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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.
1

Magmatic Stoping and a Case Study from the Åva Ring Complex, Finland

Lagergren, Hanna January 2012 (has links)
Magmatic stoping is a term that has been controversial almost since it was first mentioned over a century ago. Scientists have been arguing whether it plays an important part as an emplacement process of magma chambers, or whether it takes place at all. With growing evidence for both pro- and counterar guments the debate becomes tenser and the question raised is whether it is possible to find a unanimous answer. Magmatic stoping is often associated with the presence of xenoliths, “foreign” rocks that have been enclosed by magma. As parts of the roof or walls in the magma chamber detach, the pieces become trapped in it if they don’t have time to dissolve before the magma cools. The new cavities make room for a growing chamber and the possibility for magmatic stoping to be a volumetrically significant process is as well in discussion. The problematic starts early, beginning with the definitions of words like stoping, xenoliths, and rafts which are not unified. Natural findings of xenoliths in plutons are rare and speak against stoping but are often explained by xenoliths that possibly sunk down to the floor of magma chambers and become inaccessible for researchers. Nowadays there are several explanations to these statements that will be both presented and discussed in this thesis. A case study is also made from the Åva ring complex in Finland, and it has been shown to provide a fairly clear idea of the evidence for magmatic stoping. With remote sensing xenoliths have been mapped and measured and the results show that magmatic stoping is an abundant process and not something to be dismissed.
2

Indium Analysis and Small-scale Distribution in Sulphides from the Lindbom Prospect, Långban Area, Western Bergslagen Ore Province

Lindeberg, Tomas January 2013 (has links)
Indium is extensively used in LCD screens and solar cells. It is mainly produced as a byproduct during ore processing. With ever increasing demand for indium and most of the production being restricted to a few countries new sources for indium are needed. In Sweden, the westernmost Bergslagen is the only area, which is known to exhibit minerals with essential indium. The indium mineralisations at Långban, the Linbom prospect, which are studied in this bachelor’s thesis show several trends. The most notable is the copper indium trend seen in sphalerite. A likely substitution based on similar ionic radii and charges is Cu1++ In3+ ↔ 2Zn2+.Usually when cassiterite is associated with similar polymetalic indium bearing mineralisations as at Långban there is also high concentrations in cassiterite. This has previously not observed in Sweden, however during this project concentrations were indeed found in cassiterite.
3

Mikroskopering av opaka faser - en studie från Skyttgruvan, Falun.

Brismo Ploetz, Marcus January 2013 (has links)
In nature there are about 4,500 minerals identified. These can roughly be divided into two groups, opaque phases and non-opaque phases, with the exception that some opaque phases also may act as a non-opaque phase in different circumstances. The division is made on the basis of the optical properties. Opaque phases are nontransparent, which means that a different type of microscope must be used. A conventional microscope uses transmitted light while the microscope for opaque phases or the ore microscope uses reflected light. The reason is that ore minerals often behave in an opaque manner. An ore mineral is actually a regular mineral but with the difference that it is economically advantageous to mine. Many sulphide and oxide minerals are classified as ore minerals. Sulfide and oxide ores are often associated with a particular type of formation environment and are found in a few areas in Sweden. Bergslagen, Skelleftefältet and Norrbotten belong to these areas. The purpose of this studie is to identify the mineralization from Skyttgruvan and Näverbergsgruvan in Falun by using a microscope. / I naturen finns cirka 4,500 mineral identifierade. Dessa kan grovt sett delas upp i två grupper nämligen opaka faser och icke-opaka faser, då bortses dock från undantaget att vissa opaka faser också kan beteé sig som icke-opaka faser under olika omständigheter. Uppdelningen är gjord utifrån mineralens optiska egenskaper. Opaka faser är icke genomskinliga vilket innebär att en annan typ av mikroskop än de konventionella måste användas. Ett konventionellt mikroskop använder sig av genomfallande ljus samtidigt som mikroskop för opaka faser använder sig av påfallande ljus, ett så kallat malmmikroskop. Anledningen till att de kallas just så är för att malmineral ofta är opaka. Ett malmmineral är egentligen ett vanligt mineral men som är ekonomiskt fördelaktigt att bryta. Idag är många sulfid- och oxidmineral klassade som malmmineral. Sulfid och oxidmineral är ofta associerade med en viss typ av bildningsmiljö. Denna typ av bildningsmiljö går att finna spår av på några platser i Sverige. Bergslagen, Skelleftefältet och Norrbotten hör till dessa områden. Syftet med denna studie är att identifiera de opaka faserna som påträffats i stuffer som samlats in från Skyttgruvan och Näverbergsgruvan.
4

How Water, Ice, and Sediment Deform the Earth: Novel Developments and Applications of Models of Glacial Isostatic Adjustment

Kuchar, Joseph 26 November 2018 (has links)
Sea-level change in response to the growth and melt of ice sheets and glaciers is a process called glacial isostatic adjustment (GIA). This includes deformation of the surface of the Earth itself in response to the extreme mass exchanges between the oceans and continents, as well as changes to the gravitational potential that describe the sea surface in response to the redistribution of surface mass as well as mass within the Earth. This thesis describes four research projects I've conducted in the field of GIA modelling. Most GIA models represent the lithosphere, the outermost layer of the Earth, as functionally elastic. However, there is a large temperature gradient within the lithosphere that would lead to a reduction in viscosity with depth. Therefore, in Chapter 2, I developed and incorporated more realistic lithosphere structure into the GIA model, and demonstrate that this added structure results in a time-dependence to the response of the lithosphere. While the usual inputs to a GIA model are the ice load and Earth description, there are regions where other processes need to be accounted for. In the Mississippi Delta region, processes associated with the deposition of sediment carried by the Mississippi River are strong drivers of local sea-level change, and include isostatic adjustment as well as compaction of the sediment layers over time. Therefore, in Chapter 3, I incorporated a treatment of sediment isostatic adjustment into the GIA model and applied it to the Mississippi Delta region. Our results indicate that the sediment isostatic adjustment signal is important in the vicinity of the delta, but small otherwise. By comparing model projections to GPS measurements, we demonstrate that most subsidence in the region is due to non-isostatic processes (such as sediment compaction). Data used to constrain GIA models are generally sensitive to both ice and Earth structure. Therefore data parametrizations that are insensitive to one input or the other are valuable constraints. One such commonly used parametrization is the postglacial decay time. Previous research has shown that the decay times are relatively insensitive to the ice history, and therefore provide a more robust constraint on Earth structure. In Chapter 4 I tested the extent of the ice insensitivity of decay times by considering a suite of ice reconstructions. I found that decay times are sensitive to ice history, and that the sensitivity depends on the location of the data relative to the geometry of the ice sheet. In particular, my results suggest that James Bay (in Hudson Bay) is a location that should not be used in a decay time analysis. The GIA model applied in the projects described above is a 1-D, spherically symmetric model. However, it is known that the Earth's viscous structure is likely to feature significant lateral variation. This is evident in the differences in viscosities found in this thesis between what satisfies the RSL data in Hudson Bay (in Chapter 4) and the Gulf coast of the US (Chapter 3), as well as various previous studies. Therefore, in Chapter 5, I applied a 3-D model with lateral viscous structure determined by seismic shear wave velocity models, to determine whether incorporating this more realistic structure could resolve this apparent discrepancy. I demonstrated that the fit to relative sea level data on the Atlantic and Gulf coasts of the US can be significantly improved by incorporating lateral viscous structure, but also that there is significant uncertainty associated with the more complex viscous structure.
5

Big Remote Sensing Data and Machine Learning for Assessing 21st Century Flooding and Socioeconomic Exposures

Sherpa, Sonam Futi 28 April 2023 (has links)
Over the past decades, we have seen escalating costs associated with the direct socioeconomic impacts of hydrometeorological events and climate extremes such as flooding, rising sea levels due to climate change, solid earth changes, and other anthropogenic activities. With the increasing population in the era of changing climate, the number of people suffering from exposure to extreme events and sea level rise is expected to increase over the years. To develop resilience plans and mitigation strategies, hindcast exposure models, and calculate the insurance payouts, accurate maps of flooding extent and socioeconomic exposure at management-relevant resolution (102m) are needed. The growing number and continually improving coverage of Earth-observing satellites, an extensive archive of big data, and machine learning approaches have transformed the community's capacity to timely respond to flooding and water security concerns. However, in the case of flood extent mapping, most flood mapping algorithms estimate flood extent in the form of a binary map and do not provide any information on the uncertainty associated with the pixel class. Additionally, in the case of coastal inundation from sea level rise, most future projections of sea-level rise lack an accurate estimate of vertical land motion and pose a significant challenge to flood risk management plans. In this dissertation, I explore an extensive archive of available remotely sensed space-borne. synthetic aperture radar (SAR) and interferometric SAR measurements for 1) Large-scale flood extent mapping and exposure utilizing machine learning approaches and Bayesian framework to obtain probabilistic flood maps for the 2019 flood of Iran and 2018 flood of India and 2) Assessment of relative sea-level rise flooding for coastal disaster resilience in the Chesapeake Bay. Lastly, I investigate how climate change affects hydrology and cryosphere to 3) understand cryosphere-climate interaction for hazard risk and water resources management. / Doctor of Philosophy / Flooding increased exponentially in recent decades due to changes in climate and human activities. With an increasing number of people and flooding events, exposure to such events has been enhanced. The presence of satellites in space, the increase in revisit-time, and better tools and techniques to map flood extents have transformed society's ability to respond to hazard and water-related issues. To develop risk management plans and project how many people will be affected by hazards, and calculate the insurance payouts, accurate maps of flooding extent, and socioeconomic exposure at management-relevant resolution are needed. However, in terms of flood mapping, most flood maps do not provide information on how much water is there on a particular map. In addition, in the case of coastal flooding coming from sea level changes, current methods for future scenarios of flooding, do not accurately account for how the ocean is rising with respect to the land-encompassing movement of the land. This causes a significant challenge to coastal flood risk management plans. Therefore, in this dissertation, I explore large datasets from satellites for 1) Accurate flood extent mapping and 2) Estimation of coastal flood from relative sea level rise. Lastly, I also, examine how climate change is affecting ice and water changes to 3) Understand the role of climate on the water for hazard risk and water management.
6

Measuring Low Fault Strain Rate with Synthetic Aperture Radar: Application to the Pacific-North America Plate Boundary

Gourmelen, Noel 28 October 2009 (has links)
I use Synthetic Aperture Radar Interferometry (InSAR) to study the present deformation in the Western Basin and Range and Basin and Range - Sierra Nevada transition. I process 350 SAR data over 190·103 km2 for the period 1992 to 2002. Both stacking and time series processing were applied to produce precise (mm/yr) and high-resolution velocity map for the area. Two new processing techniques have been developed. The first technique solves for the long wavelength ambiguities of the InSAR derived velocity map that arise due to uncertainty in the orbital parameter of the satellite. The technique assimilates continuous GPS data into the InSAR time-series processing. The second technique extracts the horizontal and vertical components of the deformation field from two adjacent radar tracks. I applied stacking to study the transient deformation across the Central Nevada Seismic Belt and interseismic strain accumulation across the Eastern California Shear Zone. I show that the current deformation across the Central Nevada Seismic Belt can be explained by a combination of inter-seismic, post-seismic and anthropogenic deformation. The Post-Seismic deformation is associated with visco-elastic relaxation of the Earth's mantle in response to a centennial earthquake sequence of five ~M7 earthquakes along the Central Nevada Seismic Belt. The anthropogenic deformation is a response of the bedrock to water withdrawal in support of mining activity. A more evolved time-series approach that solves for orbital errors is applied across the Eastern California Shear Zone. The study shows that the Hunter Mountain - Panamint Valley fault system accommodates ~5 mm/yr, a faster rate than geological averages. The region of strain accumulation is a narrow band of ~10 km centered on the Hunter mountain fault, and indicates a very shallow locking depth in agreement with an active low angle normal fault system.
7

The tectonic evolution of northwest Svalbard

Pettersson, Carl Henrik January 2010 (has links)
Svalbard represents the uplifted and exhumed northwest corner of the Barents Sea Shelf. Pre-Carboniferous rocks of Svalbard are divided into the Eastern, Northwestern and Southwestern Terranes, were amalgamated during the Caledonian Orogen and are separated by north-south-trending strike-slip faults. Even though our knowledge of Svalbard’s pre-Carboniferous history has increased dramatically during the last two decades, a major issue remains: Where did the different tectonostratigraphic terranes of Svalbard originate? The answer to this question has profound significance for the entire eastern Laurentian margin, which spans two supercontinent cycles, from the amalgamation and breakup of Rodinia to the amalgamation of Pangea. This thesis constrains the tectonothermal evolution of Svalbard’s Northwestern Terrane (NWT) using ion microprobe and LA-ICP-MS U-Pb zircon geochronology and electron microprobe thermobarometry on metasediments, clastic rocks and granitoids. Detrital zircon age populations of metasediments from the NWT suggests that they (e.g. the Krossfjorden Group) were deposited at c. 1000 Ma in a remnant ocean basin setting outboard the Eastern Grenville Province and were subsequently deformed and intruded by Late Grenvillian granitoids during the final suturing of Rodinia. Thus, a northern branch of the Grenvillian/Sveconorwegian orogeny is not present. This older history of the NWT is extensively overprinted by Late Caledonian deformation and metamorphism, with peak metamorphic conditions of 850 °C at >6 kbars, and subsequent migmatization of the Krossfjorden Group at c. 420 Ma. Based on these data, together with the detrital zircon age population from overlying Late Silurian-Early Devonian clastic rocks, a unifying model is proposed involving fragments from the Grampian orogen and Avalonian crust originally accreted to the Laurentian margin, subsequently transported northwards along sinistral strike-slip faults during Scandian deformation. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: In press.
8

Temporala och spatiala egenskaper i makroseismiska katalogdata 1375-2000

Andersson, Sara January 2011 (has links)
I Sverige uppmäts årligen runt 700 jordskalv, men ytterst få skalv är av ansenlig styrka. Andelen skalv som vi människor har förmåga att känna av är därav relativt liten. Denna studie är baserad på makroseismisk katalogdata över svenska jordskalv mellan åren 1375-2000. Att studien är makroseismisk innebär att den är icke-instrumentell och därmed baserad på mänskliga observationer i de jordbävningsdrabbade områdena. Katalogen som legat till grund för undersökningen består av 883 fall och innehåller information om tid för skalvet, utbredning och styrka. All erhållen data har sorterats i Matlab efter egenkomponerade sorteringsprogram. Resultaten har redovisats i diagramform, varav vissa sedan plottats i ArcGIS för geografisk visualisering. Syftet med undersökningen har varit att analysera erhållen katalogdata och om möjligt finna förklaringar till varför jordskalvsfrekvensen tett sig som den gjort genom tiden. Framförallt har fokus legat på tidsberoende variationer och att försöka tolka koncentrationen av jordskalv kring januari, vilken kan skådas i majoriteten av rapportens diagram. Teorier som frostknäppar, årstidscykler, och veckodag tas upp för diskussion i rapporten och analyseras huruvida dessa kan utgöra möjliga faktorer till resultatet.   Makroseismiska undersökningar innehar alltid stora osäkerheter eftersom de baseras på källor vars tillförlitlighet i många fall kan ifrågasättas. Denna rapport har därför huvudsakligen baserats på analys av tre tidsintervall, där hänsyn tagits till samhällets utveckling och därmed källmaterialets homogenitet och trovärdighet. Med tanke på de osäkerheter som en makroseismisk undersökning innebär är det möjligt att någon händelse av icke-seismiskt ursprung är inkluderad i katalogen. Svårigheten är bara att avgöra hur omfattande mängd av katalogdata dessa händelser utgör.
9

Malmbildande processer och Bergslagen : - Med exemplifiering från en silver-rik sulfidmineralisering vid Dammen nära Dannemora

Nordström, Albin January 2012 (has links)
Den här rapporten beskriver malmbildande processer och Bergslagens malmgeologi. En beskrivning av malmmikroskopet ges tillsammans med identifikationskriterier för de mineral som påträffats i en mikroskopisk studie som gjorts på fyra stuffer från Dammen nära Dannemora, inkluderande vanliga och påträffade malmtexturer. Två av proverna analyserades med mikrosond. / This report gives a description of ore-forming processes and an introduction to Bergslagen ore-geology. The polarization microscope is described together with a number of identification-criteria of specifik minerals found during a study of four geological specimens from Dammen close to Dannemora, including a description of common ore textures. Two of the samples were also analyzed with an electon probe microanalyzer
10

Oxygen Isotope Signatures of the Apatite-Iron Oxide Ore at Grängesberg

Weis, Franz January 2011 (has links)
The origin of apatite iron oxide ores, like the deposit at Grängesberg in the Bergslagen mining district, has been a subject of much discussion through the years. Some support a formation by hydrothermal fluids while others suggest that the ore is orthomagmatic, i.e. formed directly from a magma as suggested for the iron ore deposits of El Laco in Chile or the deposits in Kiruna, although also these two are still subjected to controversies. In 2009 sampling was done on drillcores through the Grängesberg ore. On these samples an oxygen isotope study on magnetite, quartz and whole rock samples from both the ore and its host rocks was conducted in order to obtain new knowledge about the ore forming processes. The data allowed modeling to simulate a possible origin by different magmas or hydrothermal fluids as well as a possible temperature of formation. In addition, the data set was compared to published oxygen isotope analyses of the possible magmatic iron ores of Kiruna and El Laco. The results of the Grängesberg analysis revealed that the ore in the area seems to have an origin from both magmatic and hydrothermal sources.

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