Fluid flow in cataclastic thrust fault zones in sandstones, Sub-Andean Zone, southern Bolivia     

Pierre Labaume  Simon M. F. Sheppard  Isabelle Moretti   《Tectonophysics》2001,340(3-4):141-172

The Bolivian Sub-Andean Zone (SAZ) corresponds to a Neogene thrust system that affects an about 10-km thick Palaeozoic to Neogene siliciclastic succession. The analysis of macro and microstructures and cement distribution in thrust fault zones shows that they are sealed by quartz at depths >3 km, due to local silica transfer by pressure-solution/precipitation activated at temperatures >70–90 °C. At shallower depths, faults have remained open and could be preferential drains for lateral flow of carbonate-bearing fluids, as shown by the occurrence of carbonate cements in fractures and their host-sandstone. Due to decreasing burial, resulting from foothill erosion during fault activity, critically buried fault segments can be affected by non-quartz-sealed structures that post-date initial quartz-sealed structures. The integration of textural, fluid inclusion and isotopic data shows that carbonates precipitated at shallow depth (<3 km), low temperature (<80 °C) and relatively late during the thrusting history. Isotopic data also show that precipitation occurred from the mixing of gravity-driven meteoric water with deeper formation water bearing carbonate carbon derived from the maturation of hydrocarbon source rocks (Silurian and Devonian shales). The combined microstructural and isotopic analyses indicate that: (i) fluid flow in fault zones often occurred with successive pulses derived from different or evolving sources and probably related to episodic fault activity, and (ii) at a large-scale, the faults have a low transverse permeability and they separate thrust sheets with different fluid histories.  相似文献   

Transformation of Monoaromatic hydrocarbons to organic acids in anoxic groundwater environment     

Isabelle M. Cozzarelli  Robert P. Eganhouse  Mary Jo Baedecker 《Environmental Geology》1990,16(2):135-141

The transformation of benzene and a series of alkylbenzenes was studied in anoxic groundwater of a shallow glacial-outwash aquifer near Bemidji, Minnesota, U.S.A. Monoaromatic hydrocarbons, the most water-soluble components of crude oil, were transported downgradient of an oil spill, forming a plume of contaminated groundwater. Organic acids that were not original components of the oil were identified in the anoxic groundwater. The highest concentrations of these oxidized organic compounds were found in the anoxic plume where a decrease in concentrations of structurally related alkylbenzenes was observed. These results suggest that biological transformation of benzene and alkylbenzenes to organic acid intermediates may be an important attenuation process in anoxic environments. The transformation of a complex mixture of hydrocarbons to a series of corresponding oxidation products in an anoxic subsurface environment provides new insight into in situ anaerobic degradation processes.  相似文献   

Effect of the environment on the hydrochemical characteristics of an alluvial aquifer following an exceptional multiyear drought (Mediterranean seashore,herault, France): Part II— Climatology and agronomy     

Jean-Claude Grillot  Isabelle Chaffaut  Moumtaz Razack 《Environmental Geology》1988,11(2):175-181

The hydrochemical evolution of an alluvial groundwater located along the Mediterranean seashore is analyzed with respect to its agricultural and climatic environment, including degree of saturation of the soil; types of cultures, chemical fertilizers and phytosanitary treatments; selective irrigations of the cultivated areas; precipitations. It is shown that the environmental effect on the groundwater's vulnerability depends on two groups of factors:

1.

Transfers from surface to groundwater of nitrates, chlorides, sulfates, and potassium, which are governed by: (a) the climatic conditions before the agricultural activities begin, (b) the kinds of agricultural activities and their distribution in time with respect to a given climatic context. Phenomena of retention and/or rapid diffusion are related to the sedimentary heterogeneities of the reservoir and to the differences of ternperatures between irrigation waters and precipitations.

2.

Cationic exchanges related to the presence of clays of Montmorillonite-Kaolinite type.

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In-situ high-temperature Raman spectroscopic studies of aluminosilicate liquids     

Isabelle Daniel  Philippe Gillet  Brent T. Poe  Paul F. McMillan 《Physics and Chemistry of Minerals》1995,22(2):74-86

We have measured in-situ Raman spectra of aluminosilicate glasses and liquids with albite (NaAlSi₃ O₈) and anorthite (CaAl₂Si₂O₈) compositions at high temperatures, through their glass transition range up to 1700 and 2000 K, respectively. For these experiments, we have used a wire-loop heating device coupled with micro-Raman spectroscopy, in order to achieve effective spatial filtering of the extraneous thermal radiation. A major concern in this work is the development of methodology for reliably extracting the first and second order contributions to the Raman scattering spectra of aluminosilicate glasses and liquids from the high temperature experimental data, and analyzing these in terms of vibrational (anharmonic) and configurational changes. The changes in the first order Raman spectra with temperature are subtle. The principal low frequency band remains nearly constant with increasing temperature, indicating little change in the T-O-T angle, and that the angle bending vibration is quite harmonic. This is in contrast to vitreous SiO₂, studied previously. Above Tg, intensity changes in the 560–590 cm^?1 regions of both sets of spectra indicate configurational changes in the supercooled liquids, associated with formation of additional Al-O-Al linkages, or 3-membered (Al, Si)-containing rings. Additional intensity at 800 cm^?1 reflects also some rearrangement of the Si-O-Al network.  相似文献   

Bathymay : la structure sous-marine de Mayotte révélée par l'imagerie multifaisceaux     

Jean-Christophe Audru  Pol Guennoc  Isabelle Thinon  Olivier Abellard 《Comptes Rendus Geoscience》2006,338(16):1240-1249

The BATHYMAY marine survey was carried out in January 2004 around the French volcanic island of Mayotte, onboard the research vessel Marion Dufresne 2. Multibeam bathymetry revealed for the first time the morphology of the whole outer slope. Preliminary interpretations show broad canyons that deeply incise the slope, numerous volcanoes and huge landslides. Large submarine plateaus are also highlighted, bounded by steep cliffs and active normal faults. A model for Mayotte is suggested, in which eruptive activity, sometimes influenced by normal faulting, was concentrated along a N140° regional line (the Comoros archipelago axis), with landslide activity concentrated on the northeastern and southwestern flanks of this line. To cite this article: J.-C. Audru et al., C. R. Geoscience 338 (2006).  相似文献   

Numerical modelling of direct current electrical resistivity for the characterisation of cracks in soils   总被引：5，自引：0，他引：5  

Jeanne Tabbagh  Anatja Samouëlian  Alain Tabbagh  Isabelle Cousin 《Journal of Applied Geophysics》2007,62(4):313-323

Fractures or cracks in rocks and soils are thin planar features of high resistivity, embedded in a more conductive bulk volume. In soils, several processes, particularly swelling and shrinkage of clays, result in cracks and can regenerate macroporosity. Their detection and the assessment of their evolution necessitate the use of non-invasive techniques. Although cracks have a major influence on the electrical resistivity of bulk material their complete geometrical characterisation achieved through the use of electrical resistivity measurements remains difficult due to the lack of appropriate inversion models. An inversion model based on the method of moments (MoM) has been developed, and is presented here. Direct simulations demonstrate the model's ability to reconstruct real experimental data. The influence of various object parameters on the model's accuracy was tested, showing that the model is sensitive to all the geometric characteristics of a crack. The inversion of both simulated and experimental data has demonstrated the model's ability to calculate the initial position, width and depth of several different cracks.  相似文献   

Comparison between chironomid-inferred July temperatures and meteorological data AD 1850–2001 from varved Lake Silvaplana,Switzerland     

Isabelle Larocque  Martin Grosjean  Oliver Heiri  Christian Bigler  Alex Blass 《Journal of Paleolimnology》2009,41(2):329-342

Inferred temperatures from chironomids preserved in the varved sediment of Lake Silvaplana in the Eastern Swiss Alps were compared with instrumental data obtained from a meteorological station in Sils-Maria, on the shore of Lake Silvaplana, for the time interval 1850–2001. At near-annual resolution, the general patterns of chironomid-inferred temperature changes followed the meteorological record over the last ∼150 years (r _Pearson = 0.65, P = 0.01) and 87% of the inferences had deviations from the instrumental data below the root-mean-square error of prediction (RMSEP). When the inferences were compared with a 2-year running mean in the meteorological data, 94% of the inferences had differences with the instrumental data below the RMSEP, indicating that more than half of the inaccurate inferences may have been due to errors in varve counting. Larger deviations from the instrumental data were also obtained from samples with low percentages of fossil taxa represented in the training set used for temperature reconstruction and/or assemblages with poor fit to temperature. Changes in total phosphorus (TP, as inferred by diatoms) and/or greater precipitation were possible factors affecting the accuracy of the temperature reconstruction. Although these factors might affect the quantitative estimates, obtaining >80% accurate temperature inferences suggests that chironomid analysis is a reliable tool for reconstructing mean July air temperature quantitatively over the last ∼150 years in Lake Silvaplana.  相似文献   

Variational coupling of Plinian column models and data: Application to El Chichón volcano     

Isabelle Charpentier 《Journal of Volcanology and Geothermal Research》2008

Many efforts have been done in the modelling of Plinian columns. However, until now, the inverse problem of the reconstruction of a Plinian event from observed data has been only roughly tackled. This paper discusses the efficient variational data assimilation (VDA) that manages the optimization iterate sequence by means of gradient computations. Theoretical developments of VDA are presented for both the Woods equations and a generic system allowing for the modelling of the Navier–Stokes equations. Two- and three-dimensional unsteady Plinian models being based on the latters, VDA could be clearly performed on their differentiable subset of equations.  相似文献   

Long-term evolution (1988–2008) of Zostera spp. meadows in Arcachon Bay (Bay of Biscay)     

Plus Martin  Dalloyau Sébastien  Trut Gilles  Auby Isabelle  Xavier de Montaudouin  Éric Emery  Noël Claire  Viala Christophe 《Estuarine, Coastal and Shelf Science》2010

The spatial variability of seagrass meadows in Arcachon Bay, was studied between 1988 and 2008 using a combination of mapping techniques based on aerial photographs for intertidal dwarf-grass (Zostera noltii) beds and acoustic sonar for permanently submerged eelgrass (Zostera marina) populations. The results show a severe decline over the period for both species, as well as an acceleration of the decline since 2005 for Z. noltii. The total surface regression over the studied period is estimated to be 22.8 km² for Z. noltii and 2.7 km² for Z. marina, which represent declines of 33 and 74% respectively.  相似文献   

Putative transcription factor binding sites and polymorphisms in the proximal promoter of the PRL‐A gene in percomorphs and European sea bass (Dicentrarchus labrax)     

Isabelle Boutet  Nolwenn Quéré  Frédéric Lecomte  Jean‐François Agnèse  Bruno Guinand 《Marine Ecology》2008,29(3):354-364

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