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| 2. |
- 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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| 3. |
- Nysten,, Per
(författare)
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Age of the rhyolite hosting the Ultevis Mn-Fe-Ba-As mineralisation, northern Sweden
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A feldspar-porphyric Svecofennian rhyolite associated with Mn-mineralisations at Ultevis, west of Jokkmokk, northern Sweden, has been dated to 1872 ± 9 Ma. This figure also gives a maximum age of deposition of the stratigraphically overlaying sedimentary rock sequence (the Snavva–Sjöfall group). The position of Mn-Fe-Ba-As-F-U-(W-Mo) mineralisations is discussed in relation to the transition from volcanic to sedimentary environments in the Tjåmotis–Ultevis area.
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| 4. |
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| 5. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Ling, Johan, 1968, et al.
(författare)
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Moving metals II: Provenancing Scandinavian Bronze Age artefacts by lead isotope and elemental analyses
- 2014
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Ingår i: Journal of Archaeological Science. - : Elsevier BV. - 0305-4403 .- 1095-9238. ; 41, s. 106-132
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Tidskriftsartikel (refereegranskat)abstract
- The first part of this research published previously proved without doubt that the metals dated to the Nordic Bronze Age found in Sweden were not smelted from the local copper ores. In this second part we present a detailed interpretation of these analytical data with the aim to identify the ore sources from which these metals originated. The interpretation of lead isotope and chemical data of 71 Swedish Bronze Age metals is based on the direct comparisons between the lead isotope data and geochemistry of ore deposits that are known to have produced copper in the Bronze Age. The presented interpretations of chemical and lead isotope analyses of Swedish metals dated to the Nordic Bronze Age are surprising and bring some information not known from previous work. Apart from a steady supply of copper from the Alpine ores in the North Tyrol, the main sources of copper seem to be ores from the Iberian Peninsula and Sardinia. Thus from the results presented here a new complex picture emerges of possible connectivities and flows in the Bronze Age between Scandinavia and Europe. © 2013 Elsevier Ltd.
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| 10. |
- 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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