| 1. |
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| 2. |
- Frank, Katherine, et al.
(författare)
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Variability in the Geological, Mineralogical, and Geochemical Characteristics of Base Metal Sulfide Deposits in the Stollberg Ore Field, Bergslagen District, Sweden
- 2019
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Ingår i: Economic geology and the bulletin of the Society of Economic Geologists. - Littleton, Colorado : Society of Economic Geologists. - 0361-0128 .- 1554-0774. ; 114:3, s. 473-512
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Tidskriftsartikel (refereegranskat)abstract
- The Stollberg ore field occurs in the Bergslagen region of south-central Sweden, a polydeformed ca. 1.9 Ga igneous province dominated by bimodal felsic and mafic rocks. Sulfide mineralization is hosted by metavolcanic rocks, marble, and skarn and consists of massive to semimassive polymetallic sulfides and iron oxide in a semiregional F2 syncline termed the Stollberg syncline. The dominant country rocks are rhyolitic pumice breccia and rhyolitic ash-siltstone with minor mafic sills metamorphosed to the amphibolite facies. On the eastern limb of the Stollberg syncline, sulfide mineralization occurs as stratabound premetamorphic replacement of volcaniclastic rocks and limestone that grades into iron formation. The development of skarn assemblages is the result of low-temperature replacement of limestone and volcaniclastic rocks rather than formation by high-temperature metasomatism or synmetamorphic or late hydrothermal replacement of marble. Metamorphosed, hydrothermally altered rocks on the eastern limb are dominated by the assemblages garnet-biotite and gedrite-albite. Silica-altered rocks are generally subordinate in the Stollberg ore field; however, sulfides at Gränsgruvan, on the western limb of the syncline, are located in a silicified zone along with metamorphosed, altered rocks dominated by sericite and the assemblage quartz-garnet-pyroxene. Although the Tvistbo and Norrgruvan prospects along the northern end of the syncline are small, they show geologic characteristics that are transitional to deposits found on the western and eastern limbs of the syncline. Ore at Tvistbo is hosted by skarn and is spatially associated with quartz-garnet-pyroxene rocks, whereas sulfides at Norrgruvan are hosted by quartz-fluorite rocks that are similar to those hosting the Brusgruvan deposit on the eastern limb of the syncline.Whole-rock analyses of variably altered host rocks in the Stollberg ore field suggest that most components were sourced from felsic volcaniclastic rocks and that Zr, Ti, Al, Hf, Nb, Sc, Th, Ga, U, and rare-earth elements (REEs) were immobile during alteration. These rocks are enriched in light REEs, depleted in heavy REEs, and have negative Eu anomalies, whereas sulfide-bearing rocks (Fe- and base metal-rich) and altered rocks in the ore zone show the same REE pattern but with positive Eu anomalies. Indicators of proximity to sulfides in altered rocks in the Stollberg ore field include positive Eu anomalies, an increase in the concentration of Pb, Sb, As, Tl, Ba, Ba/Sr, and K2O, as well as an increase in a modified version of the Ishikawa alteration index, which accounts for the presence of primary Ca in an original limestone component. Garnet and pyroxene enriched in either Ca or Mn are also considered to be pathfinders to ore. Cooling of an acidic, reduced hydrothermal fluid that carried sulfur and metals, which became neutralized as it reacted with limestone, is likely responsible for the formation of sulfides in the Stollberg ore field. The nature of the host rock types, the style of the alteration spatially associated with sulfide mineralization, and the spatial association with iron formation bear some resemblance to volcanogenic massive sulfide and Broken Hill-type deposits. However, the stratabound replacement of limestone by sulfides distinguishes it from these deposit types and is a so-called SVALS-type ore system, which is a class of stratabound, volcanic-hosted, limestone-skarn deposits restricted to the Bergslagen district.
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| 3. |
- Kampmann, Tobias, et al.
(författare)
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Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U-Pb geochronology on zircon and monazite
- 2016
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Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 278, s. 52-68
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Tidskriftsartikel (refereegranskat)abstract
- U–Th–Pb (zircon and monazite) ion probe data have provided constraints on the timing of emplacement and metamorphism of magmatic rocks close to the Palaeoproterozoic, Falun base metal sulphide deposit in the Bergslagen lithotectonic unit, Fennoscandian Shield, Sweden, and, thereby the timing of mineralisation. Hydrothermal alteration and mineralisation at Falun are constrained to a short interval of several million years between a 207Pb/206Pb weighted average age of 1894 ± 3 Ma for a rhyolitic sub-volcanic rock in the felsic volcanic to sub-volcanic host rock suite, and a 207Pb/206Pb weighted average age of 1891 ± 3 Ma for a post-sulphide, porphyritic dacite dyke. Magmatism also included the emplacement of granite plutons with igneous crystallization ages of 1894 ± 3, 1894 ± 2 Ma and 1893 ± 3 Ma. The felsicsub-volcanic to volcanic activity and the emplacement of dacite dykes and granite plutons overlap in age within their respective analytical uncertainties, indicating hydrothermal alteration and sulphide mineralisation inside a narrow time span of intense magmatic activity, and burial of the supracrustal rocks.Two distinct patchy and homogeneous metamorphic monazite types in a felsic volcanic rock around and hydrothermally altered rocks at the Falun deposit yield 207Pb/206Pb weighted average ages of 1831 ± 8 Ma and 1822 ± 5 Ma, respectively. These ages fall well within the temporal range of a younger1.84–1.81 Ga (M2) metamorphic episode during the 2.0–1.8 Ga Svecokarelian orogeny, with the older episode (M1) inside the Bergslagen lithotectonic unit at around 1.86 Ga. This shows the major influence of the M2 event in the north-western part of this unit, leading to a complete resetting of the U–Th–Pb isotopesystem in monazite.
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| 4. |
- Kampmann, Tobias, et al.
(författare)
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Timing of magmatism and mineralisation at Falun, a major base metal sulphide deposit in the Fennoscandian Shield, Sweden
- 2015
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Ingår i: Mineral Resources in a Sustainable World. - 9782855550664 ; , s. 591-594
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Konferensbidrag (refereegranskat)abstract
- U-Pb (zircon) ion probe geochronology on key lithologies at the Palaeoproterozoic Falun Zn-Pb-Cu-(Au-Ag) sulphide deposit in the south-western part of the Fennoscandian Shield has been carried out. Results suggest that dominantly felsic sub-volcanic intrusion, hydrothermal alteration, ore formation and intrusion by dykes and plutons took place in a short time interval between 1894 ± 3 Ma and 1891 ± 3 Ma. Analogues to intra-arc VMS mineralisation in Peru are discussed.
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| 5. |
- Lindh, Magnus, et al.
(författare)
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Evolution of reproductive phenology in annual social insects competing for floral resources
- 2018
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Ingår i: Evolutionary Ecology Research. - 1522-0613. ; 19:6, s. 707-722
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Tidskriftsartikel (refereegranskat)abstract
- Question: How does reproductive timing in annual social insects evolve under intraspecific exploitation competition and in response to a changing environment? The latter includes shifts in resource abundance, mortality, season length, and resource peak timing, factors often associated with climate change. Background: Climate and land use are changing. Evolutionary ecology must learn to predict how organisms are affected by, and might adapt to, such changes. Classic theory predicts how the timing of reproduction in organisms with an annual life-cycle (including many plants and social insects) optimally balances their phases of growth and reproduction with seasonal resource distributions. But theory has yet to take into account interactions within or between species. Method: We use invasion analysis to calculate the evolutionarily stable reproduction time by extending a classic model of annual social insects (such as bumblebees) to include competition for seasonally variable resources. There are two types of (colony) production: vegetative (workers) and reproductive (queens). The initial worker density in the landscape depends on the density of the surviving queens from the previous year. Reproduction time is approximated as a sudden (bang-bang) switch from vegetative to reproductive production during the season. We compare the evolutionarily stable strategy (ESS) with the classical optimization result without competition. We also compare it with the strategy that maximizes population size under resource competition. Results and conclusions: Under resource competition, the ESS reproduction time occurs earlier than the optimum predicted by classic theory. But the ESS is later than the strategy that maximizes population size. Thus phenological adaptation to environmental change is likely to reduce population sizes. Both the ESS and the optimal reproductive time change more slowly than do shifts in seasonal resource peaks. Hence a growing asynchrony between peak flowering times and the timing of bumblebee reproduction – often interpreted as a phenological mismatch – may actually be an adaptive response of pollinators in this system.
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| 6. |
- Ozolins, D., et al.
(författare)
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Second European multi-disciplinary conference of national strategies for Chlamydia trach. and human papillomavirus NSCP conf. in Berlin, 2013 enhanced detection, management and surveillance of sexually transmitted infections in Europe are essential!
- 2013
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Ingår i: International journal of immunopathology and pharmacology. - : SAGE Publications. - 0394-6320 .- 2058-7384. ; 26:4, s. 839-845
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for updated guidance on detection, management and surveillance of sexually transmitted infections (STIs). Chlamydia, gonorrhoea and syphilis reporting needs to be mandatory in more European countries to aid collection of data. More widespread Chlamydia screening is needed in many countries as this is the only way to reduce complications. The role of Human Papillomavirus (HPV) screening in a situation where the prevalence of HPV infection has dropped significantly was also discussed in the context of the high cost of screening, the need for a relatively complex infrastructure, particularly in developing countries, and falling vaccination costs. An integrated HPV vaccination and screening policy could be the most appropriate with vaccination at 9-13 years as recommended by WHO and a single HPV screen at 35-39 years, possibly repeated thereafter every 10 years. Female and male HPV vaccination programmes could lead to near elimination of genital warts in both females and males. Surveillance of STIs should be intensified where needed; additional or better quality data should be collected including reasons for testing, denominator data to estimate positivity rates, diagnostic methods, concurrent STIs, sexual orientation and country of acquisition; more analytical rather than descriptive epidemiology is needed.
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| 7. |
- Ripa, Magnus, et al.
(författare)
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Bergslagen, etapp 1 : Profilkartering av berggrunden i området Sala–Jugansbo
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Berggrundsgeologisk kartering och geofysiska mätningar har gjorts i huvudsak längs några profiler i Sala-Jugansboområdet. Avsikten var att utreda vissa stratigrafiska och strukturella förhållanden hos ytbergarterna samt att dokumentera berggrundens magnetiska egenskaper och mönster i ett område bland annat kring Banmossens wollastonitförekomst.Undersökningarna visar på en asymmetrisk antiklinal-synklinalstruktur i området mellan Broddbo och Jugansbo. Antiklinalen består mest av metasedimentära bergarter och synklinalen av metavulkaniter med underordnade karbonatstenar. De metasedimentära bergarterna i antiklinalen kan lateralt motsvara en del av de vulkaniter som finns i Jugansboomådet. Lokalt är bergarterna dock starkt deformerade vilket gör stratigrafiska korrelationer osäkra. Synklinalens stratigrafiskt översta delar består av skarnbandade vulkaniska silt- till sandstensformationer och pimpstensförande metaryoliter, vilka har givit en preliminär SIMS U-Pb zirkonålder på 1 902,9 ± 8,9 Ma. De äldre intrusiva bergarterna längs en öst–västlig profil förbi Banmossen domineras av metabasiter. De varierar i sammansättning och bildar lokalt komplicerade hybridbergarter vid kontakter mot metagrantoider. Variationer i magnetitinnehåll ger tillsammans med diverse strukturer upphov till ett komplicerat magnetmönster.
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| 8. |
- Ripa, Magnus, et al.
(författare)
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Continental magmatic arc and siliciclastic sedimentation in the far-field part of a 1.7 Ga accretionary orogen
- 2020
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Ingår i: Sweden. - : Geological Society of London. ; , s. 253-268
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Trachyandesitic to trachybasaltic lavas, interlayered siliciclastic sedimentary rocks and subaerial ignimbrites with a rhyolitic to trachydacitic composition lie unconformably above metamorphic rocks in west-central Sweden. These volcanic rocks erupted at 1711 + 7/−6 to 1691 ± 5 Ma and belong to a high-K, calc-alkaline to shoshonitic suite deposited in a continental arc setting. Positive ɛNd values and Nb/Yb ratios in the trachyandesitic to trachybasaltic rocks indicate an enriched mantle source. Coeval, 1710 ± 11 to 1681 ± 16 Ma plutonic and subvolcanic rocks are mainly granitic or quartz syenitic in composition. Subordinate components include quartz monzonite, quartz monzodiorite and monzogabbro or gabbro. ɛNd values in the range −1.0 to + 1.1 overlap with those in the inferred 1.9–1.8 Ga source rocks. All these rocks belong to the youngest phase of the lithodemic unit referred to as the Transscandinavian Igneous Belt. This magmatic province extends in a roughly NNW direction for at least 900 km, variably deformed and metamorphosed equivalents occurring inside and beneath younger orogenic belts to the south (Sveconorwegian) and north (Caledonian). The part of the province in west-central Sweden addressed here represents a far-field and shallow crustal component in this 1.7 Ga accretionary orogenic system.
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| 9. |
- Ripa, Magnus, et al.
(författare)
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Dolerites (1.27–1.25 Ga) and alkaline ultrabasic dykes (c. 1.14 Ga) related to intracratonic rifting
- 2020
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Ingår i: Sweden. - : Geological Society of London. ; , s. 315-323
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Doleritic sills, lopoliths and dykes were emplaced into the Paleoproterozoic craton in central Sweden at 1271–1264, 1259–1256 and c. 1247 Ma, a complex temporal zonation occurring in a WSW–ENE direction. The dolerites are subalkaline to alkaline and show predominantly gabbroic, with a trend towards monzogabbroic and quartz monzodioritic, compositions. Positive ɛNd and ɛHf values suggest a significant depleted mantle component in the source volume of the parental magmas. Dyke orientations indicate extension, at least locally, in a northwesterly direction, consistent with a magma flow direction determined using the anisotropy of magnetic susceptibility values. Intracratonic rifting linked to the break-up of the supercontinent Columbia, back-arc extension above a subduction boundary in a westwards-retreating mode or a mantle plume tail above a continental hotspot have all been proposed for the tectonic setting. Renewed intracratonic rifting at c. 1.14 Ga in the coastal area in northeasternmost Sweden resulted in the emplacement of alkaline ultrabasic dykes, including carbonatites (beforsites), silico-carbonatites and lamprophyres, in a north–south direction along an older shear belt. The broader tectonic setting of this extensional event is not known.
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| 10. |
- Ripa, Magnus, et al.
(författare)
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Magmatism (1.6–1.4 Ga) and Mesoproterozoic sedimentation related to intracratonic rifting coeval with distal accretionary orogenesis
- 2020
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Ingår i: Sweden. - : Geological Society of London. ; , s. 269-288
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Separate pulses of magmatic activity involving the emplacement of plutons with predominantly granitic or bimodal granitic and gabbroic composition, as well as dolerite dykes, occurred in a cratonic setting in eastern Sweden at c. 1.59–1.58 Ga, c. 1.53–1.50 Ga and c. 1.47–1.44 Ga; anorthosite, monzodiorite and syenitoid rocks are locally present. Most of the granites have been compared with rapakivi granites in Finland and elsewhere. Isotopic data (Hf in zircons and ɛNd values) from the plutons in north-central Sweden show contamination by an Archean source. Siliciclastic rocks dominated by aeolian or deltaic sandstones overlie c. 1.58 Ga or c. 1.50 Ga plutons, are intercalated with 1.46 Ga basaltic lavas and were deposited prior to the emplacement of 1.27–1.25 Ga dolerites. The magmatic rocks are subalkaline (tholeiitic) to alkaline and the mafic components have been compared with continental flood basalts, suggesting an intracratonic, rift-related tectonic setting for the magmatism and sand deposition. These rocks constitute the westerly part of a late Paleoproterozoic to early Mesoproterozoic magmatic province in northern Europe, located along roughly north–south- and WSW–ENE-trending linear belts. This tectonic development was coeval with accretionary orogenic activity further to the west and SW.
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