The Marathon PGM-Cu deposit is hosted by the Coldwell alkaline complex, which consists predominantly of gabbro and syenite and was emplaced at 1108 Ma as part of the Mid-Continent Rift System. Mineralization at the Marathon PGM-Cu deposit is hosted by the Two Duck Lake Gabbro (TDLG), a fresh olivine-bearing gabbro. The Marathon deposit contains several zones of mineralization including the Basal Zone, the Main Zone and the W-Horizon. The W-Horizon is a high-grade PGE zone characterized by low S, low Cu/Pd and high Cu/Ni. The sulphide mineral assemblage is predominantly chalcopyrite and bornite. This contrasts with the Main Zone where the dominant sulphide mineral assemblage is chalcopyrite and pyrrhotite. The Main Zone contains higher S, higher Cu/Pd and shows a decrease in Cu/Pd and pyrrhotite/chalcopyrite from base to top. Four drill holes were selected for detailed analysis to characterize the W-Horizon style of mineralization. Detailed petrographic study of the pristine and largely unaltered TDLG shows that wide spread hydrothermal alteration is not responsible for the mineralization. Detailed outcrop mapping shows that the TDLG intruded as a series of multiple intrusions in a dynamic magmatic system. Geochemical studies through the W-Horizon show that the mineralization is not the result of crystallization in a layered intrusion. The results of geochemical assays and electron microprobe analysis of olivine grains show that the chemistry through the TDLG hosting the W-Horizon is erratic. This data supports the TDLG intruding as a series of sills in a dynamic conduit environment. The calculated sulphide metal tenors for the W-Horizon are higher than can be explained by closed system R Factor models. Multistage dissolution upgrading in an open system is examined as the process forming the W-Horizon. This model is able to produce the sulphide metal tenors observed in the W-Horizon. Sulphur loss also affects grades and tenors and was examined through geochemical and petrological data. The change in sulphide mineral assemblage from a pyrrhotite and chalcopyrite (S-rich) to chalcopyrite and bornite (S-poor) supports S-loss. Whole rock S and Se contents are also analyzed to investigate S loss, a lower S/Se indicates that sulphur has been removed from the system. Average S/Se values are ~800 for the W-Horizon, ~1980 for the Main Zone and ~1700 in unmineralized samples. The very low S/Se observed within the W-Horizon supports S-loss. Sulphur loss in a dynamic magmatic conduit system is proposed for the formation of the W-Horizon mineralization. In this model sulphur undersaturated basaltic magma interacted with an immiscible sulphide liquid in a magma conduit, resulting in the dissolution of sulphide into the basaltic melt and PGE enrichment.

Meta-mafic intrusions with an intrusion age of 1.6-0.9 Ga are found along a north-south trend in theTransitional section of the Eastern Segment in Sweden. These intrusions are garnet-bearing and thus anexception to other meta-mafic intrusions found in Sweden. Meta-mafic intrusions that are garnet-bearingare usually found in the Caledonides to the northeast and in the south west of Sweden where the pressureshave been naturally high due to orogenic events or subduction.The study was conducted on these intrusions around the community of Ölme, to understand themetamorphic and metasomatic history of the area. The focus lies on the transition from magmaticgabbroic intrusions to metamorphosed metagabbros and highly foliated garnet-amphibolites. AveragePT estimates was calculated using THERMOCALC and classical geothermobarometry, so that acomparison between the qualitative and quantitative data could be made.The study indicates metamorphism at amphibolite to upper amphibolite facies conditionsfor the metagabbros and the garnet-amphibolites.Average PT-estimates for the garnet-amphibolites gives metamorphic peak temperatures of 680°-730° Cwith pressures of 9.0-11.0 kbar at the Träfors locality, and metamorphic peak temperatures of 660°-770° Cwith pressures of 9.5-11.0 kbar at the Skråkvik locality. These results are comparable to research donefurther to the south on similar intrusions, with temperatures of 700° C and pressures of 10 kbar.It is concluded that the meta-mafic intrusions at the Skråkvik locality have been metamorphosed in adry system, in contrast to the Träfors locality which seems to have been affected by more pervasiveretrograde metamorphism and fluid-rock interaction. It is also concluded that mafic intrusionscan preserve their magmatic textures even under high pressure conditions.

The Marathon PGM-Cu deposit is hosted by the Coldwell alkaline complex, which consists predominantly of gabbro and syenite and was emplaced at 1108 Ma as part of the Mid-Continent Rift System. Mineralization at the Marathon PGM-Cu deposit is hosted by the Two Duck Lake Gabbro (TDLG), a fresh olivine-bearing gabbro. The Marathon deposit contains several zones of mineralization including the Basal Zone, the Main Zone and the W-Horizon. The W-Horizon is a high-grade PGE zone characterized by low S, low Cu/Pd and high Cu/Ni. The sulphide mineral assemblage is predominantly chalcopyrite and bornite. This contrasts with the Main Zone where the dominant sulphide mineral assemblage is chalcopyrite and pyrrhotite. The Main Zone contains higher S, higher Cu/Pd and shows a decrease in Cu/Pd and pyrrhotite/chalcopyrite from base to top. Four drill holes were selected for detailed analysis to characterize the W-Horizon style of mineralization. Detailed petrographic study of the pristine and largely unaltered TDLG shows that wide spread hydrothermal alteration is not responsible for the mineralization. Detailed outcrop mapping shows that the TDLG intruded as a series of multiple intrusions in a dynamic magmatic system. Geochemical studies through the W-Horizon show that the mineralization is not the result of crystallization in a layered intrusion. The results of geochemical assays and electron microprobe analysis of olivine grains show that the chemistry through the TDLG hosting the W-Horizon is erratic. This data supports the TDLG intruding as a series of sills in a dynamic conduit environment. The calculated sulphide metal tenors for the W-Horizon are higher than can be explained by closed system R Factor models. Multistage dissolution upgrading in an open system is examined as the process forming the W-Horizon. This model is able to produce the sulphide metal tenors observed in the W-Horizon. Sulphur loss also affects grades and tenors and was examined through geochemical and petrological data. The change in sulphide mineral assemblage from a pyrrhotite and chalcopyrite (S-rich) to chalcopyrite and bornite (S-poor) supports S-loss. Whole rock S and Se contents are also analyzed to investigate S loss, a lower S/Se indicates that sulphur has been removed from the system. Average S/Se values are ~800 for the W-Horizon, ~1980 for the Main Zone and ~1700 in unmineralized samples. The very low S/Se observed within the W-Horizon supports S-loss. Sulphur loss in a dynamic magmatic conduit system is proposed for the formation of the W-Horizon mineralization. In this model sulphur undersaturated basaltic magma interacted with an immiscible sulphide liquid in a magma conduit, resulting in the dissolution of sulphide into the basaltic melt and PGE enrichment.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

The rheology and strength of the lower crust play a key role in lithosphere dynamics, influencing the orogenic cycle and how plate tectonics work. Despite their geological importance, the processes that cause weakening of the lower crust and strain localization are still poorly understood. Through microstructural analysis of naturally deformed samples, this PhD aims to investigate how weakening and strain localization occurs in the mafic continental lower crust. Mafic granulites are analysed from two unrelated continental lower crustal shear zones which share comparable mineralogical assemblages and high-grade deformation conditions (T > 700 °C and P > 6 Kbar): the Seiland Igneous Province in northern Norway (case-study 1) and the Finero mafic complex in the Italian Southern Alps (case-study 2). Case-study 1 investigates a metagabbroic dyke embedded in a lower crustal metasedimentary shear zone undergoing partial melting. Shearing of the dyke was accompanied by infiltration of felsic melt from the adjacent partially molten metapelites. Findings of case-study 1 show that weakening of dry and strong mafic rocks can result from melt infiltration from nearby partially molten metasediments. The infiltrated melt triggers melt-rock reactions and nucleation of a fine-grained (< 10 µm average grain size) polyphase matrix. This fine-grained mixture deforms by diffusion creep, causing significant rheological weakening. Case-study 2 investigates a lower crustal shear zone in a compositionally-layered mafic complex made of amphibole-rich and amphibole-poor metagabbros. Findings of case-study 2 show that during prograde metamorphism (T > 800 °C), the presence of amphibole undergoing dehydration melting reactions is key to weakening and strain localization. Dehydration of amphibole generates fine-grained symplectic intergrowths of pyroxene + plagioclase. These reaction products form an interconnected network of fine-grained (< 20 µm average grain size) polyphase material that deforms by diffusion creep, causing strain partitioning and localization in amphibole-rich layers. Those layers without amphibole fail to produce an interconnected network of fine grained material. In this layers, plagioclase deforms by dislocation creep, and pyroxene by microfracturing and neocrystallization. Overall, this PhD research highlights that weakening and strain localization in the mafic lower crust is governed by high-T mineral and chemical reactions that drastically reduce grain size and trigger diffusion creep.

Os Plutons Palermo (ca. 250 km2) e Rio Negro (ca. 130 km2) afloram na região Alto Rio Negro (PR) e fazem parte da Província Graciosa, uma província Neoproterozóica (ca. 580 Ma) constituída por granitos e sienitos na região S-SE do Brasil. Em ambos os plutons afloram variedades de rochas graníticas, predominantes, e gabro-dioríticas, bem como rochas híbridas, principalmente granodioritos. Estes plutons apresentam zonamento em geral bem marcado, que é tipicamente inverso caso do Pluton Rio Negro. As rochas graníticas principais correspondem a sieno- e monzogranitos predominantes e álcali-feldspato granitos e quartzo monzonitos subordinados de natureza metaluminosa a levemente peraluminosa. São rochas com estruturas maciças e texturas variadas que apresentam como associação mineral máfica típica hb + bi ± all + zr + ap ± ti + mt + ilm); as rochas gabro-dioríticas incluem gabro-dioritos e quartzo monzogabro-dioritos metaluminosos com estruturas maciças e granulações fina a média, caracterizadas pela associação cpx ± opx + hb + bt ± ti ± ap ± zr. A composição dos plagioclásios nestas rochas varia no intervalo de labradorita a andesina. As rochas híbridas são principalmente granodioritos que se caracterizam por uma variedade de estruturas e texturas indicativas de desequilíbrio, compatíveis com processos de coexistência e mistura parcial entre líquidos ácidos e básico-intermediários que formaram os granitos principais e os gabro-dioritos. Estas rochas são mais comuns no Pluton Rio Negro. A associação mineral máfica é similar, mas com abundâncias distintas de fases, à observada para os granitos principais. Nas rochas graníticas os anfibólios são Fe-hornblenda e Fe-edenita, com valores 0,65 < fe# < 0,95, os valores mais elevados ocorrendo nos álcali-feldspato granitos, as biotitas apresentam 0,71 < fe# < 0,99, observando-se que o componente annítico é também maior nestas últimas rochas. No caso das rochas gabro-dioríticas, os valores fe# variam entre 0,48 e 0,59, 0,41 e 0,56, 0,47 e 0,53 e 0,54 a 0,57 para ortopiroxênio, clinopiroxênio, anfibólio e biotita, respectivamente. As composições médias de orto- e clinopiroxênio coexistentes são \'Wo IND.46\'\' En IND.30\'\' Fe IND.24\' e \'Wo IND.3\'\' En IND.42\'\'Fe IND.55\' e a sugerem uma possível afinidade toleítica, ou cálcio-alcalina, para magma original. Os padrões de elementos terras raras revelam fatores de enriquecimento entre 1-10, 50-70, 100-300 em relação à composição condrítica para ortopiroxênio, clinopiroxênio e anfibólio nas rochas estudadas, com fracionamento bem marcado dos elementos leves em relação aos pesados no ortopiroxênio, não observado no caso de clinopiroxênio e anfibólio. Todos os padrões são caracterizados por anomalia negativa bem marcada de Eu. As pressões de cristalização dos magmas foram estimadas entre 1-3,5 kbar, mas os valores acima de ca. 2 kbar possivelmente não tenham significado real, dadas as composições mais ferroanas dos anfibólios. Temperaturas de saturação de zircão e/ou apatita e de equilíbrio entre orto- e clinopiroxênio, anfibólio-plagioclásio indicam intervalos de cristalização entre ca. 1000 e 750° C para as rochas gabro-dioríticas e entre ca. 900 e 670° C para os granitos principais. As paragêneses minerais e os valores obtidos para o número fe# em biotita em equilíbrio com feldspato alcalino e magnetita apontam para condições de cristalização relativamente oxidantes para as rochas félsicas, exceto os álcali-feldspato granitos, e máfico-intermediárias, superiores ao tampão QFM. / The Palermo (ca. 250 km2) and Rio Negro (ca. 130 km2) Plutons crop out in the so called Alto Rio Negro region , Parana state, making part of the Graciosa Province, a NeoProterozoic province (ca. 580 Ma) constituted by granites and syenites in S-SE Brazil. The plutons are made predominant granitic rocks, gabbro-diorites, as well as hybrid rocks constituted mainly by granodiorites. Both plutons show compositional a zoning pattern, which is inversed in the case of the Rio Negro Pluton. The main granitid rocks are mainly metaluminous to slightly peraluminous syeno- and monzogranites with subordinate quartz monzonites and alkcali-feldspar granites. They show a massive structure and a variety of textures, with hb + bi ± all + zr + ap ± ti + mt + ilm as the typical mafic mineral association. Gabbro-dioritic rocks include fine- to medium-grained metaluminous gabro-diorites and quartz monzogabrros and diorites with massive strucure characterized by the mafic mineral associations with cpx ± opx + hb + bt ± ti ± ap ± zr. In these rocks, the plagioclase compositions vary between labradorite and andesine. Hybrid rocks are mainly granodiorites characterized by several strucures and textures indicative of desiquilibrium and mingling/partial mixing between the silicic and basic-intermediate melts that formed the mainn granites and the gabbro-diorites. Such rocks are more abundant in the Rio Negro Pluton. The mafic mineral association is similar, but in contrasted relative abundance, to the ones found in the main granites. In the main granites the amphiboles are Fe-horblende and Fe-edenite, with 0.65 < fe# < 0.95, the higher among these values appearing in the alkali-feldspar granites. Biotite present 0.70 < fe# < 0.99 and the annitic component are also higher in the later rocks. In the case of the gabbro-dioritic rocks, the fe# numbers range between 0.48 and 0.59, 0.41 and 0.56, 0.47 and 0.53 and 0.54 and 0.57 in ortopyroxene, clinopyroxene, amphibole and biotite, respectively. The averaged compositions of coexisting orto- and clinopyroxene are \'Wo IND.46\'\'En IND.30\'\'Fe IND.24\' and \'Wo IND.3\'\'En IND.42\'\'Fe IND.55\' and suggest a tholeiitic or calk-alkaline nature of the original melts. Rare earth element patterns reveal enrichment factors up to 1-10, 50-70, 100-300 relative to the chondritic composition in ortopyroxene, clinopyroxene and amphibole, respectively, with a well marked fractionation of the heavy over the light rare earths in the case of the ortopyroxene, a feature not observed in clinopyroxene and amphibole. All patterns show a notable Eu negative anomaly. Melts crystallization pressures were estimated to be between 1 and 3.5 kbar; however values higher than ca. 2 kbar seems to be unrealistic given the ferroan compositions of some amphiboles. Zircon and apatite saturation temperatures coupled with ortopyroxene-clinopyroxene and amphibole-plagioclase equilibrium temperatures suggest crystallization intervals between ca. 1000 - 750° C in the case of the gabbro-diorites and ca. 900 - 670° C in the case of the main granites. Mineral paragenesis and fe# values in biotite in equilibrium with alkali-feldspar and magnetite suggests relative oxidizing crystallization conditions for the acid and basic-intermediate melts, higher than the QFM buffer, the alkali-feldspat granites being a possible exeption.

Subduction zones are regions of intense earthquake activity up to great depth. Sources are located inside the subducting lithosphere and, as a consequence, seismic radiation from subduction zone earthquakes is strongly affected by the interior slab structure. The wave field of these intraslab events observed in the forearc region is profoundly influenced by a seismically slow layer atop the slab surface. This several kilometer thick low-velocity channel (wave guide) causes the entrapment of seismic energy producing strong guided wave phases that appear in P onsets in certain regions of the forearc. Observations at the Chile-Peru subduction zone presented here, as well as observations at several other circum-pacific subduction zones show such signals. Guided wave analysis contributes details of immense value regarding the processes near the slab surface, such as layering of subducted lithosphere, source locations of intraslab seismicity and most of all, range and manner of mineralogical phase transitions. <br><br> Seismological data stem from intermediate depth events (depth range 70 km - 300 km) recorded in northern Chile near 21 Grad S during the collaborative research initiative " Deformation Processes in the Andes" (SFB 267). A subset of stations - all located within a slab-parallel transect close to 69 Grad W - show low-frequency first arrivals (2 Hz), sometimes followed by a second high-frequency phase. <br><br> We employ 2-dimensional finite-difference simulations of complete P-SV wave propagation to explore the parameter space of subduction zone wave guides and explain the observations. Key processes underlying the guided wave propagation are studied: Two distinct mechanisms of decoupling of trapped energy from the wave guide are analyzed - a prerequisite to observe the phases at stations located at large distances from the wave guide (up to 100 km). Variations of guided wave effects perpendicular to the strike of the subduction zone are investigated, such as the influence of phases traveling in the fast slab. Further, the merits and limits of guided wave analysis are assessed. Frequency spectra of the guided wave onsets prove to be a robust quantity that captures guided wave characteristics at subduction zones including higher mode excitation. They facilitate the inference of wave guide structure and source positioning: The peak frequency of the guided wave fundamental mode is associated with a certain combination of layer width and velocity contrast. The excitation strength of the guided wave fundamental mode and higher modes is associated with source position and orientation relative to the low-velocity layer. <br><br> The guided wave signals at the Chile-Peru subduction zone are caused by energy that leaks from the subduction zone wave guide. On the one hand, the bend shape of the slab allows for leakage at a depth of 100 km. On the other, equalization of velocities between the wave guide and the host rocks causes further energy leakage at the contact zone between continental and oceanic crust (70 km depth). Guided waves bearing information on deep slab structure can therefore be recorded at specific regions in the forearc. These regions are determined based on slab geometry, and their locations coincide with the observations. <br><br> A number of strong constraints on the structure of the Chile-Peru slab are inferred: The deep wave guide for intraslab events is formed by a layer of 2 km average width that remains seismically slow (7 percent velocity reduction compared to surrounding mantle). This low-velocity layer at the top of the Chile-Peru slab is imaged from a depth of 100 km down to at least 160 km. Intermediate depth events causing the observed phases are located inside the layer or directly beneath it in the slab mantle. The layer is interpreted as partially eclogized lower oceanic crust persisting to depth beyond the volcanic arc. / Subduktionszonen sind bis in große Tiefen von intensiver Erdbebentätigkeit geprägt. Die Erdbebenquellen befinden sich in der subduzierten Lithosphäre (Slab), ihr Wellenfeld wird deshalb stark von der internen Slab-Struktur beeinflusst. Eine Schicht mit reduzierter seismischer Geschwindigkeit im oberen Bereich der Platte kann als Wellenleiter für diese Signale fungieren. In der nur wenige Kilometer dicken Schicht entstehen sogenannte geführte Wellen, die in Teilen des Forearc beobachtet werden. Diese Phasen bergen wertvolle Informationen über die Struktur nahe der Slab-Oberfläche, wie zum Beispiel Dicke der Schichtung, Herdlokationen und vor allem Tiefe und Art mineralogischer Umsetzungen. <br><br> Die Beobachtungen stammen von mitteltiefen Beben (70 km - 300 km) im Untersuchungsgebiet in Nord-Chile und wurden im Rahmen des Sonderforschungsbereich 267 " Deformationsprozesse in den Anden" aufgezeichnet. Stationen in einem Streifen um 69 Grad W, der sich parallel zum Streichen der Subduktionszone erstreckt, zeigen niederfrequente Ersteinsätze, denen teilweise höherfrequente Phasen folgen. <br><br> Mit Hilfe eines 2-dimensionalen Finite-Differenzen-Algorithmus werden die P-SV Wellenausbreitung simuliert, und die Beobachtungen erklärt. Zentrale Fragestellungen zu Wellenleitern in Subduktionszonen werden untersucht: Es werden zwei Mechanismen, die das Auskoppeln seismischer Energie aus dem Wellenleiter ermöglichen beschrieben - eine Grundvoraussetzung für das Auftreten von geführten Wellen in großen Entfernungen vom Wellenleiter (bis zu 100 km). Des weiteren werden Stärken und Grenzen der Analyse von geführten Wellen erörtert. <br><br> Die Spektren der geführten Wellenzüge erweisen sich als robuste Messgröße, um die Charakteristika des Wellenleiters zu bestimmt. Struktur des Wellenleiters und Quellpositionen können so für festgelegte Quell-Empfänger-Geometrien abgeleitet werden. Die Peak-Frequenz der Grundmode wird durch eine Kombination aus Dicke der Schicht und Geschwindigkeitskontrast bestimmt. Die Stärke der Anregung der Grundmode und höherer Moden lässt auf die Lage und Orientierung der Erdbebenquelle relativ zur Schicht schließen. Geschwindigkeitskontrast, Schichtdicke und Quellposition sind von herausragender Bedeutung, um mineralogische Interpretationen des Wellenleiters zu überprüfen. <br><br> Aufbauend auf die Simulationen werden die Beobachtungen interpretiert und Auskunft über die Struktur der Chile-Peru Subduktionszone erhalten: Eine dünne Schicht an der Slab-Oberfläche (durchschnittlich 2 km dick) trägt geringere seismische Geschwindigkeiten als der umgebende Mantel und fungiert als Wellenleiter für intra-platten Ereignisse in Tiefen von 100 bis mindestens 160 km. Ereignisse, die geführte Wellen hervorrufen, liegen in dieser Schicht oder direkt darunter im subduzierten Mantel. Um zu den Stationen in der Forearc-Region zu gelangen, entkoppelt ein Teil der geführten Wellen in einer Tiefe von circa 100 km aus der Niedergeschwindigkeitsschicht. Die Krümmung des Slab erlaubt das Austreten der Wellen und nimmt auch Einfluss auf die Pulsformen. <br><br> Der Wellenleiter in der Chile-Peru Subduktionszone ergibt sich als unregelmäßige Schicht mit reduzierter seismischer Geschwindigkeit, in der geführte Wellen entstehen, in unterschiedlichen Tiefen wieder austreten, und an die freie Oberfläche gelangen. Die Beobachtungsgebiete befinden sich im Forearc und werden durch die Geometrie und Struktur der subduzierten Platte festgelegt. <br><br> Die nur wenige Kilometer dicke, seismisch langsame Schicht an der Oberfläche des Chile-Peru Slab legt nahe, dass die Unterkruste der subduzierten Platte bis in große Tiefen besteht und nicht vollständig eklogitisiert ist. Abgeleitete Schichtdicke, Geschwindigkeitskontrast

Os Plutons Palermo (ca. 250 km2) e Rio Negro (ca. 130 km2) afloram na região Alto Rio Negro (PR) e fazem parte da Província Graciosa, uma província Neoproterozóica (ca. 580 Ma) constituída por granitos e sienitos na região S-SE do Brasil. Em ambos os plutons afloram variedades de rochas graníticas, predominantes, e gabro-dioríticas, bem como rochas híbridas, principalmente granodioritos. Estes plutons apresentam zonamento em geral bem marcado, que é tipicamente inverso caso do Pluton Rio Negro. As rochas graníticas principais correspondem a sieno- e monzogranitos predominantes e álcali-feldspato granitos e quartzo monzonitos subordinados de natureza metaluminosa a levemente peraluminosa. São rochas com estruturas maciças e texturas variadas que apresentam como associação mineral máfica típica hb + bi ± all + zr + ap ± ti + mt + ilm); as rochas gabro-dioríticas incluem gabro-dioritos e quartzo monzogabro-dioritos metaluminosos com estruturas maciças e granulações fina a média, caracterizadas pela associação cpx ± opx + hb + bt ± ti ± ap ± zr. A composição dos plagioclásios nestas rochas varia no intervalo de labradorita a andesina. As rochas híbridas são principalmente granodioritos que se caracterizam por uma variedade de estruturas e texturas indicativas de desequilíbrio, compatíveis com processos de coexistência e mistura parcial entre líquidos ácidos e básico-intermediários que formaram os granitos principais e os gabro-dioritos. Estas rochas são mais comuns no Pluton Rio Negro. A associação mineral máfica é similar, mas com abundâncias distintas de fases, à observada para os granitos principais. Nas rochas graníticas os anfibólios são Fe-hornblenda e Fe-edenita, com valores 0,65 < fe# < 0,95, os valores mais elevados ocorrendo nos álcali-feldspato granitos, as biotitas apresentam 0,71 < fe# < 0,99, observando-se que o componente annítico é também maior nestas últimas rochas. No caso das rochas gabro-dioríticas, os valores fe# variam entre 0,48 e 0,59, 0,41 e 0,56, 0,47 e 0,53 e 0,54 a 0,57 para ortopiroxênio, clinopiroxênio, anfibólio e biotita, respectivamente. As composições médias de orto- e clinopiroxênio coexistentes são \'Wo IND.46\'\' En IND.30\'\' Fe IND.24\' e \'Wo IND.3\'\' En IND.42\'\'Fe IND.55\' e a sugerem uma possível afinidade toleítica, ou cálcio-alcalina, para magma original. Os padrões de elementos terras raras revelam fatores de enriquecimento entre 1-10, 50-70, 100-300 em relação à composição condrítica para ortopiroxênio, clinopiroxênio e anfibólio nas rochas estudadas, com fracionamento bem marcado dos elementos leves em relação aos pesados no ortopiroxênio, não observado no caso de clinopiroxênio e anfibólio. Todos os padrões são caracterizados por anomalia negativa bem marcada de Eu. As pressões de cristalização dos magmas foram estimadas entre 1-3,5 kbar, mas os valores acima de ca. 2 kbar possivelmente não tenham significado real, dadas as composições mais ferroanas dos anfibólios. Temperaturas de saturação de zircão e/ou apatita e de equilíbrio entre orto- e clinopiroxênio, anfibólio-plagioclásio indicam intervalos de cristalização entre ca. 1000 e 750° C para as rochas gabro-dioríticas e entre ca. 900 e 670° C para os granitos principais. As paragêneses minerais e os valores obtidos para o número fe# em biotita em equilíbrio com feldspato alcalino e magnetita apontam para condições de cristalização relativamente oxidantes para as rochas félsicas, exceto os álcali-feldspato granitos, e máfico-intermediárias, superiores ao tampão QFM. / The Palermo (ca. 250 km2) and Rio Negro (ca. 130 km2) Plutons crop out in the so called Alto Rio Negro region , Parana state, making part of the Graciosa Province, a NeoProterozoic province (ca. 580 Ma) constituted by granites and syenites in S-SE Brazil. The plutons are made predominant granitic rocks, gabbro-diorites, as well as hybrid rocks constituted mainly by granodiorites. Both plutons show compositional a zoning pattern, which is inversed in the case of the Rio Negro Pluton. The main granitid rocks are mainly metaluminous to slightly peraluminous syeno- and monzogranites with subordinate quartz monzonites and alkcali-feldspar granites. They show a massive structure and a variety of textures, with hb + bi ± all + zr + ap ± ti + mt + ilm as the typical mafic mineral association. Gabbro-dioritic rocks include fine- to medium-grained metaluminous gabro-diorites and quartz monzogabrros and diorites with massive strucure characterized by the mafic mineral associations with cpx ± opx + hb + bt ± ti ± ap ± zr. In these rocks, the plagioclase compositions vary between labradorite and andesine. Hybrid rocks are mainly granodiorites characterized by several strucures and textures indicative of desiquilibrium and mingling/partial mixing between the silicic and basic-intermediate melts that formed the mainn granites and the gabbro-diorites. Such rocks are more abundant in the Rio Negro Pluton. The mafic mineral association is similar, but in contrasted relative abundance, to the ones found in the main granites. In the main granites the amphiboles are Fe-horblende and Fe-edenite, with 0.65 < fe# < 0.95, the higher among these values appearing in the alkali-feldspar granites. Biotite present 0.70 < fe# < 0.99 and the annitic component are also higher in the later rocks. In the case of the gabbro-dioritic rocks, the fe# numbers range between 0.48 and 0.59, 0.41 and 0.56, 0.47 and 0.53 and 0.54 and 0.57 in ortopyroxene, clinopyroxene, amphibole and biotite, respectively. The averaged compositions of coexisting orto- and clinopyroxene are \'Wo IND.46\'\'En IND.30\'\'Fe IND.24\' and \'Wo IND.3\'\'En IND.42\'\'Fe IND.55\' and suggest a tholeiitic or calk-alkaline nature of the original melts. Rare earth element patterns reveal enrichment factors up to 1-10, 50-70, 100-300 relative to the chondritic composition in ortopyroxene, clinopyroxene and amphibole, respectively, with a well marked fractionation of the heavy over the light rare earths in the case of the ortopyroxene, a feature not observed in clinopyroxene and amphibole. All patterns show a notable Eu negative anomaly. Melts crystallization pressures were estimated to be between 1 and 3.5 kbar; however values higher than ca. 2 kbar seems to be unrealistic given the ferroan compositions of some amphiboles. Zircon and apatite saturation temperatures coupled with ortopyroxene-clinopyroxene and amphibole-plagioclase equilibrium temperatures suggest crystallization intervals between ca. 1000 - 750° C in the case of the gabbro-diorites and ca. 900 - 670° C in the case of the main granites. Mineral paragenesis and fe# values in biotite in equilibrium with alkali-feldspar and magnetite suggests relative oxidizing crystallization conditions for the acid and basic-intermediate melts, higher than the QFM buffer, the alkali-feldspat granites being a possible exeption.

This thesis presents the results of a combined magnetic fabric and palaeomagnetic analysis of lower crustal rocks exposed in the Oman (Semail) ophiolite. This has long been an important natural laboratory for understanding the construction of oceanic crust at fast spreading axes and its subsequent tectonic evolution, but magnetic investigations in the ophiolite have been limited. Analyses presented here involve using: (i) magnetic anisotropies as a proxy for magmatic petrofabrics in lower crustal rocks in order to contribute to outstanding questions regarding the mode of accretion of fast-spread oceanic crust; and (ii) classical palaeomagnetic analyses to determine the nature of magnetization in these rocks and gain further insights into the regional-scale pattern of tectonic rotations that have affected the ophiolite. The extensive layered gabbro sequences exposed in the Semail ophiolite have been sampled at a number of key localities. These are shown to have AMS fabrics that are layer-parallel but also have a regional-scale consistency of the orientation of maximum anisotropy axes. This consistency across sites separated by up to 100 km indicates large-scale controls on fabric development and may be due to consistent magmatic flow associated with the spreading system or the influence of plate-scale motions on deformation of crystal mushes emplaced in the lower crust. Detailed analysis of fabrics in a single layer and across the sampled sections are consistent with either magmatic flow during emplacement of a melt layer into a lower crustal sill complex, or traction/drag of such layers in response to regional-scale stresses (e.g. mantle drag). Together, results support formation of the layered gabbros by injection of melt into sill complexes in the lower crust. New anisotropy data from the overlying foliated gabbros sampled at two key localities also provide insights into the style of melt migration at this crustal level. Fabrics are consistent with either focused or anastomosing magmatic upwards flow through this layer, reflecting melt migration beneath a fossil axial melt lens. Previous palaeomagnetic research in lavas of the northern ophiolitic blocks has demonstrated substantial clockwise intraoceanic tectonic rotations. Palaeomagnetic data from lower crustal sequences in the southern blocks, however, have been more equivocal due to complications arising from remagnetization. Systematic sampling resolves for the first time a pattern of remagnetized lowermost gabbros and retention of earlier magnetizations by uppermost gabbros and the overlying dyke-rooting zone. Results are supported by a positive fold test that shows that remagnetization of lower gabbros occurred prior to Campanian structural disruption of the Moho. NW-directed remagnetized remanences in the lower units are consistent with those used previously to infer lack of significant rotation of the southern blocks. In contrast, E/ENE-directed remanences in the uppermost gabbros imply a large, clockwise rotation of the southern blocks, of a sense and magnitude consistent with that inferred from extrusive sections in the northern blocks. Hence, without the control provided by systematic crustal sampling, the potential for different remanence directions being acquired at different times may lead to erroneous tectonic interpretation.

Les études présentées dans cette thèse de maîtrise concernent quelques applications d'unités de stockage lithiques d'énergie thermique à haute température couplées à des guides d'ondes métalliques afin de fournir le rayonnement infrarouge aux cibles choisies. Le contexte de cette étude est le besoin de stocker l'énergie fluctuante de sources renouvelables telles que l'énergie éolienne et l'énergie solaire photovoltaïque. Les deux matériaux lithiques qui ont été choisis pour le stockage d'énergie étaient des blocs de gabbro et des briques réfractaires en olivine fabriquées par la firme Stiebel Eltron. La température de stockage varie de 500 à 900 degrés Celsius. À ces températures des puissances infrarouges de plusieurs centaines de watts peuvent être couplées dans de grands guides d'ondes métalliques creux et peuvent être guidées aux secteurs où le chauffage est désiré. Deux moyens de stocker l'énergie solaire dans le stockage lithic à hautes températures ont été étudiés : 1 - la lumière du soleil est focalisée dans les fibres optiques pénétrant les unités lithiques de stockage, et 2 - l'électricité provient des capteurs solaires photovoltaïques. Les domaines d'application qui ont été étudiés étaient : 1 - stockage thermique pour les maisons, 2 - sous-ensembles infrarouges de distribution pour garder la nourriture chaude et pour le chauffage d'espace, et 3 - un système de chauffage pour une station lunaire.