| 1. |
- Töger, Johannes, et al.
(författare)
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Blood flow imaging by optimal matching of computational fluid dynamics to 4D-flow data
- 2020
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 84:4, s. 2231-2245
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Three-dimensional, time-resolved blood flow measurement (4D-flow) is a powerful research and clinical tool, but improved resolution and scan times are needed. Therefore, this study aims to (1) present a postprocessing framework for optimization-driven simulation-based flow imaging, called 4D-flow High-resolution Imaging with a priori Knowledge Incorporating the Navier-Stokes equations and the discontinuous Galerkin method (4D-flow HIKING), (2) investigate the framework in synthetic tests, (3) perform phantom validation using laser particle imaging velocimetry, and (4) demonstrate the use of the framework in vivo. Methods: An optimizing computational fluid dynamics solver including adjoint-based optimization was developed to fit computational fluid dynamics solutions to 4D-flow data. Synthetic tests were performed in 2D, and phantom validation was performed with pulsatile flow. Reference velocity data were acquired using particle imaging velocimetry, and 4D-flow data were acquired at 1.5 T. In vivo testing was performed on intracranial arteries in a healthy volunteer at 7 T, with 2D flow as the reference. Results: Synthetic tests showed low error (0.4%-0.7%). Phantom validation showed improved agreement with laser particle imaging velocimetry compared with input 4D-flow in the horizontal (mean −0.05 vs −1.11 cm/s, P <.001; SD 1.86 vs 4.26 cm/s, P <.001) and vertical directions (mean 0.05 vs −0.04 cm/s, P =.29; SD 1.36 vs 3.95 cm/s, P <.001). In vivo data show a reduction in flow rate error from 14% to 3.5%. Conclusions: Phantom and in vivo results from 4D-flow HIKING show promise for future applications with higher resolution, shorter scan times, and accurate quantification of physiological parameters.
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| 2. |
- Lindh, Anders, et al.
(författare)
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A model for granite evolution based on non-equilibrium magma separation : evidence from the Gharib and Qattar fluorite-bearing granites, Eastern Desert, Egypt
- 2019
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Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 108:4, s. 1201-1232
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Tidskriftsartikel (refereegranskat)abstract
- We present 77 new granite whole-rock analyses from the Qattar and Gharib areas, Eastern Desert, Egypt. Both areas include a “normal” granite and either a hypersolvus (Gharib) or an almost plagioclase-free granite (Qattar) enriched in fluorite. According to earlier results, F influences element distribution in granitic melts forming complexes with specific elements as Nb, Ta, Ga, Hf, Th, Zn, Sn, whereas F excludes Ba and Sr. We use principal component analyses to split the granite into chemical groups allowing an unbiased study of the inter-group element distribution. This adds the heavy REEs and Y to the earlier lists of elements with an affinity for F. The light REEs show a decreasing affinity with decreasing atomic mass; fluorine separates Sm from Nd, whereas Zr follows La. Opposite to some, but in accordance with other earlier results, the ratio Nb/Ta is higher in the fluorite-enriched than in the other granite. Weak tetrad effects are present. Zircon in the hypersolvus granite is high in common lead. We suggest F to be instrumental for separating Pb 2+ from Pb 4+ . Two hypotheses may explain the occurrence of the two contrasting granites: they have either different sources, or they are co-magmatic, but the magma was split into two discrete types. We apply the second hypothesis as our working hypothesis. The liquidus has a gentler slope with pressure than the diapir requiring crystallisation to be most important in the lower part of the magma chamber. Our hypothesis suggests that globules of magma, enriched in volatile components, form during crystallisation due to slow diffusion rates in the crystallizing magma. Elements accompanying F are distributed into this magma batch, which has a lowered density and viscosity than the rest of the magma due to its increased contents of volatile components. A mushroom-formed diapir rises, forming the hypersolvus (or almost plagioclase-free) granite. Due to an edge effect, it is concentrated close to the wall of the magma chamber. The size and form of the outcropping granite depend on the intersection of the diapir with the erosion surface. Fluorine only makes it possible to follow the process. The model may be generalised to explain the diversification of non-F enriched granite, since the buoyancy of a magma batch several thousand m 3 in size has a much larger impact on the system than the small negative buoyancy of crystals or small crystal aggregates. A-type granite classified merely from its trace element content may form from separated F-enriched magma batches. This may be the reason for their high frequency in the Eastern Desert.
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| 3. |
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| 4. |
- Claeson, Dick
(författare)
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U-Pb zircon age of metagranite with relict phenocryst texture at Linavare, map sheet 27K Nattavaara, Norbotten county
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Norrbotten, Sweden is a key area of Europe for future exploration and mining. To establish age relations for magmatic activity and metamorphic overprinting in this area, the sampled rock was selected (Fig. 1, 2, 21). This rock occurs at Linavare as mega-xenoliths of strongly deformed, foliated, recrystallised and low-radiation metagranite in massive subvolcanic granite to rhyolite porphyry that was age determined to 1870 ± 6 Ma, giving a lower age of the high-grade metamorphic event (this issue). The age of the regional metamorphic event may be deduced from the age of these two rocks, occurring between their igneous crystallisation ages. Determine the magmatic age of the metagranite is the main aim and if the zircon display metamorphic rims or overgrowths, these should be studied too.
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| 5. |
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| 6. |
- Kathol, Benno
(författare)
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U–Pb zircon age of a granodioritic gneiss from Rimokojan at Stora Luleälven, Norrbotten County, northern Sweden
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A granodioritic gneiss from Rimokojan at Stora Luleälven north of Jokkmokk in the central part of Norrbotten County, has been dated using U–Pb SIMS analyses of zircon. The sampled gneiss occurs within a massif of granodioric to tonalitic gneisses together with strongly deformed basic dykes and intrusions of almost undeformed gabbro to diorite of the Haparanda suite. This rock association occurs in the southern part of a distinct magnetic anomaly in the area of the Muddus National Park. Analyses of oscillatory zoned zircon domains from the Rimokojan gneiss sample yielded a weighted average 207Pb/206Pb age of 2668 ± 3 Ma (2σ) which is interpreted to date the protolith at c. 2.67 Ga. This figure is similar to other age determinations of Archaean rocks in southeastern Norrbotten County (2.70–2.64 Ga). Field relations suggest that the gneiss protolith has been deformed during at least two different deformational events which both predate the emplacement of the 1.91–1.87 Ga Haparanda suite. Two analyses of low Th/U, cathodoluminescence (CL)-dark unzoned zircon rims from the same sample are interpreted to date a metamorphic event at c. 2.61 Ga.
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| 7. |
- Lynch, Edward, et al.
(författare)
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Geology, lithostratigraphy and petrogenesis of c. 2.14 Ga greenstones in the Nunasvaara and Masugnsbyn areas, northernmost Sweden
- 2018
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Ingår i: SGU Rapporter och meddelanden. - Uppsala : Sveriges geologiska undersökning. - 0349-2176. ; 141, s. 19-77
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Tidskriftsartikel (refereegranskat)abstract
- Two Palaeoproterozoic greenstone successions in the Nunasvaara and Masugnsbyn areas of north-central Norrbotten (northernmost Sweden) have been investigated to (1) characterise their primary depositional features; (2) establish lithostratigraphic correlations between both areas; and (3) gain insights into the petrogenesis of greenstone-type volcano-sedimentary successions in this sector of the Fennoscandian Shield.In the Nunasvaara area (Vittangi greenstone group), a partly conformable, polydeformed, approximately 2.4 km thick greenstone sequence mainly consists of basaltic (tholeiitic) metavolcanic and metavolcaniclastic rocks (amygdaloidal lava, laminated tuff). Intercalated metasedimentary units include graphite-bearing black schist, and pelite. The uppermost part consists of amphibolitic pelite with intercalated metacarbonate layers and rare meta-ironstone, metachert and meta-ultrabasic horizons. Numerous metadoleritic sills occur throughout the package.In the Masugnsbyn area (Veikkavaara greenstone group) a relatively conformable approximately 3.4 km thick greenstone sequence displays lithological, geochemical and geophysical characteristics similar to that at Nunasvaara. This succession consists of a dominant basaltic metatuff sequence overlain by metasedimentary units towards the top (e.g. meta-ironstone, metachert, amphibolitic schist, calcitic and dolomitic marbles). Minor metadolerite sills occur in the metatuffs. Near the base of the metatuff package, a graphitic black schist horizon occupies a similar stratigraphic position to a prominent black schist layer at Nunasvaara (here named the Nunasvaara member). This unit is a key marker horizon providing lateral correlation between both successions and also acts as a useful strain marker for reconstructing deformational events.Both greenstone successions record the effects of overprinting syn-to late-orogenic (Svecokarelian) tectonothermal events. These include complex, polyphase ductile deformation (D1 to D3 events at Nunasvaara, forming the Nunasvaara dome), peak amphibolite facies metamorphism, metasomatic-hydrothermal alteration and late-stage retrogression and brittle faulting (composite D4 at Nunasvaara). Locally, these overprinting processes formed metamorphic graphite, skarn-related Fe ± Cu and hydrothermal Cu ± Pb ± Mo mineralisation.U-Pb SIMS zircon dating of a metadolerite dyke from Nunasvaara and a metadolerite sill from Masugnsbyn have yielded mean weighted 207Pb/206Pb ages of 2 144 ±5 Ma (2σ, n = 10) and 2 139 ±4 Ma (2σ, n = 5) Ma, respectively. These precise dates constrain the timing of hypabyssal mafic magmatism, provide a minimum age for the deposition of the volcanic and sedimentary rocks, and identify a new approximetly 2.14 Ga episode of tholeiitic magmatism in this sector of the Fennoscandian Shield. Whole-rock initial εNd values for greenstone meta-igneous units range from +0.4 to +4.0 at Nunasvaara (n = 11) and +0.4 to +3.7 at Masugnsbyn (n = 7). These data indicate a juvenile depleted to partly enriched mantle (asthenospheric or lithospheric) as a major source of the tholeiitic melts. Corresponding trace element systematics have enriched mid-ocean ridge (E-MORB)-type signatures, and indicate minor assimilation of Archaean continental crust (i.e. Norrbotten craton) during magma ascent and storage. Overall, the combined geological, geochemical and isotopic characteristics of the greenstones are consistent with protolith formation within an incipient oceanic basin (epieric Norrbotten Seaway) during approximetly 2.14 Ga rifting and sagging of the Norrbotten craton.
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| 8. |
- Lynch, Edward, et al.
(författare)
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Petrological and structural character of c. 1.88 Ga meta-volcanosedimentary rocks hosting iron oxide-copper-gold and related mineralisation in the Nautanen–Aitik area, northern Sweden
- 2018
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Ingår i: SGU Rapporter och meddelanden. - Uppsala : Sveriges geologiska undersökning. - 0349-2176. ; 141, s. 107-150
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Tidskriftsartikel (refereegranskat)abstract
- The petrological and deformation characteristics of a Palaeoproterozoic meta-volcanosedimentary sequence in the Nautanen–Aitik area (near Gällivare, northern Sweden) are presented. The investigated sequence (part of the Muorjevaara group) predominantly comprises metavolcaniclastic rocks displaying variable grain size, textural and syn-depositional features (e.g. grading, cross-laminae, compositional banding). Locally, poorly sorted agglomerate-like horizons with coarser clasts (lapilli-to block-size) occur. Interbedded sections of mainly fine-grained, volcanogenic (epiclastic) metasedimentary rocks contain syn-depositional features that suggest a sub-aqueous, relatively shallow depositional environment. Locally preserved cross-laminae in this unit provide evidence of way-up and paleocurrent directions. Intercalations of pelite, mica schist and amphibolitic schist also occur throughout the sequence. In general, least altered samples indicate a predominantly intermediate (basaltic andesitic to andesitic), calc-alkaline composition for the sequence.U-Pb SIMS zircon dating of a meta-andesite horizon, intercalated within the sequence, has yielded a precise U-Pb concordia age of 1 878 ± 7 Ma (2σ, n = 12). This date constrains the timing of intermediate volcanism and the deposition of syn-volcanic epiclastic material. By inference, it also provides an estimate for the age of Muorjevaara group rocks hosting the Nautanen Cu-Au and Aitik Cu-Au-Ag deposits. When combined with lithogeochemical signatures, the new age also confirms a genetic link between the metavolcaniclastic package and gabbroic to dioritic intrusions in the area (e.g. the c. 1.88 Ga Aitik stock). Additionally, several zircon cores record 207Pb/206Pb apparent ages between c. 1.90 and 1.89 Ga, suggesting inheritance of marginally older volcanic ± plutonic material not exposed at the present erosion level.The Nautanen–Aitik area contains the roughly north-northwest-trending Nautanen deformation zone (NDZ), a major composite brittle-ductile structure hosting hydrothermal iron oxide-Cu-Au (IOCG)-style mineralisation (e.g. the Nautanen deposit). Here, the bedrock is relatively intensely altered and sheared, and has been transposed into a sub-parallel high-strain zone predominantly consisting of a composite planar penetrative fabric. Outside the high-strain zone, relatively large-scale approximately north-northwest-aligned folds and discordant brittle structures occur. Magnetic susceptibility and VLF-resistivity modelling of the NDZ confirm that composite planar structures mainly dip steeply to the west-southwest and continue at depth.
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| 9. |
- Martinsson, Olof, et al.
(författare)
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Age and character of late-Svecokarelian monzonitic intrusions in northeastern Norrbotten, northern Sweden
- 2018
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Ingår i: SGU Rapporter och meddelanden. - Uppsala : Sveriges geologiska undersökning. - 0349-2176. ; 141, s. 381-400
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Tidskriftsartikel (refereegranskat)abstract
- Palaeoproterozoic magmatism in northern Norrbotten shows a complex evolution, with several different plutonic suites ranging in age 1.93–1.70 Ga. Here we present data for three monzonitic intrusions from different parts of the area. They are petrographically and chemically similar, consisting mainly of perthite, augite and orthopyroxene, with megacrysts of poikilitic biotite as a characteristic minor component, and with high Sr and Ba. The intrusions have been dated at 1.80 Ga and may be part of a more extensive magmatic event in northern Sweden, including other chemically similar monzonitic and gabbroic intrusions, which often occur as ring dykes at the Merasjärvi gravity high (MGH) in northeastern Norrbotten. The monzonitic intrusions have A-type signatures and chemical characteristics overlapping those of rocks in arc and within-plate settings. These intrusions may thus have formed in either a back arc setting related to eastward subduction associated with the Transscandinavian Igneous Belt further west (TIB 1), or through a separate igneous event caused by a mantle plume.
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| 10. |
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