No description available.

Anisotropy of magnetic susceptibility (AMS) have been used with great success for determining the internal structure and fabrics of Jurassic and Cretaceous plutons of felsic-intermediate compositions in the White-Inyo Range of eastern California. However, application of the AMS techniques to the Mount Barcroft pluton, located in the northern White Mountains, has yielded anomalous scalar and directional AMS data indicative of unprecedented heterogeneity on the meter-kilometer scale. The 165 Ma Mount Barcroft pluton is primarily of granodiorite composition and was intruded into the Barcroft Structural Break, a northeast striking, steeply dipping structure that juxtaposes Mesozoic metavolcanic rocks to the north against Proterozoic-Paleozoic metasedimentary rocks to the south. Two oriented hand samples (A and B) were collected at each of 78 sites distributed on a 1 kilometer grid pattern across the 5 by 15 kilometer Mount Barcroft pluton and oriented cores were prepared from these hand samples for AMS analysis. Microstructure identification of single thin sections prepared for each sample site yielded primarily magmatic with minor solid-state structures. A highly heterogeneous distribution of scalar parameters (Km, P%, F%, L%, T) was documented both between sample sites and between the A and B cores at individual sites. The heterogeneity may be the result of complex mineral assemblages and the interaction between different magnetic mineral species ranging from single domain to pseudo-single domain to multidomain magnetite. More problematic are the directional parameters between A and B cores in orientation and fabric type (e.g. prolate and oblate susceptibility ellipsoids) occur which cannot be readily explained by a complex mineral assemblage. Different fabric types in A and B cores at individual sample sites could be the result of discrete, temporally unrelated, magma pulses of variable composition and viscosity. Heterogeneity of scalar and directional AMS parameters in the Mount Barcroft pluton, and its contrast with the homogeneous AMS signatures within similar age plutons to the south, may provide evidence for a previously unrecognized magma source beneath the northern White Mountains. / Master of Science

<p>The physical properties of the coarse fraction of the till (0.4 to 20 cm) and the surface boulders have been studied at two different sites in Sweden. The research work included: development of a new image analysis software for 3D size and shape measurements of particles; lithological analysis on multiple size fractions in till and magnetic susceptibility survey on coarse till clasts, surface boulders and local bedrock.</p><p>The new 3D image analysis method provides an enormous amount of size and shape data for each particle in the coarse fraction (2 to 20 cm) in till. The method is suitable for field study, cost effective and the software is executable in Matlab. The field imaging method together with the image analysis software give non subjective results of size and shape of coarse particles and makes it feasible and easy to study representative sample size, which is one tonne for testing clasts of size up to 20 cm.</p><p>The lithological analysis of the multiple size fraction of the till clasts has been investigated on six different size fractions of the till (0.4 to 20 cm); the result of the different samples from the two sites shows that this method can potentially be used as a stratigraphic tool in the areas where there is no unique indicator lithologies.</p><p>The magnetic susceptibility has been made on the surface boulders, the 6-20 cm till fraction and on insitu bedrock outcrops near to the study sites. The method has good potential for determining stratigraphic relationships between different till units as well as for determining the provenance ofcoarse clasts and surface boulders.</p>

No description available.

No description available.

No description available.

No description available.

Analyse pétrophysique et anisotropie des roches détritiques dans des systèmes en compression et sous influence de failles actives : Exemple des prismes de Taiwan et du prisme de Nankai (Japon)L'objectif de cette thèse est l'étude de la déformation enregistrée par des roches d'origine détritique dans des domaines sujets au raccourcissement tectonique sub-horizontal (Layer Parallel Shortening) et à des failles actives. Cette étude est basée sur la caractérisation de diverses propriétés physiques et de leur anisotropie à l'échelle de l'échantillon dans le but de décrire à plus grande échelle la structure d'un prisme d'accrétion. Deux prismes ont ainsi été échantillonnés, le premier est le prisme inactif de Taiwan dans le cadre du projet TCDP et le second considéré comme actif celui de Nankai dans le cadre du projet NanTroSeiZE. La microstructure d'une roche sédimentaire, y compris en l'absence de déformation tectonique, présente toujours une ou plusieurs caractéristique(s) anisotrope(s) liée(s) à la forme, à l'orientation préférentielle ou à l'arrangement de ses éléments constitutifs. De nombreux travaux ont porté sur les conséquences de ces anisotropies sur les propriétés physiques, d'abord dans un but prédictif, puis selon une démarche inverse visant à caractériser, à l'aide de modèles, microstructures et histoire tectonique associée. Dans cette thèse la confrontation des résultats obtenus pour différentes propriétés physiques (principalement vitesses des ondes acoustiques, susceptibilité magnétique et aimantation rémanente) met en évidence des réponses sélectives liées à un fort contrôle de la lithologie.Au niveau de prisme de Taiwan, deux résultats majeurs ont été obtenus. D'une part, la comparaison des anisotropies magnétiques et acoustiques a permis de montrer une évolution différentielle de la déformation entre les roches riches en matrice (siltite) par et celles plus riches en grain sableux (grès). D'autre part, les résultats combinés de l'anisotropie des ondes P, l'étude microstructurale et la minéralogie magnétique, montrent un comportement particulier des échantillons situé dans le mur de la faille FZB1136, considérée comme responsables du séisme de Chi-Chi en 1999. Un réseau de structures dilatantes fortement perméable à permis la circulation de fluides, de néo-cristallisation de calcite et de néoformation de minéraux magnétique. Sur le prisme de Nankai, une estimation de la quantification de la déformation enregistrée par les échantillons du prisme est modélisée en utilisant le modèle de March et les paramètres de susceptibilité magnétique. Les différents travaux réalisés dans cette thèse mettent en évidence un couplage direct de certaines propriétés physiques mesurées avec certains effets de déformation, chaque propriété caractérisant un point précis de la fabrique enregistré dans les roches.Mots-clefs : Anisotropie, susceptibilité magnétique, vitesses d'ondes ultrasoniques, déformation, fabrique, microstructures, faille inverse, TCDP, NanTroSeiZE. / Petrophysics of sedimentary rocks in compressive regime near active faults: examples of the Taiwan and Nankai accretionary prismsThe objective of this PhD is to study the deformation recorded by detrital rocks in areas subject to sub-horizontal tectonic shortening (Layer Parallel Shortening) and active faults. This study is based on the characterization of various physical properties and their anisotropy at sample scale in order to describe larger-scale structure of an accretionary prism. Two prisms have been sampled, the first is the inactive in Taiwan prism (TCDP project) and the second active the Nankai prism (NanTroSeiZE project).Sedimentary rocks microstructures, regardless of the degree to which they were loaded tectonically, always present some anisotropic characteristic emerging from a preferential shape, orientation or distribution of its constituents. Numerous studies have focused on the effect of such anisotropies on physical properties, first for prediction purposes, then to conversely get diffuse strain insight through the use of various effective medium models. In this thesis, the comparison between results obtained in discrete samples for various physical properties (essentially acoustic wave velocities, magnetic susceptibility and remanent magnetization) reveals selective responses due to a strong lithologic control.In TCDP, two significant results are reported. On the one hand, comparison of magnetic and acoustic anisotropy showed a differential evolution of deformation between the matrix-rich rocks (siltstones) and those with coarser granular fraction (sandstone). On the other hand, the combined results of the anisotropy of P waves velocity, microstructural analysis and magnetic mineralogy, show a peculiar behavior of the samples located in the wall of the fault FZB1136, considered to be responsible of the Chi-Chi earthquake in 1999. A network of highly permeable dilatant structures allowed the circulation of fluids, neo-crystallization of calcite and neoformation of magnetic minerals. On the Nankai prism, an estimate of quantifying the deformation recorded by the samples of the prism is modeled using a simple March-type model and the parameters of magnetic susceptibility. The various work in this thesis show a direct coupling of physical properties measured with some aspect of deformation, each property characterizing a specific point of the fabric recorded in rocks.Keywords : Anisotropy, magnetic susceptibility, ultrasonic wave velocity, strain, fabric, microstructures, thrust fault, TCDP, NanTroSeiZE.

A química mineral e de rocha e determinações de susceptibilidade magnética (SM) de granitóides sin- e tardi orogênicos (610- 600 Ma) localizados na porção oriental do batólito Agudos Grandes (porção central do Cinturão Ribeira, SE do Brasil) foram utilizadas para determinar as condições de cristalização e as implicações em sua petrogênese. Os granitos sin-orogênicos são metaluminosos e têm índice de cor (IC) entre 8 e 15, dado por hornblenda, biotita, titanita e magnetita (unidade HBgd). As temperaturas liquidus obtidas pelo geotermômetro de saturação em apatita decrescem de 1000 a 950º C com o fracionamento. As temperaturas solidus obtidas pelo geotermômetro hornblenda-plagioclásio, variam de 720 a 800º C e mostram aumento sistemático em direção a leste, refletindo diminuição da a(H2O) dos magmas. As pressões obtidas por geobarometria de Al em hornblenda variam muito pouco (3,6 a 4,5 kbar) mostrando não haver variações significativas no nível de exposição do batólito. Esses granitos cristalizaram sob condições fortemente oxidantes (DNNO ³ + 2), como revelado pela alta SM, pelas composições da biotita e da ilmenita reliquiar e pelo consumo da ilmenita sob fO2 acima do buffer TMQA. Os granitóides tardi-orogênicos (maciço Piedade) variam de metaluminosos a marginalmente peraluminosos. A unidade metaluminosa portadora de titanita e magnetita (BmgT; IC=8) cristalizou sob condições comparáveis às dos granitos sin-orogênicos. As demais unidades são formadas por granitos com biotita e ilmenita (± muscovita e magnetita) e IC variável entre 15 e 5. Essas rochas em geral cristalizaram sob condições mais reduzidas (QFM a DNNO = + 2), como revelado pela SM mais baixa e pela composição de biotita e ilmenita, mas localmente foram afetadas por processos de oxidação pós-magmática. As temperaturas liquidus obtidas a partir do geotermômetro de saturação em apatita para todas as rochas do maciço Piedade são tão elevadas quanto as dos granitos sin-orogênicos. Estimativas de pressão são precárias, mas as composições de muscovitas sugerem valores da ordem de 4 kbar. Os dados obtidos no presente trabalho são consistentes com modelos que admitem um vínculo genético entre os granitos sin- e tardi-orogênicos do batólito Agudos Grandes. Em particular as tendências de variação química contínua das biotitas, com aumento progressivo do componente siderofilita para os granitos com muscovita, paralelas com a diminuição de SM e diminuição de fO2, podem sugerir que diferenças observadas refletem processos de contaminação de magmas metaluminosos por rochas metassedimentares mais reduzidas. / Magnetic susceptibility (MS) measurements and mineral and rock chemistry were used to infer crystallization conditions of syn- to late-orogenic (610-600 Ma) granites of the eastern portion of the Agudos Grandes batholith (central Ribeira Belt, SE Brazil). The syn-orogenic granites are metaluminous and have color indices (IC) of 8 to 15 given by hornblende, biotite, titanite and magnetite (unit HBgd). Liquidus temperatures obtained by apatite saturation thermometry decrease slighlty, from 1000 to 950°C with fractionation. Solidus temperatures, derived from hornblende-plagioclase thermometry, raise eastwards in the batholith from 720 to 800° C, reflecting decreasing a(H2O) of the magmas. Pressures derived from Al-in-hornblende barometry are nearly invariable (3.6 to 4.5 kbar), showing that the batholith is exposed at approximately the same level of intrusion along the studied section. These granites crystallized under strongly oxidizing conditions (DNNO ³ + 2), as revealed by high MS, by the compositions of biotite and relict ilmenite, and by ilmenite consumption due to fO2 above the TMQA buffer. The late-orogenic granites (Piedade massif) are metaluminous to marginally peraluminous. The metaluminous unit (BmgT; IC=8) bears titanite and magnetite, and crystalized under conditions comparable to those shown by the syn-orogenic massifs. The remaining units are made up of biotite + ilmenite (± muscovite and magnetite) granites with variable IC (15 to 5). These rocks crystallized mostly under more reduced conditions (QFM to DNNO = + 2), as revealed by lower MS and by the compositions of biotite and ilmenite, but were locally affected by post-magmatic oxidation processes. The liquidus temperatures obtained from apatite saturation thermometry in all granites from the Piedade massif are as high as those of the syn-orogenic massifs. Pressure estimates, based on muscovite compositions, are less reliable, but yield values around 4 kbar. The data obtained in this work are consistent with models which admit a genetic link between the syn-orogenic and the late-orogenic granites of the Agudos Grandes batholith. Continuous chemical variation of biotites, with the siderophyllite component increasing steadily towards the muscovite-bearing granites, and parallel decreasing of MS and fO2 suggest that contamination of metaluminous magmas by more reduced metasediments could explain most of the variation observed.

O trabalho envolve o estudo de amostras de poli(o-metoxianilina) (POMA) , dopadas com ácido trifluoracético (TFA) através das técnicas de espectroscopia de Ressonância Paramagnética Eletrônica (RPE) de onda contínua e pulsada. O sinal de RPE observado é atribuído a elétrons desemparelhados na cadeia polimérica, denominados pólarons. Uma vez que estes pólarons possuem carga elétrica e spin eletrônico, os estudos de RPE podem fornecer informações a respeito de sua mobilidade e sobre as propriedades de transporte no material em escala microscópica. O efeito da presença de oxigênio molecular, O2, (S=1), sobre a forma da linha CW é estudado em função do grau de dopagem e do envelhecimento das amostras. O alargamento observado da linha de RPE deve-se a processos de colisão entre o pólaron móvel e os spins localizados do O2. Durante uma colisão, os dois spins interagem entre si através de interações de troca magnética, produzindo spin-flips simultâneos. Uma vez que os spins fixos estão fortemente acoplados com a rede, o processo de relaxação spin-rede do pólaron torna-se muito eficiente, produzindo o alargamento da linha. Como resultado deste processo de colisões, a dependência da largura de linha em função da temperatura mostra um máximo em torno de 190 K. Modelos teóricos serão apresentados, a partir dos quais serão estimados os valores para a mobilidade do pólaron, raio de ação da interação pólaron-oxigênio e constantes de acoplamento. Amostras sintetizadas na presença de oxigênio possuem tempos de relaxação muito curtos em toda a faixa de temperatura estudada (2-280 K), impossibilitando a observação da RPE pulsada. Amostras envelhecidas mostram um comportamento diferente, característico da substituição do oxigênio por água, que leva ao cancelamento do efeito de alargamento. Nestas amostras, assim como em amostras sintetizadas em atmosfera inerte, estudos adicionais de RPE pulsada permitem, através de técnicas associadas ao eco de spins eletrônicos, ESE, a obtenção dos tempos de relaxação spin-spin e spin-rede, assim como o estudo das interações hiperfinas entre pólaron e núcleos vizinhos, 1H, 13C e 14N, que não são resolvidas no espectro CW. A quantificação e qualificação de núcleos interagentes, os quais possuem desdobramentos hiperfinos fracos, podem ser realizadas através das técnicas uni e bidimensionais, como ESEEM, 2DESEEM e HYSCORE. / Continuous wave (CW) and pulsed Electron Paramagnetic Resonance (EPR) techniques are used to study structural and dynarnical properties of poly(o-metoxyaniline) (POMA) doped in trifluoroacetic (TFA) solution. The observed EPR spectrum is attributed to chain unpaired electron spins named polarons. Since polarons carry both charge and spin, EPR studies can provide information about charge transport properties of the material on a microscopic scale. The width of the EPR signal reflects the interaction of the polarons with their environments. In the present study, special attention is given to the EPR linewidth, which is usually broadened by the presence of molecular oxygen, O2, (S=1). The oxygen induced linewidth is explained by the mutual spin flips occurring during the collision of a mobile polaron with fixed paramagnetic O2. The temperature dependence of the linewidth shows a maximum around 190K associated with these collision processes. Such effects are studied as a function of doping concentration, sample aging and vacuum conditions. From a theoretical model proposed in the field, some parameters, associated with the polaron mobility and exchange interaction between polaron and oxygen, are estimated. All synthesized samples have very short spin relaxation times in all the studied temperature range (2-280K), making impossible their observation by the pulsed EPR techniques. Aged samples show a different behavior; their long relaxation times seem to indicate that the substitution of O2 by H2O has promoted the canceling of the broadening effect. Studies are under progress to establish a sample preparation procedure in which the resulting samples are free of molecular oxygen. Aged samples have been used to perform preliminary studies conducted by the pulsed EPR techniques. Spin-echo spectroscopy and relaxation time measurements were interpreted on the basis of the interaction of the polaron with neighboring nuclei, such as 1H, 13C e 14N, which are not resolved in the CW spectra. To better understand the nature of the CW and pulsed EPR spectroscopy, one special chapter will introduce the several techniques, which are commonly employed in our research.