| 1. |
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| 2. |
- Albrecht, Lena Gunlög
(författare)
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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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| 3. |
- Andersson, Jenny
(författare)
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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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| 4. |
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| 5. |
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| 6. |
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| 8. |
- Fransson, Liisa
(författare)
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Recovery from Acidification - Policy Oriented Dynamic Modeling
- 2004
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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.
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| 9. |
- Hellman, Fredrik
(författare)
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Precambrian and Caledonian history of Svalbard’s West Ny Friesland Terrane
- 2000
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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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| 10. |
- Hermansson, Tobias
(författare)
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The tectonic evolution of the western part of the Svecofennian orogen, central Sweden : Insight from U/Pb and 40Ar/39Ar geochronology at Forsmark
- 2007
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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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| 11. |
- Holme, Kirsten
(författare)
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Geochemical Development of Proterozoic Granites in the SW Baltic Shield
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The plutonic rocks in the Western Segment of the Southwestern Swedish Gneiss Complex show a distinct geochemical evolution. The 1.6 Ga Åmål granitoids and Slottsbron migmatites are a quartz dioritic to granodioritic, calc-alkaline rock suite with smooth, but somewhat fractionated, REE and other trace-element patterns. The younger microcline granites of the 1.5 Ga and 1.3 Ga generations are evolved rocks having fractionated REE patterns with deep negative Eu anomalies. The 1.5 Ga granites vary from calc-alkalic, metaluminous granodiorites to evolved alkali-calcic peraluminous leucogranites. The REE and other trace-element patterns are less evolved than those of the 1.3 Ga rocks. The 1.3 Ga granites are the most evolved intrusions in the area. Granites with a bimodal geochemical character occur. All rocks can be ascribed to one of three types: i. The HUS1 type is homogeneous, alkali-calcic with high SiO2 content and is often leucocratic. ii. The SS2 type has a large geochemical variation, but shows regular inter-element relationships. It is alkali-calcic and has the most evolved REE patterns. iii. In the TYP3 type, calc-alkaline compositions are common. They are the least evolved rocks of this generation. The differences within the 1.3 Ga generation itself are partly due to a variety of source rocks, but also to different melting conditions. The chemical variation suggests that the SS2 type formed at deeper levels than the HUS1 and 1.5 Ga granites. The degree of melting was probably also higher than for the two latter types. The TYP3 rocks are likely to have formed at shallow levels, but with a higher degree of melting than the HUS1 rocks. A model based on isotopic, major- and trace-element data is consistent the theory that rocks similar to the Åmål granitoids are the source rock for the HUS1 type but not for the SS2 type. The epsilonNd(1.3) values for one of the HUS1-type rocks are, however, outside the known range of the time integrated epsilonNd(1.3) for the Åmål granitoids and could have a more primitive origin. Rocks from the Eastern Segment differ from those of the WS. The 1.7 Ga Mårdaklev granite has an evolved appearance similar to the HUS1 type, but no coeval rocks in the WS have this characteristic. The compositions of the 1.4 TTK intrusions vary between monzonite and granite - a trend not found in the Western Segment. The differences in geochemical character reflect differences in geological settings. The TTK intrusions of the Eastern Segment are interpreted to have formed at deep levels in a thicker and more evolved continental crust than the roughly coeval granites in the Western segment. The calc-alkaline character of the 1.6 Ga generation rocks suggests a less evolved, subduction related setting. The younger granites are derived from ensialic crust and variations in composition are interpreted to reflect different source rocks and different levels of magma generation. This investigation supports earlier suggestions that the evolutions of the Eastern and Western Segments were separate before Sveconorwegian time.
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| 12. |
- Holtstam, Dan, 1963-
(författare)
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Cronstedt 300 år
- 2022
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Ingår i: Geologiskt forum. - : Geologiska Föreningen. - 1104-4721. ; 114, s. 12-16
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Axel Fredrik Cronstedt (1722-1765) är en av de mest kända svenskarna inom mineralogin. Han beskrev nya grundämnen och mineral samt presenterade ett nydanande klassificeringssystem. Detta byggde på mineralens kemiska sammansättning snarare än deras yttre egenskaper.
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| 13. |
- Holtstam, Dan, 1963-
(författare)
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Speaking of anniversaries: Who was the first modern mineralogist?
- 2022
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Ingår i: Geological Society of Sweden, 150 year anniversary meeting, Uppsala, August 17–19 2022, Abstract volume.. - Uppsala. - 9789198783308 ; , s. 86-87
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Konferensbidrag (refereegranskat)abstract
- Mineralogy is among the oldest sciences and a core discipline of geology. Already in the Neolithic period, the recognition and use of various minerals was important knowledge for humans. Writers of the Antiquity on the subject, Theophrastus and Pliny the Elder, treated rocks and minerals from a natural-philosophical point of view. Polymaths like Avicenna (Persia) and Shen Kuo (China) in the 11th century AD also documented the minerals known to exist then. European authors of the Renaissance, with Georgius Agricola as the foremost, used the intrinsic physical properties of minerals to describe and classify them in systematic way, an approach that essentially established mineralogy as a science. In Sweden, there was little development in the field before the 18th century (a notable exception is the contributions of Urban Hjärne). During the Age of Liberty*, works relating to various aspects of minerals, by natural scientists like Johan Gottschalk Wallerius, Henrik Teofil Scheffer, Carl Linnaeus and Torbern Bergman, came to have a wide influence, far beyond Sweden’s borders. Among the mineralogists active in this dynamic period, Axel Fredrik Cronstedt stands out as an exeptionally innovative and forsighted character.
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| 14. |
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| 15. |
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| 16. |
- Johansson, Eva, et al.
(författare)
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Expertsystem för bedömning av bergmaterialens mekaniska egenskaper
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektets syfte var att utveckla ett system för bedömning av bergmaterialens mekaniska egenskaper baserat på bergartens petrografiska egenskaper som ballastmaterial. Genom att välja provserier efter de petrografiska egenskaper som enligt tidigare forskning och praktiska erfarenheter påverkar olika bergartsgruppers mekaniska egenskaper skapades dataunderlag för klassificeringssystemet. Projektet fokuserade på de i Sverige mest exploaterade bergartsgrupperna, nämligen magmatiska djup- och gångbergarter och deras omvandlingsprodukter, metasedimentära bergarter och metavulkaniter. Sammanlagt har 34 bergartstyper analyserats angående deras petrografiska och mekaniska egenskaper och resultaten utvärderades statistiskt. Med hjälp av erhållna data, statistik och praktisk erfarenhet utvecklades klassificeringssystemet för bedömning av bergmaterialens mekaniska egenskaper baserat på bergarternas petrografiska beskrivning. Systemet för klassificeringsnyckeln består av fyra utvalda bergartsgrupper, vilkas mekaniska egenskaper med varierande säkerhet kan bedömas efter europeiska standardiserade kategorier. Utöver klassificeringsnycklar innehåller dokumentet metoder för beskrivning av objektet, provtagning samt väldokumenterade datablad med resultat från petrografiska och mekaniska analyser. För att uppnå bättre och mer nyanserad bedömningssäkerhet rekommenderas komplettering av systemets dataunderlag.
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| 17. |
- Johansson, Eva, et al.
(författare)
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Utveckling av expertsystem för bedömning av bergmaterialens mekaniska egenskaper : komplement till VTI rapport 715
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- På uppdrag av Trafikverket kompletterade och vidareutvecklade Luleå tekniska universitet/Envix Nord AB i samarbete med VTI expertsystemet för bedömning av bergmaterialens mekaniska egenskaper, baserat på beskrivning av bergartens petrografiska egenskaper. Projektets mål är att möjliggöra en bedömning av bergmaterialens kvalitet och praktiska användning i projekteringsstadiet. Projektets första del publicerades som VTI rapport 715. Fortsättningsprojektets syfte är att förbättra expertsystemets bedömningssäkerhet genom tillförandet av kompletterande analysresultat åtföljda av multivariat utvärdering. Projektet genomfördes genom analyser av utvalda kompletterande prov, multivariat utvärdering av det kompletterade underlaget samt kvalitetsförbättring av bedömningssystemets klassificeringsnycklar. Expertsystemet bygger på 43 utvalda bergmaterial. För den multivariata utvärderingen användes PCA och PLS. Nycklarnas säkerhetsnivåer skärptes och inverkan av fler petrografiska parametrar på de mekaniska egenskaperna verifierades. De petrografiska variabler som visade sig ha störst inverkan på de mekaniska egenskaperna för granitoider är kornstorlek, kornstorleksfördelning och glimmerhalt. Utvärderingen pekade på ett starkt samband mellan glimmerhalt och foliationsgrad, vilket även resulterar i en tydlig skillnad mellan massformiga och folierade granitoider. Beträffande gabbroider var det mikrosprickfrekvens, glimmerhalt, kornstorleksfördelning och kornstorlek som uppvisade inverkan på de mekaniska egenskaperna. Utvärderingen indikerade att metamorfosgraden främst har positiv påverkan på kulkvarnsvärdet. De lågmetamorfa gabbroiderna har bättre kulkvarnsvärde än de magmatiska varianterna. Dock inverkar även såväl glimmerhalt som kornstorlek. Gabbroider med glimmerhalt 5–-15 % har bättre mekaniska egenskaper än de med lägre (>5 %). Multivariat utvärdering är lämpligt för att verifiera de mekaniska egenskapernas beroende av flera olika petrografiska egenskaper
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| 18. |
- Jonsson, Erik, 1967-
(författare)
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Fissure-hosted mineral formation and metallogenesis in the Långban Fe-Mn-(Ba-As-Pb-Sb...) deposit, Bergslagen, Sweden
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Långban deposit in the Bergslagen ore province is one of the most mineral-rich and complex localities on Earth. Yet, despite more than 100 years of research, much about its origin and evolution has remained unknown. In this study, new data from studies of field geology, mineral assemblages, fluid inclusions, and stable as well as radiogenic isotopes enable interpretations of the origins and evolution of this deposit in more detail. The initial stage of mineral formation took place in association with ca. 1.89 Ga (Svecofennian) felsic volcanism. C and O isotope data suggest that the stratabound Fe-Mn oxide ores were formed from volcanic-hydrothermal processes, indicating protore precipitation from a seawater-derived fluid modified through interaction with magmatic rocks. These most likely comprised the then unconsolidated pile of mainly felsic volcanic material. Possibly, the relative abundance of stratabound mineralisations in this area could be an effect of the nearby, ca. 1.89-1.88 Ga Horrsjö subvolcanic complex, which is likely to have created extensive and long-lived hydrothermal activity coeval with the formation of the local volcanic and carbonate rocks. Pb isotope systematics in minerals from different paragenetic stages implicate volcanogenic Bergslagen-type ore Pb as the dominant source of Pb in the deposit, with a minor input of a more radiogenic component that may have been derived from epiclastic sediments. S isotope data exhibit a very large range, which is interpreted as being largely the result of post-Svecofennian remobilisation of magmatic sulphur that had originally been precipitated as syn-volcanic sulphides. This remobilisation was initiated during Svecokarelian regional amphibolite facies metamorphism. Calcites hosted by skarn only exhibit isotope compositions (C, O) indicative of decarbonation and calc-silicate formation during regional metamorphism, and no evidence for overprinting by granite-derived fluids. Thus, C, O, and Pb isotope data refute previous hypotheses about influence from post-Svecokarelian granites during the evolution of the deposit. Typical vein assemblages formed during regional metamorphism and the subsequent retrograde evolution. A suggested small increase in T during the late or post-Svecokarelian stage may have been related to the TIB magmatism. The unique fissure-controlled Ba-As-Mn-Pb…mineralisation formed in a brittle-tectonic setting. O, S and Pb isotope data together with mineralogical and fluid inclusion evidence suggest that these exotic assemblages formed in a shallow crustal setting (P~atmospheric, T~180°C to room-temperature) from surface water (possibly seawater) modified through water-rock interaction. Metals were transported by a moderately saline Ca-Na-Cl-dominated aqueous fluid that had probably leached these metals from the pre-existing mineralisation at some depth. Although Cl was present, e.g. as early Pb oxychlorides, in locally significant amounts prior to fissure mineralisation, it was probably introduced extensively in the active fluid of the fissure stage. The leached components were reprecipitated in the fissure system during repeated fracturing, where sporadic open-system conditions led to fluid boiling and massive precipitation of baryte-bearing assemblages. It is suggested that the large mineralogical diversity within the fissure system mainly reflects variations in fissure substrate, combined with variable lateral position in respect to the boiling zone. The former governed paragenetic variation through reactions between wallrocks and fluid. That a majority of necessary components for the formation of fissure assemblages was sequestered from the local host rocks and pre-existing mineralisation is not least suggested by the complete absence of mineralised fissures outside the mining area. The most reasonable candidates for the tectonothermal regime leading to fissure mineralisation in the Långban deposit are; 1) the post-1.78 Ga evolution of the TIB; 2) late-Proterozoic extension and basic magmatism; 3) the ca. 1.0 Ga Sveconorwegian orogeny. A concluding stage of calcite precipitation from low-temperature meteoric waters enriched in organic carbon probably took place during the Phanerozoic.
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| 19. |
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| 20. |
- Kjellman, Johan, 1961-, et al.
(författare)
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Mathieu-Alexandre Allizeau (1774–1835) : Crystal model making in times of change
- 2022
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Ingår i: Mineralogical Record. - 0026-4628. ; 53:6, s. 759-783
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- The founders of crystallography in the 18th century recognized immediately thatthe study of such a challenging, three-dimensional subject was greatly aided bythe use of crystal models. Mathieu-Alexandre Allizeau—mineral dealer, instrumentmaker, inventor of educational toys and games, arts and curiosities collector—supplied crystal models during a time in which the science was advancing fromHaüy’s primitive forms to what would become our modern-day crystal systems.
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| 21. |
- Kjellman, Johan, 1961-, et al.
(författare)
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On the historical crystal model sets in the mineral collections of Abraham Gottlob Werner of the TU Bergakademie Freiberg
- 2020
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Ingår i: Abraham Gottlob Werner und die Geowissenschaften seiner Zeit. - Freiberg. - 9783860126356 ; , s. 149-179
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In 1823 A. von Weissenbach listed in the catalog of the Äußere-Kennzeichen-Sammlung (External characteristics collection) of the Werner-Museum among other items several early crystal model collections. In 2012 we were able to recover and identify these collections as well as some other model sets pertaining to the early history of crystallography. Additional documentation over some of these sets was found in Werner’s correspondence and his other scientific estate. This is a remarkably rich source for studies of material culture and scientific change and exchange, crystal model collections are usually highly depleted and information on them sparing to nonexistent.That such early model sets often are exquisitely made and examples of skilful craftsmanship can be seen in the exhibits in the Krüger-Haus in Freiberg. However, in our paper we want to describe and highlight the contemporary crystallographic thinking of each part of this important suite of crystal model sets representing the toughts of Linnaeus, Werner, Romé de l’Isle, Haüy, etc. from the late 18th to early 19th centuries, provisionally divided into three groups: (1) The oldest model sets pertain to Werner’s early years. These comprise a small wooden collection made after the plates of the Swedish naturalist C. Linnaeus’ Systema Naturae 1768, a collection of models hammered and carved in lead purported to have been made by Werner himself, and 55 wooden models that must be one of the earliest sets produced in more than one copy. (2) Model sets representing Werner’s ‘developed’ crystallographic thinking. This was first presented in 31 paragraphs in Von den äußerlichen Kennzeichen der Foßilien 1774. We will discuss how it evolved, our sources being the model sets made in Freiberg by C. I. Löscher, and contemporary texts. (3) Model sets arriving from abroad. To these count four collections in brass, wood, and porcelain made by pioneering French model makers, and one set of gypsum models made by F. X. M. Zippe.These collections are in Freiberg either because Werner had chosen them or that they were sent to him due to his reputation. Werner’s use of, response and comments to the different model sets will suggest to us his attitude to the developing new science of crystallography for over 40 years.
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| 22. |
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| 23. |
- Kortekaas, Marloes
(författare)
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Post-Glacial History of Sea-Level and Environmental Change in the Southern Baltic Sea
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A new palaeoenvironmental record of the post-glacial history of the southern Baltic Sea (~14 ka to present) is presented. During this period, large water level and salinity changes occurred in the Baltic Basin due to opening and closing of connections to the North Atlantic. Previous attempts to establish a detailed chronology for these palaeoenvironmental changes have been conducted mainly in coastal settings, where organic material for 14C dating is abundant. Many of these records are, however, discontinuous due to large water level fluctuations. In the relatively deep water of the Arkona Basin (45 m deep) in the southern Baltic Sea the sediment record is expected to be more or less continuous, but lack of organic material for 14C dating has impeded previous studies. Here, palaeoenvironmental change in the Arkona Basin is reconstructed on the basis of geochemical, sedimentological, mineral magnetic and palaeontological investigations. Additionally, independent physically based chronological control is, for the first time, obtained using Optically Stimulated Luminescence (OSL) dating on fine quartz sand from a ~10.86 m long sediment core. Tests of luminescence characteristics confirmed the suitability of the material for OSL dating and the ages agree well with the available AMS 14C ages on shells; in contrast, bulk sediment 14C ages are generally ~1000 years too old. Stratigraphic marker horizons in this deep basin are now absolutely dated, allowing comparison and testing of existing models of post-glacial Baltic Sea regional development. Glacial varved clay was deposited during the Baltic Ice Lake stage and a sand layer representing the Baltic Ice Lake drainage to the North Atlantic is dated to ~11.6 ka. This event is followed by a period of low water level and enhanced influence from the Oder River. A period of very rapid sedimentation occurs between ~10.9 and ~10.4 ka and is attributed to the Ancylus Lake transgression. A first anomalous slightly brackish water inflow is recorded at ~9.8 ka, but there is no clear evidence for fully brackish conditions until ~6.5 ka. At that time, the lithologic change to clay gyttja represents a distinct shift in the circulation mode, with the onset of a high-productivity, brackish circulation system in the southern Baltic. Post-depositional diffusion of sulphur from the clay gyttja most likely explains the presence of greigite (Fe3S4) concretions in the underlying silty clay unit. With this new chronology an anomaly appears between the classical model of the Littorina transgressions with brackish conditions starting ~8.5 ka, supported by studies in coastal lagoons, and our first clear brackish/marine influence occurring as late as ~6.5 ka based on studies performed in the deeper basins. This implies that the circulation system of the present Baltic Sea, with fully brackish conditions and the Danish-German Straits as the dominant inflow areas, only started from ~6.5 ka onwards.
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| 24. |
- Lagerblad, Björn, et al.
(författare)
-
Bergkrossmaterial som ballast
- 2008
-
Rapport (refereegranskat)abstract
- Concrete is a product that in the fresh state shall be able to flow and fill a form without segregating. This gives demands on flow properties and workability of the fresh concrete. Between 60 and 70 volume % of concrete consists of aggregate and thus its properties are fundamental for flowability. Presently in Sweden concrete is made from natural glaciofluvial aggregates in sizes less than 8 mm and with stones from local crushed rocks._x000D_ _x000D_ Locally in Sweden there is a lack of good natural aggregates. Moreover, for environmental reasons the government wants to preserve remaining gravel pits especially those in eskers. As a consequence one must find an alternative aggregate. Concrete is a bulk commodity and a cheap building material. Thus it is only crushed rocks that locally and in sufficient amounts can replace natural aggregates. The rock quarries in Sweden are mainly destined to give good coarse aggregate. In this process one also gets fine aggregates but this product is not optimized for concrete production._x000D_ _x000D_ The main problem is thus to replace the natural fine aggregate in a cost effective way with crushed rocks. Fine aggregates from crushed rocks develop other properties than natural aggregates. This is especially the case in Sweden with predominant granitic rocks. As a consequence concrete with crushed fine aggregates must be proportionated differently. The aim of this project has been to find quality criteria for fine aggregates from crushed rocks to be used in concrete and to measure how to improve the properties. Another important aspect is to find systems for quality insurance for continuous concrete production. The tools used are mainly classification of the aggregates to correlate this with rheological properties. Most effort has been put on understanding the influence of different fine material from granitoid rocks falling through the 2-mm sieve. The reason is that it is this material that causes most problems. The results have, however, been correlated against the properties of (0-16 mm) concrete. Material from 16 different rock quarries have been analysed in great detail and some additional ones in less detail. They have been compared with natural glaciofluvial aggregates. All of the material has been studied by petrographic and image analysis, laser sieve, sand equivalent test and methylen blue test._x000D_ _x000D_ The results show that there is a large variation in properties of fine aggregates from the crushed granites. The reason is that granite is regarded as the mineral composition of a family with varying amounts of different minerals and the different granites have different textures. This is reflected especially in the fine material. The finest fractions contain pure minerals and the geometry of these mineral particles is given by the crystallographic form. One mineral that especially hinders the flow is free mica due to its flaky mineral form. Larger particles are normally composed of rock fragments, i.e. several minerals. In which fraction free mineral grains starts to appear depends on the texture of the granitoids. The amount of free mica grains in the fractions below the 0,5 mm sieve varies from almost none to almost 50 %. There may, however, also be problems related to extreme amounts of filler, variation in grading curve, weathering, clay formation and hydrothermal alteration._x000D_ _x000D_ The main method to analyse flow and workability has been different rheometers where one can split between yield stress and plastic viscosity. The yield stress gives the force to set the particle slurry in motion while the plastic viscosity measures the force needed to keep it in motion. Rheological tests on the different material have been conducted on micro mortar (<0.25 mm) mortar (< 2 mm) and concrete (<16 mm). One finds that the properties of the micro mortar strongly influence that of the mortar, which in turn influences that of the concrete. To a certain degree by careful proportioning it is possible to reduce the influence of the fine material but it is not possible to eliminate it. Some of the fine materials from crushed rocks can almost directly replace natural sand while other fine aggregates are very difficult to use in concrete production._x000D_ _x000D_ This work gives a basic understanding of how to characterise fine aggregate (0-2 mm) in such a way that it gives information on how it will affect the rheological properties of concrete. Moreover, it gives information about how to improve the properties and methods for quality control. A major problem is, however, that there is no single test to be used. This work indicates that one must first do a general characterisation and based on this work develop a method or methods for quality assurance that considers the specific properties of the material from the individual stone quarry. _x000D_
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| 25. |
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| 26. |
- Langhof, Jörgen, 1965-
(författare)
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Eric Thomas Svedenstierna
- 2017
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Ingår i: Svenskt biografiskt lexikon. ; 169, s. 512-517
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 27. |
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| 28. |
- Langhof, Jörgen, 1965-
(författare)
-
Jacob Berzelius och norsk mineralogi
- 2009
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Ingår i: Kongsberg mineralsymposium. - Kongsberg : Norsk Bergverksmuseum. - 0800-1855. ; :41, s. 50-53
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Langhof, Jörgen, 1965-, et al.
(författare)
-
Molybdofyllitens ursprung spårat
- 2015
-
Ingår i: Långbansnytt. - Långbanssällskapet. - 1650-4968. ; 21:1, s. 9-13
-
Tidskriftsartikel (populärvet., debatt m.m.)
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| 33. |
- Langhof, Jörgen, 1965-
(författare)
-
Personporträtt - Erik Ygberg
- 2014
-
Ingår i: Långbansnytt. - Stockholm : Långbanssällskapet. - 1650-4968. ; 20:2, s. 4-6
-
Tidskriftsartikel (populärvet., debatt m.m.)
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| 34. |
- Langhof, Jörgen, 1965-, et al.
(författare)
-
Vanadinit - ett nytt mineral för Jakobsberg
- 2014
-
Ingår i: Långbansnytt. - Stockholm : Långbanssällskapet. - 1650-4968. ; 20:2, s. 11-12
-
Tidskriftsartikel (populärvet., debatt m.m.)
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| 35. |
- Lindhagen, Adam
(författare)
-
Caleacte : Production and Exchange in a North Sicilian Town c. 500 BC-500 AD
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The study deals with the ancient town of Caleacte, modern Caronia, on the north coast of Sicily. Information provided by ancient textual sources, epigraphy and archaeology on the economic conditions and framework of the site and its micro-region are presented in the first chapter. Production and exchange through a diachronic perspective of nearly 1,000 years is illustrated through the study of pottery, mainly transport amphorae but also fine ware and lamps, dating primarily to the late 4th c. BC-late 4th c. AD. The material and the amphora fabrics are presented in an illustrated catalogue, which constitutes one of the few detailed publications of Roman material, especially of amphorae, from Sicily. Transport amphorae functioned in Antiquity as containers for mainly wine, oil and fish products. They constitute one of the most valuable sources we possess for acquiring knowledge on ancient economy. Thin-section analysis is used as an important method for indicating possible origins of amphorae, in addition to other information based on, for example, quantification, morphology, textual sources, epigraphy, kiln finds, and tituli picti, with an emphasis on local products. Through the study of patterns of production and supply based on the testimony of the amphorae, fine ware and lamps, important trends in the local production and supply of goods and commodities were discerned. These trends were compared with the evidence from other Sicilian sites and with cargoes from Sicilian shipwrecks in order to establish whether the find situation at Caronia agreed with, and could be inserted into, the general Sicilian framework. The patterns of production of supply are then combined with the general economic evidence to identify the motivating forces behind exchange at Caleacte, Sicily and the South Tyrrhenian. Several pieces of evidence could be singled out in favour of market behaviour following the forces of supply and demand. In the last chapter, the trends and patterns examined in the study are viewed from a Braudelian perspective in order to establish a hierarchy and single out the most important forces behind production and exchange at Caleacte.
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| 36. |
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| 37. |
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| 38. |
- Olausson, Peter, 1956-
(författare)
-
På mineraljakt i västra Värmland : några notiser om en anteckningsbok från 1800-talet
- 2007
-
Ingår i: Bergslagshistoria. - Karlstad : Föreningen Bergslagsarkiv. - 1653-2848. ; 19, s. 37-40
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Artikeln beskriver den mineralogiska och lokalhistoriska verksamheten, som bedrevs av Olof Jönsson Granström från Gräsmark under 1800-talets senare del. Granströms arbete för att lokalisera malmförekomster m m har noterats i ett par bevarade anteckningsböcker.
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| 39. |
- 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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| 40. |
- Rimsa, Andrius
(författare)
-
Understanding Zircon Geochronology - Constraints from Imaging and Trace Elements
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Formation of incipient charnockite in Söndrum, SW Sweden and the Kerala Khondalite Belt (KKB), S. India is accompanied by zircon growth. The age of the dehydration event is constrained by dating newly formed zircon to 1397±4 Ma (2?, MSWD=1.7) in Söndrum and ca. 520-510 Ma in S. India by secondary ionization mass spectrometry (SIMS). The formation of incipient charnockites correlates with regional magmatic or metamorphic events. In Söndrum, SW Sweden, charnockitisation is simultaneous with the formation of the Varberg Charnockite- Granite Association (CGA). Identical ages for incipient charnockite formation in studied localities in the KKB, S. India imply that charnockitisation is a major regional event related to the latest stage of Pan-African orogeny. Commonly observed bulk rock HREE depletion in incipient charnockites is not caused by zircon dissolution but by involvement of garnet as a reactant in the dehydration reactions. The Kerala Khondalite Belt, S. India, previously believed to be an entirely supracrustal belt, in fact contains magmatic rocks as a major lithological component. Ages (SIMS U-Pb on zircon) of magmatic garnet-biotite gneiss (1877±24; 2?, MSWD=0.6), augen gneiss (1891±36; 2?, MSWD=1.04) and massive charnockite (1865±16; 2?, MSWD=0.41) identify a previously unknown, Paleoproterozoic magmatic major crust forming event in the Kerala Khondalite Belt, S.India. Two distinct metamorphic events at 580-550 Ma and 520-510 Ma, identical in age in three studied localities of garnet biotite ortho- and paragneiss and augen gneiss, have been identified. The pervasive 580-550 Ma regional metamorphic event dates deformation and migmatisation of the magmatic and sedimentary rocks in the Kerala Khondalite Belt during Pan-African orogeny. The second metamorphic event is related to formation of the incipient charnockites. The entire population of magmatic oscillatory zoned zircons in a migmatised granitic sample from the Tjärnesjö intrusion, SW Sweden, experienced brittle hydraulic fracturing and rapid healing. The oscillatory zoned zircon fragments are rotated but not dispersed. Fractures between individual fragments are sealed by newly formed CL-bright zircon. Both the internal structure of fractured zircons and the LREE-enriched, low-Th character of CL-bright zircon suggest that cracks between oscillatory zoned zircon fragments were rapidly sealed after fracturing by hydrothermal CL-bright zircon. Zircon fracturing and crack-sealing has been dated by SIMS U-Pb on zircon to 920 ± 51 Ma with a limit for the youngest possible age of 960 ± 16 Ma provided by sector zoned rims that form overgrowths on the fractured cores.
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| 41. |
- Sparrenbom, Charlotte
(författare)
-
Constraining the Southern Part of the Greenland Ice Sheet since the Last Glacial Maximum from Relative Sea-Level Changes, Cosmogenic Dates and Glacial-Isostatic Adjustment Models
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New results are presented from the investigation of relative sea-level changes in the Nanortalik and Qaqortoq-Narsarsuaq areas in SW Greenland from c. 11 000 cal. years BP to the present. Isolation and transgression sequences from seven lakes and seven tidal basins are identified using some of the traditional methods such as stratigraphic description, magnetic susceptibility, saturated induced remanent magnetisation (SIRM), loss on ignition, and macrofossil analyses. Macrofossils and bulk sediments have been dated by AMS radiocarbon dating. We also demonstrate that the use of the new XRF-scanning technique, combined with lithological description, pinpointed macrofossil analyses and radiocarbon dating, provide a quick and effective way of investigating isolation contacts/transgression sequences for the reconstruction of sea-level changes. In SW Greenland, the initial relative sea level fall was rapid and present-day level was reached at ~9000 cal. yr BP and continued falling until at least 8800 cal. yr BP. Between 8000 and 6000 cal. yr BP sea level reached its lowest level of around ~10 m below h.a.t. The late Holocene transgression was more gradual as it occurred over a longer time interval. Present sea-level was reached between ~2000-0 cal. yr BP. We have used glacial-isostatic adjustment models to determine the ice sheet evolution in southern Greenland from the LGM until the present. The sea-level observations from the Nanortalik and Qaqortoq areas are used to constrain the different ice-model scenarios tested. In situ produced cosmogenic 10Be and 26Al in bedrock and erratics give inference concerning the basal regime in the two areas. Our ice sheet history reconstruction shows an ice sheet extending to the shelf edge from 26,500 cal. yr BP until 22,000 cal. yr BP, followed by rapid retreat. By 12,000 cal. yr BP, the ice margin was inland of the present-day coast and by 10,500 it had reached the present margin. The ice sheet was smaller than at present from 10,500 cal. yr BP and reached a minimum of 30 km inland of the present-day margin at 9000 cal. yr BP. The neo-glacial re-advance started before 6500 cal. yr BP and the present-day margin was reached by 5500 cal. yr BP. The ice sheet was cold-based in the Nanortalik area, but warm-based and eroding in the Qaqortoq area during the Late-glacial.
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| 42. |
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| 43. |
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| 44. |
- Wigforss-Lange, Jane
(författare)
-
Geochemical and sedimentary signatures of Phanerozoic events.
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Geological and biological catastrophic events have occurred repeatedly in the Earth's history, leaving traces in the global stratigraphical record in the form of sedimentary features, geochemical anomalies and biotic turnovers. This thesis focuses on the sedimentological and geochemical signatures of several key events in the Phanerozoic stratigraphical record, and aims to interpret the different signals and the causal mechanisms behind each of these events. Three intervals are investigated; the Upper Silurian (late Ludfordian), Jurassic-Cretaceous and the Cretaceous-Paleogene (K-T) boundaries. Sedimentological investigations coupled with analyses of major and trace element concentrations and of carbon and oxygen isotopic compositions were undertaken on drillcore and outcrop samples of Late Silurian age from central Scania, Sweden. Sedimentological and trace element analyses were performed on samples from the Jurassic-Cretaceous transition from Scania, Sweden and on ejecta sediments from the K-T transition along the Mexico-Belize border, close to the Chicxulub impact site. The common characteristic of these successions is that they represent special depositional environments related to exceptional short-lived events. The geochemical event in the Upper Silurian sedimentary rocks is marked by carbon and oxygen isotope anomalies in marine carbonates. The ?13C values increase from ca +1 ? to +10 ?, which represent the heaviest values recorded in this interval from Baltica. The ?18O values rise from ca -10 ? to -5 ? and show a somewhat unstable pattern. None of the conventional mechanisms for 13C enrichment can independently cause a ?13C shift in the oceanic dissolved inorganic carbon (DIC) that would answer to the observed magnitude of change. Thus, multiple causes are suggested herein. The isotopic excursions coincide with a mass occurrence of cyanobacteria, and the most extreme ?13C values may be explained by 13C enrichment in DIC through regional increases in photosynthetic activity, probably superimposed on an already 13C enriched (ca +3 ? to +5 ?) ocean. This initial anomaly still lacks a reasonable explanation. In the Scanian deposits an evaporitic environment is confirmed by the presence of e.g. cerebroid ooids, which form in highly saline waters and it is suggested that evaporation is responsible for the 18O enrichments. Degassing of CO2 may also explain the 13C enrichment in deposits that are not closely associated with cyanobacteria. It is, however, arguable whether evaporation, although prolonged and widespread, could modify the carbon isotope composition in deep marine settings. Still, it is possible that the pCO2atmos and cyanobacteria-stromatolites may be linked in some way that in turn links to the ?13C anomaly. However, the causes of the event remain enigmatic and further analyses of ?13C and ?18O from various environments (e.g. paleosols and lake sediments) and from different parts of the world are required. Sedimentary beds reflecting an atypical event were identified in the Jurassic-Cretaceous transition (within the Vitabäck Clays) at Eriksdal, Sweden. Samples were selected from an excavated ditch for geochemical, mineralogical and palynological analyses. Additional sedimentological studies where performed in field. Well-preserved assemblages of miospores and for the first time, dinoflagellates were identified in the Vitabäck Clays. The palynological assemblage corroborates an Early Cretaceous (Berriasian) age. The Vitabäck Clays consist predominantly of greenish to dark grey clays, but a coarse-grained unit is enclosed within the homogenous fine-grained sediments and these beds are also recognized by anomalous sedimentary structures and fossil content. The relatively short succession (ca 1.5 m) documents a change in energy of the transport media by the sharp erosive base, coarse-grained lithology, the incorporation of plant fragments and a fauna of mixed terrestrial and marine origin. This anomalous succession is herein interpreted to represent a tsunami deposit, possibly generated by tectonic activity or by an asteroid impact, the Mjølnir impact in the Barents Sea being a possible candidate. The Cretaceous-Paleogene boundary event relates to the Chicxulub impact in Mexico. The Upper Cretaceous Barton Creek Dolomite and the overlying two-layered ejecta deposit, collectively spanning the K-T boundary, were sampled at several sites along the Mexico-Belize border. The employed sedimentological and geochemical investigations document the chaotic circumstances following the impact. The geochemical analyses provided a genetic link between the proximal ejecta, the target rocks and K-T boundary deposits at other sites. There has been considerable debate as to whether this particular impact in fact took place at the K-T boundary. The results of this study envisage that the Chicxulub impact produced the global K-T boundary layer.
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| 45. |
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| 46. |
- Kjellman, Johan, 1961-
(författare)
-
A quarter millenium of morphological Crystal Models - the makers, the materials, the collections - a current project on retrieving their history
- 2012
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A quarter millenium of morphological Crystal Models – the makers, the materials, the collections – a current project on retrieving their history.Crystal models (CM) and crystal model collections (CMC) made of paper, wood, clay, metal, glass, etc. have been manufactured, developed, and used as an aid in the fields of mineralogy and crystallography from the 1760’s to 1920’s (Figure 1). CM have for example been used to display ideal morphology of different mineral species or relationship between crystal forms; visualize different crystallographic and physical concepts, e. g. symmetry, crystallographic and optical axes, twinning, etc. Earlier geometrical models, such as platonic and archimedian bodies, known since Antiquity and perhaps originally inspired by natural crystals, were often present in the art and the curiosity cabinets of the Rennaisance era. In the early 20th c. the progress in crystal structure determination shifted the focus in crystallography and crystal modelling from outer morphology and symmetry to inner structural relations. Still, morphological CM were produced and used throughout the century.Apart from a few attempts to describe special CMC, drawing on the collections in the BMNH in London and Teylers Museum in Haarlem, very little has been written about CMC (Tandy 1998; Touret 2004).CMC could and should be complimentary research objects of early crystallography. In their time some CMC conveyed new concepts, many times under direct supervision of the inventor, and by studying them new aspects, blind alleys or pitfalls in the history of crystallography may come to light. The locations of CMC from different schools, may reflect scientific connections and influences, etc. But without any precise knowledge about the different sets and makers no such research can be made, they will remain just CM. The two main institutional uses of CMC – exhibit and education – can also pose potential threats to them, those of being worn in crystallography class or being dispersed both in education and exhibits. Banalized descriptions, e.g. “antique models” or “Krantz models”, is typical if such CM are marketed, ultimately then often losing their institutional provenance. The aim of this study is to provide the mineralogical community with a deeper knowledge of the old CMC: their makers and scientists, when, where, and what of the sets were made, and how many models they contained. And not the least, where we can see typical sets of the different CMC.How can this work be done? By a synergetic approach from three directions: (i) by studying literature, both primary books and catalogs listing/treating CMC, and different kinds of secondary literature, (ii) by Internet searches, especially utilizing the facility of searching words in OCR scanned texts, e.g. Google Books, Gallica, an effective tool for finding information which else would be almost impossible to retrieve; (iii) by surveying important collections and their archives, some of which are digitized.In this presentation I will give a few examples of what I have accomplished so far by this method.Tandy, P. 1998. Crystallography and the geometric modelling of minerals: a reflection on the models in the Natural History Museum, London. The Geological Curator 6(9): 333 – 338.Touret, L. 2004. Crystal models: milestone in the birth of crystallography and mineralogy as sciences. pp. 43 – 58 in Dutch Pioneers of the Earth Sciences. Ed. by R.W. Visser and J. Touret, Koninklijke Nederlandse Akademie van Wetenschappen, Amsterdam.
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| 47. |
- Abdu, Yassir Ahmed Mohamed, 1966-
(författare)
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Mössbauer Spectroscopy of Meteoritic and Synthetic Fe-Ni Alloys
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis reports on the results of investigating Fe-containing minerals in meteorites, with focus on Fe-Ni minerals and their magnetic properties, along with some synthetic Fe-Ni analogues. The New Halfa meteorite, which fell in Sudan 1994, has been studied using Mössbauer spectroscopy, X-ray diffraction, and electron microprobe analysis techniques, and classified as an ordinary L-type chondrite of petrologic type 4. Mössbauer spectra of taenite-enriched samples from the metal particles of the New Halfa (L4) and Al Kidirate (H6) meteorites identify the following γ (fcc) Fe-Ni phases: the ferromagnetic atomically ordered taenite (tetrataenite) with ~ 50 at % Ni, the ferromagnetic disordered taenite with ~ 50 at % Ni, the low-Ni (~ 25 at %) paramagnetic taenite (antitaenite). The presence of the superstructure of tetrataenite is confirmed by synchrotron X-ray diffraction.Fe-rich γ (fcc) Fe-Ni alloys with compositions Fe79Ni21, Fe76Ni24, and Fe73Ni27, which serve as synthetic analogues of antitaenite, are prepared by mechanical alloying and subsequent annealing at 650 °C. The Mössbauer results indicate that these alloys are inhomogeneous and contain a high moment (HM) ferromagnetic Ni-rich phase (> 30 at % Ni) and a low moment (LM) paramagnetic Fe-rich phase, which orders antiferromagnetically at low temperature. The coexistence of these phases is attributed to phase segregation occurring on short range, probably nanometer scale, consistent with the Fe-Ni phase diagram below 400 °C where there is a miscibility gap associated with a spinodal decomposition in alloys with < 50 at % Ni.The combined high field Mössbauer spectroscopy and SQUID magnetometry results on these alloys at room temperature indicate large induced local magnetic moments in the paramagnetic part of the sample, which increases with increasing the Ni content. The results, when compared with the high field Mössbauer results on antitaenite from the metal particle of Al Kidirate and New Halfa meteorites may be used to estimate the Ni content of antitaenite in meteorites.High pressure 57Fe Mössbauer spectroscopy measurements up to ~ 41 GPa have been carried out at room temperature using the diamond anvil cell (DAC) technique in order to investigate the magnetic properties of γ (fcc) 57Fe53Ni47 alloy. The results indicate a pressure induced Invar effect at ~ 7 GPa and a non-magnetic or paramagnetic state above 20 GPa, demonstrating the volume dependence of the magnetic moment of γ (fcc) Fe-Ni alloys.
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| 48. |
- Bahroudi, Abbas, 1964-
(författare)
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The Effect of Mechanical Characteristics of Basal Decollement and Basement Structures on Deformation of the Zagros Basin
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two fundamental structural elements, basement architecture and basal decollement, play a significant role in the evolution of a tectonically active region. Using different approaches (field data, literature review and analogue models) this thesis demonstrates that these two elements affected the deformation style in the Zagros fold-thrust belt during Mesozoic extensional and Cenozoic contractional episodes. Reassessment of available data suggests a new configuration for the basement to Zagros basin that consists of basement faults with three different trends. Complicated interrelationships of these basement faults divide the Zagros basin into two major basement blocks, active and passive. This model associated with geological evidence suggests that deformation in the basement due to the convergence between Arabia and Iran is not restricted to the Zagros Mountains but already involves a considerable part of the Arabian platform. However, deformation in the cover units is not only governed by the deformation in the basement, which are decoupled from each other by the Hormuz salt in many parts in the Zagros fold-thrust belt. Geological evidence shows that there is a clear relationship between activity of the Hormuz structures and the basement faults in the Zagros basin. Extended analogue models indirectly show how Hormuz types of basal decollement associated with the opening of Neo-Tethys can control the distribution, number, width and geometry of faults, penetrative strain, and diapirism. Analogue models shortened from one-end show that the spatial distribution of the Hormuz salt in the Zagros belt map viscous and frictional decollements to the thin-skinned deformation. Shortening of the cover results in formation of partitioning of strain into transpressional zones, different topographic wedges and differential sedimentation of growth sediments along the Zagros belt. Model results supported by geological and geophysical data sets suggest that some of the faults previously attributed to basement could have developed above the initial lateral boundaries between viscous and frictional basal decollements.
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| 49. |
- Bastani, Mehrdad, et al.
(författare)
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Delineating hydrothermal stockwork copper deposits using controlled-source and radio-magnetotelluric methods : A case study from northeast Iran
- 2009
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Ingår i: Geophysics. - : Society of Exploration Geophysicists. - 0016-8033 .- 1942-2156. ; 74:5, s. B167--B181
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Tidskriftsartikel (refereegranskat)abstract
- Radio- and controlled-source-tensor magnetotelluric (RMT and CSTMT) methods are used to target hydrothermal veins of copper mineralization. The data were acquired along six eastwest- and three north-south-trending profiles, covering an area of about 500 x 400 m(2). The tensor RMT data were collected in the 10-250-kHz frequency band. A double horizontal magnetic dipole transmitter in the 4-12.5-kHz frequency range allowed us to constrain the deeper parts of the resistivity models better. To obtain optimum field parameters, ground magnetic profiling was conducted prior to the RMT and CSTMT surveys. Although the study area (in Iran) is remote, a number of radio transmitters with acceptable signal-to-noise ratio were utilized. The 2D inversion of RMT data led to unstable resistivity models with large data misfits. Thus, the RMT data were used to complement and analyze the near-surface resistivity anomalies observed in the 2D CSTMT models. Analyses of strike and dimensionality from the CSTMT data suggests that the low-resistivity structures are mainly three dimensional; therefore, 2D inversion of determinant data is chosen. Independent 2D inversion models of the determinant CSTMT data along crossing profiles are in good agreement. Known copper mineralization is imaged well in the CSTMT models. The thinning of the conductive overburden correlates very well with magnetic highs, indicating the bedrock is resistive and magnetic. In this sense, the magnetic and electromagnetic fields complement each other. Analysis of the 2D resistivity models indicates the volcanic rock deepens at the center of the study area. This zone is associated with a magnetic low and therefore is recommended for detailed exploration work.
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| 50. |
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