Publications ORBi OA
Bookmark and Share    
Full Text
Peer Reviewed
See detailThe electronic nose as a warning device of the odour emergence in a compost hall
Nicolas, Jacques ULg; Romain, Anne-Claude ULg; Ledent, Catherine

in Sensors and actuators. B, Chemical (2006), 116(1-2), 95-99

A self-made electronic nose consisting in a sensor array of six commercial tin oxide gas sensors is used to monitor the odour emission from a compost facility. Supervised data processing tools, such as ... [more ▼]

A self-made electronic nose consisting in a sensor array of six commercial tin oxide gas sensors is used to monitor the odour emission from a compost facility. Supervised data processing tools, such as discriminant analysis, are able to recognize, in real time, the odour of compost with respect to other possible sources in the hall. The paper shows that with unsupervised methods, such as principal component analysis, it is not essential to identify all the possible odour sources during the learning phase. The closeness to the compost group centroid could be used as an indicator of the compost odour level. Alternatively, by a suitable calibration from olfactory measurements, the signals generated by the sensor array can be used to estimate the odour emission rate from the compost hall. Such real time monitoring should allow to assess and to anticipate the annoyance in the surrounding. [less ▲]

Detailed reference viewed: 103 (59 ULg)
Full Text
Peer Reviewed
See detailAbout automatic learning for advanced sensing, monitoring and control of electric power systems
Wehenkel, Louis ULg; Glavic, Mevludin; Geurts, Pierre ULg et al

in Proceedings of the Second Carnegie Mellon Conference in Electric Power Systems: Monitoring, Sensing, Software and its Valuation for the Changing electric Power Industry (2006)

The paper considers the possible uses of automatic learning for improving power system performance by software methodologies. Automatic learning per se is first reviewed and recent developements of the ... [more ▼]

The paper considers the possible uses of automatic learning for improving power system performance by software methodologies. Automatic learning per se is first reviewed and recent developements of the field are highlighted. Then the authors’ views of its main actual or potential applications related to power system operation and control are described, and in each application present status and needs for further developments are discussed. [less ▲]

Detailed reference viewed: 59 (4 ULg)
Full Text
Peer Reviewed
See detailOn multi-area security assessment of large interconnected power systems
Wehenkel, Louis ULg; Glavic, Mevludin; Ernst, Damien ULg

in Proceedings of the Second Carnegie Mellon Conference in Electric Power Systems: Monitoring, Sensing, Software and its Valuation for the Changing electric Power Industry (2006)

The paper introduces a framework for information exchange and coordination of security assessment suitable for distributed multi-area control in large interconnections operated by a team of transmission ... [more ▼]

The paper introduces a framework for information exchange and coordination of security assessment suitable for distributed multi-area control in large interconnections operated by a team of transmission system operators. The basic idea of the proposed framework consists of exchanging just enough information so that each operator can evaluate the impact in his control area of contingencies both internal and external to his area. The framework has been thought out with the European perspective in mind where it is presently not possible to set up a transnational security coordinator that would have authority to handle security control over the whole or part of the European interconnection. Nevertheless, it can also be considered as an approach to handle security control in North-American Mega-RTOs, where it could help to circumvent problems of scalability of algorithms and maintainability of data by distributing them over the TSOs under the authority of the RTO. [less ▲]

Detailed reference viewed: 34 (0 ULg)
Full Text
Peer Reviewed
See detailEnsembles of extremely randomized trees and some generic applications
Wehenkel, Louis ULg; Ernst, Damien ULg; Geurts, Pierre ULg

in Proceedings of Robust Methods for Power System State Estimation and Load Forecasting (2006)

In this paper we present a new tree-based ensemble method called “Extra-Trees”. This algorithm averages predictions of trees obtained by partitioning the inputspace with randomly generated splits, leading ... [more ▼]

In this paper we present a new tree-based ensemble method called “Extra-Trees”. This algorithm averages predictions of trees obtained by partitioning the inputspace with randomly generated splits, leading to significant improvements of precision, and various algorithmic advantages, in particular reduced computational complexity and scalability. We also discuss two generic applications of this algorithm, namely for time-series classification and for the automatic inference of near-optimal sequential decision policies from experimental data. [less ▲]

Detailed reference viewed: 62 (5 ULg)
Full Text
Peer Reviewed
See detailAutomatic learning of sequential decision strategies for dynamic security assessment and control
Wehenkel, Louis ULg; Glavic, Mevludin; Geurts, Pierre ULg et al

in Proceedings of the IEEE Power Engineering Society General Meeting 2006 (2006)

This paper proposes to formulate security control as a sequential decision making problem and presents new developments in automatic learning of sequential decision making strategies from simulations and ... [more ▼]

This paper proposes to formulate security control as a sequential decision making problem and presents new developments in automatic learning of sequential decision making strategies from simulations and/or information collected from real-life system measurements. The exploitation of these methods for the design of decision making strategies and control policies in the context of preventive and emergency mode dynamic security assessment and control is discussed and further opportunities for research in this area are highlighted. [less ▲]

Detailed reference viewed: 26 (4 ULg)
Full Text
Peer Reviewed
See detailDamping control by fusion of reinforcement learning and control Lyapunov functions
Glavic, Mevludin; Wehenkel, Louis ULg; Ernst, Damien ULg

in Proceedings of the 38th North American Power Symposium (NAPS 2006) (2006)

The main idea behind the concept, proposed in the paper, is the opportunity to make control systems with increased capabilities by synergetic fusion of the domain-specific knowledge and the methodologies ... [more ▼]

The main idea behind the concept, proposed in the paper, is the opportunity to make control systems with increased capabilities by synergetic fusion of the domain-specific knowledge and the methodologies from control theory and artificial intelligence. The particular approach considered combines Control Lyapunov Functions (CLF), a constructive control technique, an Reinforcement Learning (RL) in attempt to optimize a mix of system stability and performance. Two control schemes are proposed and the capabilities of the resulting controllers are illustrated on a control problem involving a Thyristor Controlled Series Capacitor (TCSC) for damping oscillations in a four-machine power system. [less ▲]

Detailed reference viewed: 28 (2 ULg)
Full Text
Peer Reviewed
See detailMulti-area security assessment: results using efficient bounding method
Wehenkel, Louis ULg; Glavic, Mevludin; Ernst, Damien ULg

in Proceedings of the 38th North American Power Symposium (NAPS 2006) (2006)

We present our recent results on using previously introduced framework for multi-area security assessment in large interconnections. The basic idea of the framework is exchanging just enough information ... [more ▼]

We present our recent results on using previously introduced framework for multi-area security assessment in large interconnections. The basic idea of the framework is exchanging just enough information so that each operator can evaluate the impact in his control area of contingencies both internal and external to his area. We provide illustrations based on a localization concept known as efficient bounding method and recently introduced approximate DC model of the European interconnected system. In this paper we focus on four transmission system operators (within the approximate DC model): Belgium, France, Germany, and Netherlands (for both Summer and Winter-peak load conditions). [less ▲]

Detailed reference viewed: 22 (3 ULg)
Full Text
Peer Reviewed
See detailComparative assessment of old and new suboptimal control schemes on three example processes
Journee, Michel ULg; Schweickhardt, T.; Allgöwer, Frank

in Proceedings of the 13th IFAC Workshop on Control Applications of Optimisation, Paris (2006)

Detailed reference viewed: 6 (2 ULg)
Full Text
See detailLe karst
Ek, Camille ULg; Schyns, Jean-Christophe; Ozer, André ULg

in Direction générale de l'aménagement du territoire, du logement et du patrimoine (Ed.) Les risques majeurs en Région wallonne (2006)

Detailed reference viewed: 154 (40 ULg)
Full Text
Peer Reviewed
See detailVereinfachtes Verfahren zur Abschätzung der Wirkung der Nichtlinearität der aerodynamischen Koeffizienten
Denoël, Vincent ULg; Sedlacek, Gerhard

in Stahlbau (2006), 75(5), 380-388

Wind analysis of a structure subjected to non-linear random dynamic loading Since the early developments in wind engineering, aerodynamic coefficients have been linearized in turbulence analysis. On the ... [more ▼]

Wind analysis of a structure subjected to non-linear random dynamic loading Since the early developments in wind engineering, aerodynamic coefficients have been linearized in turbulence analysis. On the other hand general and complex methods based on generalized power spectral densities can now handle this kind of non linearity. Between these two extremes, it would be desirable to give simple estimation of the effects of the non linearity of aerodynamic coefficients on the response of structures. This paper aims at giving an overview of these general and complex methodologies (that could be applied in other contexts), and, in a second step, presenting an original procedure to give estimation of the effects of the non linearity of aerodynamic coefficients. This procedure will be illustrated on the drag coefficient of the Viaduct of Millau [less ▲]

Detailed reference viewed: 36 (3 ULg)
Full Text
See detailSimultaneous use of hydrogeological and geophysical data for groundwater protection zone delineation by co-conditional stochastic simulations
Rentier, Céline; Dassargues, Alain ULg

in Stauffer, Fritz; Dassargues, Alain (Eds.) Quantitative Geology from Multiple Sources: S10 Use of multiple sources in conditioning/calibrating groundwater flow and transport models (2006)

Delineation of protection zones is performed by the use of stochastic simulations integrating all available data. In practice, due to the few available measurements of the main parameters, it can be very ... [more ▼]

Delineation of protection zones is performed by the use of stochastic simulations integrating all available data. In practice, due to the few available measurements of the main parameters, it can be very useful to integrate other data to reduce the uncertainty of the results. Most of the solute spreading is governed by the hydraulic conductivity (K) spatial variability at different scales. A stochastic approach adding measured piezometric heads and electrical resistivity data is presented. Results are discussed on a synthetic and on a practical case. Delineating the ‘Capture zone Probability Distribution’ (CaPD) for a given time, it is shown how the uncertainty can be reduced. The methodology can be used in real applications when little or no information is available about the hydraulic properties, through the conditioning on other data sets. [less ▲]

Detailed reference viewed: 36 (7 ULg)
Full Text
Peer Reviewed
See detailGenetic parameters and evaluation of rear legs (rear view) for Brown Swiss and Guernseys
Wiggans, G. R.; Thornton, L. L. M.; Neitzel, R. R. et al

in Journal of Dairy Science (2006), 89(12), 4895-4900

Genetic parameters were estimated for rear legs (rear view; RLRV) and 15 current linear type traits of Brown Swiss and Guernsey dairy cattle. The Brown Swiss Cattle Breeders' Association of the USA and ... [more ▼]

Genetic parameters were estimated for rear legs (rear view; RLRV) and 15 current linear type traits of Brown Swiss and Guernsey dairy cattle. The Brown Swiss Cattle Breeders' Association of the USA and the American Guernsey Association began scoring RLRV in 2004. For Brown Swiss, 8,502 records were available for 7,676 cows in 417 herds; Guernsey data included 5,437 records for 4,749 cows in 229 herds. Nine unknown-parent groups were defined for each breed, each with 2 birth years. The model included fixed effects for the interaction of herd, appraisal date, and parity; appraisal age within parity; and lactation stage within parity and random effects for animal, permanent environment, and residual error. The multitrait analysis for RLRV and the 15 linear type traits used canonical transformation, multiple diagonalization, and a decelerated expectation-maximization REML algorithm. For Brown Swiss, heritability was 0.102 for RLRV and ranged from 0.099 for rear legs (side view) to 0.453 for stature. For Guernseys, heritability ranged from 0.078 for RLRV to 0.428 for stature. For Brown Swiss, the highest genetic correlation with RLRV was 0.71 for rear udder width; the most negative correlation was -0.19 with rump angle. For Guernseys, the highest genetic correlations with RLRV were 0.43 for rear udder width and 0.42 for body depth; the most negative correlation was -0.46 with rear legs (side view). With heritability near 0.10, RLRV should be useful in selection for improved locomotion. Release of genetic evaluations for RLRV began in May 2006 for Brown Swiss and Guernseys. [less ▲]

Detailed reference viewed: 30 (0 ULg)
Full Text
Peer Reviewed
See detailAccounting for heterogeneous variances in multitrait evaluation of Jersey type traits
Gengler, Nicolas ULg; Wiggans, G. R.; Thornton, L. L. M. et al

in Journal of Dairy Science (2006), 89(8), 3143-3151

The multitrait genetic evaluation system for type traits was modified to estimate adjustments for heterogeneous variance (HV) simultaneously with estimated breeding values (EBV) for final score and 14 ... [more ▼]

The multitrait genetic evaluation system for type traits was modified to estimate adjustments for heterogeneous variance (HV) simultaneously with estimated breeding values (EBV) for final score and 14 linear traits. Each variance within herd, year, and parity was regressed toward a predicted variance, which was determined by fitting a model with fixed effects of the mean final score for herd, size of the contemporary group, appraisal month, and year-season and a random effect for herd-appraisal date. Herd-appraisal date was included as a random effect to regress the observed heterogeneity for a given herd-appraisal date toward the fixed effects. Method R was used to estimate variances for the heterogeneity model in each EBV iteration. To evaluate the effect of the adjustment, parent averages were calculated from evaluations with recent appraisals removed. The adjustment slightly improved correlations within birth year between those parent averages and EBV from current data on bulls for most traits, but did not improve correlations for final score, strength, dairy form, teat length, or foot angle. Annual trends for EBV were lower with HV adjustment than for unadjusted EBV for all traits except final score and rump angle for cows and rump width for bulls, which were essentially unchanged. Standard deviations of Mendelian sampling (evaluation minus mean of parent evaluations) declined less over time for HV-adjusted than for unadjusted evaluations. The slope at year 2000 of Mendelian-sampling standard deviations from HV-adjusted evaluations ranged from 10.0% for udder depth to 42.7% for teat length compared with the slope for unadjusted evaluations. This HV adjustment, which was implemented for USDA evaluations in May 2001 for Jerseys and in 2002 for other breeds, improves the accuracy of evaluations, particularly comparisons over time, by accounting for the change in variation. [less ▲]

Detailed reference viewed: 33 (4 ULg)
Full Text
See detailRessources en eaux souterraines: caractérisation pour une gestion durable en liaison avec l’aménagement du territoire
Dassargues, Alain ULg

in Les Risques majeurs en Région Wallonne / Prévenir en aménageant (2006)

Detailed reference viewed: 43 (6 ULg)
Full Text
See detailReactive transport modelling of a groundwater contamination by ammoniacal liquor
Haerens, Bruno; Prommer, Henning; Lerner, David N. et al

(2006)

A reactive transport modeling study was carried out to assess the fate of a groundwater contamination by ammoniacal liquor from a former coking plant and the associated geochemical response. The ... [more ▼]

A reactive transport modeling study was carried out to assess the fate of a groundwater contamination by ammoniacal liquor from a former coking plant and the associated geochemical response. The simulations over a 45-year period provide a conclusive explanation and quantitative description of all measured data from observation wells down gradient of the contaminant source. It is shown that cation exchange exerts the main control on the fate of the ammonium plume as it strongly retards the migration of dissolved ammonium. The sorption of ammonium is accompanied by the elution of native cations, an effect that can be seen in some observation wells where ammonium is absent. While phenol has not been detected in the observation wells in recent years, the modeling results suggest that it has completely degraded in the aquifer, which is inferred from the agreement between the simulated and the observed geochemical fingerprint that the degradation of phenol imposes on groundwater composition. [less ▲]

Detailed reference viewed: 201 (2 ULg)
Full Text
See detailSecondary data value for geostatistical estimation of flow and transport parameters in low-permeability media
Huysmans; Dassargues, Alain ULg

in Stauffer, Fr.; Dassargues, Alain (Eds.) Quantitative Geology from Multiple Sources: S10 Use of multiple sources in conditioning/calibrating groundwater flow and transport models (2006)

This study investigates the relative data value of different types of secondaryinformation to estimate the flow and transport parameters in low-permeability media. Data from four boreholes in two ... [more ▼]

This study investigates the relative data value of different types of secondaryinformation to estimate the flow and transport parameters in low-permeability media. Data from four boreholes in two different clay formations are analyzed. Cross-validation is used to estimate the relevance of the different types of secondary data. The flow and transport parameters (hydraulic conductivity, diffusion coefficient and diffusion accessible porosity) are first estimated by kriging using primary information only and then estimated by co-kriging using primary information and one type of secondary information (grain size, gamma ray and resistivity). The kriging residuals, i.e. the difference between the estimated and the measuredvalues, of the different kriging and co-kriging variants are compared to evaluate the relevance of each type of secondary information. This analysis shows that in the different clays and the different boreholes, different types of secondary information result in the largest improvement of the estimates of the flow and transport parameters. It is not possible to determine the "best" type of secondary information for improving the estimation of the flow and transport parameters of low-permeability media. This probably depends on local factors such as the quality of the loggings and the amount of nearby primary and secondary data. [less ▲]

Detailed reference viewed: 47 (2 ULg)
Full Text
See detailClassification of groundwater samples in wetlands using selforganizing maps
Peeters, Luk; Dassargues, Alain ULg

in Stauffer, Fr; Dassargues, Alain (Eds.) Quantitative Geology from Multiple Sources: S10 Use of multiple sources in conditioning/calibrating groundwater flow and transport models (2006)

Groundwater chemistry in groundwater-fed wetlands often is the result of mixing of discharging groundwater and rainfall in combination with chemical reactions altering the chemical composition, mostly due ... [more ▼]

Groundwater chemistry in groundwater-fed wetlands often is the result of mixing of discharging groundwater and rainfall in combination with chemical reactions altering the chemical composition, mostly due to changes in redox conditions. In this study, a Self-Organizing Map is used to classify chemical groundwater samples of three groundwaterfed wetlands in Belgium in order to identify the origin of groundwater and to deduce redox conditions in the wetlands. The Self-Organizing Map (SOM) algorithm is an unsupervised neural network technique to represent a multidimensional dataset on a two-dimensional grid in a topology-preserving way, allowing investigation of non-linear, complex relationships between variables and grouping of the data (Kohonen, 1995). The SOM is trained with data from a regional groundwater monitoring network and rainfall data. The resulting SOM is able to distinguish between samples of different origin or redox conditions within the regional aquifers. Subsequently, samples of the three wetlands are shown to the SOM and each sample is classified as having a chemical composition comparable to rainfall or to one of the regional aquifers. [less ▲]

Detailed reference viewed: 46 (4 ULg)
Full Text
See detailStochastic analysis of the recharge uncertainty of a regional aquifer in extreme arid conditions
Rojas, Rodrigo; Dassargues, Alain ULg

in Stauffer, Fr.; Dassargues, Alain (Eds.) Quantitative Geology from Multiple Sources: S10 Use of multiple sources in conditioning/calibrating groundwater flow and transport models (2006)

The Pampa del Tamarugal Aquifer (PTA) is an important source of groundwater in northern Chile. Since the study area is situated in the Atacama Desert, the estimation of groundwater recharge based on ... [more ▼]

The Pampa del Tamarugal Aquifer (PTA) is an important source of groundwater in northern Chile. Since the study area is situated in the Atacama Desert, the estimation of groundwater recharge based on conventional hydrological methods is subject to large uncertainties. To account for variations in the groundwater balance, caused by uncertainties in the average recharge rates, randomly generated recharge values with different levels of uncertainty are simulated using a groundwater flow model. Results show that evaporation and groundwater outflows are insensitive to the recharge uncertainty, while the storage terms can vary considerably. Considering current groundwater abstraction and random recharge rates, it is unlikely that the cumulative discharged volume from the aquifer, after a 45 years simulation period, will be larger than 12% of the estimated groundwater reserve. Simulated groundwater heads fluctuations due to uncertainties in the average recharge rates are more noticeable in certain areas. These fluctuations could explain anomalies in the observed groundwater heads in these areas. [less ▲]

Detailed reference viewed: 64 (3 ULg)
Full Text
See detailComparison of Kohonen's Self-Organizing Map algorithm and principal component analysis in the exploratory data analysis of a groundwater quality dataset
Peeters, Luk; Dassargues, Alain ULg

(2006)

Groundwater monitoring networks typically yield large, multivariate datasets. Analysis and interpretation of these datasets starts with an exploratory data analysis in order to summarize the available ... [more ▼]

Groundwater monitoring networks typically yield large, multivariate datasets. Analysis and interpretation of these datasets starts with an exploratory data analysis in order to summarize the available data, extract useful information and formulate hypotheses for further research. Exploratory data analysis is mostly focussed on finding related variables and groupings of similar observations. Traditionally multivariate statistical techniques like principal component analysis (PCA) are used for this purpose. In PCA a linear dimensionality reduction of the original, high dimensional dataset is carried out in order to identify orthogonal directions (principal components) of maximum variance in the dataset based on linear combinations of correlated variables. Projections of the original data in the subspace defined by the principal components can be used to identify groups in the data and to reveal relationships between variables (Davis, 1986). In this study, principal component analysis is compared to Kohonen's self-organizing map (SOM) algorithm. The SOM-algorithm is an artificial neural network technique designed to carry out a non-parametric regression process that is mainly used to represent high-dimensional, nonlinearly related data items in a topology-preserving, often two-dimensional display, and to perform unsupervised classification and clustering (Kohonen, 1995). Both PCA and SOM are applied to a hydrochemical dataset from a monitoring network in two sandy, phreatic aquifers in Central Belgium. The monitoring network consists of 47 monitoring wells each equipped with three filters at different depths, in which 14 variables are measured. The first aquifer, the Diest sands aquifer is of Late Miocene age and consists of coarse, glauconiferous sands and sandstones (Laga et al., 2001). The second aquifer, the Brussels sands aquifer, is of Middle Eocene age and is an heterogeneous formation consisting of an alteration of highly and poorly calcareous sands, locally silicified (Laga et al., 2001). Both techniques succeed in distinguishing between both aquifers and reveal the relationships between variables. The main advantage of PCA is the mathematical quantification of correlation between variables and the expression of the original data in the subspace defined by the principal components. The visualization of the SOM-analysis on the other hand allows a straightforward interpretation of the dataset structure in which even non-linear relationships between variables can be identified. Additionally, the SOM-algorithm can handle a limited amount of missing values in the dataset, contrary to PCA. [less ▲]

Detailed reference viewed: 292 (3 ULg)
Full Text
See detailCaractérisation isotopique des eaux du granite et de l’auréole métamorphique d’Oulmès (Maroc central)
Olive, Philippe; Dassargues, Alain ULg; Griere, Olivier et al

in Integrated Water Resources management and Challenges of the Sustainable Development (2006)

Dans le bassin d’Oulmès sont exploitées et commercialisées par la société des Eaux Minérales d’Oulmès qui constitue le plus gros embouteilleur d’eaux minérales du Maroc :Sidi Ali Lala Haya. Le pluton ... [more ▼]

Dans le bassin d’Oulmès sont exploitées et commercialisées par la société des Eaux Minérales d’Oulmès qui constitue le plus gros embouteilleur d’eaux minérales du Maroc :Sidi Ali Lala Haya. Le pluton granitique, d’âge hercynien, d’Oulmès est un granite à biotite et muscovite. Il présente une fracturation très marquée et un système filonien très développé. L’altération, très poussée, se manifeste par une arénitisation généralisée qui s’étend en profondeur. Le kaolin caractérise cette altération d’origine hydrothermale. L’eau de Lalla Haya émerge dans les granites à la faveur de fissures à une température de 42°C, il s’agit d’une eau carbo-gazeuse, bicarbonatée sodique. L’auréole métamorphique générée par ce granite englobe la formation des schistes en dalles, roches métapélitiques cambro-ordoviciennes homogènes. L’eau de Sidi Ali est faiblement minéralisée, elle aussi bicarbonatée sodique avec une pression partielle de CO2 non négligeable L’utilisation de l’outil isotopique a permis de préciser un certain nombre de points concernant la recharge et l’écoulement des eaux souterraines dans le bassin d’Oulmès. Les teneurs en 18O d’une vingtaine de sources situées autour du site et étagées entre 300 et 2000 m s’alignent suivant un gradient de -0,21 ‰ / 100 m. La zone de recharge commune des eaux du granite et des schistes en dalle se situe vers 1100/1300 m. De plus le rapport 18O/D pour ces deux types d’eau indique un appauvrissement en 18O de près de 1 ‰ dû à un échange avec le CO2 magmatique. Le temps de séjour moyen des eaux dans l’auréole métamorphique est de quelques dizaines d années (présence de 3H thermonucléaire) et, au moins, de plusieurs centaines d’années dans les eaux du massif granitique (absence de 3H thermonucléaire). De la remontée de CO2 magmatique, à 14C mort, il résulte que la teneur en 14C du carbone minéral dissous est quasiment nulle et qu’il vieillit, plus ou moins, les activités en 14C du carbone minéral dissous des eaux de l’auréole. En conclusion l’eau qui s’infiltre dans les fractures du massif granitique où elle se réchauffe suivant un gradient géothermique d’environ 40°C/km. Comme le géothermomètre Na/K indique une température de 165 °C, elle atteint une profondeur de l’ordre de 2 à 3 km. Elle s’est enrichie en CO2 magmatique et remonte par effet de gaz lift et donne naissance à Lalla Haya. Cette remontée ne se limite pas au seul massif granitique mais s’étend à l’auréole métamorphique en profitant des fractures du massif et des filons de quartz en provenance du batholite où elle se mélange, en proportions variables, aux eaux récentes qui se sont infiltrées directement sur les schistes en dalles. Ce sont ces fluides hydrothermaux qui ont donné naissance aux dépôts hydrothermaux autrefois exploités en mines (Sn). [less ▲]

Detailed reference viewed: 478 (12 ULg)