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Sökning: AMNE:(Mineralogy)

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1.
  • Guldris Leon, Lorena, 1983, et al. (författare)
  • Understanding Mineral Liberation during Crushing Using Grade-by-Size Analysis - A Case Study of the Penuota Sn-Ta Mineralization, Spain
  • 2020
  • Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 10:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Coarse comminution test-work and modeling are powerful tools in the design and optimization of mineral processing plants and provide information on energy consumption. Additional information on mineral liberation characteristics can be used for assessing the potential of pre-concentration stages or screens in the plant design. In ores of high-value metals (e.g., Ta, W), standard techniques-such as the mineralogical quantification of grain mounts by quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) or chemical analysis by X-ray fluorescence (XRF) can be challenging, due to the low relative abundance of such valuable minerals. The cost of QEMSCAN is also a limiting factor, especially considering the large number of samples required for the optimization of coarse comminution. In this study, we present an extended analytical protocol to a well-established mechanical test of interparticle breakage to improve the assessment of coarse mineral liberation characteristics. The liberation of ore minerals is a function of the rock texture and the difference in size and mechanical properties of the valuable minerals relative to gangue minerals and they may fraction in certain grain sizes if they behave differently during comminution. By analyzing the bulk-chemistry of the different grain size fractions produced after compressional testing, and by generating element by size diagrams, it is possible to understand the liberation characteristics of an ore. We show, based on a case study performed on a tantalum ore deposit, that element distribution can be used to study the influence of mechanical parameters on mineral liberation. This information can direct further mineralogical investigation and test work.
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2.
  • Sundvall, Rickard, 1976- (författare)
  • Water as a trace component in mantle pyroxene: Quantifying diffusion, storage capacity and variation with geological environment
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this study, distribution and diffusion of water in pyroxene are examined in an effort to explain the water content variation observed in natural pyroxene. Water is a common trace component in many nominally anhydrous minerals (NAMs) from the Earth's crust and mantle and greatly impacts their physical properties. Therefore, it is crucial to constrain the processes that control water incorporation in these minerals. The pyroxene group has a fairly simple mineral chemistry, the highest amount of water and the greatest water content variation measured in mantle NAMs. Therefore, they are ideal for a case study such as the present. The redox reaction: OH- + Fe2+ ↔ O2- + Fe3+ + ½H2, is believed to control water diffusion in many NAMs having sufficiently high iron contents. Nevertheless, reactions involving vacancies and charge-deficient substitutions which are mainly controlled by cation diffusion are also present and have reaction kinetics that is significantly slower than the redox exchange. Therefore, diffusion and reaction kinetics were studied in (1) synthetic diopside with ~0.7 wt % FeO which allows the study of contributions from both types of reactions (i.e. Fe-redox and cation diffusion). These results were then compared (2) with reaction kinetics in pure synthetic diopside. The diffusion rates are faster in Fe-free diopside, as reaction kinetics is dominated by cation diffusion in samples with low Fe contents. Next (3), water content variation and zonation were investigated in natural pyroxene using high resolution FTIR imaging. The results show no water zonation and a correlation between mantle source and water content. Finally (4), thermal annealing experiments in H2 on natural pyroxene show little or no re-hydration capacity for mantle samples. Altogether, the results indicate that the water contents of most mantle pyroxenes do reflect mantle conditions and that many types of reactions controlling water uptake and release seem to be present in pyroxene.
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3.
  • Corpolongo, A., et al. (författare)
  • SHERLOC Raman Mineral Class Detections of the Mars 2020 Crater Floor Campaign
  • 2023
  • Ingår i: Journal of Geophysical Research - Planets. - : John Wiley and Sons Inc. - 2169-9097 .- 2169-9100. ; 128:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The goals of NASA's Mars 2020 mission include searching for evidence of ancient life on Mars, studying the geology of Jezero crater, understanding Mars' current and past climate, and preparing for human exploration of Mars. During the mission's first science campaign, the Perseverance rover's SHERLOC deep UV Raman and fluorescence instrument collected microscale, two-dimensional Raman and fluorescence images on 10 natural (unabraded) and abraded targets on two different Jezero crater floor units: Séítah and Máaz. We report SHERLOC Raman measurements collected during the Crater Floor Campaign and discuss their implications regarding the origin and history of Séítah and Máaz. The data support the conclusion that Séítah and Máaz are mineralogically distinct igneous units with complex aqueous alteration histories and suggest that the Jezero crater floor once hosted an environment capable of supporting microbial life and preserving evidence of that life, if it existed. 
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4.
  • Olsson, Ingela (författare)
  • Thermal history of the Phanerozoic sedimentary succession of Skåne, southern Sweden, and implications for applied geology
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Post-depositional thermal conditions have been investigated throughout the Phanerozoic sedimentary succession in Skåne. Clay mineralogy and illite crystallinity have been the main tools for the Lower Palaeozoic strata. Within the Mesozoic sequence thermal influence was examined using RockEval pyrolysis and vitrinite reflectance analysis. Clay mineralogy of the Lower Palaeozoic shales and mudstones is generally very uniform with illite and chlorite present. Illite crystallinity values (Kübler index) for these rocks range between 0.41–1.2 (delta degrees two theta) (air-dried), indicating diagenetic to high-diagenetic/anchimetamorphic conditions. In SW Skåne a trend with improved illite crystallinity in the more deeply buried and older strata is observed. This is to be expected in a sedimentary basin subjected to burial controlled diagenetic/thermal impact only. However, in the Sorgenfrei-Tornquist Zone (STZ), where illite crystallinity data show no obvious relationship with stratigraphical position, a more complex thermal history is implied. Most striking in the illite crystallinity data from the STZ is perhaps the improved illite crystallinity recorded for the Upper Silurian Colonus Shale and Öved-Ramsåsa Group, i.e., the youngest Palaeozoic strata in Skåne. High-grade illites there indicate a Post-Silurian thermal event, probably caused by the intrusion of numerous dolerite dykes during the Permian and Carboniferous. Besides thermal effects close to intersecting dykes, the subsequent superficial effusives have constituted more extensive thermal impact on the uppermost part of the sedimentary column. In the proximity of intruding dykes anomalous clay mineralogy has been observed, in contact-metamorphosed shale. For example kaolinite has been found at Åkarpsmölla, where a 40 m wide dolerite dyke intrudes Upper Cambrian Alum Shale. Swelling clay minerals, exotic to the Colonus Shale in Skåne, has been identified in the dolerite quarry at Rönnarp. Here a mixed-layer chlorite/smectite mineral was present in the innermost contact-zone, whereas illite was lacking. Mesozoic thermal conditions generally indicate low to moderate palaeotemperatures in the range of c. 40–90 degrees (C). These data are in agreement with burial estimates and suggest that burial imposed the main diagenetic impact. A deviation from this picture of limited thermal influence has been observed from the Höör Sandstone in Central Skåne and is also indicated in SW Skåne close to the Svedala Fault. Hot fluids derived from tectonic and volcanic activity are believed to have affected these strata causing their anomalous thermal maturity.
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5.
  • Wilson, Wendell E., et al. (författare)
  • Pyrosmalite-(Fe) from the Bjelke mine, Nordmark, Filipstad, Värmland, Sweden.
  • 2019
  • Ingår i: The Mineralogical Record. - Tucson, Arizona. ; 50:60, s. 679-708
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • The ancient Nordmark mines in southwestern Sweden haveyielded 111 different minerals and harbor the type localities for 13 species. Largecrystals of pyrosmalite-(Fe), though collected well over a century ago at theBjelke mine (the type locality), remain the world’s finest.
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6.
  • Sundvall, Rickard, 1976-, et al. (författare)
  • Dehydration-hydration mechanisms in synthetic Fe-poor diopside
  • 2009
  • Ingår i: European journal of mineralogy. - Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung. - 0935-1221 .- 1617-4011. ; 21:1, s. 17-26
  • Tidskriftsartikel (refereegranskat)abstract
    • Small amounts (ppm) of OH in nominally anhydrous minerals (NAMs) can have a dramatic effect on the physical properties of the upper mantle. The pyroxenes of the upper mantle have been shown to incorporate substantial numbers of protons forming hydroxyl ions. Enstatite and diopside are the most important endmembers of the pyroxenes in terms of bulk volume in the upper mantle. To further constrain the behavior of hydroxyl ions in clinopyroxene, the dehydration-hydration mechanisms of synthetic 57Fe-doped diopside were investigated. Dehydration was carried out by stepwise heating in air of crystals synthesized at high pressure under water-saturated conditions. FTIR spectra were obtained after each step. Mössbauer spectra were recorded for three of the crystals when there had been a significant decrease in FTIR absorbance intensity. From the Mössbauer spectra we see an increase in the Fe3+ doublet with successive dehydration, although this increase is less than the decrease in OH in terms of atoms per formula unit. This means that the dehydration only partly follows the redox reaction OH− + Fe2+ = O2− + Fe3+ + ½H2, and that additional reactions occur. Hydration experiments were conducted on one crystal in the same manner as the dehydrations, with the exception that hydrogen gas was used during heating. Hydration experiments resulted in re-hydration of the sample to 73 % of the original amount of OH.   The calculated Arrhenius equation derived from the diffusion rates during dehydration along [010] yields an activation energy (Ea) of −292 ± 50 kJ mol−1, and D0 = 10±1.9 + 2.3 m2 s−1. The result of the rehydration experiment agrees well with the established diffusion law. Diffusion rates determined for synthetic diopside are almost two orders of magnitude slower than for synthetic enstatite with comparable Fe contents. Compared to natural diopside, diffusion rates in these synthetic samples are slower, probably because of the low iron content. Ea is similar to that of dehydration of pure and low-Fe enstatite.
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7.
  • Sundvall, Rickard, 1976-, et al. (författare)
  • Hydrogen defect saturation in natural pyroxene
  • 2011
  • Ingår i: Physics and chemistry of minerals. - : Springer. - 0342-1791 .- 1432-2021. ; 38:5, s. 335-344
  • Tidskriftsartikel (refereegranskat)abstract
    • Dehydration via the redox reaction: OH- + Fe2+ ↔ O2- + Fe3+ + ½H2, is believed to be a commonly occurring process in pyroxenes and other nominally anhydrous minerals (NAMs) from the upper mantle and appears to be fast enough to allow significant dehydration during magma ascent. Nevertheless, the mobility of hydrogen incorporating defects is controlled by cation diffusion with approximately two orders of magnitude slower reaction kinetics than the iron redox-reaction, and host defects have a much higher likelihood to be preserved than the hydrogen itself. Therefore, restoring hydrogen into the structure would be possible by driving the redox-reaction backwards, as long as temperature and time are limited so not to change the defect state of the crystal structure. Here we investigate the re-hydration capacity of megacryst and xenocryst ortho- and clinopyroxene by stepwise thermal annealing of crystallographically oriented samples in 1 atm. H2. H concentration was measured by FTIR spectroscopy after each annealing step. Most samples show only a small increase in water content up to a presumed saturation level, after which further heat treatments in H2 resulted in a slight decrease in water contents. However, two of the studied samples, both fairly Fe rich megacrysts, are significantly rehydrated. Some samples or crystal sections exhibit a practically inert behavior, with minor fluctuations around initial water concentrations. Present results indicate that most mantle pyroxene has not been substantially dehydrated during late stage magma processes, and that restoring water is possible in samples which have lost considerable amounts of water.
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8.
  • Sundvall, Rickard, 1976- (författare)
  • Hydrogen diffusion and storage mechanisms in diopside
  • 2008
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Hydrogen is a widespread trace element in many nominally anhydrous minerals (minerals without water or hydroxyl ions in their structural formula) from the Earth's crust and mantle. The hydrogen is normally incorporated in the form of hydroxyl ions and can be regarded as structurally bound water. The most important minerals of the upper mantle: olivine, orthopyroxene, clinopyroxene and garnet, all contain small but significant amounts of hydrogen. This means that the upper mantle has the capacity to store the equivalent of several world oceans. To know how much water there is in the Earth's interior is important knowledge, as small differences in mantle water content influences models of mantle dynamics. The mantle plays an important role in the hydrological cycle as water in oceanic crust and sediments is subducted at converging plate boundaries and again released through volcanic eruptions during millions of years. Detailed knowledge of the amount of water that is retained within the mantle for longer periods of time (~109 years) is still lacking. Investigating the water content of the mantle is a task shared between the fields of mineralogy, petrology, geophysics, and theoretical physics (i.e. atomistic models). My approach as a mineralogist has been to investigate in detail the mechanisms that are responsible for water incorporation in nominally anhydrous upper mantle minerals, with a special emphasis on the pyroxenes as they can carry substantial amounts of water, up to 1300 ppm H2O. The fundamental questions here are how much of the original xenolith water is lost during transport to the surface and if the spectroscopic features measured in the minerals are representative for mantle conditions. The redox reaction: Fe2+ + OH- ↔ Fe3+ + O2- + ½H2, which is relatively fast, is thought to be the dominant hydrogen exchange reaction in many minerals (Ingrin & Skogby, 2000). The reaction is fast enough to suggest that water in nominally anhydrous minerals equilibrates with the transporting magma and related fluids during ascent to the surface. Nevertheless, several studies show systematic variations in water content with geological environment (Bell & Rossman, 1992; Peslier et al., 2002), implying a complex relationship between host mineral, mantle source region, magma type and eruption style.   This thesis is focused on the dehydration-hydration mechanisms in diopside, the most common variety of clinopyroxene in the upper mantle. The approach has been to study the kinetics and temperature dependence of the reactions controlling hydrogen diffusion in synthetic Fe-poor diopside. Other reactions are likely to be obscured by the iron redox reaction if measured in natural mantle diopside containing several wt% FeO. Therefore, synthetic diopside with very low amounts (0.7 wt% FeO) of iron had to be used in order to measure the influence and co-dependence of the iron redox reaction with other possible reactions. The experiments were carried out by stepwise heating of the samples in both air and hydrogen. After each step, OH-absorbance was measured using Fourier Transform Infrared spectroscopy, and the relative amounts of ferric and ferrous iron was monitored by Mössbauer spectroscopy. When comparing the amounts of ferric iron and hydrogen (in atoms per formula unit), there is considerable deviation from the ideal 1:1 relationship expected from the iron redox reaction. The dehydration process is reversible to a great extent and re-hydration continues even after all iron is reduced. The results of this study show that other reactions apart from the iron redox reaction are active, and that they are significantly slower. If these slower reactions are active in mantle diopsides, there is a possibility that they may preserve signatures from the mantle source region.  
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9.
  • Sundvall, Rickard, 1976-, et al. (författare)
  • Hydrogen diffusion in synthetic Fe-free diopside
  • 2009
  • Ingår i: European journal of mineralogy. - Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung. - 0935-1221 .- 1617-4011. ; 21:5, s. 963-970
  • Tidskriftsartikel (refereegranskat)abstract
    • Hydrogen is a widespread trace element in many nominally anhydrous minerals (NAMs) in the Earth's crust and mantle and has profound influence on the physical properties of the host mineral. Of all NAMs from the upper mantle, clinopyroxenes have been shown to contain the highest amount of hydrogen. This study focuses on the dehydration kinetics of pure diopside along [010] and [100]* by thermal annealing under normal atmospheric pressure. The diopside crystals used were synthesized at high pressure under water-saturated conditions. FTIR spectra were obtained after each step, including untreated samples. The Arrhenius equation gives an activation energy (Ea) of -331 ± 50 kJ mol-1 and D0 = 100.9 ± 2.3 m2 s-1 for diffusion along [010]. Diffusion along [100]* gives an Ea-value of -312 ± 55 kJ mol-1 with D0 = 100.5 ± 2.4 m2 s-1. Therefore, our experimental results show no difference between diffusion along [010] and [100]* (within error limits). The diffusion rate in pure synthetic diopside is about one order of magnitude faster than for synthetic diopside with very low Fe contents. A suitable explanation for this behavior is that in the case of low Fe diopside, the rate-limiting process for the protons associated with Fe is probably Fe-diffusion. In contrast, in pure diopside all protons are associated to Mg-defects, which are more mobile than Fe. Nevertheless, compared to natural diopside with appreciable Fe contents, diffusion rates in these synthetic samples are several orders of magnitude slower.
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10.
  • Sundvall, Rickard, 1976- (författare)
  • Water as a trace component in upper mantle pyroxenes
  • 2008
  • Ingår i: EURISPET (European Intensive Seminars in Petrology) – Petrology of the lithosphere in extensional settings. Budapest, August 21-31, 2008.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Hydrogen is a widespread trace element in many nominally anhydrous minerals (NAMs) from the Earth's crust and mantle. Hydrogen is normally incorporated in the form of hydroxyl ions and can be regarded as structurally bound water. The most important minerals of the upper mantle: olivine, orthopyroxene, clinopyroxene and garnet, all contain small but significant amounts of hydrogen, and the upper mantle has a capacity to store the equivalent of several world oceans. The main objective of this project is to investigate in detail the mechanisms that are responsible for water incorporation in upper mantle pyroxenes (and synthetic analogues) as pyroxenes can carry substantial amounts of water, up to 1300 wt ppm H2O. Fundamental questions are how much of the original xenolith water that is lost during transport to the surface and if the spectroscopic features measured in the minerals are representative for mantle conditions. The redox reaction: Fe2+ + OH- ↔ Fe3+ + O2- + ½H2, which is relatively fast, is thought to be the dominant hydrogen exchange reaction in many minerals (Ingrin & Skogby, 2000). The reaction is fast enough to suggest that water in NAMs equilibrates with the transporting magma and related fluids during ascent to the surface. Nevertheless, several studies show systematic variations in water content with geological environment (Bell & Rossman, 1992; Peslier et al., 2002), implying a complex relationship between host mineral, mantle source region, magma type and eruption style. The current part of the project  is focused on the dehydration-hydration mechanisms in diopside, the most common variety of clinopyroxene in the upper mantle. The approach has been to study the kinetics and temperature dependence of the reactions controlling hydrogen diffusion in synthetic Fe-poor diopside. Other reactions are likely to be obscured by the iron redox reaction if measured in natural mantle diopside containing several wt% FeO. Therefore, synthetic diopside with very low amounts (0.7 wt% FeO) of iron had to be used in order to measure the influence and co-dependence of the iron redox reaction with other possible reactions.
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11.
  • Sundvall, Rickard, 1976-, et al. (författare)
  • Water in upper mantle pyroxene megacrysts and xenocrysts – a survey study
  • 2011
  • Ingår i: American Mineralogist. - : Mineralogical Society of America. - 0003-004X .- 1945-3027. ; 96:0809 Aug-Sept, s. 1215-1227
  • Tidskriftsartikel (refereegranskat)abstract
    • Water content, mineral chemistry and oxidation state of clino- and orthopyroxene xenocrysts and megacrysts was investigated by FTIR (Fourier Transform Infrared) spectroscopy – including FPA (Focal Plane Array) detector mapping, Mößbauer spectroscopy and electron microprobe. A variety of tectonic settings, ages and modes of emplacement are represented by 23 samples from 6 areas (Massif Central, France; Letseng, Lesotho; Colorado, USA; Kakanui, New Zealand; Oahu, Hawaii; New South Wales, Australia). The xenocrysts are from both garnet and spinel peridotites – including lherzolite and harzburgite varieties, and one sample of clinopyroxenite. Water contents vary between ~10 and 600 wt ppm. Samples from Massif Central, Colorado, Kakanui and Hawaii have rather high water contents: 180 – 600 wt ppm. The samples from Lesotho and New South Wales have considerably lower amounts: ~10 – 300 wt ppm. Water contents of xenocrysts and megacrysts from New South Wales vary within a narrow range (clinopyroxene: ~50 wt ppm, orthopyroxene: 15-20 wt ppm), whereas the water content of the Lesothian samples scatter considerably. No significant correlations are observed between water content, mineral chemistry, or oxidation state of the samples. FPA mapping reveals homogenous distribution of water in the pyroxene lattice. The results are compared to available literature and research on hydrogen diffusion in natural mantle pyroxene. Altogether, the data suggest that pyroxene found in fresh peridotite xenoliths partly reflects the water content of the mantle source region. On the other hand, variable mineral chemistry and water contents of megacryst pyroxenes indicate processes such as magmatic equilibration, magma mixing and contamination.
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12.
  • Mohammad, Yousif, 1976, et al. (författare)
  • The Kuradawe Granatic Pegmatite from the Mawat Ophiolote, Northeastern Iraq: Anatomy, Mineralogy, Geochemistry, and Petrogenesis
  • 2016
  • Ingår i: Canadian Mineralogist. - : Mineralogical Association of Canada. - 0008-4476 .- 1499-1276. ; 54:4, s. 989-1019
  • Tidskriftsartikel (refereegranskat)abstract
    • The highly evolved Kuradawe granitic pegmatite dike is hosted in a harzburgite-dunite succession of the Mawat ophiolite in northeastern Iraq. It consists mainly of quartz, orthoclase, albite, tourmaline, and muscovite. Accessory minerals include cordierite, andalusite, monazite-(Ce), biotite, zircon, Nb-rich rutile, chlorapatite, chlorite, Sc-bearing columbite-(Fe), uraninite, U-rich thorite, and xenotime-(Y). The internal structure of the pegmatite consists of border, wall, intermediate, and core zones. Plagioclase composition increases from Ab(92) to Ab(97) towards the core. Whole rock major oxides such as MgO, Al2O3, and CaO decrease and SiO2 increases toward the core. Na2O, K2O, and total FeO are enriched in specific zones. Among the trace elements, incompatible elements such as Sr, Ba, and Zr decrease and the compatible elements Ni and Cr slightly increase toward the core. The pegmatite is characterized by the dominance of tourmaline; muscovite as the dominant mica; normative corundum; high contents of SiO2, Al2O3, A/CNK, and Rb; low contents of CaO and Sr; and a high total FeO/MgO ratio in biotite. These features suggest an affinity with calc-alkaline peraluminous S-type granite in a subduction-related, syncollisional setting. The pegmatite is classified as beryl-columbite subtype of the LCT family. The restricted occurrence of high-temperature cordierite in the border zone may suggest that the pegmatite was overprinted by modal metasomatism during intrusion into the mantle rocks. Zircon saturation geothermometry indicates inward crystallization at temperatures of 782 degrees C in the border zone, 717 degrees C in the wall zone, and 550 degrees C in the intermediate zones. Geochemical data suggest that inward crystallization typified the formation of the pegmatite. DULLA K.L., 2015, Petrogenesis and geochronology of plagiogranite rocks in Penjween ophiolite, Kurdistan region, NE Iraq
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13.
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14.
  • Akselsson, Cecilia, et al. (författare)
  • Relations between elemental content in till, mineralogy of till and bedrock mineralogy in the province of Småland, southern Sweden
  • 2006
  • Ingår i: Geoderma. - : Elsevier BV. - 0016-7061. ; 136:3-4, s. 643-659
  • Tidskriftsartikel (refereegranskat)abstract
    • Information on soil mineralogy is essential for weathering rate calculations. Quantitative mineralogical analyses are expensive and time-consuming, and thus indirect methods of determining the mineralogical composition are important, for example estimating the composition based on the elemental content in till (total concentrations), or based on information about the underlying bedrock. The mineralogical composition and the elemental content in till were analysed in two areas in southern Sweden, at 10 sites in each area. There were significant differences between the areas regarding both elemental content and optically determined mineralogy. The content of calcium was significantly higher in one area, 5ESV, and there were tendencies in this direction also for magnesium and iron. The potassium content was significantly higher in the other area, 6FNV. The variation in soil chemistry between the areas can be explained by higher contents of the minerals biotite, homblende and epidote in the first area (5ESV) and higher contents of K-feldspar in the second (6FNV). Normative mineralogy was determined based on the elemental content. A comparison between the normative mineralogy and the optically determined mineralogy showed great similarities which indicates that there is good potential for using elemental content for estimating the mineralogical composition. The difference in till composition between the areas could not be explained by the underlying bedrock, which indicates that the information available on the bedrock is not sufficient for estimation of the till mineralogical composition.
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15.
  • Albrecht, Lena Gunlög (författare)
  • Early structural and metamorphic evolution of the Scandinavian Caledonides: a study of the eclogite-bearing Seve Nappe Complex at the Arctic Circle, Sweden
  • 2000
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In the Seve Nappe Complex of the Swedish Caledonides, coronitic diabases pass into eclogites; sometimes the transition occurs within one and the same boudin. Calculated pressure-temperature conditions for the eclogite facies stage are 20-27 kbar and 650-750°. Protolith corona-dolerite dykes share the T-MORB signature with the rift-dolerites of the Sarek and Särv Nappes, indicating similar origin. Eclogites are hosted by metasedimentary rocks and a metavolcanic unit, the Tjidtjak Metavolcanite, serving as basement for deposition of sediments in rapidly subsiding rift-basins. Ion-probe datings of zircons from the metavolcanite give a preliminary intrusion age at 952±27 Ma. Dating of titanite from calc-silicate horizons within the Grapesvare Nappe, Seve Nappe Complex supports the existence of a Finnmarkian phase of subduction and eclogitization c. 475-500 Ma ago, which is about 100 Ma prior to the main Scandian thrusting. Structures which formed prior to, or early during eclogitization have been recrystallized but are occasionally preserved in domains between anastomosing shear zones. Formation of the latter, and of non-cylindrical folds was triggered by the presence of rigid eclogite boudins. Eclogitization was followed by extreme ductile deformation during rapid exhumation and retrogression of the eclogites. Folding is interpreted as a continuous process where early folds were consecutively refolded, sheared into tubular folds and deformed in new shear zones resembling shear bands at metre-scale. The overall deformational regime was vertical thinning during eastward general shear, possibly due to oblique compression during the exhumation phase. In the Scandian thrusts, strong lineations, lineation-parallel folds and occasional sheath folds indicate a component of oblique compression early during foreland-directed nappe emplacement. In schists and phyllites of lower nappes, horizons containing C'-type shear bands and asymmetric folds alternate, demonstrating a continuous interaction between thickening and thinning during foreland-directed translation. At the margin of the Nasafjäll Window, folded basal thrusts of both upper and lower tectonic units demonstrate that lower thrusts were active after movements on higher thrusts had stopped. North and west of the Nasafjäll Window, earlier SE-vergent structures have been overprinted by later N and NW vergent structures showing movements away from the centre of the window. This may have been an effect of increased topography caused by the stacking of the Nasafjället Window, indicating that this occurred late during the Scandian collision.
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16.
  • Andersson, Jenny (författare)
  • Sveconorwegian orogenesis in the southwestern Baltic Shield - Zircon geochronology and tectonothermal setting of orthogneisses in SW Sweden
  • 2000
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The Mylonite zone (MZ) is a prominent late-Sveconorwegian lithological terrane boundary in the SW Baltic Shield along which large-scale crustal block movements took place during the Sveconorwegian orogeny. The southern section of the MZ also defines a conspicuous metamorphic break separating upper amphibolite and high-pressure granulite facies rocks in the parautochthonous Eastern Segment (ES), from middle amphibolite facies rocks in the overlying Western Segment (WS). Zircon geochronology and structural and metamorphic data for orthogneisses across the southern section of the MZ do not support previous interpretations for the MZ to have originated as a pre-Sveconorwegian (>=1.55 Ga) amalgamation zone of Gothian terranes. East of the MZ, in the parautochthonous ES, the oldest orthogneisses are dated at 1.70-1.68 Ga supporting the concept that these rocks are reworked equivalents to the youngest rocks of the 1.85-1.66 Ga Transscandinavian Igneous Belt of the Sveconorwegian foreland. West of the MZ, in the allochthonous southern WS, the oldest orthogneisses are dated at 1.59 Ga, which confirms that these rocks represent an igneous event, not recognised east of the MZ in the Sveconorwegian parautochthon. Datings of augen gneisses in the southern WS at 1.33-1.31 Ga also contradict previous “stitching granite” correlation with 1.40-1.38 Ga granite-monzonite magmatism in the underlying ES, across the MZ. Investigation of field relations, deformational fabrics and metamorphic character, combined with zircon and titanite chronology of orthogneisses in the southern ES and the WS demonstrate that these rocks underwent regional penetrative ductile deformation, high-grade metamorphism and anatexis during the Sveconorwegian orogeny. The high-grade metamorphism and anatexis is dated at 0.99-0.96 Ga. Ductile deformation internal to the southern ES is dated at 0.96 Ga, and a lower age limit for this deformation is set by post-tectonic pegmatite-granite dyke intrusions dated at 0.95 Ga. In the southern ES, regional, pre-Sveconorwegian high-grade metamorphism, anatexis, and felsic vein injections are dated at 1.46-1.42 Ga. The tectonothermal character of this early event is unclear due to penetrative late Sveconorwegian tectonic transposition and metamorphic recrystallisation in the upper amphibolite to high-pressure granulite facies, followed by amphibolite facies retrogression. Evidence for high-grade metamorphism and anatexis prior to 1.46 Ga is lacking. A difference in timing and character of Sveconorwegian metamorphism and deformation within and between the ES and the WS indicates a complex build-up of lithological and/or metamorphic terranes. Models of the Paleo- and Mesoproterozoic geological evolution of this part of the Baltic continent must therefore be based on an understanding of the large-scale Sveconorwegian crustal block movements taking place prior to final juxtaposition in late Sveconorwegian time.
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17.
  • Andersson, Stefan S., et al. (författare)
  • Mineral paragenesis and sulphide trace element distribution in the metamorphosed Lovisa Zn-Pb deposit, Bergslagen (Sweden), as revealed by 3D X-ray tomography, ore petrography and LA-ICP-MS analysis
  • 2022
  • Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 140
  • Tidskriftsartikel (refereegranskat)abstract
    • This study encompasses the ore mineralogy, textures and sulphide trace element chemistry of the Palaeoproterozoic Lovisa stratiform Zn-Pb deposit and the stratigraphically underlying Lovisa Fe Formation in the Bergslagen ore province (Sweden). We investigate the relative timing of formation and subsequent modifications of its ores in relation to the c. 1.87-1.80 Ga Svecokarelian orogeny. The Lovisa Zn-Pb deposit consists of several different ore types. The massive sphalerite-galena ore is distinctly deformed, exhibiting a multiple-scale "ball ore" texture with rounded silicate clasts within a deformed, fine-grained sulphide matrix. Underlying the massive ore is a locally folded, sphalerite-rich laminated ore, interpreted to represent a metamorphosed relict primary lamination. Several generations of sphalerite-galena fracture fillings and veins occur adjacent to the main ore zones and they cross-cut early ductile structures and metamorphic features. The trace element signatures of the sphalerite-galena infillings generally mimic those of the two main ore zones, thus supporting an origin by localised remobilisation of the primary sulphide ore and demonstrating limited trace element redistribution during this process. In contrast, discrete sulphosalt-rich fracture fillings cross-cutting earlier galena-chalcopyriterich fracture fillings and veinlets in the Lovisa Fe Formation suggest a significant but still relatively localised redistribution of metals. Trace element mapping of sulphides from the Lovisa Zn-Pb deposit reveals that inclusion-free overgrowths on pyrite crystals are locally Co-enriched compared to the cores, which resulted from the redistribution of Co during late metamorphic processes. Combined textural and geochemical evidence suggest that the originally syngenetic exhalative sulphide ore at Lovisa was locally strongly affected by polyphase deformation and remobilisation. This was initiated during the first stage of amphibolite facies grade regional metamorphism and deformation (D1, c. 1.87-1.85 Ga) but is mostly evident from the later stages (D2) and the evolution to retrograde and brittle conditions (c. 1.83-1.80 Ga and later).
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18.
  • Andersson-Sköld, Yvonne, et al. (författare)
  • Quick clay - A case study of chemical perspective in Southwest Sweden
  • 2005
  • Ingår i: Engineering Geology. - : Elsevier BV. - 0013-7952. ; 82:2, s. 107-118
  • Tidskriftsartikel (refereegranskat)abstract
    • Quick clay, a soil that changes from normal firm ground to a liquid mass when it is disturbed, has been involved in most of the large and serious clay slides in Sweden, Norway and Canada. The location, time of occurrence and size of quick clay slides are difficult to predict and large slides may cause great devastation. Some geochemical studies of Swedish quick clay were done in the 1960s and early 1970s, but no systematic studies of the interrelationships of pore water chemistry, mineralogy, geotechnical properties and other parameters on quick clays in Sweden have been published. Such studies are of national and general interest because of the many combinations of rock flour source areas and sedimentation conditions that occurred across central Sweden and into the Baltic Sea area during deglaciation. In this study, geotechnical properties related to the in situ chemistry at one quick clay site were extensively studied, and spot sampling was conducted at two other locations in Southwest Sweden. In this area the clay minerals mainly are non-expanding phyllosilicate minerals (illite) and primary minerals (quartz, feldspar), which is consistent with previous studies of quick clay mineralogy. Extensive leaching has occurred at all three locations. At the extensively studied site, Surte, the lowest salinity was found at the greatest depth, inferring that the leaching by fresh water was accomplished by water movement upward and laterally through the sediment from the underlying bedrock. This is consistent with the local setting where bedrock hills rise sharply to over 100 in above the marine sediment surface. An artesian pressure would also be anticipated at this location. There is a correlation (negative) between sensitivity and salinity but there is an indication that the maximum salinity or electrical conductivity consistent with the quick clay behaviour is higher than reported elsewhere. However, for high sensitivities the salinity is about the same as reported elsewhere. In the deepest part of the borehole, there is a higher content of Fe and Al in the pore water, indicating reduced state. Further work is needed to confirm the difference in salinity and to investigate the possible interplay of salinity and potential dispersing agents such as the role of anoxic conditions, in this region. Further work is especially needed in the locations where the sediment accumulation occurred under lower salinity conditions. At all three locations, high remoulded shear strength and low sensitivity have been seen near the surface together with a decrease in pore water cation concentrations. (c) 2005 Elsevier B.V. All rights reserved.
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19.
  • Andrén, Margareta, et al. (författare)
  • Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland
  • 2016
  • Ingår i: Journal of Geophysical Research - Solid Earth. - 2169-9313 .- 2169-9356. ; 121:4, s. 2315-2337
  • Tidskriftsartikel (refereegranskat)abstract
    • Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northernIceland, from October 2008 to June 2015 revealed (1) a long-term decrease in concentration of Si and Naand (2) an abrupt increase in concentration of Na before each of two consecutive M > 5 earthquakes whichoccurred in 2012 and 2013, both 76 km from Hafralækur. Based on a geochemical (major elements and stableisotopes), petrological, and mineralogical study of drill cuttings taken from an adjacent borehole, we areable to show that (1) the long-term decrease in concentration of Si and Na was caused by constant volumereplacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fracturesand (2) the abrupt increase of Na concentration before the first earthquake records a switchover tononstoichiometric dissolution of analcime with preferential release of Na into groundwater. We attributedecay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fracturedor porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are anincrease of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixingbetween groundwater components. Both could have been triggered by preseismic dilation, which was alsoinferred in a previous study by Skelton et al. (2014). The mechanism behind preseismic dilation so far from thefocus of an earthquake remains unknown.
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20.
  • Arm, Maria, et al. (författare)
  • Förutsägelse av långtidsegenskaper hos restprodukter : teknik och miljö i vägar
  • 2009
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • In Sweden, use of industrial by-products is still hindered by concern for their long-term properties. This report describes a three-year research project aiming to identify the key processes of ageing related to the usefulness of by-products in roads; investigate the consequences of these processes for technical and environmental properties of the by-products, and propose a method for accelerated ageing to predict long-term properties. The project has compared naturally aged samples of two by-products used as sub-bases in existing asphalt paved roads with samples of fresh by-products from producers' piles. Steel slag of electric arc furnace type and municipal solid waste incinerator (MSWI) bottom ash were chosen. The samples were thoroughly characterized in order to identify which ageing processes had been crucial. The working hypothesis was that ageing processes lead to changes in pH, effective particle size and mineralogy, which in turn determine leaching, stiffness and stability of the material. One of the conclusions from the project is that the test results confirmed that the pavement edge material is ageing faster than the road centre material is.
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21.
  • Aulestia, Shane, et al. (författare)
  • Effect of increased vertical stress on the state of grains in tailings
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The mining industry has experienced rapid growth, leading to the accumulation of substantial mine waste, commonly referred to as tailings. Tailings are typically stored in tailings storage facilities, conventionally consisting of an impoundment surrounded by tailings dams. The construction of tailings dams can involve various methods, with the upstream method being commonly used in the industry. It is crucial to comprehend the long-term mechanical and geochemical behavior of deposited tailings to ensure the safety of upstream constructed tailings dams. The mineral composition, particle size distribution, and particle shape all affect the susceptibility to particle breakage or physical alternation. Therefore, there is an interest in understanding how grain size and grain shape relate to mineral composition and potential particle breakage to ensure the understanding of the long-term mechanical behavior. This study focuses on characterizing deposited tailings from various depths and investigates the impact of increased vertical stress on tailings, particularly examining the potential for crushing effects. The findings highlight the importance of considering these factors for a comprehensive understanding of tailings behavior and their implications for the long-term safety of tailings dams.
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22.
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23.
  • Bhadani, Kanishk, 1991, et al. (författare)
  • Applied Calibration and Validation Method of Dynamic Process Simulation for Crushing Plants
  • 2021
  • Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 11:9
  • Tidskriftsartikel (refereegranskat)abstract
    • There is a need within the production industry for digitalization and the development of meaningful functionality for production operation. One such industry is aggregate production, characterized by continuous production operation, where the digital transformation can bring operational adaptability to customer demand. Dynamic process simulations have the ability to capture the change in production performance of aggregate production over time. However, there is a need to develop cost-efficient methodologies to integrate calibrations and validation of models. This paper presents a method of integrating an experimental and data-driven approach for calibration and validation for crushing plant equipment and a process model. The method uses an error minimization optimization formulation to calibrate the equipment models, followed by the validation of the process model. The paper discusses various details such as experimental calibration procedure, applied error functions, optimization problem formulation, and the future development needed to completely realize the procedure for industrial use. The validated simulation model can be used for performing process planning and process optimization activities for the crushing plant's operation.
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24.
  • Brämming, Mats, et al. (författare)
  • Characterization of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process
  • 2019
  • Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 90:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In the Basic Oxygen Steelmaking (BOS) process, a heterogeneous emulsion‐solid mix will form, consisting of an emulsion of liquid slag and metal droplets, in which 2nd phase particles of undissolved fluxes and solid in‐blow precipitates are suspended. When the carbon in the metal droplets reacts with iron oxide, small bubbles of CO gas are formed. If the upward movement of these bubbles is obstructed by the physical properties of the emulsion‐solid mix, foaming will occur. Certain process conditions may lead to an excessive foam growth, in the worst case forcing foam out of the vessel. This undesired process event is known as “slopping”. Extensive studies during recent decades have shown that emulsion characteristics strongly connected to foaming are: viscosity, surface tension, and density. The extent of foaming is also dependent on bubble size; foaming increasing with smaller bubble size. However, investigations into the influence of the mineralogy and morphology of the emulsion‐solid mix on foaming in basic oxygen steelmaking are scarce. In this work, samples from trials in a 6‐tonne pilot plant BOS vessel are examined by XRD and with SEM for the determination of emulsion‐solid mix mineralogy and morphology at different stages of the oxygen blow. The study confirms the importance of tight process control in order to minimize the emulsion‐solid mix apparent viscosity and, hence, the foam height, but this without over‐oxidizing the liquid slag phase, which would result in increased gas generation within the slag‐metal emulsion.
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25.
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26.
  • Coney, Louise, et al. (författare)
  • Geochemical and mineralogical investigation of the Permian-Triassic boundary in the Continental Realm of the Southern Karoo Basin, South Africa
  • 2007
  • Ingår i: Palaeoworld. - : Elsevier BV. - 1875-5887 .- 1871-174X. ; 16, s. 67-104
  • Tidskriftsartikel (refereegranskat)abstract
    • Mineralogical and geochemical studies of the non-marine Permian–Triassic (P–Tr) boundary across two stratigraphically wellconstrained sections (Commando Drift Dam and Wapadsberg, Eastern Cape Province) in the southern Karoo Basin, South Africa, have been undertaken to provide further input on the cause of this mass extinction event, and so has a sedimentological and geochemical evaluation of a third P–Tr boundary section at Injusiti (Kwazulu-Natal) in the eastern Karoo Basin, South Africa. The Commando Drift Dam section has been constrained by previous palaeontological and palaeomagnetic work, with a palaeomagnetic reversal positioned 5.3m above the palaeontological P–Tr boundary. The Wapadsberg section has been constrained palaeontologically. All these P–Tr sections studied here mostly comprise mudstones, together with siltstones, sandstones, and in the southern Karoo Basin, carbonate nodular horizons. A change in colour of the mudstones from green-grey to red-brown takes place at the palaeontologically defined boundary. Variations in the major and trace element abundance profiles are usually limited to the carbonate nodular horizons, besides the overall effects of weathering. Bulk carbon isotopic studies of the Commando Drift Dam section revealed a negative δ13Cbulk excursion (background values of −15 to −20‰, with total extent of excursion to −24.9‰) 2 cm below the palaeontological boundary, followed by a gradual recovery and then another decrease in values leading towards the palaeomagnetic boundary. Above this boundary recovery to less negative δ13Cbulk values (ca. −18‰) occurs. The organic carbon record from the Commando Drift Dam (southern Karoo Basin) and Injusiti (eastern Karoo Basin) oscillates between −26.1 and −28.9‰, which is comparable to previous studies of different sections in the southern Karoo Basin. The magnitude of both the bulk and organic carbon isotopic variation can be interpreted to indicate a number of inputs (due to the fluctuating values) of organic carbon. The carbon isotope data for carbonates in the Injusiti section are different from the results on carbonates from other studies, but more work to expand this dataset is necessary. The palynological studies on the Commando Drift Dam section reveal the presence of a low diversity flora composed principally of bryophytes, lycophytes, and gymnosperms. These forms, including several Late Permian key-species, are traces of the surviving plants enduring after the major extinction-pulse. The presence of fungal palynomorphs and dearth of pollen/spores related to photosynthetic plants some metres above the palaeontological P–Tr boundary demonstrate similarities to the pattern of floral extinction at the Cretaceous–Palaeogene (K–Pg) boundary. The timing of vertebrate extinctions in the Karoo Basin has so far not been determined, but the 252.5 Ma age for a single zircon crystal from Commando Drift Dam dated here gives a maximum constraint on the age of the event bed, which is in agreement with the accepted age of the boundary. No evidence for impact-produced microdeformation features were found in quartz grains from either the Wapadsberg or Commando Drift Dam sections. Also, siderophile element data (including platinum group element (PGE)concentrations) do not support the possible presence of a meteoritic component at the boundary. Thus, a link between impact and P–Tr extinction is not indicated by the results of this study.
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27.
  • Cruz-Uribe, A. M., et al. (författare)
  • Trace element and isotopic zoning of garnetite veins in amphibolitized eclogite, Franciscan Complex, California, USA
  • 2021
  • Ingår i: Contributions to Mineralogy and Petrology. - : Springer Science and Business Media LLC. - 0010-7999 .- 1432-0967. ; 176:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Here we present major element, trace element, and oxygen isotope data for garnet from an amphibolitized eclogite block from Ring Mountain, Franciscan Complex, California, USA. Garnetite veins 1-5 cm thick are laterally continuous up to 10 m within an Mg-rich blackwall zone of the eclogite block. Complex major and trace element zoning patterns reveal multiple stages of garnet growth in both the matrix and garnetite veins. Similarities in major and trace element zoning between matrix and vein garnet suggest that crystallization of the garnetite veins began toward the end of matrix garnet core growth, and continued throughout the garnet growth history of the rock. Oscillatory zoning in rare-earth elements suggests garnet growth in pulses, with matrix-diffusion-limited growth in between pulses. Oxygen isotope analyses of matrix and vein garnet have a range in delta O-18 values of 5.3-11.1 parts per thousand. Differences in delta O-18 values of up to similar to 4 parts per thousand between garnet core and rim are observed in both the matrix and vein; garnet cores range from 9.8 to 11.1 parts per thousand (median 10.4 parts per thousand), garnet mantles range from 8.3 to 10.0 parts per thousand (median 9.7 parts per thousand), and garnet rims range from 5.8 to 7.8 parts per thousand (median 6.7 parts per thousand). Late-stage vein crystallization appears as a garnet "cement" that fills in a network of small (typically 5-50 mu m) garnet cores, and likely crystallized from an amorphous phase. The low delta O-18 values of this latest stage of garnet growth are consistent with interaction with serpentinites, and likely represent the physical incorporation of the eclogite block into the serpentinite matrix melange.
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28.
  • Damineli, Bruno L., et al. (författare)
  • Effects of filler mineralogy on the compressive strength of cementitious mortars
  • 2021
  • Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 299
  • Tidskriftsartikel (refereegranskat)abstract
    • Substituting cement with fillers is crucial to formulate cost-effective cementitious materials with low CO2 emissions. However, despite limestone, there is a lack of knowledge of fillers from other mineralogical sources for use in cementitious pastes. This study investigates the effects of characteristics of fillers from 6 mineralogical sources on the reactivity and compressive strength of the cementitious pastes, which could allow increasing industrial possibilities. The filler density and the paste total bound water content allowed to determine the paste porosity, which has a much better fit with the compressive strength than the water-binder ratio.
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29.
  • Davidsson, Björn J. R., et al. (författare)
  • Physical properties of morphological units on Comet 9P/Tempel 1 derived from near-IR Deep Impact spectra
  • 2009
  • Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 201:1, s. 335-357
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we analyze near-infrared thermal emission spectra of the spatially resolved nucleus Of Comet 9P/Tempel 1 obtained by the NASA spacecraft Deep Impact. Maps of spectral reddening. the product X' between the beaming function and directional emissivity, as well as Suit ace temperature are constructed. Thermophysical modeling is used to estimate the degree of small scale surface toughness and thermal inertia by detailed reproduction of the empirical temperature map. Mie and Hapke theories are Used in combination with numerically Calculated beaming functions to analyze the X' trial and place constraints oil composition and grain size of the Surface material. We show that it is absolutely mandatory to include small scale Surface roughness in thermophysical modeling of this object, since the resulting self treating is vital for reproducing the measured temperatures. A small scale self heating parameter in the range 0.6 <= xi <= 0.75 is common, but smoother areas where 0.2 <= xi <= 0.3 are also found. Contrary to models neglecting small scale surface roughness, we find that the thermal inertia of Comet 9P/Tempel 1 generally is high (1000-3000 J m(-1) K-1 s(-1/2)). although it may be substantially lower (40-380 Jm(-2) K-1 s(-1/2)) in specific areas. We obtain a disk-averaged reddening of 3.5% kA(-1), with statistically significant local variations around that value on a +/- 1.0% kA(-1) level. vast regions appear covered by small (similar to 0.1 mu m) highly absorbing grains such as carbon or iron-rich silicates. Other regions appear dominated by somewhat larger (similar to 0.5 mu m) and/or less absorbing grains such as troilite or magnesium-rich silicates. Surface variations in reddening, roughness, thermal inertia, composition and/or grain size are moderately to strongly correlated to the locations of morphological units oil the surface. The existence of morphological units with differing physical properties may be primordial. hence reflecting a diversity in the building block cometesimals, or resulting front evolutionary processes. (c) 2009 Elsevier Inc. All rights reserved.
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30.
  • De Marco, Anna, et al. (författare)
  • Litter inhibitory effects on soil microbial biomass, activity, and catabolic diversity in two paired stands of Robinia pseudoacacia L. and Pinus nigra Arn
  • 2018
  • Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 9:12
  • Tidskriftsartikel (refereegranskat)abstract
    • Research Highlights: Plant cover drives the activity of the microbial decomposer community and affects carbon (C) sequestration in the soil. Despite the relationship between microbial activity and C sequestration in the soil, potential inhibition of soil microbial activity by plant cover has received little attention to date.Background and Objectives: Differences in soil microbial activity between two paired stands on soil at a very early stage of formation and a common story until afforestation, can be traced back to the plant cover. We hypothesized that in a black locust (Robinia pseudoacacia L.) stand the high-quality leaf litter of the tree, and that of the blackberry (Rubus fruticosus L.) understory had an inhibitory effect on soil microbial community resulting in lower mineralization of soil organic matter compared to the paired black pine (Pinus nigra Arn.) stand.Materials and Methods: We estimated potential mineralization rates (MR), microbial (MB), and active fungal biomass (AFB) of newly-shed litter, forest floor, and mineral soil. We tested the effects of litters' water extracts on soil MR, MB, AFB and its catabolic response profile (CRP).Results: Newly-shed litter of black locust had higher MR than that of blackberry and black pine; MR, MB, and AFB were higher in forest floor and in mineral soil under black pine than under black locust. Water extracts of black locust and blackberry litter had a negative effect on the amount, activity of microorganisms, and CRP.Conclusions: The results demonstrate the potential for black locust and blackberry litter to have a marked inhibitory effect on decomposer microorganisms that, in turn, reduce organic matter mineralization with possible consequences at the ecosystem level, by increasing C sequestration in mineral soil.
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31.
  • de Vries, Bernard L., et al. (författare)
  • Laboratory mid-IR spectra of equilibrated and igneous meteorites. Searching for observables of planetesimal debris
  • 2018
  • Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 307, s. 400-416
  • Tidskriftsartikel (refereegranskat)abstract
    • Meteorites contain minerals from Solar System asteroids with different properties (like size, presence of water, core formation). We provide new mid-IR transmission spectra of powdered meteorites to obtain templates of how mid-IR spectra of asteroidal debris would look like. This is essential for interpreting mid-IR spectra of past and future space observatories, like the James Webb Space Telescope. First we present new transmission spectra of powdered ordinary chondrite, pallasite and HED meteorites and then we combine them with already available transmission spectra of chondrites in the literature, giving a total set of 64 transmission spectra. In detail we study the spectral features of minerals in these spectra to obtain measurables used to spectroscopically distinguish between meteorite groups. Being able to differentiate between dust from different meteorite types means we can probe properties of parent bodies, like their size, if they were wet or dry and if they are differentiated (core formation) or not. We show that the transmission spectra of wet and dry chondrites, carbonaceous and ordinary chondrites and achondrite and chondrite meteorites are distinctly different in a way one can distinguish in astronomical mid-IR spectra. Carbonaceous chondrites type <3 (aqueously altered) show distinct features of hydrated silicates (hydrosilicates) compared to the olivine and pyroxene rich ordinary chondrites (dry and equilibrated meteorites). Also the iron concentration of the olivine in carbonaceous chondrites differs from ordinary chondrites, which can be probed by the wavelength peak position of the olivine spectral features. The transmission spectra of chondrites (not differentiated) are also strongly different from the achondrite HED meteorites (meteorites from differentiated bodies like 4 Vesta), where the latter show much stronger pyroxene signatures. The two observables that spectroscopically separate the different meteorites groups (and thus the different types of parent bodies) are the pyroxene-olivine feature strength ratio and the peak shift of the olivine spectral features due to an increase in the iron concentration of the olivine.
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32.
  • Decree, S., et al. (författare)
  • In-situ trace element and Sr isotope signature of apatite: A new key to unravelling the genesis of polymetallic mineralisation in black shales of the Early Cambrian Niutitang Formation, Southern China
  • 2022
  • Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368. ; 150
  • Tidskriftsartikel (refereegranskat)abstract
    • The Early Cambrian Mo-Ni-PGE sulphidic black shale in the Niutitang Formation on the margin of the Yangtze Craton (Southern China) is known for its extremely high metal concentrations. It is also very rich in phosphate that formed contemporaneously with the sulphides. Detailed petrological as well as in-situ trace element and Sr isotope analyses of authigenic apatite revealed new information on the metallogenesis of this enigmatic rock unit. In the ore bed, apatite forms nodules or is found in phosphatic (phoslithoclasts) and sulphide clasts. In the latter, the replacement of organic matter and sulphides by apatite microspherules suggests a microbially mediated phosphogenesis. Enrichment in middle rare earth elements emphasizes the role played by Fe-oxyhydroxides and organic matter in element scavenging. Moderately reducing conditions are supported by a lack of Ce and Eu anomalies. The trace element signature of apatite and its initial 87Sr/86Sr (0.7032-0.7190), which is -for a group of analyses -well below the signature of Lower Cambrian seawater, points to some contribution from mafic rock-sourced hydrothermal brines. This effectively explains the exceptional enrichment of Ni and PGE in the sulphides. Seawater remains, however, the preferred source for other elements such as P and Mo.
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33.
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34.
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35.
  • Dunér, David (författare)
  • Världsmaskinen. Emanuel Swedenborgs naturfilosofi
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The Swedish natural philosopher Emanuel Swedenborg (1688–1772) thought in his early scientific career that the world was like a gigantic machine, following the laws of mechanics and geometry. The work presented here is a study of his mechanistic worldview and metaphorical way of thinking up to the year 1734, examining most of his fields of interest, from geometry and metaphysics to technology and mining engineering. After that year he left the mechanistic explanations and turned to an organic worldview, and some years later, in 1745, he entered the spiritual world. The study is based on a cognitive view that there are special cognitive abilities, especially metaphorical conceptualization, that cause human beings to think in one way or another. “Space” is an introductory chapter on the concept of space, about his experiences of space gained through optical instruments and his orientation in the intellectual milieu, and of the spatial world with the aid of geometry. “The sign” treats especially some particular sign systems, such as those of arithmetic and algebra, and the classification of the world by categories in number systems, coinage, measures, weights and volumes. “The wave” follows Swedenborg’s use of the metaphor of the wave, not only in such scientific disciplines as hydrology, acoustics, optics and neurology but also in poetry and music. “The sphere” concerns the sphere as the figure of movement, the relationship between technology and science, and analogies, proportions and mental models as important tools for inventing scientific theories, especially in mechanics, physics and chemistry. “The point” has its point of departure in the indivisible point of mathematics. “The spiral” is Swedenborg’s most admired geometrical figure. He wrote about the windings of the spirals in geometry, particle physics, astronomy, and in the nature of the soul. “Infinity” is limited to Swedenborg’s last mechanistic work, De infinito (1734), where he made a strict distinction between the finite and the infinite. “Conclusion” gives an overview of the major themes of his anatomical and physiological studies from the end of the 1730s to 1745, and his spiritual writings to 1772.
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36.
  • Edlmann, K., et al. (författare)
  • Mineralogical properties of the caprock and reservoir sandstone of the Heletz field scale experimental CO2 injection site, Israel; and their initial sensitivity to CO2 injection
  • 2016
  • Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 48, s. 94-104
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents the initial database of the mineralogy of the caprock and reservoir sandstones of the Heletz field scale experimental CO2 injection site, Israel. The XRD mineralogy results show that the Heletz caprock has K-feldspar as the primary mineral (40%) followed by kaolinite (15%) and plagioclase feldspar (12%) then illite (6%) and muscovite (6%) with minor quartz, calcite, pyrite, chlorite and ankerite with traces of siderite. The Heletz reservoir rock is primarily quartz (70%) followed by K-feldspar (12%) and plagioclase feldspar (4%) with minor illite, kaolinite, muscovite, chlorite ankerite and pyrite with traces of dolomite, calcite and siderite. "Cook and look" bench experiments were conducted on the Heletz caprock and reservoir sandstone samples to identify if there was any immediate mineral reactivity that would influence permeability on exposure to CO2 that may cause concerns during well completion and initial injection of CO2 at Heletz. The sandstone exhibited reactivity under brine dis-equilibrium which was observed in the field with loss of injectivity which was restored by injecting KCL into the well and performing 20 swab-suctions. The caprock revealed no reactivity of immediate concern to the well completion and injection strategy and will retain its integrity.
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37.
  • Emami, Mohammadamin, et al. (författare)
  • A time-dependent statistical evaluation of the ceramic manufacturing process based on the mineralogical chemical analysis : [Une évaluation statistique liée au temps du processus de fabrication de la céramique, basée sur l’analyse chimique minéralogique]
  • 2020
  • Ingår i: ArchéoSciences, revue d’archéométrie. - : OpenEdition. - 1960-1360 .- 2104-3728. ; 44:2, s. 145-159
  • Tidskriftsartikel (refereegranskat)abstract
    • The mineralogical adaptation in an inhomogeneous ancient ceramic matrix has an important function for their characterisation. In the current work, ceramic pieces from two workshops, Haft Tappeh and Chogha Zanbil were subjected to routine analysis. The aim of this study was to clustering the ceramics based on longitudinal statistical analysis and modelling to understand about the evaluation of manufacturing processes in an area through definite period of time. In order to characterise and classify non-homogenous ceramic matrices, the mineralogy and extent of recrystallization is often determined using a combination of analyses, most notably polarization microscopy, XRF and QXRD with Rietveld refining. Following analysis, a clustering model showing the variation in chemical and mineralogical composition of the ceramic pieces was created and a novel statistical modelling approach employed which compared the QXRD patterns to the cluster analyses. With these investigations it is possible to obtain a model of statistically measurements of essential issues in manufacturing processes based on the mineralogical- chemical characteristics. The data suggests that the varieties via developing the technology, obtain a quantitative modification of assortments over the time in definite groups of materials.
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38.
  • Evertsson, Magnus, 1967, et al. (författare)
  • CFD simulation of a centrifugal air classifier used in the aggregate industry
  • 2014
  • Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875. ; 63, s. 149-156
  • Tidskriftsartikel (refereegranskat)abstract
    • The aggregate industry in Sweden is investigating methods to improve the quality of manufactured sand (aggregate smaller than 2 mm produced by crushing rock) for concrete production. A common way to improve the shape of the particles is to use a vertical shaft impact (VSI) crusher. However, the crushing process creates a large amount of fines (particles smaller than 63 mu m) that are not desirable in concrete mixes. The aggregate industry in Sweden is therefore investigating methods to reduce the amount of fines produced by the manufacturing of sand. One method being investigated is air classification. A centrifugal air classifier used in the aggregate industry was investigated using computational fluid dynamics (CFD) to improve the understanding of the influence of the geometric design of the classifier on the cut size and the resulting particle size distribution. Simulations were performed with a CFD model using an Euler-Lagrange approach. The simulation results show that the classification results are affected by air flow velocity, particle shape, particle size, the geometry of the air classifier and turbulence in the air flow. (C) 2014 Published by Elsevier Ltd.
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39.
  • Fors, Hjalmar, 1971- (författare)
  • Mutual Favours : The social and scientific practice of eighteenth-century Swedish chemistry
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The dissertation is a study of the creation of chemistry as a science in eighteenth-century Sweden. It is argued that the chemists in the study participated in a network for exchange of scientific facts and all kinds of favours, in which science was both conducted, negotiated and created. A number of relationships between chemists are analyzed with regards to two central eighteenth-century institutions: the patron-client relationship and the egalitarian ideal of reciprocity articulated in the eighteenth-century Republic of Letters.In the first half the background to the success of Swedish chemistry is sketched out. It is discussed which groups supported chemistry and for what reasons. There is a discussion of the theoretical and methodological changes that were initiated by Torbern Bergman when he took over the chair of chemistry in Uppsala. Bergman's attempts to marginalize his two major opponents, Johan Gottschalk Wallerius, the previous holder of the Uppsala chair and Gustav von Engeström, the head of the Board of Mines laboratory in Stockholm, are also analyzed.In the second half the focus shifts to the interaction of university chemistry with industry. It is shown how industrial processes gradually came to be redefined as a kind of “coarse chemistry”, a process which benefited both engineers employed at industrial installations and university chemists. The many themes explored in the study are brought together in an analysis of Carl Wilhelm Scheele’s adoption into the network of Swedish chemists. The dissertation concludes with a survey of the more general conclusions.
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40.
  • Fransson, Liisa (författare)
  • Recovery from Acidification - Policy Oriented Dynamic Modeling
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Dynamic biogeochemistry models are important tools for determining the time-scales of recovery from acidification. In the review process of the 1999 UNECE LRTAP Gothenburg protocol, results from dynamic models will probably be included when determining further reductions of acidifying emissions. This thesis describes modeling of recovery from acidification using the dynamic multi-layer soil chemistry model SAFE. Sulfate adsorption was added to SAFE, modeled by a sulfate concentration and pH dependent isotherm. A method to parameterize this isotherm was developed and the isotherm was parameterized for a total of 20 sites, whereof 18 are located in Sweden, 1 in Germany and 1 in Poland. The SAFE model including sulfate adsorption was applied to 19 of these. The addition of sulfate adsorption improved the predictions of sulfate dynamics, especially at sites where there had been large deposition changes and where sulfate adsorption capacity is high. Three of the modeled sites are well-studied single-sites and 16 sites are a part of regional study. Differences in data requirements and model output for the different types of studies are discussed from a policy perspective. The influence of climate driven changes in sea-salt deposition and of changes in forest practices and vegetation on model predictions of recovery is also discussed. The SAFE model applications show that many sites in Sweden and Europe are still severely acidified and that soil recovery will require both further emission reductions and many decades of time.
  •  
41.
  • Godinho, Jose (författare)
  • Dissolution of fluorite type surfaces as analogues of spent nuclear fuel : Production of suitable analogues and study the effect of surface orientation on dissolution
  • 2011
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • It is accepted worldwide that the best final solution for spent nuclear fuel is to bury it in deep geological repositories. Despite the physical and chemical barriers that are supposed to isolate the nuclear waste for at least 100.000 years, some uncertainty factors may cause underground water to get in contact with the nuclear waste. Due to radioactivity and oxidation under air, dissolution experiments using UO2 pellets are difficult and frequently lead to incoherent results. Therefore, to enable a detailed study of the influence of microstructure and surface properties on the stability of spent nuclear fuel over time, it is necessary to produce analogues that closely resemble nuclear fuel in terms of crystallography and microstructure. At the same time, in-depth understanding of dissolution phenomena is crucial to geological processes such as dissolution precipitation creep and solvent mediated phase transformations. My thesis is based in two manuscripts. Paper I reports the microstructures obtained after sintering CaF2 powders at temperatures up to 1240°C. Pellets with microstructure, density and pore structure similar to that of UO2 spent nuclear fuel pellets were obtained in the temperature range between 900°C and 1000°C. Paper II reports how differences of surface chemistry and crystal symmetry, characteristics of each surface orientation, affect the topography of CaF2 pellets described in paper I during dissolution. I propose that every orientation of the fluorite structure can be decomposed in the three reference surfaces {100}, {110} and {111}. The {111} is the most stable surface with a dissolution rate of the top surface of 1,13x10-9 mol.m-2.s-1, and {112} the less stable surface with a dissolution rate 34 times faster that {111}. Surfaces that expose both Ca and F atoms in the same plan dissolve faster, possibly because the calcium is more susceptible to be solvated. The faster dissolving surfaces are replaced by the more stable {111} and {100} surfaces which causes the development of roughness on the top surface and stabilizes the surface on high energy sites; i.e. pores or grain boundaries. The main consequences of these observations are i) the increase of the total surface area; ii) the decrease of the overall surface energy. I present a dissolution model for surfaces of crystal with different surface energies. The main conclusions are: a) dissolution rates calculated from surface area are over estimated to the real dissolution rate; b) dissolution rates are faster at the beginning of dissolution and tend to diminish with time until a minimum value is reached.
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42.
  •  
43.
  • Grotzinger, John P., et al. (författare)
  • Curiosity's Mission of Exploration at Gale Crater, Mars
  • 2015
  • Ingår i: Elements. - : Mineralogical Society of America. - 1811-5209 .- 1811-5217. ; 11:1, s. 19-26
  • Tidskriftsartikel (refereegranskat)abstract
    • Landed missions to the surface of Mars have long sought to determine the material properties of rocks and soils encountered during the course of surface exploration. Increasingly, emphasis is placed on the study of materials formed or altered in the presence of liquid water. Placed in the context of their geological environment, these materials are then used to help evaluate ancient habitability. The Mars Science Laboratory mission—with its Curiosity rover—seeks to establish the availability of elements that may have fueled microbial metabolism, including carbon, hydrogen, sulfur, nitrogen, phosphorus, and a host of others at the trace element level. These measurements are most valuable when placed in a geological framework of ancient environments as interpreted from mapping, combined with an understanding of the petrogenesis of the igneous rocks and derived sedimentary materials. In turn, the analysis of solid materials and the reconstruction of ancient environments provide the basis to assess past habitability.
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44.
  • Guldris Leon, Lorena, 1983, et al. (författare)
  • Evaluation of Refractory Metal Concentrations in Nano-Particulate Pressed-Powder Pellets Using LA-ICP-MS
  • 2022
  • Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 12:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Whole-rock geochemical analysis is a standard method to measure the chemical composition of ores. Analysis of refractory ore metals such as Ta and W typically requires fused bead and acid digestion followed by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled mass spectrometry (ICP-MS). Since these techniques are time-consuming and expensive, there is a demand for methods that can quantitatively measure low elemental concentration of refractory ore metals using a less expensive and simple approach. This paper evaluates preparation and analytical procedures developed to obtain whole-rock element concentrations of ore samples and mineral concentrates. It shows that the production of nano-particulate pressed-powder pellets followed by LA-ICP-MS analysis of W and Ta ores can be used to determine, within the error margin, the concentrations of the refractory metals W, Ta, Nb, and Sn compared to a reference values obtained by solution analysis. The results have implications for developing a commercially viable method for analysis of refractory elements to benefit mineral processing given the simplicity and resource-efficiency of the combined pressed pellet production and laser ablation analytical methodology.
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45.
  • Guntoro, Pratama Istiadi, 1993-, et al. (författare)
  • 3D Ore Characterization as a Paradigm Shift for Process Design and Simulation in Mineral Processing
  • 2021
  • Ingår i: Berg- und Huttenmännische Monatshefte (BHM). - : Springer. - 0005-8912 .- 1613-7531. ; 166:8, s. 384-389
  • Tidskriftsartikel (refereegranskat)abstract
    • Current advances and developments in automated mineralogy have made it a crucial key technology in the field of process mineralogy, allowing better understanding and connection between mineralogy and the beneficiation process. The latest developments in X‑ray micro-computed tomography (µCT) have shown a great potential to let it become the next-generation automated mineralogy technique. µCT’s main benefit lies in its capability to allow 3D monitoring of the internal structure of the ore sample at resolutions down to a few hundred nanometers, thus excluding the common stereological error in conventional 2D analysis. Driven by the technological and computational progress, µCT is constantly developing as an analysis tool and successively it will become an essential technique in the field of process mineralogy. This study aims to assess the potential application of µCT systems, for 3D ore characterization through relevant case studies. The opportunities and platforms that µCT 3D ore characterization provides for process design and simulation in mineral processing are presented.
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46.
  • Guntoro, Pratama Istiadi, 1993- (författare)
  • X-ray microcomputed tomography (µCT) as a potential tool in particle-based geometallurgy
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In recent years, automated mineralogy has become an essential tool in geometallurgy. Automated mineralogical tools allows the acquisition of mineralogical, textural, and liberation information of ore samples. Such information is essential in the context of geometallurgy where it is needed for estimating the process response of the ores. Most automated mineralogical tools currently in application are based on two-dimensional (2D) microscopy analysis, which are subject to stereological error when analyzing three-dimensional (3D) object such as ore particles. Recent advancements in X-ray microcomputed tomography (μCT) have indicated great potential of such system to be the next automated mineralogical tool. μCT’s main advantage lies in its ability in monitoring 3D internal structure of the ore at resolutions down to few microns, eliminating stereological error obtained from 2D analysis. Aided with the continuous developments of computing capability of 3D data, it is only the question of time that μCT system becomes an interesting alternative automated mineralogical tool for ore characterization.This study systematically evaluates the applicability of μCT as an alternative tool for ore characterization in the context of geometallurgy. The focus has been to assess the potential strengths of 3D data generated from μCT as well as how such data can offer a new perspective in characterizing the ore. Some of the limitations of 3D μCT data in describing the ore were also discussed, with alternative methods proposed to address these limitations. The main hypothesis of the study is that 3D data generated from μCT can be of a value in a geometallurgical program. This study has been conducted in three different parts in order to systematically test the hypothesis. The first part of the study evaluated the use of μCT to obtain mineralogical characteristics of the ore. Mineralogy of the ore is the cornerstone information needed to proceed with further characterization of the ore. It is therefore important to establish whether μCT are capable to obtain such information. The study demonstrated the well-known limitation of μCT, namely its difficulty when dealing with minerals of similar attenuation. The study demonstrated how machine-learning based methods complemented with 2D data from automated mineralogy could address the limitation.The capability of μCT for ore texture characterization was evaluated in the second part of the study. The main strength of μCT for core scanning is highlighted in the study, in which the possibility of using μCT for automated drill core recognition was demonstrated. Some of the popular texture analysis methods in 2D such as Local Binary Pattern (LBP) and Association Index Matrix (AIM) were extended to 3D in order to capture the textural pattern in drill core samples. Furthermore, a classification scheme based on these textural characteristics was devised for the automated recognition of the drill cores. An accuracy of 84-88% was achieved in the classification scheme, illustrating the potential of μCT for such task.The last part of the study concerns the use of μCT for mineral liberation modeling. Combining both mineralogical and textural information obtained from the previous parts of the study, a liberation model to forecast particle population from the 3D ore texture was created. The model was based on various breakage types such as preferential, phase boundary, and random breakage. The contribution of each breakage type to the final particle population could then be adjusted with actual particles produced from experimental comminution. Accurate forecasting of particle population is one of the key componentin the particle-based geometallurgy, in which the particle carries the ore characteristics to the beneficiation process. Utilizing these particles in a process modeling and simulation would give some idea about the process response of the ore. The integration of 3D data from μCT with the liberation model could potentially complete the link from ore characteristics to the process behavior in the framework of particle-based geometallurgy.Combination of these three parts of the study can open up a 3D path of particle-based geometallurgy. The study has demonstrated the efficient extraction of crucial ore characteristics such as texture, mineralogy, and mineral liberation using μCT. Key limitations and potential measures to address them have also been discussed in the study. Coupled with a framework for process simulation using such ore characteristics as an input, the 3D path of particle-based geometallurgy can be realized. Future research should be dedicated to develop such framework, as the establishment of μCT as an alternative ore characterization tool should also be motivated by from the downstream processes, i.e.whether the 3D μCT data can unlock a new perspective in process modeling and simulation compared to the conventional 2D data. This new perspective can help to build more accurate process prediction and production forecasting, which can ultimately guide the decision-making process for efficient resource management as the essential core of a geometallurgical program.
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47.
  • Guntoro, Pratama Istiadi, 1993-, et al. (författare)
  • X-ray Microcomputed Tomography (µCT) for Mineral Characterization : A Review of Data Analysis Methods
  • 2019
  • Ingår i: Minerals. - Basel, Switzerland : MDPI. - 2075-163X. ; 9:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The main advantage of X-ray microcomputed tomography (µCT) as a non-destructive imaging tool lies in its ability to analyze the three-dimensional (3D) interior of a sample, therefore eliminating the stereological error exhibited in conventional two-dimensional (2D) image analysis. Coupled with the correct data analysis methods, µCT allows extraction of textural and mineralogical information from ore samples. This study provides a comprehensive overview on the available and potentially useful data analysis methods for processing 3D datasets acquired with laboratory µCT systems. Our study indicates that there is a rapid development of new techniques and algorithms capable of processing µCT datasets, but application of such techniques is often sample-specific. Several methods that have been successfully implemented for other similar materials (soils, aggregates, rocks) were also found to have the potential to be applied in mineral characterization. The main challenge in establishing a µCT system as a mineral characterization tool lies in the computational expenses of processing the large 3D dataset. Additionally, since most of the µCT dataset is based on the attenuation of the minerals, the presence of minerals with similar attenuations limits the capability of µCT in mineral segmentation. Further development on the data processing workflow is needed to accelerate the breakthrough of µCT as an analytical tool in mineral characterization.
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48.
  • Halama, R., et al. (författare)
  • Boron isotope record of peak metamorphic ultrahigh-pressure and retrograde fluid-rock interaction in white mica (Lago di Cignana, Western Alps)
  • 2020
  • Ingår i: Contributions to Mineralogy and Petrology. - : Springer Science and Business Media LLC. - 0010-7999 .- 1432-0967. ; 175:3
  • Tidskriftsartikel (refereegranskat)abstract
    • This study presents boron (B) concentration and isotope data for white mica from (ultra)high-pressure (UHP), subduction-related metamorphic rocks from Lago di Cignana (Western Alps, Italy). These rocks are of specific geological interest, because they comprise the most deeply subducted rocks of oceanic origin worldwide. Boron geochemistry can track fluid-rock interaction during their metamorphic evolution and provide important insights into mass transfer processes in subduction zones. The highest B contents (up to 345 mu g/g B) occur in peak metamorphic phengite from a garnet-phengite quartzite. The B isotopic composition is variable (delta B-11 = - 10.3 to - 3.6%) and correlates positively with B concentrations. Based on similar textures and major element mica composition, neither textural differences, prograde growth zoning, diffusion nor a retrograde overprint can explain this correlation. Modelling shows that B devolatilization during metamorphism can explain the general trend, but fails to account for the wide compositional and isotopic variability in a single, well-equilibrated sample. We, therefore, argue that this trend represents fluid-rock interaction during peak metamorphic conditions. This interpretation is supported by fluid-rock interaction modelling of boron leaching and boron addition that can successfully reproduce the observed spread in delta B-11 and [B]. Taking into account the local availability of serpentinites as potential source rocks of the fluids, the temperatures reached during peak metamorphism that allow for serpentine dehydration, and the high positive delta B-11 values (delta B-11 = 20 +/- 5) modelled for the fluids, an influx of serpentinite-derived fluid appears likely. Paragonite in lawsonite pseudomorphs in an eclogite and phengite from a retrogressed metabasite have B contents between 12 and 68 mu g/g and delta B-11 values that cluster around 0% (delta B-11 = - 5.0 to + 3.5). White mica in both samples is related to distinct stages of retrograde metamorphism during exhumation of the rocks. The variable B geochemistry can be successfully modelled as fluid-rock interaction with low-to-moderate (< 3) fluid/rock ratios, where mica equilibrates with a fluid into which B preferentially partitions, causing leaching of B from the rock. The metamorphic rocks from Lago di Cignana show variable retention of B in white mica during subduction-related metamorphism and exhumation. The variability in the B geochemical signature in white mica is significant and enhances our understanding of metamorphic processes and their role in element transfer in subduction zones.
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49.
  • Hellman, Fredrik (författare)
  • Precambrian and Caledonian history of Svalbard’s West Ny Friesland Terrane
  • 2000
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis deals mainly with age-investigations of metasedimentary and magmatic rocks of Ny Friesland, located in the northeastern Svalbard. However, the provenance of quartz-porphyry clasts in a Devonian conglomerate have also been investigated in northwestern Svalbard. This information is important for reconstructions of plate movements in the high Arctic during the Caledonian orogeny and earlier tectono-thermal events. It is also important for understanding the regional geological processes in the Svalbard Caledonides. The Svalbard Caledonides is composed of three terranes, the Northwestern, Southestern and the Eastern terranes, which are separated by large transcurrent faults. In the Eastern Terrane, the rocks of western Ny Friesland are dominated by a major antiformal thrust-stack, including four nappes. They are thrust together and folded during the Caledonian orogeny. The schists and gneisses are generally metamorphosed in amphibolite facies. Each thrust sheet contains granitic-gneisses of c. 1750 Ma age, which are overlain by metasediments. In this thesis, detrital zircons from metasediments have been dated and show that the metasediments in each nappe contain zircons of equal or younger age than the granitic-gneisses. It is therefore concluded that the metasediments are younger than the granitic gneisses. The detrital zircon ages from all the three upper nappes fall generally in three age groups, 1700-1750, 1850-2050, and 2500-2800 Ma. The lowest nappe contains slightly different age-populations of 1200-1300, 1650-1720 and 2500-2700 Ma. These sediments have probably been deposited in the Neoproterozoic but could be as young as Ordovician. In one of the thrust-sheets a quartz-monzonite have been dated to 2709 ±28 Ma and show that the basement complex also includes some older rocks. The rocks of western Ny Friesland differ greatly from those further to the east in Ny Friesland and on Nordaustlandet, which is dominated by Grenville-age metasediments and granites. The data obtained on western Ny Friesland support previous suggestions that the Eastern Terrane can be divided into two parts, the West Ny Friesland Terrane and the Nordaustlandet Terrane. The pre-Caledonian position of the West Ny Friesland Terrane is suggested to be close to Northeastern Greenland based on the remarkable similarities of the rocks and the ages. In the Northwestern Terrane, close to the mountain Lilljeborgfjellet, large quartz-porphyry clasts in a Devonian conglomerate have been dated to c. 1740 Ma, an age not previously determined in the Northwestern Terrane. It is concluded that the transportation cannot exceed a few kilometres; affinity to the West Ny Friesland Terrane is suggested where ages are similar. It is proposed that the terrane boundary between the West Ny Friesland Terrane and the Northwestern Terrane may be located along the Breibogen-Bockfjorden Fault instead of the Billefjorden Fault which previously has been suggested to be the main terrane boundary on Svalbard.
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50.
  • Hermansson, Tobias (författare)
  • The tectonic evolution of the western part of the Svecofennian orogen, central Sweden : Insight from U/Pb and 40Ar/39Ar geochronology at Forsmark
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The Forsmark area, in the western part of the Svecofennian orogen, central Sweden, is situated between two major Palaeoproterozoic tectonic domains that show contrasting histories with respect to timing of igneous activity, ductile deformation and metamorphism. At Forsmark, WNW to NW trending, ductile deformation belts anastomose around tectonic lenses with an inferred lower degree of ductile strain. Geological features common to both of the adjacent tectonic domains are found in the area, which, consequently, is of key importance for the understanding of the tectonic evolution of the Svecofennian orogen in this region. U/Pb zircon dating (6 ages), in combination with detailed field work, have revealed the existence of two calc-alkaline igneous suites at Forsmark. The older and most voluminous plutonic suite intruded at 1.89-1.87 Ga. It is affected by penetrative ductile deformation under amphibolite-facies metamorphic conditions. The younger, less voluminous and hypabyssal suite intruded at 1.86-1.85 Ga, during the waning stages of penetrative deformation and, thus, constrains the main phase of penetrative ductile amphibolite-facies deformation to between 1.87 and 1.86 Ga. Cross-cutting granite dykes, belonging to the younger suite, place an absolute minimum age for this deformational event to c. 1.85 Ga. U/Pb titanite data (4 ages) support the constraints on the penetrative deformation. However, the data also suggest that the Forsmark area has been affected by one or more tectonothermal events after the intrusion of the 1.85 Ga granite dykes. This is confirmed by 40Ar/39Ar hornblende data (16 ages), which demonstrate the existence of two age generations, 1.83-1.82 Ga and 1.81-1.80 Ga, that are suggested to represent resetting of the argon isotope system in response to retrogressive, lower amphibolite- to upper greenschist-facies deformation restricted to discrete high-strain zones within the broader deformation belts. Furthermore, the data suggest that cooling to c. 500 °C took place at around 1.85 Ga and that the area then remained at similar temperatures until the 1.81-1.80 Ga tectonothermal event, during which it was uplifted to higher crustal levels. In addition, 40Ar/39Ar muscovite (5 ages) and biotite (29 ages) data suggest that cooling to 350 °C occurred around 1.75-1.70 Ga, whereas cooling to 300 °C took place at 1.73-1.66 Ga. The estimated uplift rate was at this time c. 22 m/m.y. The Forsmark data, in combination with a compilation of available geochronological data for the time interval 1.91-1.84 Ga in central Sweden, point to the existence of at least two major tectonic cycles. Each cycle is characterised by igneous activity associated with extension, a short interval of compression (c. 10 m.y.), and migration of the tectonic activity. In this thesis, two contrasting conceptual tectonic models, which may explain the cyclic tectonic evolution of the western Svecofennian orogen in central Sweden, are discussed. The favoured model involves continuous subduction beneath a single active continental margin, combined with alternating subduction hinge retreat and advance. This model includes migration of what has been described as tectonic switching in some younger orogenic belts.
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