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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

The Darling granite batholith

Schoch, A. E.(Aylva Ernest) 09 1900 (has links)
Thesis (PhD) -- Stellenbosch Univesrsity, 1972. / The Darling batholith is characterised by large scale hybridisation, but mainly consists of the coarsely porphyritic Darling granite. This granite changes gradationally into a biotite-rich variety which occupies a roughly elliptical area with a major, northwesterly trending axis of 30 km. The biotite granite envelops a large irregular body of hybrid granodiorite. Small intrusions of younger granite occur within the batholith namely the Klipberg and Contreberg granites and possibly the biotite-rich Dassenberg granite. Dassen Island is underlain by fine-grained granite which could be related to either the younger or coarsely porphyritic granites. A prominent northwesterly trending mylonite zone can be traced through Darling to Swartberg, and ultimately to Trekoskraal in the Saldanha batholith, but is not continuous since it occasionally changes into gneissic granite and is also interrupted by the younger intrusives. Quantitative mapping included measurement of matrix grain size, average maximum phenocryst length, xenolith distribution density, quartz nodule distribution density and average size, lineation, dark mineral index and gneissosity. On Dassen Island the distribution of tourmaline nodules was , determined. The results are displayed as small scale contour maps which show strong correlation between the various parameters. The average values of matrix grain size, average phenocryst length and xenolith distribution density are respectively 2-5mm, 20-60mm and 0-1,5 per m² for the Darling granite, and 1-2 mm, 5-20 mm and 1-9 per m² for the hybrid granodiorite. It was found that the matrix grain size decreases with increase in hybridisation. The spotty distribution pattern of tourmaline nodules on Dassen Island indicates addition of boron by assimilation of metamorphites and a late stage liquid immiscibility process. The granites :.have normal mineralogy and the K-feldspar of the phenocrysts is maximum microcline (Δ = 0,9 - 1,0). The hybrid granodiorite contains much pinitised cordierite and locally garnet. The deeply pleochroic bioti te is probably of the 2M1 polytype and has a higher Fe:Mg ratio in the hybrid granodiorite than in the granite (2,8 - 3,0 vs. 2,2 - 2,3). The intimately associated chlorite seems to be of the Ia polytype. The cordierite is of the normal and low temperature type with average intensity index of 2,7 , distortion index of 0,3 and 2 a of 63°. The xenoliths are predominantly quartzitic metagraywackes, but lime-rich types holding sphene and diopside were occasionally encountered. Thirteen new chemical analyses and thirty-one previously published analyses are used to calculate average composite analyses of the various rock types. The results of calculations employing Barth standard cell values indicate that the hybrid granodiorite could have originated by reaction between granite magma and Malmesbury quartzitic metagraywacke and pe-lite with a little limestone. A "granite differentiation index" based on weight percentages of (Ti02 + MgO + FeO + Fe2O3) and (Si02 + Na2O + K2O) shows a linear relationship between the granites in probable order of age. The magmatic differentiation trend is separated from the hybridisation trend on a 6alk - 2(al - alk) - (100 - 2al) diagram. Mesonorms and their cordierite variants are used to effect comparison with the experimental granitic system of von Platen (1965). The Darling and Contreberg granites plot near the relevant cotectic surfaces. A pilot experimental study of melting behaviour indicates that the Contreberg granite is closer to a minimum melt composition than the Darling granite. Comparison of alkali values with a M Na2O - M K2O Schreinemakers diagram of Korzhinskii (1959), shows that the alkali ratio of the older analyses may be incorrect, and indicates that the dark minerals have a greater effect on plagioclase composition than the amount of K-feldspar. The classification of granites by means of Harpum diagrams is shown to have little relevance to the reconstruction of the ancient thermodynamical variants. The Darling granite is correlated with the Hoedjies Point granite of the Saldanha batholith and on geochronological evidence probably corresponds in age (500- 600 m.y.) with the Cape Peninsula granite. The younger granites of Darling are tentatively correlated with the Cape Columbine granite of the Saldanha batholith. The northeastern boundary of the Darling batholith is a major fault, the Colenso fault, which is considered to extend as far as Northwest Bay, Saldanha. It is proposed that the Darling batholith occupies a down-faulted block within a graben and that the hybrid granodiorite represents a remnant synform of the roof rocks intruded by the granite. The younger granites constitute only four percent by volume of the batholith and may represent anatectic melts from a nearby subjacent source.
82

The history of deformation and fluid phenomena in the top of the wilderness suite, Santa Catalina Mountains, Pima County, Arizona

Young, David Paul January 1988 (has links)
No description available.
83

Geochemistry of mafic dykes from the Discovery Bay granitic pluton, Hong Kong

Wong, Lai-man, Kennis., 王麗敏. January 2004 (has links)
published_or_final_version / Applied Geosciences / Master / Master of Science
84

Características de escoamentos decorrentes de diferenças de densidades / Characteristics of flows due density differences

Silva, Selma Vargas da 19 December 2002 (has links)
Neste trabalho analisam-se escoamentos de correntes de densidade tipo plumas, intrusões e corrente de fundo em torno de obstáculos. Os experimentos foram realizados em duas fases. Na primeira fase dos ensaios, a estratificação ambiente e a obtenção das correntes foram obtidas variando-se a densidade de soluções de água e sal. A visualização das correntes foi feita utilizando-se permanganato de potássio e sua dispersão foi obtida através do registro em câmera filmadora. Na segunda fase, os ensaios de plumas foram realizados com equipamento a laser de vapor de cobre (LVC) envolvendo o método de velocimetria a laser por processamento de imagens (VLPI). Nesta fase, observou-se grande dificuldade na visualização das partículas do escoamento e foi necessário a confecção de um sistema de aquecimento de água para a obtenção do escoamento superficial. É apresentado um modelo numérico em linguagem FORTRAN baseado no método das diferenças finitas para discretização da equação de Navier-Stokes e a obtenção de velocidades longitudinais e transversais. Observou-se, neste trabalho, a importância da visualização do fenômeno de correntes superficiais e intrusivas, tendo em vista a extrema sensibilidade destes fenômenos para com as condições de trabalho (alterações sutis geram grandes diferenças no escoamento obtido). Pode-se concluir que o método VLPI produz resultados satisfatórios para o campo de vetores de velocidade. As correntes intrusivas apresentaram configurações diversas para mesmas condições de escoamento, o que demonstra a necessidade de maiores estudos. O modelo numérico se mostrou coerente para determinados experimentos, mas as condições particulares da entrada dos reservatórios mostra que há a necessidade de implementações para uma forma mais abrangente de situações. / Unstable gravity currents flows like buoyant surface jet (BSJ), intrusions and dense currents around obstacles are analysed in this research. The experiments were performed in two phases. In the first one, the environmental stratification as well as the current flows were obtained varying the density of the water and salt solutions. The current visualization were possible by the use of the KMnO4 dye and its dispersion was recorded by video camera. In the second phase, the runs with plumes were evaluated with a laser vapour copper (LVC) equipment using the processing image velocimetry (PIV) method. In this phase, it was observed a great difficulty in the particle flow visualization and it was necessary a war water system to simulate overflow. It\'s presented a numerical model in fortran language based in the finit difference method to discretisize the Navier-Stokes equation and obtain the transversal and longitudinal velocities. It was noted in this research, the relevance of the visualization in overflows and intrusive flows because of the extreme sensitivity of these phenomenos to work conditions (slightly modifications generates great differences in the flow behaviour). It concludes that the PIV method results good data for vectors velocity field. The intrusive currents show many configurations to the same flow conditions which requires further investigations. The numerical model has shown coherance to particular experiments, but source particularities justifies the necessity of implementation to larger situations.
85

Petrografia e geoquímica das rochas intrusivas básicas da porção sudeste do Cinturão Dom Feliciano, RS

Barbosa, Laércio Dal Olmo January 2017 (has links)
A participação de líquidos magmáticos extraídos do manto, registrados sob a forma de intrusões dioríticas, gabroicas e de rochas máficas-ultramáficas, tem sido apontada como uma componente determinante na geração de magmas intermediários a ácidos, em ambientes orogênicos a pós-colisionais. Neste contexto, a colocação de líquidos basálticos hidratados na base da crosta também é considerada um importante marcador petrogenético, já que além de fornecer calor, pode ainda contribuir com líquidos residuais fracionados, essenciais à geração de magmas evoluídos. Além disso, magmas pouco diferenciados podem igualmente ascender e atingir níveis superiores da crosta, interagindo com câmaras magmáticas silicosas. Assim, estas rochas acabam por registrar tanto os processos de extração e transporte de magmas do manto, resultando na acresção vertical de material à crosta, quanto os processos de interação entre esses dois componentes. Na porção sudeste do Cinturão Dom Feliciano (RS), constituída majoritariamente por granitoides, ocorrem rochas dioríticas e gabroicas de extensão reduzida (1 a 7 km) e caráter dominantemente básico, na região compreendida entre os municípios de Pinheiro Machado e Pedro Osório. Nesta dissertação, por meio da caracterização geológica, mineralógica, petrográfica e geoquímica destas rochas, propõe-se a separação de duas associações principais. A “Associação I” (AI) engloba os corpos do Passo da Fabiana, Passo da Olaria, Arroio Santa Fé e Desvio Herval, constituindo-se por rochas gabroicas comumente cumuladas, por vezes estratificadas A “Associação II” (AII), diorítica a gabroica, compreende rochas isótropas a localmente foliadas, nas ocorrências do Alto Alegre, Passo dos Machados e Campo Bonito. As duas associações são subalcalinas, com afinidade cálcio-alcalina médio-K (AI) e médio a alto-K (AII), exibindo altos teores de alumina (Al2O3 > 17%), mesmo para os termos não cumulados. Maiores valores de CaO e Mg# na AI, e de álcalis, P2O5, Zr, Nb, Y, e total de ETR na AII, bem como padrões distintos de ETR, referendam a separação das associações. O controle no posicionamento das rochas básicas por descontinuidades litosféricas é sugerido pelas assinaturas magnéticas, que teriam possibilitado a ascensão e colocação destes magmas em níveis superiores da crosta. Como processos petrogenéticos, sugere-se a participação de líquidos derivados do manto em câmaras magmáticas supracrustais, seja como pulsos precursores do magmatismo associado aos granitoides, ou por eventos de reabastecimento destes reservatórios, como predominantes na AI. Já na AII, rica em anfibólio, processos envolvendo a colocação e evolução de magmas do manto nas DCHZ (deep crustal hot zones), originando líquidos hidratados, parecem ser mais expressivos. / The participation of mantle-derived melts, recorded as dioritic, gabbroic and mafic-ultramafic rocks, has been identified as a determinant component in the generation of intermediate to acid magmas, in orogenic to post-collisional settings. In this context, the emplacement of hydrous basaltic liquids at the base of the crust is also considered an important petrogenetic marker, not only providing heat, but also producing residual fractionated liquids, essential to the generation of evolved magmas. Furthermore, less differentiated magmas can also ascend and reach upper crustal levels, interacting with silicic magma chambers. Therefore, this rocks record both magma extraction and transport processes from the mantle, resulting in vertical material accretion to the crust, as well as the interaction between these two components. In the southeastern portion of Dom Feliciano Belt (RS), which is composed mainly by granitoids, minor dioritic and gabbroic rocks occur (1 to 7 km), with predominantly basic character, in the region between Pinheiro Machado and Pedro Osório. This thesis presents geological, mineralogical, petrographic and geochemical characterization of these rocks, proposing thus the separation of two main associations. The "Association I" (AI) comprises the bodies Passo da Fabiana, Passo do Olaria, Arroio Santa Fé and Desvio Herval, and is composed by gabbroic rocks, commonly as cumulates, sometimes in layered intrusions The "Association II" (AII), dioritic to gabbroic, comprises isotropic to locally foliated rocks, in the occurrences of Alto Alegre, Passo dos Machados and Campo Bonito. Both associations are subalkaline, with medium-K (AI) and medium to high-K (AII) calc-alkaline affinity, showing high-alumina contents (Al2O3 > 17%), even for the non-cumulated terms. Higher CaO and Mg# values in AI, and alkalis, P2O5, Zr, Nb, Y, and total REE in AII, as well as distinct REE patterns, support the proposed associations. The control on the emplacement of the basic rocks by lithospheric discontinuities is suggested by magnetic signatures, which would have enabled the ascent and emplacement of these magmas to upper crustal levels. As petrogenetic processes, the participation of mantle-derived liquids in supracrustal magma chambers is suggested, either as precursor pulses of the magmatism associated with the granitoids, or by replenishment events in these reservoirs, as prevalent in AI. In the AII, amphibole-rich, processes involving the emplacement and evolution of mantle-derived magmas in DCHZ (deep crustal hot zones), originating hydrous liquids, seems to be more expressive.
86

Levantamento gravimétrico na Jazida Carbonífera Morungava-Chico Lomã, RS

Cavalheiro, Mara Lia Dias January 2016 (has links)
A presente dissertação foi desenvolvida conforme a norma 103 do Programa de Pós Graduação em Geociências da Universidade Federal do Rio Grande do Sul, que prevê a submissão da dissertação de mestrado em forma de artigo, antecedido de estado da arte do tema proposto. Na região sudeste da Bacia do Paraná estão localizados depósitos de carvão economicamente importantes nos estados do Paraná, Santa Catarina e Rio Grande do Sul. Esses depósitos são frequentemente muito alterados por intrusões vulcânicas. O objetivo principal desse estudo é mapear essas intrusões ígneas que afetam o nível de alteração térmica do carvão (rank) da Jazida carbonífera Morungava-Chico Lomã no RS. A Jazida Morungava-Chico Lomã foi descoberta no século passado e nunca foi minerada. É caracterizada por rochas orgânicas do Permiano, carvão e folhelho betuminoso, na porção sul da Bacia do Paraná. A aquisição gravimétrica foi realizada na área do depósito Morungava e na área do depósito Chico-Lomã. Para ambas a escolha dos locais de aquisição foi baseada em furos de sondagem anteriormente realizados. Com os dados dos furos de sondagem foram elaborados seguintes mapas temáticos: profundidade da primeira ocorrência de carvão; espessura cumulativa do carvão; profundidade da primeira ocorrência de diabásio; espessura cumulativa do diabásio; espessura cumulativa do diabásio na Formação Irati e espessura cumulativa do diabásio na Formação Rio Bonito. Na elaboração do artigo submetido foi realizada a sobreposição das isolinhas das espessuras cumulativa do carvão e do diabásio nos mapas de anomalia Bouguer filtrados. Essas sobreposições apresentaram correlações e auxiliaram na interpretação dos dados gravimétricos. A orientação preferencial predominante das anomalias foi NE-SW e uma orientação subsidiária de direção NW-SE, o que sugeriu um controle estrutural sobre a ocorrência de diques e/ou soleiras, sob os altos gravimétricos. Em Chico Lomã a ocorrência de uma extensa anomalia Bouguer positiva formando um trend de orientação NE-SW foi correlacionada a unidades geológicas da Planície Costeira do Rio Grande do Sul: altos gravimétricos caracterizaram a Barreira I e baixos gravimétricos, os Sistemas Lagunares I e II. O método gravimétrico se mostrou eficaz para a caracterização da jazida por meio da correlação de anomalias gravimétricas positivas com as ocorrências de diabásio. / The present dissertation was developed according to standard 103 of the Graduate Program in Geosciences of the Federal University of Rio Grande do Sul, which provides for the submission of the dissertation in the form of article, predates by state of the art proposed theme. In the southeastern region of the Paraná Basin are located economically important coal deposits in the states of Parana, Santa Catarina and Rio Grande do Sul. These deposits are often much altered by volcanic intrusions. The objective of this study is to map the igneous intrusions affecting the thermal change of level of coal (rank) of the coal deposit Morungava-Chico Lomã in RS. The coal deposit Morungava-Chico Lomã was discovered in the last century and has never been mining. It is characterized by organic rocks of the Permian, coal and bituminous shale, in the southern portion of the Paraná Basin. The gravimetric acquisition was carried in área of the deposit Morungava and in the area of the deposit Chico-Lomã. For both areas the choice of acquisition locations was based on previously conducted drilling holes. With data from the holes drilling were prepared these thematic maps: depth of the first occurrence of coal; cumulative thickness of coal; depth of the first occurrence of diabase; cumulative thickness of diabase; cumulative thickness of diabase in Irati Formation and cumulative thickness of the diabase in Rio Bonito Formation. In the elaboration of article submitted the overriding of the isolines of cumulative thickness of coal and diabase in the filtered Bouguer anomaly maps was performed. These overrides presented correlations and assisted in the interpretation of gravity data. The predominant preferential orientation of the anomalies was NE-SW and a subsidiary orientation NW-SE direction, suggesting a structural control on the occurrence of dikes and/or sills, on gravimetric high. In Chico Lomã the occurrence of an extensive positive Bouguer anomaly forming a trend of NE-SW orientation was correlated with geological units of Rio Grande do Sul Coastal Plain: gravimetric characterized the high Barrier I and low gravimetric, Systems Lagunar I and II. The gravimetric method proved efficient for the characterization of the deposit through the correlation of positive gravity anomalies with occurrences of diabase.
87

Características de escoamentos decorrentes de diferenças de densidades / Characteristics of flows due density differences

Selma Vargas da Silva 19 December 2002 (has links)
Neste trabalho analisam-se escoamentos de correntes de densidade tipo plumas, intrusões e corrente de fundo em torno de obstáculos. Os experimentos foram realizados em duas fases. Na primeira fase dos ensaios, a estratificação ambiente e a obtenção das correntes foram obtidas variando-se a densidade de soluções de água e sal. A visualização das correntes foi feita utilizando-se permanganato de potássio e sua dispersão foi obtida através do registro em câmera filmadora. Na segunda fase, os ensaios de plumas foram realizados com equipamento a laser de vapor de cobre (LVC) envolvendo o método de velocimetria a laser por processamento de imagens (VLPI). Nesta fase, observou-se grande dificuldade na visualização das partículas do escoamento e foi necessário a confecção de um sistema de aquecimento de água para a obtenção do escoamento superficial. É apresentado um modelo numérico em linguagem FORTRAN baseado no método das diferenças finitas para discretização da equação de Navier-Stokes e a obtenção de velocidades longitudinais e transversais. Observou-se, neste trabalho, a importância da visualização do fenômeno de correntes superficiais e intrusivas, tendo em vista a extrema sensibilidade destes fenômenos para com as condições de trabalho (alterações sutis geram grandes diferenças no escoamento obtido). Pode-se concluir que o método VLPI produz resultados satisfatórios para o campo de vetores de velocidade. As correntes intrusivas apresentaram configurações diversas para mesmas condições de escoamento, o que demonstra a necessidade de maiores estudos. O modelo numérico se mostrou coerente para determinados experimentos, mas as condições particulares da entrada dos reservatórios mostra que há a necessidade de implementações para uma forma mais abrangente de situações. / Unstable gravity currents flows like buoyant surface jet (BSJ), intrusions and dense currents around obstacles are analysed in this research. The experiments were performed in two phases. In the first one, the environmental stratification as well as the current flows were obtained varying the density of the water and salt solutions. The current visualization were possible by the use of the KMnO4 dye and its dispersion was recorded by video camera. In the second phase, the runs with plumes were evaluated with a laser vapour copper (LVC) equipment using the processing image velocimetry (PIV) method. In this phase, it was observed a great difficulty in the particle flow visualization and it was necessary a war water system to simulate overflow. It\'s presented a numerical model in fortran language based in the finit difference method to discretisize the Navier-Stokes equation and obtain the transversal and longitudinal velocities. It was noted in this research, the relevance of the visualization in overflows and intrusive flows because of the extreme sensitivity of these phenomenos to work conditions (slightly modifications generates great differences in the flow behaviour). It concludes that the PIV method results good data for vectors velocity field. The intrusive currents show many configurations to the same flow conditions which requires further investigations. The numerical model has shown coherance to particular experiments, but source particularities justifies the necessity of implementation to larger situations.
88

Magmatic Evolution and Eruptive History of the Granitic Bumping Lake Pluton, Washington: Source of the Bumping River and Cash Prairie Tuffs

King, John Frederick 24 May 1994 (has links)
The 25 Ma Bumping Lake pluton ranges in composition from quartz diorite to granite with the granitic facies comprising approximately 90% of the pluton's surface area. The granite may be classified as calcalkaline, peraluminous and I-type with some Stype characteristics. A late-stage, mafic-poor facies fills cooling related extensional fractures. The pluton was passively emplaced into the Ohanapecosh Formation at a shallow level in the crust. Contact relationships vary from sharp where the contact is vertical to gradational at the roof of the pluton. Where gradational, stoped xenoliths from the roof of the pluton increase in size, angularity and retain more of their primary textures as the contact is approached. Spacial trends in major and trace elements support the interpretation that xenoliths were stoped and assimilated into the melt The predicted Rayleigh number for the pluton when molten is 107 and the predicted Reynolds number is approximately 10-9. Based on these values, the magma of the pluton probably did not convect, and if it did, convection was weak and not a significant process. Based on variations in Eu/Eu* and Sr values, plagioclase fractionation was an important process in the petrogenesis of the pluton. Additionally, fractionation of accessory minerals rich in light rare-earth elements (LREE) resulted in successive depletion of LREE with progressive differentiation. Two separate regions of the pluton are highly differentiated as indicated by high Si02 values, high Rb/Zr ratios, and low Zr and Ti02 values. Mapping by the author indicates that the pluton projects beneath the Mount Aix caldera. Dates of three tuffs derived from the caldera are equivalent to the pluton, and two of these tuffs are chemically indistinguishable from the granite facies of the pluton. This implies that the Bumping Lake pluton represents the chilled remains of the magma chamber that fed the Mount Aix caldera.
89

Détection d'intrusions comportementale par diversification de COTS : application au cas des serveurs web

Majorczyk, Frédéric 03 December 2008 (has links) (PDF)
L'informatique et en particulier l'Internet jouent un rôle grandissant dans notre société. Un grand nombre d'applications critiques d'un point de vue de leur sécurité sont déployées dans divers domaines comme le domaine militaire, la santé, le commerce électronique, etc. La sécurité des systèmes informatiques devient alors une problématique essentielle tant pour les individus que pour les entreprises ou les états. Il est donc important de définir une politique de sécurité pour ces systèmes et de veiller à son respect. Néanmoins les mécanismes de sécurité préventifs mis en place ne sont pas incontournables. Il est nécessaire de mettre en œuvre des outils permettant de détecter toute violation de la politique de sécurité, c'est-à-dire toute intrusion. Ces outils sont appelés des systèmes de détection d'intrusions ou IDS. Souvent en collaboration avec les IDS, il est possible de mettre en place des outils et techniques de tolérance aux intrusions. Ces outils et techniques ont pour objectif que les intrusions affectant un composant du système n'entrainent pas de violations de la politique de sécurité du système global.<br />Notre travail s'inscrit dans le domaine de la détection d'intrusions, de manière essentielle, et permet une certaine tolérance aux intrusions. Contrairement aux méthodes de détection classiques en détection comportementale pour lesquelles il est nécessaire de définir et construire un modèle de référence du comportement de l'entité surveillée, nous avons suivi une méthode issue de la sureté de fonctionnement fondée sur la programmation N-versions pour laquelle le modèle de référence est implicite et est constitué par les autres logiciels constituant l'architecture. Nous proposons l'utilisation de COTS en remplacement des versions spécifiquement développées car développer N-versions est couteux et est réservé à des systèmes critiques du point de vue de la sécurité-innocuité. D'autres travaux et projets ont proposé des architectures fondées sur ces idées. Nos contributions se situent à différents niveaux. Nous avons pris en compte dans notre modèle général de détection d'intrusions les spécificités liées à l'utilisation de COTS en lieu et place de versions spécifiquement développées et proposé deux solutions pour parer aux problèmes induits par ces spécificités. Nous avons proposé deux approches de détection d'intrusions fondées sur cette architecture : l'une suivant une approche de type boite noire et l'autre suivant une approche de type boite grise. Notre méthode de type boite grise peut, en outre, aider l'administrateur de sécurité à effectuer un premier diagnostic des alertes. Nous avons réalisé une implémentation de ces deux approches dans le cadre des serveurs web et avons évalué pratiquement la pertinence et de la fiabilité de ces deux IDS.
90

Paleomagnetism of Jurassic plutons in the central Klamath Mountains, southern Oregon and northern California

Schultz, Karin L. 11 February 1983 (has links)
An understanding of the tectonic history of the Klamath Mountains is crucial for a valid paleogeographic reconstruction of the Pacific Northwest. However, prior to this study there were very few paleomagnetic (PM) data from the Klamath Mountains (KN), which resulted in conflicting interpretations about the role of the KM province in the tectonic evolution of western North America. Twenty-eight sites from five unmetamorphosed Middle Jurassic KM plutons with K-Ar ages ranging from 161 to 139 m.y.B.P. yielded stable PM results showing (1) a direction for the 160 in.y.B.P. Ashland pluton (D=324°, I=163°, α₉₅=8°, n=6) nearly concordant with the coeval expected direction (D=337°, 1=54°) and (2) clockwise rotated directions for the plutons of Grants Pass (D=045°, I=67°, α₉₅=12°, n=4), Greyback (D=083°,I=63°, α₉₅=9, n=9), and the Wooley Creek batholith and Slinkard pluton combined (D=037°, 160°, α₉₅=ll°, n=9). Tectonic interpretations of these PM data are difficult; two interpretations are offered to explain the observed directions. In the first, the mean PM direction of the four plutons with discordant directions (D=057°, 1=65°, α₉₅=7°, n=22) is restored to the expected 150 m.y.B.P. (the average K-Ar age for these four plutons) direction by rotation of a rigid block ~87° in a counterclockwise sense about a vertical axis (the possibility of tilt of these four plutons is disregarded in this interpretation). The Ashland pluton which shows no rotation is problematic. Either there was (is) a tectonic boundary west of the Ashland pluton, separating it from the rotation of the others, or the Ashland pluton was influenced both by clockwise rotation and tilt, the combined effect producing an essentially concordant PM direction. In the second interpretation we distinguish between the northern KN, intruded by the Grants Pas and Greyback Mountain plutons, and the southern region intruded by the Wooley Creek batholith and the Ashland and Slinkard plutons. The bases for this distinction are recent geologic and gravity studies which suggest that post-Middle Jurassic uplift of the domal Condrey Mountain Schist may have caused radially outward tilt of its adjacent terranes and plutons intruded therein, causing some of the observed discordances in their PM directions. Thus, in the second interpretation it is envisioned that (a) the northerly portion of the KM, intruded by the Grants Pass and Greyback plutons, was affected primarily by clockwise rotation about a vertical axis, and (b) discordant directions for the remaining plutons intruded farther south are due primarily to tilt in response to Condrey Mountain uplift. Based on the observed inclinations, there is no evidence of transport of the Klamath Mountain province along lines of longitude since Middle Jurassic time. Tectonic interpretations of the PM results of this study are consistent with significant post-Middle Jurassic clockwise rotation of the Klamath Mountains. The first interpretation above yields ~87° of clockwise rotation of the terrane examined. According to the second interpretation, a clockwise rotation of ~l00° is inferred from the average of the PM results of the northern Grants Pass and Greyback plutons. Therefore, 10° to 25° of clockwise rotation of the KM may have occurred prior to the formation of the Oregon Coast Range (~55 m.y.B.P.) and the two provinces may have rotated together since post-Lower Eocene time. / Graduation date: 1983

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