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  • 1.
    Almqvist, Bjarne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Björk, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. CSIRO, Mineral Resources, Bradfield Road, West Lindfield, NSW 2070, Australia.
    Mattsson, Hannes B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Bäckström, Emma
    Nordic Iron Ore, Ludvika, Sweden.
    Marsden, Paul
    Nordic Iron Ore, Ludvika, Sweden.
    Magnetic characterisation of magnetite and hematite from the Blötberget apatite-iron-oxide deposits (Bergslagen), south-central Sweden2019In: Canadian journal of earth sciences (Print), ISSN 0008-4077, E-ISSN 1480-3313, Vol. 56, no 9, p. 948-957Article in journal (Refereed)
    Abstract [en]

    Rock magnetic measurements were carried out on drill core material and hand specimens from the Blötberget apatite-iron oxide deposit in the Bergslagen ore province, south-central Sweden, to characterise their magnetic properties. Measurements included several kinds of magnetic susceptibility and hysteresis parameters. Petrographic and scanning electron microscopy (SEM) were used to independently identify and quantify the amount and type of magnetite and hematite. Two hematite-rich samples were studied with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify the trace element chemistry in hematite and investigate the potential influence of trace elements on magnetic properties. Three aspects of this study are noteworthy. 1) Hematite-rich samples display strong anisotropy of magnetic susceptibility, which is likely to affect the appearance and modelling of magnetic anomalies. 2) The magnitude-drop in susceptibility across Curie and Néel temperature transitions show significant correlation with the respective weight percent (wt%) of magnetite and hematite. Temperature dependent magnetic susceptibility measurements can therefore be used to infer the amounts of both magnetite and hematite. 3) observations of a strongly depressed Morin transition at ca -60 to -70 C (200 to 210 K) are made during low-temperature susceptibility measurements. This anomalous Morin transition is most likely related to trace amounts of V and Ti that substitute for Fe in the hematite. When taken together, these magnetic observations improve the understanding of the magnetic anomaly signature of the Blötberget apatite-iron oxide deposits and may potentially be utilised in a broader context when assessing similar (Paleoproterozoic) apatite-iron oxide systems.

  • 2. Andersson, U. B.
    et al.
    Begg, G. C.
    Griffin, W. L.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ancient and juvenile components in the continental crust and mantle: Hf isotopes in zircon from Svecofennian magmatic rocks and rapakivi granites in Sweden2011In: Lithosphere, ISSN 1941-8264, E-ISSN 1947-4253, Vol. 3, no 6, p. 409-419Article in journal (Refereed)
    Abstract [en]

    The sources of igneous rocks in the continental crust are elusive, but they may be traced by radiogenic isotopes, which convey a message about the age and composition of the concealed parts of the continent. We investigated the Hf-isotope composition of zircon in ten rocks from central and southern Sweden. Two felsic metavolcanic rocks and two metagabbros (ca. 1.89 Ga) from Bergslagen, southern Sweden, show epsilon(Hf)(t) ranges of -1.8 to +5.1 and +2.6 to +6.8, respectively, suggesting that juvenile sources have contributed to both. A 1.85 Ga granite from southern Bergslagen shows a epsilon(Hf)(t) range of -2.6 to +4.6 for magmatic zircons, but both highly negative and positive values for inherited grains, providing evidence for both Archean and juvenile crustal sources. These and previous data confirm the existence of juvenile proto-Svecofennian crust (<2.2-1.9 Ga) with a minor Archean component, from which later crustal magmas were generated. The Hf-isotope evolution curve for this crust can be approximated by epsilon(Hf)(1.90) = 3 +/- 3 and (176)Lu/(177)Hf = 0.018. Similarly, the present data, together with data for younger mafic intrusions, can be used to infer the presence of a "mildly depleted" sub-Svecofennian mantle evolution curve with epsilon(Hf)(1.90) = 4.5 +/- 2.5 and (176)Lu/(177)Hf = 0.0315. Zircons from four out of five rapakivi intrusions (1.53-1.50 Ga) in central Sweden yield negative epsilon(Hf)(t) in the range -9.8 to -4.6, suggesting mixed Archean and juvenile Svecofennian sources. One intrusion farther south ranges between epsilon(Hf)(t) of -4.1 and -1.6, and has a larger contribution from Svecofennian crust. The data suggest that the crust in Bergslagen, southern Sweden, is dominantly Paleoproterozoic, while higher proportions of Archean material are present below central Sweden.

  • 3. Bingen, B.
    et al.
    Nordgulen, O
    Sigmond, E.M.O.
    Tucker, R.
    Mansfeld, J.
    Högdahl, Karin
    Relations between 1.19-1.13 Ga continental magmatism, sedimentation and metamorphism, Sveconorwegian province, S. Norway2003In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 124, no 2-4, p. 215-241Article in journal (Refereed)
    Abstract [en]

    The Sveconorwegian and Grenville orogenic belts display widespread 1.19–1.13 Ga Early Grenvillian continental magmatism including A-type granitoids. In the Sveconorwegian province, S Norway, bimodal 1.17–1.14 Ga metavolcanic rocks of the Telemark sector are part of this magmatism. Volcanic rocks in low- to medium-metamorphic grade are interlayered with immature and locally conglomeratic clastic metasediments and covered by a thick metasedimentary sequence. Minor unconformities are reported. New zircon U–Pb data are presented and integrated in a revised stratigraphy of the Telemark supracrustal rocks. A metarhyodacite at the base of the Nore group yields a crystallisation age of 1169±9 Ma and displays 1.7–1.5 Ga inherited zircon grains (SIMS data). A metarhyolite situated below sandstone of the Heddal group yields a crystallisation age of 1159±8 Ma. In the cover sequence, a metasandstone of the Heddal group has detrital zircon grains in the intervals 2.86–2.41 and 1.94–1.11 Ga (34 analysed grains) and a metasandstone of the Kalhovd formation in the intervals 2.85–2.74 and 2.00–1.05 Ga (41 analysed grains). These metasediments were deposited after 1121±15 Ma and 1065±11 Ma, respectively and were transformed by 1.01 Ga Late Sveconorwegian deformation and metamorphism. The metasedimentary rocks contain a significant amount of regionally derived clasts. Two deformed A-type granite metaplutons yield zircon U–Pb intrusion ages of 1146±5 Ma (Eiddal) and 1153±2 Ma (Haglebu, ID–TIMS data). The 1.19–1.13 Ga magmatism is distributed in the western part of the Sveconorwegian province, in the Telemark, Bamble and Rogaland–Vest Agder sectors, indicating that these sectors were part of a single plate at that time, which is characterised by a thin lithosphere today. The A-type geochemical signature of the felsic magmatism and the continental lithosphere signature of the associated mafic volcanism point to a continental non-compressional tectonic regime. The overlap in time between widespread 1.19–1.13 Ga continental magmatism, intermontane basin formation and Early Sveconorwegian 1.15–1.12 Ga granulite-facies metamorphism recorded in the Bamble sector suggest a thermal pulse linked to upflow of asthenospheric mantle. Deposition of the cover of clastic sediments between 1.12 and 1.01 Ga possibly reflects thermal subsidence after the 1.19–1.13 Ga event and before the Late Sveconorwegian (1.03–0.95 Ga) orogenic phases. An analogy between the 1.19–1.13 Ga evolution of the Sveconorwegian province and the Cenozoic formation of the Basin and Range province in USA is discussed.

  • 4.
    Buntin, Sebastian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Malinowski, Michal
    Polish Acad Sci, Inst Geophys, Warsaw, Poland.
    Larsson, Sven Ake
    Gothenburg Univ, Earth Sci Ctr, Dept Geol, Gothenburg, Sweden.
    Thybo, Hans
    Istanbul Tech Univ, Eurasia Inst Earth Sci, Istanbul, Turkey.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Korja, Annakaisa
    Univ Helsinki, Inst Seismol, Helsinki, Finland.
    Gorszczyk, Andrzej
    Polish Acad Sci, Inst Geophys, Warsaw, Poland.
    Emplacement and 3D geometry of crustal-scale saucer-shaped intrusions in the Fennoscandian Shield2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 10498Article in journal (Refereed)
    Abstract [en]

    Saucer-shaped intrusions of tens of meters to tens of kilometres across have been observed both from surface geological mapping and geophysical observations. However, there is only one location where they have been reported to extend c. 100 km laterally, and emplaced both in a sedimentary basin and the crystalline basement down to 12 km depth. The legacy BABEL offshore seismic data, acquired over the central Fennoscandian Shield in 1989, have been recovered and reprocessed with the main goal of focusing on this series of globally unique crustal-scale saucer-shaped intrusions present onshore and offshore below the Bothnian Sea. The intrusions (c. 1.25 Ga), emplaced in an extensional setting, are observed within both sedimentary rocks (<1.5 Ga) and in the crystalline basement (>1.5 Ga). They have oval shapes with diameters ranging 30-100 km. The reprocessed seismic data provide evidence of up-doming of the lower crust (representing the melt reservoir) below the intrusions that, in turn, are observed at different depths in addition to a steep seismically transparent zone interpreted to be a discordant feeder dyke system. Relative age constraints and correlation with onshore saucer-shaped intrusions of different size suggest that they are internally connected and fed by each other from deeper to shallower levels. We argue for a nested emplacement mechanism and against a controlling role by the overlying sedimentary basin as the saucer-shaped intrusions are emplaced in both the sedimentary rocks as well as in the underlying crystalline basement. The interplay between magma pressure and overburden pressure, as well as the, at the time, ambient stress regime, are responsible for their extensive extent and rather constant thicknesses (c. 100-300 m). Saucer-shaped intrusions may therefore be present elsewhere in the crystalline basement to the same extent as observed in this study some of which are a significant source of raw materials.

  • 5.
    Buntin, Sebastian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malinowski, Michal
    Polish Academy of Sciences.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Thybo, Hans
    University of Copenhagen, Denmark.
    Buske, Stefan
    TUBAF, Germany.
    Seismic reprocessing of the BABEL lines for improved interpretation of the whole crust – preliminary results2016In: Lithosphere 2016: Ninth Symposium On Structure, Composition And Evolution Of The Lithosphere In Fennoscandia / [ed] Ilmo Kukkonen, Suvi Heinonen, Kati Oinonen, Katriina Arhe, Olav Eklund, Fredrik Karell, Elena Kozlovskaya, Arto Luttinen, Raimo Lahtinen, Juha Lunkka, Vesa Nykänen, Markku Poutanen , Eija Tanskanen and Timo Tiira, Helsinki, Finland: University of Helsinki, Institute of Seismology , 2016, p. 9-12Conference paper (Refereed)
    Abstract [en]

    This ongoing study focuses on the reprocessing of the historical BABEL (Baltic and Bothnian Echoes from the Lithosphere, 1989) seismic lines in the Bay of Bothnia in preparation for the acquisition of a 400 km long onshore reflection and refraction profile in central part of Sweden. The main aim of the project is to increase the understanding of the tectonic evolution of the mineral-rich Bergslagen region both offshore and onshore. The seismic data have been recovered and currently being reprocessed using up-to-date processing methods and preliminary results show promising outcome from this work.

  • 6. Carlsson, Torsten
    et al.
    Bråkenhielm, Carl Reinhold
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Theology, Department of Theology.
    Andersson-Skog, Lena
    Umeå universitet.
    Forsling, Willis
    Luleå tekniska universitet .
    Hilding-Rydevik, Tuija
    Sveriges Lantbruksuniversitet .
    Johansson, Lennart
    Wene, Clas-Otto
    Chalmers Tekniska Högskola.
    Harms-Ringdahl, Mats
    Stockholms universitet.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Jarstad, Anna K.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Government.
    Kunskapslägesrapport på kärnavfallsområdet 2010: utmaningar för slutförvarsprogrammet : rapport2010Report (Other academic)
  • 7.
    Eklöf, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Sveriges Geologiska Undersökning.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Michael, Setter
    Nordic Iron Ore.
    Towards a structural framework for apatite-iron oxide deposits in the Grängesberg-Blötberget area, Bergslagen, Sweden2016Conference paper (Refereed)
  • 8.
    Eklöf, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Analogue modelling of ductile deformation at ore lenses in Grängesberg, Bergslagen, Sweden2014Conference paper (Refereed)
  • 9. Högdahl, Karin
    1.86-1.85 Ga emplacement ages for K-feldspar megacryst bearing granites from the type area for the Revsund granites in Jämtland County, central Sweden2000In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 122, no 4, p. 359-366Article in journal (Refereed)
    Abstract [en]

    The type area of the coarse-grained, K-feldspar megacrystbearing Revsund granites is located in Jämtland County. These granites cover an area of c. 6.000 km2 in the western part of northern Sweden, and their emplacement ages have been established to c. 1.80 Ga from granites located outside and at the margin of the type area. Some of the rocks originally classified as Revsund granite in the southeastern part of Jämtland have later been interpreted to belong to the early Svecofennian suite. U-Pb SIMS analyses of zircon from one such rock and two Revsund granites from the type area, yield indistinguishable ages: 1854±8, 1858±9, and 1859±11 Ma, respectively. These ages are considerably older than the established age, suggesting that there either are two magmatic events forming the Revsund granites or that further K-feldspar megacryst-bearing granites in the type area must be re-classified. The ages achieved partly overlap with the ages of the 1.84–1.85 Ga, Kfeldspar megacryst-bearing Ljusdal granitoids located to the southeast. However, these rocks are metamorphosed and penetratively deformed, and have thus experienced a different tectonometamorphic evolution than have the Revsund granites in Jämtland, which are mainly isotropic outside shear zones.

  • 10. Högdahl, Karin
    et al.
    Gromet, L.P.
    Broman, C.
    Low P-T Caledonian resetting of uranium-rich Palaeoproterozoic zircons, central Sweden2001In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 86, no 4, p. 534-546Article in journal (Refereed)
    Abstract [en]

    Uranium-rich zircons from a Paleoproterozoic, high-grade deformation zone in the Fennoscandian Shield, central Sweden, show an almost complete resetting of the U-Pb system in early Phanerozoic time. A mylonitic gneiss in the deformation zone contains two types of highly discordant (>70%), U-rich zircons: large, brown, cloudy prisms, and small milky-white irregularly shaped grains. The gneiss also contains mostly clear prismatic zircon of lower U content with mildly discordant to concordant U-Pb ages. Laser Raman spectroscopy reveals that the dark cathodoluminescent areas in brown zircons have a highly metamict crystal structure, whereas the structures of both the dark cathodoluminescent milky-white grains and the bright cathodoluminescent clear prisms have higher degrees of crystallinity.

    Age dates obtained by U-Pb SIMS analysis of 40 zircons of the three types described above range continuously from concordant at 1871 ± 11 Ma to 98% discordant at 384 ± 15 Ma. The strongly discordant zircons clearly have suffered severe disturbance at about the time of the Caledonian orogeny. However, Caledonian metamorphic temperatures and pressures in this region did not exceed 150–200 °C and 1–3 kbar, too low to strongly disturb the U-Pb systematics in non-metamict zircon by thermal means alone. Independent evidence indicates that saline fluids were circulating in the Paleoproterozoic basement rocks at this time, possibly driven by hydrological gradients generated in front of the encroaching Caledonian orogenic wedge. These low-temperature saline fluids are inferred to be responsible for causing both strong Pb loss in the mostly metamict brown zircons via a diffusive process, and the formation of small milky-white zircon via a low-temperature recrystallization or dissolution/re-precipitation process.

  • 11.
    Högdahl, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, SE-75128 Uppsala, Sweden.
    Kritikos, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Sahlström, F
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Turning yesterday´s waste into tomorrow´s treasure: searching for base and critical metals in central Sweden´s ancient mine dumps2015In: Mineral Resources In A Sustainable World / [ed] A-S André-Mayer, 2015, Vol. 1-5, p. 757-760Conference paper (Refereed)
    Abstract [en]

    Mine dumps the abundant by-products of centuries of mining in Europe have potential to become sources of a wide range of metals and minerals. Despite their variable volumes and the geometallurgical challenges involved, they are a raw material resource to include among other, not least in the context of the present societal demand to increase recycling. Until the mid-1900s the applications and therefore the markets for many metals were limited. Additionally, many were difficult to identify, and thus often missed. In numerous mining districts this resulted in rocks hosting such metals to end up as waste, that is, on the mine dumps. The present pilot project is aimed at testing the potential for such secondary resources in the classic and ancient Bergslagen ore province in south central Sweden, with a special focus on metals presently identified as "critical" for industry. The Bergslagen province, with its 1000-year-history of mining is a suitable testing ground to find out what may actually be out there. Results so far include the detection and mineralogical characterisation of variable amounts of precious and critical as well as base metal minerals, along with the main ore commodity in many old mining fields.

  • 12. Högdahl, Karin
    et al.
    Jonsson, Erik
    Selbekk, Rune
    Geological relations and U-Pb geochronology of Hyttsjö granites in the Långban-Nordmark area, western Bergslagen, Sweden2007In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 129, p. 43-54Article in journal (Refereed)
    Abstract [en]

    The Hyttsjö granites occur in the extensively mineralised Långban-Nordmark area in the westernmost part of the Bergslagen ore province. They have been classified as late Svecokarelian granites due to their homogeneous and generally isotropic appearance in addition to a WR Rb/Sr age. Moreover, they have been considered as possible candidates for supplying essential metals to epigenetic mineralisation in this classic ore district. Two Hyttsjö granites yield U-Pb zircon data ages of 1791±2 and 1793±3 Ma, respectively, which overlap with emplacement ages of the adjacent 1.80-1.78 Ga Filipstad suite belonging to the Transscandinavian Igneous Belt (TIB). Mafic rocks occur quite abundantly associated with the Filipstad-type granite (sensu lato) and various types of mafic enclaves as well as hybrid rocks are present, suggesting a co-magmatic origin. Such mafic intrusives are also exposed in the vicinity of most known Hyttsjö-type plutons. Not least our observations that the former exhibit back-veining by granitic melts suggest intimate causal and temporal relationships between granite formation and mafic TIB rocks. The Hyttsjö granites were probably produced through partial melting related to the intrusion of hot, mafic magmas in and along the border between the TIB and the Svecofennian supracrustal and subvolcanic rocks. Thus, all available observations and data suggest that the Hyttsjö granites are intimately related to and most probable a product of TIB magmatism. Also, they do not lend any support for the hypothesis that the formation of the Hyttsjö granites represent a temporally separate intrusive episode. The Hyttsjö granites are therefore unlikely to be discernibly responsible for specific mineralisation in this area.

  • 13.
    Högdahl, Karin
    et al.
    Department of Geology, Lund University, Lund, Sweden.
    Lundqvist, Th.
    Discussion on “Successive ~1.94 Ga plutonism and ~1.92 Ga deformation and metamorphism south of the Skellefte district, northern Sweden: Substantiation of the marginal basin accretion hypothesis of Svecofennian evolution” by T. Skiöld and R.W.R. Rutland, Precambrian Research 148, 181-204, 20062009In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 168, no 3-4, p. 330-334Article in journal (Refereed)
  • 14.
    Högdahl, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Nilsson, K.P.
    Sjöström, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Claesson, S.
    Multiple monazite generations in migmatites and leucogranites in east central Sweden2010In: NGF, 2010, p. 79-Conference paper (Refereed)
  • 15.
    Högdahl, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Sjöström, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Persson Nilsson, Katarina
    Geol Survey Sweden, S-75328 Uppsala, Sweden.
    Claesson, Stefan
    Swedish Museum Nat Hist, Lab Isotope Geol, S-10405 Stockholm, Sweden.
    Konecny, Patrik
    Geol Survey Slovak Republ, Bratislava 81704, Slovakia.
    Reactive monazite and robust zircon growth in diatexitesand leucogranites from a hot, slowly cooled orogen: implicationsfor the Palaeoproterozoic tectonic evolution of the central Fennoscandian Shield, Sweden2012In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 163, no 1, p. 167-188Article in journal (Refereed)
    Abstract [en]

    Monazite in melt-producing, poly-metamorphic terranes can grow, dissolve or reprecipitate at different stages during orogenic evolution particularly in hot, slowly cooling orogens such as the Svecofennian. Owing to the high heat flow in such orogens, small variations in pressure, temperature or deformation intensity may promote a mineral reaction. Monazite in diatexites and leucogranites from two Svecofennian domains yields older, coeval and younger U–Pb SIMS and EMP ages than zircon from the same rock. As zircon precipitated during the melt-bearing stage, its U–Pb ages reflect the timing of peak metamorphism, which is associated with partial melting and leucogranite formation. In one of the domains, the Granite and Diatexite Belt, zircon ages range between 1.87 and 1.86 Ga, whereas monazite yields two distinct double peaks at 1.87–1.86 and 1.82–1.80 Ga. The younger double peak is related to monazite growth or reprecipitation during subsolidus conditions associated with deformation along late-orogenic shear zones. Magmatic monazite in leucogranite records systematic variations in composition and age during growth that can be directly linked to Th/U ratios and preferential growth sites of zircon, reflecting the transition from melt to melt crystallisation of the magma. In the adjacent Ljusdal Domain, peak metamorphism in amphibolite facies occurred at 1.83–1.82 Ga as given by both zircon and monazite chronology. Pre-partial melting, 1.85 Ga contact metamorphic monazite is preserved, in spite of the high-grade overprint. By combining structural analysis, petrography and monazite and zircon geochronology, a metamorphic terrane boundary has been identified. It is concluded that the boundary formed by crustal shortening accommodated by major thrusting.

  • 16. Högdahl, Karin
    et al.
    Sjöström, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Gromet, L.P.
    Character and timing of Svecokarelian, late-orogenic ductile deformation zones in Jämtland, west central sweden2001In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 123, no 4, p. 225-236Article in journal (Refereed)
    Abstract [en]

    An anastomosing pattern of NW-SE to NNW-SSE trending, ductile shear zones have affected the Precambrian bedrock in central Jämtland. Spatially these structures are related to two major shear zone systems, the Storsjön-Edsbyn Deformation Zone (SEDZ) and the Hassela Shear Zone (HSZ). Several of the local zones occur between Lake Näkten and Lake Locknesjön and coincide with linear magnetic anomalies. The dextral kinematics recorded are emphasised by clockwise rotation of early Svecofennian rocks, that partly are arranged in a large-scale C/S pattern. Three different, ductile shear zones yield U-Pb titanite ages of 1801±1, 1799±7, and 1794±3 Ma, interpreted to date the deformation. Pale titanite overgrowths, colourless titanite, and apatite yield younger U-Pb ages (c. 1.75 Ga) which argue for a tectonic reactivation of the zones, or a later thermal and/or hydrothermal event, as indicated by intrusions of cross-cutting pegmatites and felsic dykes. A hydrothermal activity during the Caledonian orogeny is recorded in one of the deformation zones. This is shown by an altered fabric containing titanites with pale outer parts which are severely discordant in a U-Pb concordia diagram with a Palaeozoic lower intercept. Sm-Nd analyses on re-precipitated zircon grains also deviate considerably from a Palaeoproterozoic trend given by other minerals in the assemblage.

  • 17.
    Högdahl, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Nilsson, K.P.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Structural evolution of the apatite-iron oxide deposit at Grängesberg, Bergslagen, Sweden2013In: Mineral deposit research for a high-tech world, p. 1650-1553Article in journal (Refereed)
  • 18.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    New evidence for the timing of formation of Bastnäs-type REE mineralisation in Bergslagen, Sweden2013In: Mineral deposit research for a high-tech world, p. 1724-1727Article in journal (Refereed)
  • 19.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Uppsala, Sweden.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    On the occurrence of gallium and germanium in the Bergslagen ore province, Sweden2019In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 141, no 1, p. 48-53Article in journal (Refereed)
    Abstract [en]

    The presence of the critical and sought-after (semi-)metals gallium (Ga) and germanium (Ge) has previously been reported from mineralisations in the Bergslagen ore province, south central Sweden. Some of these reports were however recently shown to be questionable or erroneous. Here we summarise early analytical work on these metals in mineral deposits of the Bergslagen province, as well as briefly report new analytical data for Ga and Ge from recent, in part on-going work on different mineralisation types. The new data show that the sampled sulphide and iron oxide mineralisations in the Bergslagen province are overall not particularly enriched in Ga, and even less so with regards to Ge. One major exception is the significant Ga enrichment observed in skarn-hosted Fe-REE(-polymetallic) deposits of Bastnas type. Notably, these mineralisations also host increased contents of Ge. Based on this broader suite of sampled deposits, the suggested correlation between Ga and Al contents in previously studied material with relatively increased Ga grades, is in part contradicted, indicating that Ga is only in part sequestered through straightforward Al-substitution into aluminium silicate and oxide minerals. The mineralisations that do exhibit significantly increased Ge contents, in addition to the Bastnas-type deposits, are represented by both sulphide-dominated ones and Fe (-Mn) oxide-rich systems.

  • 20.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lindeberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Roquesite and associated Indium-bearing sulphides from a Palaeoproterozoic carbonate-hosted mineralisation: Lindbom’s prospect, Bergslagen, Sweden2013In: Canadian Mineralogist, ISSN 0008-4476, E-ISSN 1499-1276, Vol. 51, no 4, p. 629-641Article in journal (Refereed)
    Abstract [en]

    The present study describes a new discovery of the copper-indium sulfide mineral roquesite (nominally CuInS2) together with indium-bearing sulfides associated with magnetite in a carbonate-hosted, polymetallic sulfide mineralization. This occurrence, Lindbom’s Prospect, is located in the western part of the Paleoproterozoic Bergslagen ore province, Sweden. Here, roquesite occurs in indium-bearing bornite, characteristically associated with indium and copper-bearing sphalerite, as well as chalcopyrite, cuproan galena, late-stage chalcocite-digenite and covellite, variable amounts of bismuth minerals, abundant magnetite, and locally cassiterite. The indium-bearing ore mineral assemblages were studied by a combination of optical and field emission scanning electron microscopy and field emission electron probe microanalyzer (FE-EPMA) techniques. FE-EPMA analyses of roquesite yield an average composition corresponding to Cu0.93Fe0.02Zn0.06In1.00S2. It occurs as ca. 4–30 micron-sized subhedral to anhedral, often angular crystals in bornite, typically in direct contact, or in close association with, indium-bearing sphalerite. The latter has variable indium content, ranging from below detection limit to at least 1.5 wt.% In, and exhibits an average of 0.03 wt.% In. Notably, sphalerite grains show a slight enrichment of indium towards the rims and the adjacent bornite, where roquesite occurs. The associated bornite, as well as minor chalcopyrite, mostly exhibit low to very low indium contents. These are mostly below detection limit, but locally higher in bornite; average 0.01 wt.% In and maximum 0.2 wt.% In. The highest indium content observed in chalcopyrite is 0.02 wt.% In. Combining textural evidence and high-resolution mineral chemical data, we suggest that roquesite formed as a consequence of reactions between diffusion-driven indium from sphalerite, and the surrounding bornite, during regional metamorphism. Based on available evidence, it is most likely that the studied assemblages represent part of a metamorphically overprinted, in part remobilized ca. 1.89–1.88 Ga volcanic-subvolcanic hydrothermal mineralization.

  • 21.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Murashko, Mikhail
    Te-Cu-rich sudburyite - the first platinum-group-element mineral from the selenide mineralisation at Skrikerum, Sweden2014In: Neues Jahrbuch für Mineralogie - Abhandlungen, ISSN 0077-7757, Vol. 191, no 2, p. 137-144Article in journal (Refereed)
    Abstract [en]

    The rare palladium mineral sudburyite occurs as a Te-Cu-rich variety [(Pd,Cu)(Sb,Te,Se,S)] in the classic selenide-rich carbonate vein deposit Skrikerum, located in the southernmost extreme of the Bergslagen ore province in south-central Sweden. This is the first observation of a platinum-group element-(PGE)-bearing mineral in this complex Cu-Ag-Tl selenide mineralisation, and to our knowledge, the first occurrence of sudburyite in a selenide vein-type deposit. Here, we report on its assemblage and mineral chemistry, based on optical, scanning electron microscope and field emission electron microprobe studies. The Te-Cu-rich sudburyite occurs at Skrikerum as euhedral to subhedral, often atoll-like, ca. 5-30 mu m-sized crystals in a selenide fracturefilling hosted by vein calcite. Based on electron microprobe analyses, its empirical formula normalised to ideal stoichiometry is (Pd0.915Cu0.132)(Sigma 1.047)(Sb0.795Te0.152Se0.004S0.002)(Sigma 0.953). The complex host assemblage comprises athabascaite (Cu5Se4), berzelianite (Cu2Se), crookesite [Cu-7(Tl,Ag)Se-4], Cu-bearing clausthalite [(Pb,Cu)Se], eucairite (CuAgSe), Se-Cu-bearing hessite [(Ag,Cu)(2) (Te,Se)], sabatierite (Cu6TlSe4) and umangite (Cu3Se2), as well as unidentified Te-Pd-Ag-Cu-bearing, most likely oxidised compounds. The associated hessite represents the first substantiated observation of a telluride in this deposit. Sudburyite from Skrikerum is Cu-, Te-, Se-and S-bearing, but in contrast to the type locality, it does not contain measurable quantities of e.g. Ni and Bi. The Skrikerum sudburyite contains highly variable amounts of Te, from ca. 2.7 wt% to over 15 wt%. Electron microprobe data show a very good correlation between Sb and Te contents (R = 0.95), which is consistent with Te substituting for Sb, forming part of an extensive but seemingly incomplete solid-solution series towards borovskite and merenskyite in the ternary Pd-Sb-Te system. Based on the general paragenesis of the deposit and the studied assemblage, we observe that the comparatively high temperatures of formation for sudburyite suggested from other studies are not applicable here. We also report previously unpublished mineral chemical data of sudburyite from another Swedish locality, Njuggtr skliden.

  • 22.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Persson Nilsson, Katarina
    Geol Survey Sweden, SE-75128 Uppsala, Sweden.
    Hellström, Fredrik
    Geol Survey Sweden, SE-75128 Uppsala, Sweden.
    Apatite-iron oxide-hosted REE mineralisation at Kopslahyttan, NW Bergslagen, Sweden2015In: Mineral Resources In A Sustainable World / [ed] A-S André-Mayer, 2015, Vol. 1-5, p. 781-784Conference paper (Refereed)
    Abstract [en]

    Of the different types of REE mineralisation known from the Fennoscandian shield, the Palaeoproterozoic apatite-iron oxide ores of Kiruna type represent one resource type with significant potential. Here we describe an REE-rich apatite-magnetite mineralisation from the classic Bergslagen ore province in south central Sweden. Associated with moderately to weakly REE-enriched magnetite mineralisation of banded and vein types, the most apatite-rich occurrence at Kopslahyttan shows REE enrichment that is similar in both magnitude and pattern to other Kiruna type deposits. Yet, the present REE mineralogy is wholly dominated by monazite-(Ce), allanite-(Ce) and LREE-enriched epidote, the latter two often occurring as zoned crystals or aggregates. Minor xenotime-(Y) also occurs, and titanite locally hosts minor Y+HREE. The abundant fluorapatite is suggested to have been an additional, original host for REE, prior to fluid-mediated alteration leading to wholesale remobilisation of REE from the apatite. This remobilisation included dissolution-reprecipitation processes that lead to the nucleation of monazite in fluorapatite, but probably also further transport and precipitation as e.g. allanite/REE-epidote, through reactions with locally common silicates. In addition, we suggest that very coarse grained, variably Th-bearing monazite present in the mineralisation may have been a primary REE phase, in marked contrast to most other deposits of this type.

  • 23.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Grön teknik slukar sällsynta metaller2012In: Forskning & framsteg, no 7, p. 34-37Article in journal (Other (popular science, discussion, etc.))
  • 24.
    Jonsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Harris, Chris
    Weis, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Nilsson, Katarina P.
    Skelton, Alasdair
    Magmatic origin of giant 'Kiruna-type' apatite-iron-oxide ores in Central Sweden2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 1644-Article in journal (Refereed)
    Abstract [en]

    Iron is the most important metal for modern industry and Sweden is by far the largest iron-producer in Europe, yet the genesis of Sweden's main iron-source, the 'Kiruna-type' apatite-iron-oxide ores, remains enigmatic. We show that magnetites from the largest central Swedish 'Kiruna-type' deposit at Grangesberg have delta O-18 values between -0.4 and +3.7%, while the 1.90-1.88 Ga meta-volcanic host rocks have d18O values between +4.9 and +9%. Over 90% of the magnetite data are consistent with direct precipitation from intermediate to felsic magmas or magmatic fluids at high-temperature (delta O-18(mgt). > +0.9 parts per thousand, i.e. ortho-magmatic). A smaller group of magnetites (delta O-18(mgt) <= +0.9 parts per thousand), in turn, equilibrated with high-delta O-18, likely meteoric, hydrothermal fluids at low temperatures. The central Swedish 'Kiruna-type' ores thus formed dominantly through magmatic iron-oxide precipitation within a larger volcanic superstructure, while local hydrothermal activity resulted from low-temperature fluid circulation in the shallower parts of this system.

  • 25.
    Majka, Jaroslaw
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Harlov, D.
    Nilsson, K.P.
    Textural relations and mineral chemistry of REE in the Grängesberg apatite-iron oxide deposit, Sweden: the role of fluids2013In: Mineral deposit research for a high-tech world, p. 1728-1731Article in journal (Refereed)
  • 26.
    Malehmir, Alireza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Dahlin, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lundberg, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Sjöström, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Reflection seismic investigations in the Dannemora area, central Sweden: insights into the geometry of polyphase deformation zones and magnetite-skarn deposits2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, p. B11307-Article in journal (Refereed)
    Abstract [en]

    The Bergslagen region is one of the most ore prospective districts in Sweden. Presented here are results from two nearly 25 km long reflection seismic profiles crossing this region in the Dannemora mining area. The interpretations are constrained by seismic wave velocity measurements on a series of rock samples, cross-dip analysis, prestack time migration, and swath 3-D imaging, as well as by other available geophysical and geological observations. A series of major fault zones is imaged by the seismic data, as is a large mafic intrusion. However, the most prominent feature is a package of east-dipping reflectors found east of the Dannemora area that extend down to at least 3 km depth. This package is associated with a polyphase, ductile-brittle deformation zone with the latest ductile movement showing east-side-up or reverse kinematics. Its total vertical displacement is estimated to be in the order of 2.5 km. Also clearly imaged in the seismic data is a steeply dipping reflector near the Dannemora mine that extends down to a depth of at least 2.2 km. The geological nature of this reflector is not known, but it could represent either a fluid-bearing fault zone or a deep-seated iron deposit, making it an important target for further detailed geophysical and geological investigations.                   

  • 27.
    Mattsson, Hannes B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geology and Mineralogy, Åbo Akademi University, Akatemiankatu 1, 20500 Turku, Finland.
    Carlsson, Matias
    Åbo Akademi University.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    The role of mafic dykes in the petrogenesis of the Archean Siilinjärvi carbonatite complex, east-Central Finland2019In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 342-343, p. 468-479Article in journal (Refereed)
    Abstract [en]

    The Archean (~2.6 Ga) Siilinjärvi carbonatite complex in east-central Finland is crosscut by a few ultramafic lamprophyre dykes, together with a broad array of more evolved mafic dykes that range in composition from foidites to various types of alkali basalts. A possible genetic link between the primitive lamprophyres and the carbonatite complex has previously been hypothesised, but their exact relations have been unclear due to the regional metamorphic overprint (i.e., greenschist facies). Here we focus on the petrology and petrography of the mafic dykes, and integrate the data to present a coherent model that can explain the genesis of the Siilinjärvi carbonatite complex. Field-relations, in combination with petrography and geochemistry, indicate that there are at least three generations of mafic dykes present. The oldest dykes (Generation I) are strongly deformed, and inferred to have been emplaced shortly after the formation of the complex itself. These dykes can be divided into two groups (i.e., ultramafic lamprophyres and Group A), where Group A comprises foidites characterised by low SiO2 (41.4–51.5 wt%) and high alkali (>10 wt% K2O) content. We interpret the foiditic magmas to have evolved from primitive ultramafic lamprophyres by fractionating a clinopyroxene-olivine dominated mineral assemblage that was devoid of feldspar. This fractionation path forced alkali-enrichment in the magmas belonging to Group A, which pushed them into the miscibility gap, and resulted in liquid immiscibility that produced moderately alkaline conjugate carbonatite(s). Subsequent fractionation of the conjugate carbonatite by predominantly calcite and apatite produced the mineralogically homogeneous carbonatite cumulate that is exposed at Siilinjärvi. Younger, less deformed, mafic dykes (belonging to Generations II and III) exhibit trace element characteristics, broadly similar to basaltic dyke swarms in the region. The younger dykes are characterised by the presence of large plagioclase crystals in thin sections. Crystallisation of a feldspar-bearing mineral assemblage resulted in only moderate enrichment of alkalis with increased fractionation, which caused the younger dykes to evolve along the more common basalt-to-trachyte series. Thus, the magmas belonging to Generations II and III at Siilinjärvi never fulfilled the conditions required to produce carbonatites by liquid immiscibility.

  • 28.
    Ogenhall, E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Sjöström, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Andersson, U.B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    The geology of the Hamrånge area, asummary of the tectonothermal evolutionin the west‐central part of the Fennoscandian Shield2010Conference paper (Refereed)
  • 29. Person, K.P.
    et al.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Weis, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Persson, L.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Skelton, A.
    The Grängesberg apatite-iron oxide deposit2013Report (Other academic)
  • 30.
    Place, Joachim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Nilsson, Katarina Persson
    Geol Survey Sweden, Uppsala, Sweden..
    Seismic characterization of the Grangesberg iron deposit and its mining-induced structures, central Sweden2015In: Interpretation, ISSN 2324-8858, E-ISSN 2324-8866, Vol. 3, no 3, p. SY41-SY56Article in journal (Refereed)
    Abstract [en]

    We have conducted a reflection seismic investigation over the apatite-iron deposit at Grangesberg in central Sweden. At the time of closure in 1989, the mine was operated using the sublevel caving method down to approximately a 650-m depth. This mining technique caused subsidence and generated a network of faults that propagated from excavated zones at depth up to the surface. The Grangesberg deposit is the largest iron oxide mineralization in central Sweden and is planned to be mined again in the coming years. It is therefore imperative to have a better understanding of the ore geometry and the fault network. A reconnaissance survey consisting of two seismic lines with a total length of 3.5 km was carried out to address these issues. The profiles intersect the Grangesberg deposit and open pit, as well as the major mining-induced fracture zone present in this area. A drop-hammer source mounted on a hydraulic truck was used to generate seismic signals; cabled and wireless receivers were used for the data recording. Preprocessing of the data first required the cable-and wirelessrecorded data sets to be merged before stacking all data available at each shot point. Source gathers exhibit reflections from the near surface, probably generated at lithological boundaries hosting the iron mineralization and other geologic structures. Deeper reflections were also observed. The metavolcanic assemblage hosting the mineralization and the anthropogenic fault network were depicted in the stacked sections, bringing in new elements to refine the geologic model of the area. This study also illustrated the ability of reflection seismic methods to delineate mining-induced structures in hard-rock environments. Low-velocity anomalies from the open pit and adjacent structures were depicted in tomographic sections along the two lines, which showed good agreement with known geologic features and the reflection seismic results.

  • 31.
    Place, Joachim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Persson-Nilsson, Katarina
    Geological Survey of Sweden.
    Reflection seismic characterization of the Grängesberg iron deposit and its mining-induced structures, central Sweden2014Conference paper (Refereed)
    Abstract [en]

    Reflection seismic investigation has been conducted on the Grängesberg apatite iron deposit. At the timeof closure in 1989, the mine was operated at about 650 m below the surface. Mining activities might beresumed in the next years, which require better understanding of (1) the ore geometry and (2) the faultnetwork which has developed up to the surface from excavated zones at depth. Two E-W orientedreflection lines with a total length of 3.5 km were acquired. The seismic lines intersect the Grängesbergore body and open pit, as well as several of the mining-induced faults. A weight drop mounted on anhydraulic bobcat truck was used as a seismic source; both cabled and wireless receivers were used for thedata recording. Preprocessing of the data first required the cable- and wireless- recorded datasets to bemerged before stacking all data available at each shot point. The dataset exhibits several shallowreflections which are likely to occur on steep lithologic or tectonic structures. Other deeper reflections arerecorded; careful processing will be carried out in order to preserve such events in final stacked sectionsand help with refining the geological model of the area.

  • 32.
    Troll, Valentin R.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Weis, Franz A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Swedish Museum Nat Hist, Dept Geosci, Frescativagen 40, S-11418 Stockholm, Sweden.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Villavagen 18,Box 670, S-75128 Uppsala, Sweden.
    Andersson, Ulf B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Luossavaara Kiirunavaara AB, Res & Dev, FK9, S-98186 Kiruna, Sweden.
    Majidi, Seyed Afshin
    Geol Survey Iran, Meraj St,Azadi Sq, Tehran 1387835841, Iran.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Åbo Akad Univ, Geol & Mineral, Domkyrkotorget 1, SF-20500 Turku, Finland.
    Harris, Chris
    Univ Cape Town, Dept Geol Sci, ZA-7701 Rondebosch, South Africa.
    Millet, Marc-Alban
    Cardiff Univ, Sch Earth & Ocean Sci, Pk Pl, Cardiff CF10 3AT, S Glam, Wales.
    Chinnasamy, Sakthi Saravanan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. NIT Rourkela, Natl Inst Technol Rourkela, Dept Earth & Atmospher Sci, Rourkela 769008, Odisha, India;Indian Inst Technol IIT Bombay, Dept Earth Sci, Mumbai 400076, Maharashtra, India.
    Kooijman, Ellen
    Swedish Museum Nat Hist, Dept Geosci, Frescativagen 40, S-11418 Stockholm, Sweden.
    Nilsson, Katarina P.
    Geol Survey Sweden, Dept Mineral Resources, Villavagen 18,Box 670, S-75128 Uppsala, Sweden;Swedish Minist Enterprise & Innovat, Div Business, Master Samuelsgatan 70, S-10333 Stockholm, Sweden.
    Global Fe-O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 1712Article in journal (Refereed)
    Abstract [en]

    Kiruna-type apatite-iron-oxide ores are key iron sources for modern industry, yet their origin remains controversial. Diverse ore-forming processes have been discussed, comprising lowtemperature hydrothermal processes versus a high-temperature origin from magma or magmatic fluids. We present an extensive set of new and combined iron and oxygen isotope data from magnetite of Kiruna-type ores from Sweden, Chile and Iran, and compare them with new global reference data from layered intrusions, active volcanic provinces, and established low-temperature and hydrothermal iron ores. We show that approximately 80% of the magnetite from the investigated Kiruna-type ores exhibit d56Fe and d18O ratios that overlap with the volcanic and plutonic reference materials (> 800 degrees C), whereas similar to 20%, mainly vein-hosted and disseminated magnetite, match the low-temperature reference samples (<= 400 degrees C). Thus, Kiruna-type ores are dominantly magmatic in origin, but may contain latestage hydrothermal magnetite populations that can locally overprint primary hightemperature magmatic signatures.

  • 33. Väisänen, Markku
    et al.
    Eklund, Olav
    Lahaye, Yann
    O'Brien, Hugh
    Fröjdö, Sören
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lammi, Marjaana
    Intra-orogenic Svecofennian magmatism in SW Finland constrained by LA-MC-ICP-MS zircon dating and geochemistry2012In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 134, no 2, p. 99-114Article in journal (Refereed)
    Abstract [en]

    We have studied plutonic rocks from the Korpo and Rauma areas of south-western Finland which can be categorized as intra-orogenic, i.e. they were intruded during a proposed extensional period between the two main Svecofennian orogenic cycles: the Fennian and Svecobaltic orogenies. The diorite from Rauma yielded an age of 1865 +/- 9 Ma and the diorite from Korpo an age of 1852 +/- 4 Ma. The adjacent garnet-bearing Korpo granite was 1849 +/- 8 Ma in age. Zircons from the granite also included inherited Archaean and older Palaeoproterozic zircons, as well as metamorphic c. 1820 Ma rims. The diorites are high-K to shoshonitic, mantle-derived magmas, rich in Fe, P, F and light rare earth elements. The Korpo granites show typical features of crustal-derived melts and form hybrids with the diorites in contact zones. Both the mantle-derived and crustal-derived intra-orogenic magmatism are considered to have had a causal effect on the subsequent late Svecofennian (Svecobaltic) thermal evolution in southern Finland which culminated in granulite facies metamorphism and large-scale crustal melting.

  • 34.
    Weis, Franz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Barker, Abigail
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Harris, C.
    Millet, M.-A.
    Nilsson, K.P.
    Iron and oxygen isotope characteristics of apatite-iron-oxide ores from central Sweden2013In: Mineral deposit research for a high-tech world, p. 1675-1678Article in journal (Refereed)
1 - 34 of 34
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