19 research outputs found

    Deformation behaviour and chemical signatures of anorthosites: : Examples from southern West Greenland and south-central Sweden

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    Plagioclase is the most abundant mineral in the lower crust and it is thus important to constrain the behaviour of plagioclase during deformation. Anorthosites, which are plagioclase-rich rocks, are common in Archaean cratons but their origin and rheological importance is still debated. The aims of this thesis are to 1) describe a newly discovered Archaean anorthosite complex (Naajat Kuuat, SW Greenland), investigate its origin and a possible genetic relationship between the anorthosite and associated mafic-ultramafic rocks and 2) to study the rheology and deformation mechanisms in plagioclase-rich rocks. The main focus of this thesis is on the deformation studies. (1) Geochemical whole-rock analyses from the Naajat Kuuat complex are indicative for an origin near a subduction zone setting. A genetic link by crystal fractionation between the anorthosite and associated mafic-ultramafic units is inferred. (2) Deformation behaviour of plagioclase is assessed from analyses of three anorthosite units deformed during different conditions. Samples were analysed using the electron backscatter diffraction technique (EBSD) in combination with optical and chemical analyses. All three case studies show significant strain localisation related to grain size reduction. A wet anorthosite deformed at dry conditions (T ~675-700°C) was dynamically recrystallised. Continuous bands of recrystallised grains developed a texture yet display microstructures and grain relationships indicative for grain size sensitive creep, suggesting that the rheology followed a Newtonian flow law. In the other two studies, samples with initially dry and wet composition, respectively, have experienced deformation during fluid present conditions at T ~550-620°C. These two samples show that fluids effectively caused reactions, replacements and aided strain localisation during deformation at mid crustal conditions.At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Manuscript; Paper 2 Manuscript; Paper 3 Manuscript

    Interaction of chemical and physical processes during deformation at fluid-present conditions : a case study from an anorthosite-leucogabbro deformed at amphibolite facies conditions

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    We present microstructural and chemical analyses of chemically zoned and recrystallized plagioclase grains in variably strained samples of a naturally deformed anorthosite-leucogabbro, southern West Greenland. The recorded microstructures formed in the presence of fluids at mid-crustal conditions (620-640 °C, 7. 4-8. 6 kbar). Recrystallized plagioclase grains (average grain size 342 Όm) with a random crystallographic orientation are volumetrically dominant in high-strain areas. They are characterized by asymmetric chemical zoning (An80 cores and An64 rims) that are directly associated with areas exhibiting high amphibole content and phase mixing. Analyses of zoning indicate anisotropic behaviour of bytownite plagioclase with a preferred replacement in the (010) direction and along the (001) plane. In areas of high finite strain, recrystallization of plagioclase dominantly occurred by bulging recrystallization and is intimately linked to the chemical zoning. The lack of CPO as well as the developed asymmetric zoning can be explained by the activity of grain boundary sliding accommodated by dissolution and precipitation creep (DPC). In low-strain domains, grain size is on average larger and the rim distribution is not related to the inferred stress axes indicating chemically induced grain replacement instead of stress-related DPC. We suggest that during deformation, in high-strain areas, pre-existing phase mixture and stress induced DPC-caused grain rotations that allowed a deformation-enhanced heterogeneous fluid influx. This resulted in local plagioclase replacement through interface-coupled dissolution and precipitation and chemically induced grain boundary migration, accompanied by bulging recrystallization, along with neocrystallization of other phases. This study illustrates a strong interaction and feedback between physical and chemical processes where the amount of stress and fluids dictates the dominant active process. The interaction is a cause of deformation and external fluid infiltration with a result of strain localization and chemical re-equilibration at amphibolite facies conditions.20 page(s

    VR för stadsplannering

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    VR Ă€r en simulerad upplevelse genom bilder, ljud och andra sensorer som simulerar enanvĂ€ndares fysiska och mentala nĂ€rvaro i en virtuell vĂ€rld. Förutom att anvĂ€ndas till spel kanVR ge nya möjligheter inom arbetslivet. Syftet med undersökningen Ă€r att ta fram nya sĂ€tt förstadsplanerare att jobba med hjĂ€lp av VR. I undersökningen vill vi besvara följandefrĂ„gestĂ€llningar: “Hur kan VR mediet anvĂ€ndas för designprocessen inom stadsplanering?”och ”Upplevs en VR applikation som ett möjligt substitut eller tillĂ€gg för designprocessen istadsplanerares arbete?”. I undersökningen har vi arbetat med VR genom att skapa enapplikation dĂ€r anvĂ€ndaren befinner sig i en virtuell vĂ€rld som grundar sig i traditionellaarbetssĂ€tt för stadsplanering. Arbetet har följt principer för tjĂ€nstedesign. Vi har haftintervjuer med tre stadsplanerare med olika erfarenheter som vi intervjuade vid tvĂ„ olikatillfĂ€llen. Första intervjun gav oss insikt i hur de jobbar och vad de skulle behöva i derasdesignprocess. DĂ€refter hade vi en andra intervju efter gestaltningen blev klar för att ta framundersökningens resultat pĂ„ hur stadsplanerare skulle kunna anvĂ€nda mediet VR inomdesignprocess för stadsplanerare. Resultatet pĂ„ de senare intervjuerna pekade pĂ„ att det fannspotential med gestaltningen vi hade tagit fram för att de skulle kunna anvĂ€nda det i derasdesignprocess. Informanterna kom med mĂ„nga förslag om hur och vad som skulle behövas iVR-applikationen för att det skulle kunna tĂ€nkas anvĂ€ndas i stadsplanering, samt specifikaförbĂ€ttringsförslag för den aktuella gestaltningen.VR is a simulated experience through images, sounds and other sensors that simulate a user'sphysical and mental presence in a virtual world. In addition to being used for games, VR canprovide new opportunities in working life. The purpose of the study was to develop new waysfor city planners to work with the support of VR. In the study, we wanted to answer thefollowing questions: "How can the VR medium be used for the design process in cityplanning?" and "Can a VR application be perceived as a possible substitute or addition to thedesign process in city planners' work?". In the survey, we have worked with VR by creatingan application where the user is in a virtual world based on traditional working methods forurban planning. The work has followed principles for service design. We have had interviewswith three city planners with different experiences that we interviewed on two differentoccasions. The first interview gave us insight into how they work and what they would needin their design process. The second interview was performed after the design of the prototypewas completed, to provide the results on how city planners could use the medium VR in theirdesign process. The results of the second round of interviews indicated that there waspotential with the design we had developed as a tool in their design process. The informantscame up with many suggestions on how and what would be needed in the VR application tomake it a useful tool in city planning, as well as specific improvement proposals for thecurrent design.

    VR för stadsplannering

    No full text
    VR Ă€r en simulerad upplevelse genom bilder, ljud och andra sensorer som simulerar enanvĂ€ndares fysiska och mentala nĂ€rvaro i en virtuell vĂ€rld. Förutom att anvĂ€ndas till spel kanVR ge nya möjligheter inom arbetslivet. Syftet med undersökningen Ă€r att ta fram nya sĂ€tt förstadsplanerare att jobba med hjĂ€lp av VR. I undersökningen vill vi besvara följandefrĂ„gestĂ€llningar: “Hur kan VR mediet anvĂ€ndas för designprocessen inom stadsplanering?”och ”Upplevs en VR applikation som ett möjligt substitut eller tillĂ€gg för designprocessen istadsplanerares arbete?”. I undersökningen har vi arbetat med VR genom att skapa enapplikation dĂ€r anvĂ€ndaren befinner sig i en virtuell vĂ€rld som grundar sig i traditionellaarbetssĂ€tt för stadsplanering. Arbetet har följt principer för tjĂ€nstedesign. Vi har haftintervjuer med tre stadsplanerare med olika erfarenheter som vi intervjuade vid tvĂ„ olikatillfĂ€llen. Första intervjun gav oss insikt i hur de jobbar och vad de skulle behöva i derasdesignprocess. DĂ€refter hade vi en andra intervju efter gestaltningen blev klar för att ta framundersökningens resultat pĂ„ hur stadsplanerare skulle kunna anvĂ€nda mediet VR inomdesignprocess för stadsplanerare. Resultatet pĂ„ de senare intervjuerna pekade pĂ„ att det fannspotential med gestaltningen vi hade tagit fram för att de skulle kunna anvĂ€nda det i derasdesignprocess. Informanterna kom med mĂ„nga förslag om hur och vad som skulle behövas iVR-applikationen för att det skulle kunna tĂ€nkas anvĂ€ndas i stadsplanering, samt specifikaförbĂ€ttringsförslag för den aktuella gestaltningen.VR is a simulated experience through images, sounds and other sensors that simulate a user'sphysical and mental presence in a virtual world. In addition to being used for games, VR canprovide new opportunities in working life. The purpose of the study was to develop new waysfor city planners to work with the support of VR. In the study, we wanted to answer thefollowing questions: "How can the VR medium be used for the design process in cityplanning?" and "Can a VR application be perceived as a possible substitute or addition to thedesign process in city planners' work?". In the survey, we have worked with VR by creatingan application where the user is in a virtual world based on traditional working methods forurban planning. The work has followed principles for service design. We have had interviewswith three city planners with different experiences that we interviewed on two differentoccasions. The first interview gave us insight into how they work and what they would needin their design process. The second interview was performed after the design of the prototypewas completed, to provide the results on how city planners could use the medium VR in theirdesign process. The results of the second round of interviews indicated that there waspotential with the design we had developed as a tool in their design process. The informantscame up with many suggestions on how and what would be needed in the VR application tomake it a useful tool in city planning, as well as specific improvement proposals for thecurrent design.

    The initiation of strain localisation in plagioclase-rich rocks: Insights from detailed microstructural analyses

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