encountered at Lac Shortt.  相似文献   

Polyphase seismic faulting in the Ivrea zone (Italian Alps) revealed by 40Ar/39Ar dating of pseudotachylytes     

François Souquière  Patrick Monié  Olivier Fabbri  Alain Chauvet 《地学学报》2011,23(3):162-170

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Carbon and suspended sediment transport in an impounded alpine river (Isère,France)     

Julien Némery  Vincent Mano  Alexandra Coynel  Henri Etcheber  Florentina Moatar  Michel Meybeck  Philippe Belleudy  Alain Poirel 《水文研究》2013,27(17):2498-2508

Carbon and total suspended sediment (TSS) loads were investigated from April 2006 to March 2008 in the mountainous watershed of the Isère River, French Alps (5570 km²). The river bed has been highly impounded for hydroelectricity production during the last century. Hydraulic flushes are managed every year to prevent TSS storage within upstream dams. The Isère River has been instrumented for high‐frequency monitoring of water, TSS by turbidity and carbon (organic, inorganic, dissolved and particulate) in order to evaluate the impact of natural floods and hydraulic flushes on annual loads. Annual TSS load which was estimated between 1.3 and 2.3 MT y^?1 (i.e. 233 to 413 T km^?2 y^?1) highlighted the high erodibility of the Isère watershed. Annual carbon load was estimated between 173 10³ T y^?1 and 199 10³ T y^?1 (i.e 31 to 36 T km^?2 y^?1). About 80% of the annual carbon loads were inorganic. The impact of hydraulic flushes on annual loads appeared limited (less than 3% for annual TSS load and about 1.5% for annual carbon load), whereas the most important natural flood event contributed to 20% of the annual TSS load and 10% of the annual carbon load. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献