Zugl.: Duisburg, Essen, Univ., Diplomarbeit, 2006

No description available.

Master-Arbeit Univ. St. Gallen, 2007.

Master-Arbeit Univ. St. Gallen, 2008.

Nous présentons ici les dispersions de phonons calculées de manière Ab-initio pour les trois chalcogénures de plomb PbS, PbSe et PbTe. Les branches acoustiques obtenues sont en très bon accord avec les expériences d'IXS ("Inelastic Neutron Scattering" - spectroscopie par diffraction inélastique de neutrons). La chaleur spécifique calculée concorde elle aussi avec les résultats expérimentaux. Enfin, le minimum particulièrement marqué de la branche optique transverse (TO) en Gamma induit par la quasi-ferroélectricité est reproduit de manière qualitative. Par ailleurs, nous observons dans nos calculs une chute prononcée sur la branche optique longitudinale (LO) en Gamma. Par le passé, cette baisse était associée à l'écrantage du champ électrique (associé au mode LO) par des porteurs libres suite à la présence d'impuretés. Mais nos calculs montrent que cela persiste même dans le cas de cristaux parfaits de chalcogénures de plomb. Nous expliquons cette chute comme une "quasi-Anomalie de Kohn" associée au faible gap électronique au point de haute symétrie L. Nous montrons que ce gap peut être réduit à zéro à la suite d'une compression de 1.8% de la constante de maille du cristal.Dans ce cas, les bandes de conduction et de valence montrent un croisement linéaire, les modes TO et LO en Gamma sont dégénérés, et une Anomalie de Kohn très forte apparaît sur le mode LO. Nos travaux apportent par ailleurs un support théorique pour l'interprétation des spectres Raman en fonction du diamètre des nanocristaux de séléniure de plomb (PbSe). En effet,le pic Raman de premier ordre se situe aux alentours de 136 cm-1 (et le pic de second ordre est situé au double de cette fréquence). Ils se décalent vers le haut avec la réduction du diamètre du nanocristal. Nous interprétons ce comportement inhabituel comme un confinement quantique du phonon optique longitudinal (LO). Cette hypothèse est validée par les calculs ab-initio des phonons de films de PbSe, avec une épaisseur allant jusqu'à 15 couches. Ces calculs tiennent compte des effets causés par l'environnement diélectrique. Le mode LO orienté perpendiculairement aux films est en effet décalé vers le haut en fréquences lorsque l'épaisseur des couches se réduit.Notre travail propose un point de départ à l'investigation du couplage électron-phonon dans le matériau massif et dans les nanocristaux de chalcogénures de plomb. Ceci pourra contribuer à une meilleure compréhension des mécanismes d'absorption de photons et à l'utilisation de ces matériaux pour les dispositifs d'émission et d'absorption de lumière. / We present ab-initio phonon dispersion relations for the three lead chalcogenides PbS, PbSe, and PbTe. The acoustic branches are in very good agreement with inelastie neutron-seattering data. Also calculations of the specific heat give good agreement with experimental data. The pronounced minimum of the transverse-optical (TO) branch at Gamma due to the near ferroelectricity of the lead chalcogenides is qualitatively reproduced. ln addition, we find a pronounced dip in the longitudinal-optieal (LO) branch at Gamma. This dip was previously explained as the effect of "free carriers" due to the presence of impurities. The calculations demonstrate that it persists also in the case of pure lead chalcogenides. We explain the dip as a "near Kohn anomaly"which is associated with the small electronic band gap at the high-symmetry point L. We show that this band-gap can be reduced to zero upon compression of the crystal lattice constant by 1.8%. In this case, the conduction and valence bands at L display a linear crossing, the TO and LO mode at Gamma are degenerate, and a very pronounced Kohn anomaly in the LO mode occurs. Furthermore, we have given theoretical and computational support for the interpretation of the diameter dependence of the Raman spectra of lead selenide nanocrystals. The first order Raman peak at about 136cm-1 and its second order overtone at twice this wave number move up in energy with decreasing nanocrystal radius. We interpret this anomalous behavior in terms of quantum confinement of the longitudinal optical (LO) phonon. This interpretation is validated by ab-initio calculations of the phonons of PbSe slabs with up to fifteen layers, taking into account the effects of dielectric embedding. The LO mode perpendicular to the slab shifts indeed upwards with decreasing layer thickness. Our work provides the starting point for the investigation of electron-phonon coupling in bulk and nanocrystalline lead chalcogenides, which should help to better understand the photon absorption mechanisms and the use of these materials in light-harvesting and light-emitting devices.

University, Diss., 2007--Würzburg.

Im Jahre 2001 wurde im Zentrum der Grube Messel, ca. 25 km südlich von Frankfurt gelegen, eine 433 m tiefe Bohrung abgeteuft. Geowissenschaftliche Ergebnisse, die durch die Bohrung gewonnen wurden, konnten die Herkunft des rundlichen Beckens durch eine Maar-Diatrem-Struktur erklären. Die erbohrten Kerne sind vom Hangenden zum Liegenden durch lakustrine Sedimente (0-240 m) und vulkaniklastische Gesteine gekennzeichnet, letztere werden durch Lapillituffe (240-373 m) and der Diatrem-Brekzie (373 433 m) beschrieben. Die Lapillituffe, auf die hier das Hauptaugenmerk gelegt wurde, sind makro- und mikroskopisch schwer differenzierbar und erscheinen als ein einzig massig auftretender, unsortierter vulkaniklastischer Körper, der hauptsächlich aus millimeter- bis zentimeter-großen juvenilen Klasten und Nebengesteinsbruchstücken aufgebaut ist. Die hier vorliegende Arbeit präsentiert die gesteinsmagnetischen Eigenschaften von Kernproben der Messel Vulkaniklastika und erklärt die Herkunft der magnetischen Anomalien, die während des Bohrprojekts 2001 detektiert wurden. Das magnetische Verhalten des eruptierten Materials bezieht sich auf feinkörnige und eisenreiche (Titano) Magnetite, die verteilt in den juvenilen Lapilli auftreten. Experimente der temperaturabhängigen Suszeptibilität sowie isothermale remanente Magnetisierungs- und Hystereseuntersuchungen an den vulkaniklastischen Proben zeigen im Sinne der Zusammensetzung, Koerzivität und Korngröße (Pseudo-Einbereichsteilchen) sehr ähnliche ferrimagnetische Eigenschaften. Das eruptierte Material mit seinen ferrimagnetischen Mineralen besaß bei der Ablagerung ein sehr ähnliches Potential zum primären Remanenzerwerb. Entmagnetisierungsversuche offenbaren Unterscheide im magnetischen Stabilitätsverhalten der erworbenen natürlich remanenten Magnetisierung (NRM). Aufheizexperimente beweisen die Akquisition einer thermisch remanenten Magnetisierung durch Temperatureffekte, die bei der Eruption und der Ablagerung des vulkanischen Gesteins im Diatrem auftraten. Die obere Lapillituffhälfte wurde bei relativ niedrigen Temperaturen (<300 °C), die unter Hälfte bei hohen Temperaturen (>>300 °C) abgelagert. Um den gesteinsmagnetischen Charakter der Messel Maar-Diatrem-Fazies besser zu verstehen, sind zusätzlich die Partikelkorngröße, der relative Anteil und die Form der juvenilen Fragmente sowie deren chemische Zusammensetzung näher untersucht und analysiert worden. Die Methodik der Bildanalyse sowie der Haupt- und Spurenelementanalyse des juvenilen Anteils ermöglicht eine klare Unterteilung der Lapillituffe. Die Kombination der Resultate der Partikelanalytik mit den gesteinsmagnetischen Befunden begünstigt die Einteilung der Vulkaniklastika in eine relativ heiße, geochemisch undifferenzierte und eine kältere, differenzierte Eruptionsphase. Somit liegt am Ende der vulkanischen Aktivität von Messel ein bivalentes Stadium zugrunde. Dabei sind die juvenilen Fragmente für die Temperaturentwicklung und Wärmebedingungen innerhalb des vulkaniklastischen Materials verantwortlich und tragen zur Herkunft der magnetischen Feldanomalien bei. Basierend auf gravimetrischen Parametern und den Ergebnissen der Magnetisierungs-eigenschaften der Pyroklastika ermöglicht ein 3D Potentialfeld-Modell der Messel Maar-Diatrem-Struktur die an der Erdoberfläche gemessenen negativen Anomalien zu erklären, sowie die Massen und Volumina der erbohrten Lithozonen zu berechnen. / In 2001 the 433 m deep Messel 2001 borehole was drilled in the centre of the Messel Pit, 25 km south of Frankfurt (Germany). Geoscientific results from this drilling clarified the origin of the circular-shaped basin as a maar-diatreme-structure. Recovered deposits consist of lacustrine sediments (0-240 m) and volcaniclastic rocks such as lapilli tuffs (240-373 m) as well as rocks of the underlying diatreme breccia (373 433 m). The lapilli tuffs, as main interest here, show little differentiation on a macro- and microscopic scale and appear as a massive and unsorted volcaniclastic body with dominating juvenile lapilli and accidental clasts mostly in the range of (sub)millimetres to centimetres in diameter. This study presents rock magnetic properties measured on core samples of the volcaniclastic units and explains the origin of downhole magnetic anomalies detected during the drilling project in 2001. Magnetic behaviour of the erupted material is related to fine-grained, Fe-rich (titano)-magnetites, which are dispersed within the juvenile lapilli. Temperature-dependent susceptibility experiments, isothermal remanent magnetisation and hysteresis investigations demonstrate similar ferrimagnetic properties throughout the volcaniclastic material, in terms of composition, coercivity and grain size (pseudo-single-domain particles) of the ferrimagnetic minerals. Thus, during emplacement of the erupted material, the ferrimagnetic minerals had the same remanence acquisition potential. However, demagnetisation experiments show different magnetic stability behaviour of the acquired natural remanent magnetisation (NRM). Heating experiments prove the acquisition of thermal remanent magnetisation (TRM) dominated by temperature effects which could have been occurred during eruption and deposition of volcanic material, forming the Messel maar-diatreme. It is assumed that the upper half of the lapilli tuffs was deposited at relatively low depositional temperatures (<300 °C), whereas the material of the lower half took advantage of higher temperatures (>>300 °C). To understand the rock magnetic character within the Messel maar-diatreme-facies, particle grain sizes, the degree of the relative fraction dominance and the shape of the juvenile fragments have been studied in more detail. Image analytical methods as well as major and trace element analyses on the juvenile fraction support the clear subdivision of the lapilli tuffs. These findings in combination with rockmagnetic data indicate a separation into a relatively hot, geochemically undifferentiated eruption phase and a colder, differentiated phase. A two-condition eruption stage at the end of the Messel volcanic activity is suggested. The juvenile particles account for the temperature evolution and heat conditions during deposition of the Messel tuffs and contribute to the origin of magnetic field anomalies. Based on gravity parameters and the results of magnetisation properties, the potential field 3D-model of the Messel subsurface explains the negative ground anomalies, calculates the mass and volume parameters of the drilled lithozones and shows the asymmetric appearance of the diatreme-structure.

As deformidades dentofaciais (DDF) compreendem alterações no equilíbrio dentofacial que comprometem a estética e a funcionalidade do sistema estomatognático. O crescimento e desenvolvimento craniofacial são influenciados pela respiração, porém as condições respiratórias nesses indivíduos são pouco abordadas na literatura. O presente trabalho teve por objetivo caracterizar a função respiratória de indivíduos com deformidade dentofacial em relação às vias aéreas superiores e inferiores, bem como aos aspectos da respiração voltados para a fonação, neste mesmo grupo de indivíduos. Para isso foram avaliados 40 indivíduos adultos, divididos em três grupos equilibrados de acordo com gênero e idade: GC (14 indivíduos com equilíbrio dentofacial, Classe I e Padrão I); DDFII (12 indivíduos com DDF, Classe II e Padrão II) e DDFIII (14 indivíduos, Classe III e Padrão III), estando os dois últimos em tratamento ortodôntico preparatório para a cirurgia ortognática. Os pacientes foram submetidos ao exame miofuncional orofacial para avaliação de tipo e modo respiratório, fluxo nasal e possibilidade de uso nasal, utilizando o Protocolo MBGR, bem como à espirometria para avaliação da capacidade respiratória. Foi realizada, ainda, a medida de fluxo aéreo expiratório utilizando espelho milimetrado e calculada a área de embaçamento provocado pelo fluxo. Também foi obtido tempo de fonação de /s/. Na comparação entre os grupos foram utilizados os testes Kruskall-Wallis e teste t; para a comparação entre os aspectos estudados foram aplicados os testes estatísticos Qui Quadrado e ANOVA; para correlações, utilizou-se Pearson e Spearman. Os resultados demonstraram maior ocorrência do tipo respiratório médio superior para os diferentes grupos. No que diz respeito ao modo, mais da metade dos participantes com DDF apresentou respiração oronasal ou oral, sendo que ao realizar a comparação entre os grupos, foi encontrada diferença entre o DDFII e os demais grupos estudados (p<0,001). Quanto ao fluxo expiratório nasal, a maioria dos indivíduos dos grupos DFFII e DDFIII apresentou fluxo reduzido unilateralmente, enquanto para o GC foi simétrico, tendo-se verificado diferença significante entre os grupos com DDF e GC (p=0,011). Quanto à possibilidade de uso nasal, os grupos DFFII e DFFIII apresentaram semelhanças, porém o grupo DFFII apresentou menor tempo de uso nasal em relação aos outros grupos (p<0,001). No escore do Protocolo MBGR, o grupo DFFII apresentou os escores mais altos, ou seja, os piores resultados, ao comparar com os demais grupos (p<0,001). Com relação aos exames objetivos (área do embaçamento do espelho de Altmann, capacidade vital e suporte de ar disponível), a análise estatística não evidenciou diferença significante entre os grupos para todos os aspectos considerados (p>0,05). Por fim, foi encontrada correlação negativa quanto ao tempo fonatório de /s/ e o escore do MBGR correspondente à função respiratória. Concluiu-se que os grupos com DDF apresentam semelhante tipo respiratório, capacidade vital e menor suporte respiratório para a fonação, se comparados ao GC. Além disso, foi verificado que os indivíduos com DDF apresentam modo respiratório oral/oronasal, possibilidade de uso nasal reduzida e menor fluxo expiratório nasal, sendo que os prejuízos na função respiratória influenciaram a utilização do ar para a fonação. / Dentofacial deformities (DFD) are comprised of alterations of the dentofacial balance that compromise the aesthetics and functionality of the stomatognathic system. Craniofacial growth and development are influenced by breathing, however, the conditions of the upper and lower airways in these individuals are poorly addressed in the literature. The present study aimed to characterize the respiratory function in individuals with dentofacial deformities in relation to the upper and lower airways, as well as the aspects of breathing focused on phonation in this same group of individuals. To do so, we evaluated 40 adult individuals who were divided into three groups, balanced by gender and age: GC (14 individuals with dentofacial balance, Class I and Standard I); DFDII (12 individuals, Class II and Standard II) and DFDIII (14 individuals, Class III and Standard III), the latter two in preparatory orthodontic treatment for orthognathic surgery. The subjects were submitted to an Orofacial Myofunctional examination for the evaluation of respiratory type and mode, nasal flow and potential of nasal ability as well as spirometry to evaluate the respiratory capacity. We even performed a measure of expiratory airflow using a graded mirror and calculated the area of haze caused by the flow in cm2, utilizing the Image Pro Plus program. A phonation time of /s/ was also obtained. The qualitative and quantitative variables were submitted to the statistical Chi Square and ANOVA tests, respectively, for the comparison between the groups we utilized the Kruskal-Wallis and t-test, and for the correlations we utilized the Pearson and Spearman tests. The results showed that regarding the respiratory tract, the most prevalent was the upper middle for the different groups. With respect to the mode, more than half of the participants with dentofacial deformities presented oro-nasal or oral breathing, and when performing a comparison between the groups, a difference was found between the DFDII and the other studied groups (p<0.001). With regards to the nasal expiratory flow, most individuals from the DFFII and DDFIII groups showed a reduced flow to the right or to the left, while the GC group was symmetrical, and significant differences were verified between the groups with DFD and GC (p=0.011). Regarding the possibility of nasal use, the DFDII and DFDIII groups presented similarities, however, the DFDII group presented the highest occurrence of possibility of nasal use under one minute when compared to the other groups (p<0.001). In the MBGR Protocol score, the DFDII group had the highest scores, in other words, the worst results when compared to the other groups (p<0.001). With regard to the objective tests (area of haze of the Altmann mirror, vital capacity and available air support), the statistical analysis presented no significant differences between the groups for all aspects considered (p>0.05). Finally, a negative correlation was found regarding the phonation time of /s/ and the MBGR score. It was concluded that individuals with DFD presented an oral / oronasal respiratory mode, a possibility of reduced nasal use, reduced expiratory nasal flow and medium / high respiratory type. Furthermore, it was verified that groups with DFD presented similar vital capacity and lower respiratory support for phonation, when compared to the GC group.

As deformidades dentofaciais (DDF) compreendem alterações no equilíbrio dentofacial que comprometem a estética e a funcionalidade do sistema estomatognático. O crescimento e desenvolvimento craniofacial são influenciados pela respiração, porém as condições respiratórias nesses indivíduos são pouco abordadas na literatura. O presente trabalho teve por objetivo caracterizar a função respiratória de indivíduos com deformidade dentofacial em relação às vias aéreas superiores e inferiores, bem como aos aspectos da respiração voltados para a fonação, neste mesmo grupo de indivíduos. Para isso foram avaliados 40 indivíduos adultos, divididos em três grupos equilibrados de acordo com gênero e idade: GC (14 indivíduos com equilíbrio dentofacial, Classe I e Padrão I); DDFII (12 indivíduos com DDF, Classe II e Padrão II) e DDFIII (14 indivíduos, Classe III e Padrão III), estando os dois últimos em tratamento ortodôntico preparatório para a cirurgia ortognática. Os pacientes foram submetidos ao exame miofuncional orofacial para avaliação de tipo e modo respiratório, fluxo nasal e possibilidade de uso nasal, utilizando o Protocolo MBGR, bem como à espirometria para avaliação da capacidade respiratória. Foi realizada, ainda, a medida de fluxo aéreo expiratório utilizando espelho milimetrado e calculada a área de embaçamento provocado pelo fluxo. Também foi obtido tempo de fonação de /s/. Na comparação entre os grupos foram utilizados os testes Kruskall-Wallis e teste t; para a comparação entre os aspectos estudados foram aplicados os testes estatísticos Qui Quadrado e ANOVA; para correlações, utilizou-se Pearson e Spearman. Os resultados demonstraram maior ocorrência do tipo respiratório médio superior para os diferentes grupos. No que diz respeito ao modo, mais da metade dos participantes com DDF apresentou respiração oronasal ou oral, sendo que ao realizar a comparação entre os grupos, foi encontrada diferença entre o DDFII e os demais grupos estudados (p<0,001). Quanto ao fluxo expiratório nasal, a maioria dos indivíduos dos grupos DFFII e DDFIII apresentou fluxo reduzido unilateralmente, enquanto para o GC foi simétrico, tendo-se verificado diferença significante entre os grupos com DDF e GC (p=0,011). Quanto à possibilidade de uso nasal, os grupos DFFII e DFFIII apresentaram semelhanças, porém o grupo DFFII apresentou menor tempo de uso nasal em relação aos outros grupos (p<0,001). No escore do Protocolo MBGR, o grupo DFFII apresentou os escores mais altos, ou seja, os piores resultados, ao comparar com os demais grupos (p<0,001). Com relação aos exames objetivos (área do embaçamento do espelho de Altmann, capacidade vital e suporte de ar disponível), a análise estatística não evidenciou diferença significante entre os grupos para todos os aspectos considerados (p>0,05). Por fim, foi encontrada correlação negativa quanto ao tempo fonatório de /s/ e o escore do MBGR correspondente à função respiratória. Concluiu-se que os grupos com DDF apresentam semelhante tipo respiratório, capacidade vital e menor suporte respiratório para a fonação, se comparados ao GC. Além disso, foi verificado que os indivíduos com DDF apresentam modo respiratório oral/oronasal, possibilidade de uso nasal reduzida e menor fluxo expiratório nasal, sendo que os prejuízos na função respiratória influenciaram a utilização do ar para a fonação. / Dentofacial deformities (DFD) are comprised of alterations of the dentofacial balance that compromise the aesthetics and functionality of the stomatognathic system. Craniofacial growth and development are influenced by breathing, however, the conditions of the upper and lower airways in these individuals are poorly addressed in the literature. The present study aimed to characterize the respiratory function in individuals with dentofacial deformities in relation to the upper and lower airways, as well as the aspects of breathing focused on phonation in this same group of individuals. To do so, we evaluated 40 adult individuals who were divided into three groups, balanced by gender and age: GC (14 individuals with dentofacial balance, Class I and Standard I); DFDII (12 individuals, Class II and Standard II) and DFDIII (14 individuals, Class III and Standard III), the latter two in preparatory orthodontic treatment for orthognathic surgery. The subjects were submitted to an Orofacial Myofunctional examination for the evaluation of respiratory type and mode, nasal flow and potential of nasal ability as well as spirometry to evaluate the respiratory capacity. We even performed a measure of expiratory airflow using a graded mirror and calculated the area of haze caused by the flow in cm2, utilizing the Image Pro Plus program. A phonation time of /s/ was also obtained. The qualitative and quantitative variables were submitted to the statistical Chi Square and ANOVA tests, respectively, for the comparison between the groups we utilized the Kruskal-Wallis and t-test, and for the correlations we utilized the Pearson and Spearman tests. The results showed that regarding the respiratory tract, the most prevalent was the upper middle for the different groups. With respect to the mode, more than half of the participants with dentofacial deformities presented oro-nasal or oral breathing, and when performing a comparison between the groups, a difference was found between the DFDII and the other studied groups (p<0.001). With regards to the nasal expiratory flow, most individuals from the DFFII and DDFIII groups showed a reduced flow to the right or to the left, while the GC group was symmetrical, and significant differences were verified between the groups with DFD and GC (p=0.011). Regarding the possibility of nasal use, the DFDII and DFDIII groups presented similarities, however, the DFDII group presented the highest occurrence of possibility of nasal use under one minute when compared to the other groups (p<0.001). In the MBGR Protocol score, the DFDII group had the highest scores, in other words, the worst results when compared to the other groups (p<0.001). With regard to the objective tests (area of haze of the Altmann mirror, vital capacity and available air support), the statistical analysis presented no significant differences between the groups for all aspects considered (p>0.05). Finally, a negative correlation was found regarding the phonation time of /s/ and the MBGR score. It was concluded that individuals with DFD presented an oral / oronasal respiratory mode, a possibility of reduced nasal use, reduced expiratory nasal flow and medium / high respiratory type. Furthermore, it was verified that groups with DFD presented similar vital capacity and lower respiratory support for phonation, when compared to the GC group.

Le Nunavut Central renferme la région où s'est développé l'un des principaux centres de dispersion glaciaire de l'inlandsis Laurentidien au cours de la dernière glaciation, soit le Dôme du Keewatin. La présence d'une forte couverture de sédiments glaciaires complique l'exploration minérale de ce territoire qui possède un fort potentiel économique, notamment en ce qui concerne les gisements aurifères. L'utilisation des dépôts de surface comme méthode de prospection représente donc une alternative prometteuse dans la recherche de gisements, mais cette approche est compliquée par une histoire glaciaire complexe caractérisée par des mouvements glaciaires variés découlant de migrations importantes de la ligne de partage des glaces du Keewatin (Keewatin Ice Divide-KID). Le but de ce projet était de vérifier la validité des méthodes de prospection glacio-sédimentaire comme outils pour l'exploration minérale. Les retombées de ce projet ont permis de fournir des contraintes sur les modes de transport glaciaire prévalant dans une région affectée par des multiples écoulements glaciaires. Les nombreuses réorganisations du KID ont eu des répercussions sur le patron de dispersion des dépôts de surface, ainsi que sur la dispersion aurifère. L'étude du contenu géochimique, pétrographique et minéralogique des tills de surface a été effectuée, et jumelée à une cartographie de détails des sédiments de surface et des mouvements glaciaires apparents. Nous avons documenté de nombreux écoulements glaciaires dont le principal est orienté vers le N-NNO. Plusieurs anomalies ainsi que des traînées de dispersion aurifères ont pu être détectées par la géochimie et le comptage des grains d'or visibles. Ces méthodes ont également permis d'établir des estimations sur les distances de transport pour les secteurs couverts par la campagne d'échantillonnage du till. Des traînées présentant des palimpsestes ont été répertoriées soulignant l'importance des remaniements causés par cet ancien centre de dispersion glaciaire. Des variations de la géomorphologie du territoire ont été documentées, par la présence d'un corridor composé de linéations glaciaires de taille variable, suggérant l'existence de variations au sein de la dynamique glaciaire locale et sur le transport glaciaire. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Dôme du Keewatin, prospection glacio-sédimentaire, dispersion aurifère, transport glaciaire, anomalie géochimique.