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  • 51.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Sarlus, Zimer
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Nordin, Roger
    Boliden Mineral AB.
    Andersson, Joel
    LKAB.
    The three dimensional crustal architecture of the Aitik Cu-Au-Ag-(Mo)-deposit and the Malmberget Fe-deposit2014Konferensbidrag (Övrigt vetenskapligt)
  • 52.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Fault-controlled sedimentation in a progressively opening extensional basin: the Palaeoproterozoic Vargfors basin, Skellefte mining district, Sweden.2013Ingår i: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 102, nr 2, s. 385-400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Vargfors basin in the central part of the Skellefte mining district is an inverted sedimentary basin within a Palaeoproterozoic (1. 89 Ga) marine volcanic arc. The fault-segmented basin formed from upper-crustal extension and subsequent compression, following a period of intense sub-marine volcanism and VMS ore formation. New detailed mapping reveals variations in stratigraphy attributed to syn-extensional sedimentation, as well as provenance of conglomerate clasts associated with tectonic activity at the transition from extension to compression. The onset of fan delta to alluvial fan sedimentation associated with basin subsidence indicates that significant dip-slip displacement accommodating rapid uplift of the intrusive complex and/or subsidence of the adjacent volcano-sedimentary domain took place along a major fault zone at the southern margin of the intrusive complex. Subsidence of the Jörn intrusive complex and/or its burial by sedimentary units caused a break in erosion of the intrusion and favoured the deposition of a tonalite clast-barren conglomerate. Clast compositions of conglomerates show that the syn-extensional deposits become younger in the south-eastern parts of the basin, indicating that opening of the basin progressed from north-west to south-east. Subsequent basin inversion, associated with the accretion to the Karelian margin, involved reverse activation of the normal faults and development of related upright synclines. Progressive crustal shortening caused the formation of break-back faults accompanied by mafic volcanic activity that particularly affected the southern contact of the Jörn intrusive complex and the northern contact of the Vargfors basin

  • 53.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Syn-extensional faulting controlling structural inversion: Insights from the Palaeoproterozoic Vargfors syncline, Skellefte mining district, Sweden2011Ingår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 191, nr 3-4, s. 166-183Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Vargfors basin in the central Skellefte district, Sweden, is an inverted sedimentary sub-basin within a Palaeoproterozoic (1.89 Ga) marine volcanic arc. The sub-basin formed from upper-crustal extension and subsequent compression, following a period of intense marine volcanism and VMS ore formation. Detailed mapping and structural analysis reveals a pattern of SE–NW-striking normal faults and interlinked NE–SW-striking transfer faults, which define distinct fault-bound compartments, each with an individual structural geometry and stratigraphy. Constraints on the deformation style and mechanisms achieved by 2D forward modelling are in agreement with the previously inferred inversion of the early normal faults during a regional crustal shortening event. A rheologically weak carbonate-rich layer at the base of the sedimentary sequence favoured the fault inversion over more distributed shortening as the controlling deformation mechanism. Transposition of sedimentary strata into the approximately SE–NW faults led to formation of asymmetric synclines that were tightened during progressive shortening. Structural analysis infers a progressive opening of the basin towards SE and NW with time. Furthermore, it is inferred that a displacement gradient was developed along the main structural grain, with decreasing dip-slip displacements towards SE and NW, both during the extension and the structural inversion.VMS deposits in the vicinity of the contact between the volcanic and the overlying sedimentary rocks were formed along early normal faults, which reacted as fluid conduits. Subsequently, the deposits were transposed into the inverted faults during crustal shortening. Consequently, the inverted faults provide a useful tool for mineral exploration in the district.

  • 54.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Dehghannejad, Mahdieh
    Uppsala University.
    Tavakoli, Saman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Geological multi-scale modelling as a tool for modern ore exploration in the Skellefte mining district, Sweden2011Ingår i: Proceedings IAMG 2011 Salzburg: Mathematical Geosciences at the crossroads of theory and practice, 2011, s. 759-Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The Palaeoproterozoic Skellefte Mining District is host to abundant ore deposits. Geological 3Dmodelling was performed using the gOcad software platform. Geological methods such as field mapping, structural analysis and facies analysis combined with geophysical techniques such as reflection seismic investigations, resistivity, magnetic, electromagnetic and gravimetric studies and analysis of potential field data provide a framework for the reconstruction of the crustal geometry and geological history of the district as a tool for modern ore exploration. Results will be furthermore utilized for kinematic 4-dimensional modelling

  • 55.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hermansson, Tobias
    Boliden Mineral AB.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Correlation between distribution and shape of VMS deposits, and regional deformation patterns, Skellefte district, northern Sweden2014Ingår i: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 49, nr 5, s. 555-573Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Skellefte district in northern Sweden is host to abundant volcanogenic massive sulphide (VMS) deposits comprising pyritic, massive, semi-massive and disseminated Zn–Cu–Au ± Pb ores surrounded by disseminated pyrite and with or without stockwork mineralisation. The VMS deposits are associated with Palaeoproterozoic upper crustal extension (D1) that resulted in the development of normal faults and related transfer faults. The VMS ores formed as sub-seafloor replacement in both felsic volcaniclastic and sedimentary rocks and partly as exhalative deposits within the uppermost part of the volcanic stratigraphy. Subsequently, the district was subjected to deformation (D2) during crustal shortening. Comparing the distribution of VMS deposits with the regional fault pattern reveals a close spatial relationship of VMS deposits to the faults that formed during crustal extension (D1) utilising the syn-extensional faults as fluid conduits. Analysing the shape and orientation of VMS ore bodies shows how their deformation pattern mimics those of the hosting structures and results from the overprinting D2 deformation. Furthermore, regional structural transitions are imitated in the deformation patterns of the ore bodies. Plotting the aspect ratios of VMS ore bodies and the comparison with undeformed equivalents in the Hokuroko district, Japan allow an estimation of apparent strain and show correlation with the D2 deformation intensity of the certain structural domains. A comparison of the size of VMS deposits with their location shows that the smallest deposits are not related to known high-strain zones and the largest deposits are associated with regional-scale high-strain zones. The comparison of distribution and size with the pattern of high-strain zones provides an important tool for regional-scale mineral exploration in the Skellefte district, whereas the analysis of ore body shape and orientation can aid near-mine exploration activities.

  • 56.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Hermansson, Tobias
    Boliden Mineral AB, Luleå tekniska universitet.
    Dehghannejad, Mahdieh
    Uppsala University, Uppsala universitet, Department of Earth Sciences, Uppsala University.
    Tavakoli, Saman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Skellefte District2015Ingår i: 3D, 4D and Predictive Modelling of Major Mineral Belts in Europe, Encyclopedia of Global Archaeology/Springer Verlag, 2015, s. 93-121Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Four-dimensional geological modelling has been conducted in the Palaeoproterozoic Skellefte mining district. 3D-modelling of volcanic-hosted massive sulphide deposits and associated host-rocks has been carried out in multiple scales from deposit to regional scale and is based on a combination of geological and geophysical investigations. A conceptual model founded on unravelling the structural control on sedimentation, volcanism and mineralization and the subsequent deformation patterns, acts as a base for geological modelling. The final 3D-model provides a structural framework in which the mineralizations can be studied by improved understanding of the structural evolution in the mine areas, and by comparing the regional structural patterns versus the form and attitude of ore deposits. Additionally, uncertainty and prospectivity models were constructed showing the distribution of data and the potential of discovering new ore deposits. Subsequent 4D-modelling adds the time aspect to the 3D-models and aims at visualizing and understanding the geological history in the district and as a support for ore targeting. Moreover, adding geological time to the modelling helps gaining confidence about both the conceptual models and the 3D-models. The final 3D- and 4D-models provide a regional three-dimensional context for both industrial and academic activities in the Skellefte district, and aid the understanding of large-scale tectonic processes.

  • 57.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hermansson, Tobias
    Boliden Mineral AB.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ore body shapes versus regional deformation patterns as a base for 3D prospectivity mapping in the Skellefte Mining District, Sweden2012Konferensbidrag (Refereegranskat)
  • 58.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Hermansson, Tobias
    Boliden Mineral AB, Luleå tekniska universitet.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The comparison of ore body shapes and regional deformat patterns as a base for prospectivity mapping in the Skellefte mining district, Sweden2012Konferensbidrag (Refereegranskat)
  • 59.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Tavakoli, Saman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Dehghannejad, Mahdieh
    Uppsala University, Uppsala universitet, Department of Earth Sciences, Uppsala University.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    From deposit to regional scale: 4-dimensional geological modelling in the Skellefte Mining District, Sweden2011Konferensbidrag (Refereegranskat)
  • 60.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Tavakoli, Saman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hermansson, Tobias
    Boliden Mineral AB.
    Dehghannejad, Mahdieh
    Uppsala University.
    Juanatey, Maria Garcia
    Uppsala University.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Juhlin, Christopher
    Uppsala University.
    A regional scale 3D-model of the Skellefte mining district, northern Sweden2013Ingår i: Mineral depostits for a high-tech world: Proceedings of the 12th SGA Biennial Meeting 2013, 12-15 August 2013, Uppsala, Sweden, Uppsala: Sveriges Geologiska Undersökning , 2013, Vol. 1, s. 62-65Konferensbidrag (Refereegranskat)
  • 61.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skyttä, Pietari
    Weihed, Pär
    Allen, Rodney
    3D-modelling of the Central Skellefte District, Sweden2009Ingår i: Smart science for exploration and mining: proceedings of the 10th Biennial SGA Meeting, Townsville, Australia 17th-20th August 2009 / [ed] Patrick Williams, James Cook University of North Queensland , 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    The central part of the Palaeoproterozoic Skellefte District in northern Sweden is host to several VMS deposits. This area is dominated by upright folds with axial surfaces trending WNW - ESE. Northeast - SW trending faults crosscut WNW - ESE trending faults and impart a distinct fault pattern. Subvertical stretching as expressed by subvertical mineral lineations as well as gently W-plunging mineral lineations parallel to the F2 fold axes indicate not only significant vertical movement, but also pronounced lateral movement. The faults formed in an extensional stage and were reactivated during a compressional stage oblique to the earlier phase. This crustal shortening caused folding and development of the main foliation. Overturned, tight to isoclinal folds within the Vargfors meta-sediments coincide with 1st and 2nd order faults and are considered to be related to reactivation of the early normal and transfer faults. A three dimensional model taking into account the structures was constructed using the GoCAD 3D-modelling software.

  • 62.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Tavakoli, Saman
    Dehghannejad, Mahdieh
    Department of Earth Sciences, Uppsala University.
    Garcia, Maria
    Department of Earth Sciences, Uppsala University.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    4-dimensional geological modelling of the Skellefte district, Sweden2010Ingår i: The international archives of the photogrammetry, remote sensing and spatial information sciences, ISPRS Commission IV - Working Group 8 , 2010, Vol. XXXVIII-4, s. 93-96Konferensbidrag (Övrigt vetenskapligt)
  • 63.
    Bauer, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Crustal Scale Shear Zones Controlling Grade and Tonnage of VMS Deposits in the Skellefte District, Northern Sweden2015Ingår i: Mineral Resources in a Sustainable World / [ed] A.S. Andre-Mayer; M. Cathelineau; P. Muchez; E. Pirard; S. Sindern, 2015, s. 45-48Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Skellefte district in northern Sweden hosts abundant Paleoproterozoic, volcanic-hosted massive sulfide (VMS) deposits. The deposits formed due to pull apart basin formation in a volcanic arc setting and utilized the syn-extensional faults as fluid conduits. By comparing the structural setting in distinct structural domains with the tonnage and Cu, Au, and Ag grades a clear coupling between VMS deposits and the size of structures becomes evident. This shows how major crustal fault zones acted as fluid conduits for the ore forming hydrothermal fluids during an extensional phase. The same structures were subsequently re-activated as shear zones and possibly enhanced secondary enrichment processes.

  • 64.
    Bejgarn, Therese
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    New styles of intrusive related copper-gold deposits in northern Sweden2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The Älgträsk Au-deposit is situated in the Jörn Granitoid Complex (JGC) immediately north of the Skellefte VMS district, northern Sweden. The Skellefte VMS district comprise a complex volcanosedimentary sequence, which has been interpreted as the remnant of a Palaeoproterozoic island arc or continental margin arc situated behind a northward dipping subduction zone. The volcanosedimentary succession was intruded by the early orogenic-synvolcanic JGC, constituting I-type, calc-alkaline granitoids at c. 1.89-1.87 Ma. The outer zone of the JGC represents the oldest part and is the most compositionally heterogeneous, ranging from gabbro to granodiorite, while younger units are of a more felsic character ranging from granodiorite to granite in composition.The Älgträsk intrusive hosted Au-deposit is situated in the southern part of the oldest JGC intrusion, mainly hosted within a coarse grained, often quartz porphyritic, granodiorite. Mineralisation occurs as veins and disseminations of mainly pyrite with locally abundant arsenopyrite, chalcopyrite, sphalerite and minor electrum within a proximal silicic to phyllic hydrothermal alteration and distal propylitic hydrothermal alteration in close vicinity to deformation zones. Geochemical data suggest that hydrothermal alteration associated with mineralisation in the granodiorite caused addition of Si, Fe and K together with a significant increase in Au, Te, Cu, Zn, As and loss of Ca and Na. Gold alloys and telluride minerals such as petzite, tellurobismuthinite, krennerite, volynskite and hessite occur intergrown within fractures, along grain boundaries or as inclusions in pyrite and/or arsenopyrite and less common by together with quartz and phengite. Besides propylitic, phyllic and silicic alteration associated with mineralisation, sodic-calcic and quartz destructive alteration characterize the deposit, although with an unclear relationship to mineralisation. The tonalite hosted Tallberg porphyry Cu-deposit, situated only 3 km west of Älgträsk, is associated with quartz brecciation and quartz feldspar porphyritic dykes. These dykes are suggested to be genetically related to similar porphyry dykes overprinted by mineralisation in Älgträsk and the tonalitic host rock in Tallberg. However, the granodiorite hosting the Älgträsk Au-deposit does not appear to be genetically related to the tonalite in Tallberg or the porphyry dykes in neither Älgträsk nor Tallberg. Both styles of mineralisation are cut by mafic dykes, tentatively correlated with 1.87 Ga magmatism, hence representing the last magmatic event in the area. The mineralising fluids at Älgträsk are suggested to have been channelled by structurally weak zones in the upper crust where deposition of sulphide minerals was followed by precious metals. Structural interpretations suggest that the Au-deposit in Älgträsk is hosted by D2 and D3 structures and thus is younger than the porphyry Cu-deposit in Tallberg. Together with the style of mineralisation and associated alteration at the Älgträsk deposit, it resembles either intrusion related Au-systems or shallow level epithermal systems often developed above younger Phanerozoic porphyry Cu-deposits. Alternatively, ductile deformation took place during subsequent tectonic events, likely causing remobilization of sulphide minerals and precious metals, e.g. from a deeper lying porphyry style mineralisation, forming an orogenic style mineralisation.

  • 65.
    Bejgarn, Therese
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Älgträsk intrusion-related Au (Cu, Zn) deposit, Skellefte district, northern Sweden: Relationships between ore forming events in the Palaeoproterozoic Jörn intrusive complex2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Palaeoproterozoic intrusion hosted and intrusion related deposits such as the Älgträsk Au±Cu±Zn, Åkerberg Au, Älgliden Cu–Ni±Au, and the porphyry style Järvträsk Cu±Mo±Zn, Granberg Cu±Mo and Tallberg Cu–Au±Mo deposits are situated in the northern part of the Skellefte District, northern Sweden. These deposits are all hosted within the oldest unit of the Jörn intrusive complex (JIC). This first synvolcanic, early orogenic phase of the JIC ranges from gabbro to granodiorite in composition and shows a alc–alkaline, I–type affinity. It intruded a continental margin or island arc volcanosedimentary succession at 1.89 Ga and is spatially, temporally and possibly genetically linked to the oldest volcanic unit in the area, which hosts over 80 volcanogenic massive sulphide deposits of varying sizes. At 1.88 Ga, the JIC was intruded by quartz–feldspar porphyritic (QFP) dykes and related hydrothermal activity formed porphyry style Cu±Mo±Au deposits. A spatial relationship with coeval mafic–ultramafic intrusions, evidence for magma mingling/mixing and porphyry style mineralisation in both the southern and northern part of the JIC suggests that the formation of porphyry style mineralisation may have been triggered by the upwelling of mafic magma and partial melting at the base of the crust.While the porphyry style deposits are dominated by both sulphides in quartz stockworks and disseminated sulphides, the Älgträsk Au deposit is structurally controlled and characterised by NE–SW striking, steeply dipping zones of intense phyllic–silicic alteration enveloped by pervasive distal propylitic alteration. The mineralisation occurs both as dissemination and in veins, dominated by pyrite and locally enriched in chalcopyrite, sphalerite, arsenopyrite, Te–minerals and gold. The mineralisation overprints QFP dykes that are associated with porphyry style mineralisation in other parts of the JIC. Whole rock lithogeochemical data from Älgträsk suggest that gold is positively correlated with SiO2, K2O and Ag, Te, Bi, Fe, Cu, Zn, Mo±As, coupled with feldspar destructive alteration and Sr depletion. Early Na–Ca alteration in the north–eastern part of the Älgträsk deposit, however, shows a depletion in base and precious metals, coupled with an enrichment in Na2O, CaO and Sr, related to the formation of secondary feldspar associated with this alteration. At Älgträsk, several stages of mineralisation occur, that likely formed during one continuous hydrothermal event. Gold is associated with both early and late stages of pyrite precipitation, although one sample from the Tallberg deposit records a transition from base metal– to precious element–rich hydrothermal activity, where gold mainly is introduced early during the later stage of hydrothermal activity. Fluid inclusions associated with gold deposition at Älgträsk are aqueous and characterised by low salinity, variable CO2/H2O, homogenisation temperatures of 150–200°C and pressures corresponding to precipitation at 3–4 km depth in hydrostatic conditions. In contrast, fluid inclusion data and trace element zonation in pyrite indicate that mineralisation in the Tallberg deposit formed from two hydrothermal fluids, one similar to the fluids associated with gold from the Älgträsk deposit. However, fluid inclusions from the Tallberg deposit generally record higher homogenisation temperatures. The results indicate that the Älgträsk deposit represent a telescoping, later phase of the hydrothermal system forming the Tallberg deposit, or alternatively Tallberg represents a similar, deeper–seated porphyry system. The 3 km long, 100 m wide, NE–SW striking mafic dyke at Älgliden, dated at 1876±1 Ma, crosscuts porphyry style mineralisation at Tallberg and, hence is younger than the formation of porphyry style mineralisation. Together with U–Pb geochronology of zircon and baddeleyite from QFP dykes and the JIC units, this indicates a c. 10 Myr age difference between the spatially related VMS and intrusion related deposits in the Skellefte district. This also tentatively corresponds to the tectonic evolution of the volcanic arc where the arc during formation of the VMS deposits was under extension, while basin inversion and exhumation of the arc during later compression or transpression is coeval with the formation of intrusive hosted Au–Cu and porphyry Cu–Au deposits.

  • 66. Bejgarn, Therese
    et al.
    Nylander, Juhani
    Boliden AB.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Årebäck, Hans
    Boliden AB.
    The Älgtrask intrusive-hosted Au (-Cu) deposit, Sweden2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The Algtrask gold deposit is located in the northern part of the Skellefte mining district, northern Sweden. It constitutes a major gold and copper exploration target for the mining company Boliden Mineral AB with an inferred mineral resource of 1.6 Mt grading 3 g/t Au. The deposit is situated in the southern margin of the Jorn Granitoid Complex (JGC), a composite, I-type, calc-alkaline batholith, which intruded into an island arc or continental margin arc volcanic succession in the early Proterozoic. The area has been affected by regional metamorphism of lower greenschist facies.Mineralization occurs as veins and disseminations in meter wide, steeply dipping, sub-parallel ENE-NE striking deformation zones within a coarse grained quartz-porphyritic granodiorite. The deposit has proximal silicic/phyllic and distal propylitic alteration. The altered zones commonly show ductile deformation, and where they are sulphide bearing, form IP-anomalies. Gabbro, equigranular tonalite, quartz-feldspar porphyritic dacitic dykes, basaltic dykes, aplitic dykes, quartz-calcite veins and episyenite have been recognized close to mineralization. The quartz-feldspar porphyritic dykes are in part altered and mineralized in a similar manner to the granodiorite.Two main mineralized zones have been distinguished at Algtrask; both contain pyrite, chalcopyrite, sphalerite and arsenopyrite and minor molybdenite, bornite, pyrrhotite, magnetite, gold and tellurides (e.g. petzite, hessite, altaite, coloradoite). Traces of native silver and bismuth have also been observed. The gold occurs as electrum (ca 80% Au) and calaverite closely associated with other tellurides. Gold and tellurides commonly occur as inclusions or in fractures in pyrite, within quartz-calcite veins or zones of phyllic-silicic alteration. Thicker bands of arsenopyrite are common in the southern zone, but do not occur in the northern zone, which suggests that the chemistry and sulphur fugacity of the ore forming fluids were different in the two mineralised zones.The Tallberg porphyry copper deposit is situated only 3 km west of Algtrask. Tallberg is characterized by quartz stockworks with disseminated pyrite, chalcopyrite, pyrrhotite and magnetite, hosted in propylitic and phyllic altered equigranular tonalite of the JGC. The similar settings, alteration and close spatial relationship, suggest a genetic link between the two deposits. The Algtrask deposit might represent a higher level epithermal system genetically linked to the Tallberg porphyry system. Ductile deformation took place during subsequent tectonic events, probably causing remobilization of sulphides and precious metals. Alternatively, a syntectonic model can be proposed in which the Algtrask deformation zones have overprinted an earlier porphyry copper system. In this model, syntectonic hydrothermal fluids may have "leached" gold from the earlier porphyry system during deformation and deposited gold in the deformation zones.

  • 67.
    Bejgarn, Therese
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Söderlund, Ulf
    Lunds universitet.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Årebäck, Hans
    Boliden Mineral AB.
    Ernst, Richard E.
    Carleton University, Ottawa.
    Palaeoproterozoic porphyry Cu-Au, intrusion-hosted Au and ultramafic Cu-Ni deposits in the Fennoscandian Shield: temporal constraints using U-Pb geochronology2013Ingår i: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 174, s. 236-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Skellefte district, northern Sweden, is known for the occurrence of 1.89 Ga Palaeoproterozoic volcanogenic massive sulphide (VMS) deposits. The deposits are hosted by the older part of a volcanosedimentary succession, which was intruded at 1.88-1.86 Ga by multiple phases of the syn-volcanic, early orogenic Jörn intrusive complex (JIC). The oldest phase of the JIC hosts different styles of mineralisation, among them porphyry Cu-Mo-Au, intrusion-related Au, and mafic-hosted Fe and Cu-Ni deposits. To discriminate between the different intrusive and ore related events, U-Pb ages of zircons have been obtained for nine intrusive phases and from Na-Ca alteration spatially related to mineralisation, while U-Pb ages of baddeleyite (ZrO2) have been used to constrain intrusive ages of three mineralised and barren mafic-ultramafic intrusive rocks.The two main JIC intrusive phases of a granodioritic-tonalitic composition in the southern study area intruded at 1887 ± 3 Ma and 1886 ± 3 Ma, respectively, and were succeeded by the intrusion of layered mafic-ultramafic intrusive rocks in the northern and southern study area at 1879 ± 1 Ma and 1884 ± 2 Ma, respectively. Emplacement of porphyry dykes took place at ca. 1877 Ma in the southern, western and northern JIC. The dykes are spatially and temporally associated with formation of porphyry style mineralisation, alteration and Au-mineralisation, as inferred from 1879 ± 5 Ma zircons in adjacent Na-Ca alteration zones. High SiO2 and Al2O3 content together with high Sr/Y ratios, mingling structures, mafic xenoliths and hornblende phenocrysts in the porphyry dykes suggest that the magma originated from hydrated partial melts, possibly from the base of the crust at a mature stage of subduction. Local extension resulted in intrusion of mafic-ultramafic rocks around 1.88 Ga prior to and after, the porphyry dykes and associated mineralisation, approximately 10 Ma after the formation of the spatially related 1.89 Ga VMS deposits in the Skellefte district. This 1.88 Ga event correlates with other 1.88 Ga mafic-ultramafic units widespread around the world, and could possibly be interpreted as a large scale response to supercontinent formation.

  • 68.
    Bejgarn, Therese
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Broman, Curt
    Stockholm University.
    Söderlund, Ulf
    Lund University.
    Large, Ross
    University of Tasmania.
    Årebäck, Hans
    Boliden Mineral AB.
    Nylander, Juhani
    Boliden Mineral AB.
    The Älgträsk Au±Cu deposit, northern Sweden: a Palaeoproterozoic porphyry-related hydrothermal system?2011Konferensbidrag (Refereegranskat)
  • 69.
    Bejgarn, Therese
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Nylander, Juhani
    Boliden Mineral AB.
    Årebäck, Hans
    Boliden Mineral AB, Earth Sciences Centre – Geology, Göteborg University.
    Söderlund, Ulf
    Lund Universitet, Department of Geology, GeoBiosphere Science Centre, Lund University.
    Ernst, Richard E.
    Geological Survey of Canada, Carleton University, Ottawa.
    Tectonomagmatic aspects of intrusive hosted Cu-Au-Mo deposits in the Skellefte District, northern Sweden2013Ingår i: Mineral deposit research for a high-tech world: proceedings / [ed] Erik Jonsson, Uppsala: Sveriges Geologiska Undersökning , 2013, s. 770-773Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Algtrask gold deposit and several low grade base metal deposits, e.g. the Tallberg porphyry deposit, are hosted by the Jam intrusive complex in the northern part of the Skellefte District, northern Sweden. The intrusive complex was emplaced at 1.89-1.86 Ga in a continental margin volcanic arc setting, and the oldest 1.89 Ga phase is coeval with volcanic rocks within the Skellefte Group, a complex volcano-sedimentary succession hosting numerous VMS deposits. The intrusive hosted deposits are associated with 1.88 Ga quartz-feldspar porphyritic intrusive rocks, which formed from 1.89 Ga recycled crust. Hence, it is interpreted that the intrusive hosted deposits formed when the arc was under transpression-compression, 10 Myr after the spatially related VMS deposits, which formed when the arc was under extension.

  • 70.
    Bejgarn, Therese
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Årebäck, Hans
    Boliden Mineral AB.
    Nylander, Juhani
    Boliden Mineral AB.
    Intrusion-related mineralization in the Palaeo-proterozoic Jörn Granitoid Complex, northern Sweden2009Ingår i: Smart science for exploration and mining: proceedings of the 10th Biennial SGA Meeting, Townsville, Australia, 17th-20th August 2009 / [ed] Patrick Williams, James Cook University of North Queensland , 2009, s. 921-923Konferensbidrag (Refereegranskat)
    Abstract [en]

    Immediately north of the Skellefte mining district, northern Sweden, the early orogenicsynvolcanic Jörn granitoid complex hosts several mineral deposits. The Jörn granitoid batholith intruded into a continental margin arc or island arc volcanic succession during the early Proterozoic, and comprises a composite, I-type, calc-alkaline batholith, ranging from granite to gabbro in composition. Several mineral deposits occur in the heterogeneous margin of the complex, i.e. the Tallberg porphyry Cu-Au-Mo, the Älgträsk Au and the Älgliden Ni-Cu-Au deposits in the south and the Näsberg Fe±PGE and Granberg porphyry Cu mineralization in the north. The known deposits indicate that the intrusion is fertile for further exploration activities and that Palaeoproterozioc synvolcanic intrusions close to VMS districts should be studied more closely to further develop genetic models which can be used to reconstruct the ore forming environments and tectonic evolution. This knowledge might be used as guidelines when exploring for new districts with economic potential in Palaeoproterozoic terrains.

  • 71. Bejgarn, Therese
    et al.
    Årebäck, Hans
    Boliden Mineral AB.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Nylander, Juhani
    Boliden Mineral AB.
    Geology, petrology and alteration geochemistry of the Palaeoproterozoic intrusive hosted Ägträsk Au deposit, Northern Sweden2011Ingår i: Geological Society Special Publication, ISSN 0305-8719, E-ISSN 2041-4927, nr 350, s. 105-132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Ägträsk intrusive hosted Au deposit, Skellefte district, northern Sweden, is situated in the oldest, most heterogeneous part of the c. 1.89-1.86 Ga Jörn granitoid complex, which intruded a complex volcano-sedimentary succession in an island arc or continental margin arc environment. The Tallberg porphyry Cu deposit, situated only 3 km west of Ägträsk, is associated with quartz feldspar porphyritic dykes. These dykes are suggested to be genetically related to similar porphyry dykes in Älgträsk and the tonalitic host rock in Tallberg. The granodiorite hosting the Ägträsk Au-deposit does not appear to be genetically related to the tonalite or the porphyry dykes.

  • 72.
    Bender, H.
    et al.
    Department of Geological Sciences, Stockholm University, Stockholm, Sweden.
    Ring, U.
    Department of Earth Sciences, Geophysics, Uppsala University, Uppsala, Sweden.
    Almqvist, B.S.G.
    Department of Earth Sciences, Geophysics, Uppsala University, Uppsala, Sweden.
    Grasemann, B.
    Department of Geodynamics and Sedimentology, University of Vienna, Vienna, Austria.
    Stephens, Michael B.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Metamorphic Zonation by Out‐of‐Sequence Thrusting at Back‐Stepping Subduction Zones: Sequential Accretion of the Caledonian Internides, Central Sweden2018Ingår i: Tectonics, ISSN 0278-7407, E-ISSN 1944-9194, Vol. 37, nr 10, s. 3545-3576Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Exhumation of the high‐grade metamorphic Seve Nappe Complex and its emplacement between lower‐grade nappes has been related to wedge extrusion in the central Scandinavian Caledonides. To test this hypothesis, the kinematic evolution of the Caledonian nappe pile is studied by systematic structural mapping in central and northern Jämtland, Sweden. Structural data, combined with petrological and quartz microstructure observations, document pervasive top‐to‐the‐ESE, foreland‐directed shearing under progressively decreasing metamorphic grade across the entire nappe pile. Mylonitic foliation, foliation‐parallel boudinage, and abundant top‐to‐the‐ESE and rare, scattered top‐to‐the‐WNW shear‐sense indicators imply foreland‐directed general shear. This deformation regime caused exhumation by concurrent thrusting and vertical ductile thinning. We propose a specific succession of in‐ and out‐of‐sequence thrusts that generated the metamorphic zonation. Our model envisions in‐sequence propagation of thrusts during exhumation of the Seve Nappe Complex, related to subduction of Baltica beneath a volcanic arc within Iapetus. Concurrently, Iapetus subducted beneath Laurentia farther to the west. When Iapetus was closed, Baltica subduction stepped westward and continued beneath Laurentia. The back stepping of subduction at the onset of continental collision caused out‐of‐sequence propagation of the orogenic wedge. Thrusting cut downsection across the existing tectonostratigraphy, emplacing units of lower metamorphic grade above the high‐grade Seve Nappe Complex. This imbrication generated the present metamorphic zonation of the Caledonian nappe pile during sustained convergence between Laurentia and Baltica.

  • 73. Berggren, Robert
    et al.
    Sandrin, Alessandro
    Elming, Sten-åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Physical properties of rocks and geophysical data as tools for targeting Fe-oxide Cu-Au mineralisations in northern Sweden2004Ingår i: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 85, nr 47Artikel i tidskrift (Övrigt vetenskapligt)
  • 74. Berglund, J.
    et al.
    Bergström, U.
    Bolvede, P.
    Bäck, J.
    Egagha, E.
    Grönberg, H.
    Lindberg, E.
    Nilsson, S.
    Nömtak, V.
    Olsson, E.
    Tillman, K.
    Weihed, Pär
    A petrological study of an east-west vertical crossection, Oia harbour, Thea (Santorini), Greece1983Rapport (Övrigt vetenskapligt)
  • 75. Berglund, J.
    et al.
    Bergström, U.
    Bolvede, P.
    Bäck, J.
    Egagha, E.
    Grönberg, H.
    Lindberg, E.
    Nilsson, S.
    Nömtak, V.
    Olsson, E.
    Tillman, K.
    Weihed, Pär
    Tektonisk och bergmekanisk studie över Nordön, södra Bohuslän1983Rapport (Övrigt vetenskapligt)
  • 76. Bergman, J.
    et al.
    Bergström, U.
    Weihed, Pär
    Genesis and structural evolution of early Proterozoic gold lode deposits in the Skellefte district, northern Sweden1989Ingår i: Abstracts: 28th International geological congress, 1989, Vol. 3, s. 459-460Konferensbidrag (Övrigt vetenskapligt)
  • 77.
    Bergman, J.
    et al.
    Uppsala University.
    Weihed, Pär
    Shear zones in the Proterozoic rocks of northern Västerbotten1993Ingår i: Ductile shear zones in the Swedish segment of the Baltic Shield: workshop : abstracts / [ed] Carl-Henric Wahlgren, Uppsala: Sveriges Geologiska Undersökning , 1993, s. 7-Konferensbidrag (Övrigt vetenskapligt)
  • 78. Bergman, J.
    et al.
    Weihed, Pär
    Volcanotectonic evolution of the central part of the early Proterozoic Skellefte volcanic arc, northern Sweden1989Ingår i: 28th international geological congress: Abstracts, 1989, Vol. Vol. 28, s. 135-Konferensbidrag (Övrigt vetenskapligt)
  • 79.
    Bergman, Stefan
    et al.
    Sveriges Geologiska Undersökning.
    Kubler, Lutz
    Sveriges Geologiska Undersökning.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Synthesis bedrock maps of northern Norrbotten, Sweden1998Ingår i: Abstracts volume: 23. Nordiske Geologiske Vintermøde, 13-16 January, Århus, 1998 / [ed] J. Richard Wilson, Århus: Århus university , 1998, s. 31-Konferensbidrag (Övrigt vetenskapligt)
  • 80.
    Bergman, Stefan
    et al.
    Geological Survey of Sweden.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Martinsson, Olof
    Eilu, Pasi
    Geological Survey of Finland.
    Geological and tectonic evolution of the northernpart of the Fennoscandian Shield2007Ingår i: Metallogeny and tectonic evolution of the Northern Fennoscandian Shield: field trip guidebook, Espoo: Geological Survey of Finland , 2007, s. 6-15Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 81.
    Bergström, U.
    et al.
    Sveriges Geologiska Undersökning.
    Lundin, I. Antal
    Sveriges Geologiska Undersökning.
    Winnes, K.
    Sveriges Geologiska Undersökning.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Berggrundskartan 23J Norsjö NO2003Övrigt (Övrigt vetenskapligt)
  • 82.
    Bergström, U.
    et al.
    Sveriges Geologiska Undersökning.
    Lundin, I. Antal
    Sveriges Geologiska Undersökning.
    Winnes, K.
    Sveriges Geologiska Undersökning.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Berggrundskartan 23J Norsjö SO2003Övrigt (Övrigt vetenskapligt)
  • 83.
    Bergström, U.
    et al.
    Sveriges Geologiska Undersökning.
    Lundin, I. Antal
    Sveriges Geologiska Undersökning.
    Winnes, K.
    Sveriges Geologiska Undersökning.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Berggrundskartan 23J Norsjö SV2003Övrigt (Övrigt vetenskapligt)
  • 84.
    Bergström, U.
    et al.
    Sveriges Geologiska Undersökning.
    Lundin, I. Antal
    Sveriges Geologiska Undersökning.
    Winnes, K.
    Sveriges Geologiska Undersökning.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Berggrundskartan Norsjö 23J NV2003Övrigt (Övrigt vetenskapligt)
  • 85.
    Bergström, U.
    et al.
    University of Gothenburg.
    Weihed, Pär
    Structural aspects of some gold mineralizations in the Skellefte District, northern Sweden1991Ingår i: Geologiska föreningens i Stockholm förhandlingar, ISSN 0016-786X, Vol. 113, nr 1, s. 42-44Artikel i tidskrift (Refereegranskat)
  • 86.
    Bhardwaj, Anshuman
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Identification and Mapping of Glacier-Like Forms (GLFs) Near Martian Subpolar Latitudes2016Konferensbidrag (Refereegranskat)
  • 87.
    Billström, K.
    et al.
    Dep. of Geological Sciences, Swedish Museum of Natural History, Stockholm, Sweden.
    Evins, P.
    WPS Consulting Group, Stockholm, Sweden.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jeon, H.
    Dep. of Geological Sciences, Swedish Museum of Natural History, Stockholm, Sweden.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Conflicting zircon vs. titanite U-Pb age systematics and the deposition of the host volcanic sequence to Kiruna-type and IOCG deposits in northern Sweden, Fennoscandian shield2019Ingår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 321, s. 123-133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Northern Norrbotten region, and in particular the Kiruna area, hosts a number of large apatite iron oxide deposits (e.g. the huge Kiirunavaara ore) of significant economic importance. Age data from rock lithologies hosting these ores, represented by metamorphosed rocks of the Porphyrite and Kiirunavaara Groups, are complex to interpret. This is illustrated by (LA-ICP-MS) data for titanite, and to some extent for rutile, which scatter considerably yielding ages within a span from ca. 2.1 Ga to 1.7 Ga. These analysed hydrothermal minerals, characterized by complex BSE images revealing darker and brighter zones, are located in ore zones and associated with e.g. strong scapolitisation, albitisation and actinolitisation. Previous (TIMS) zircon ages of host rocks, on the other hand, define a more narrower age interval between ca. 1900 and 1870 Ma, and this is supported by new U-Pb zircon results presented here. Furthermore, one coherent set of SIMS data for titanite from the Luossavaara ore favour that crystallization took place at ca 1.88 Ga, although laser ICP data from the same locality are much more complex. An implication arising from published pre-1.9 Ga laser ablation ages for titanites is that the emplacement of host rocks started already at around 2.1 Ga. As the depositional time of these rocks is crucial for the understanding of the overall crustal formation in northern Norrbotten, additional rocks were selected for age dating. New zircon age data (LA-ICP-MS and SIMS) give support to a scenario where host rocks to ores started to develop at around 1900 Ma and this calls for a re-evaluation of published LA-ICP-MS data of hydrothermal mineral phases.

    Here, we present four models that aim to explain how pre-1.9 Ga titanite ages, believed to have a questionable geological significance, may develop. The principal idea is that ≤2.1 Ga alteration events were not responsible for the crystallization of the hydrothermal minerals, instead it is believed that apparent old age domains carry excess radiogenic lead due to the effect of ≤1.9 Ga hydrothermal processes. Currently, the interpretation of U-Pb isotope data in the study area remains enigmatic, and further radiometric analyses are required.

  • 88.
    Billström, Kjell
    et al.
    Swedish Museum of Natural History.
    Bergman, Stefan
    Geological Survey of Sweden.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Post-1.9 Ga metamorphic, mineralization and hydrothermal events in northern Sweden2002Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 124, nr 4, s. 228-228Artikel i tidskrift (Refereegranskat)
  • 89.
    Billström, Kjell
    et al.
    Museum of Natural History.
    Eilu, Pasi
    Geological Survey of Finland.
    Martinsson, Olof
    Niiranen, Tero
    Geological Survey of Finland.
    Broman, Curt
    Stockholm University.
    Weihed, Pär
    Wanhainen, Christina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ojala, Juhani
    Geological Survey of Finland.
    IOCG and related mineral deposits of the northern Fennoscandian Shield2011Ingår i: Hydrothermal iron oxide copper-gold & related topics: a global perspective, Adelaide: PGC Publishing , 2011, s. 381-414Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The northernmost Fennoscandian shield comprises Archaean and Palaeoproterozoic rocks. Unlike most other shield areas, economic mineral deposits are largely restricted to its Palaeoproterozoic parts. The latter are characterised by intracratonic basin evolution between ca. 2.5 and 2.0 Ga, involving recurrent mantle hotspot activity with numerous layered intrusions, komatiite and picrite eruptions, but no signs of accretionary phases or formation of major new felsic crust. Accretion and continent-continent collision followed from ca. 1.9 to 1.8 Ga, during the Svecofennian orogeny. A range of mineralisation styles are hosted by extensive ca. 2.5 to 2.0 Ga greenstone belts and younger, subduction-related 1.9 to 1.8 Ga Svecofennian intrusive and extrusive settings. These mineralisation styles partially overlap, and individual deposits may not readily be placed into genetic classification schemes. A provisional grouping of observed mineralisation styles comprises (1) stratiform-stratabound sulphide, (2) apatite-iron, (3) skarn-related iron and BIF, and (4) epigenetic(±syngenetic?) Au and Cu-Au deposits. The descriptive section of this paper also highlights features that may relate to orogenic-gold, IOCG and 'atypical metal association' categories of mineralisation. The assumption made is that the deposition of a diverse range of ore deposits was made possible by a long and complex geological evolution. This involved an initial (sowing) stage where iron, and to some extent copper and gold, were concentrated during 2.3 to 2.1 Ga (Karelian) rock-forming processes. Following this, ore elements were mobilised during two younger (Svecofennian) stages at 1.92 to 1.87 and 1.85 to 1.79 Ga, respectively. The latter were triggered by metamorphic and magmatic episodes, and fluids liberated during these stages precipitated IOCG and related deposits when fluids met structural and chemical traps in suitable host rocks. Ore fluids are generally saline, and their development probably involved incorporation of evaporates and, at least locally, also felsic magmatism may have played a role. Skarn-related mineralisation, hosted by ca. 2.1 Ga greenstones, occurs both as a BIF type in Sweden (formed at around 2.1 Ga), and as a gold-copper enriched variety (the result of Svecofennian epigenetic processes) in the Kolari region of Finland. The huge Kiirunavaara deposit is the type example of apatite iron ores, and is here considered to have formed from a magma at ca. 1.88 Ga, although it also has features best explained by a magmatic-hydrothermal overprint. A younger, less prominent, stage of apatite iron ore formation took place at approximately 1.78 Ga. Epigenetic gold and copper-gold deposits are particularly hard to classify as these show mixed ore characteristics, and to some extent this is likely to be due to multiple mineralisation stages (cf. the huge, low grade Aitik deposit in Sweden which is interpreted to be a hybrid porphyry-IOCG-type of ore). Structurally controlled, orogenic-gold mineralisation is common in the Central Lapland greenstone belt, although there are also gold deposits with enhanced contents of e.g., copper, cobalt and uranium (e.g., at Saatopoora). The latter, sometimes referred to as being of an 'atypical metal association' type, could potentially also include syngenetic mineralisation (e.g., at Juomasou). The range of epigenetic (±syngenetic) gold and copper-gold deposits could possibly be related to a vague east-west trend defined by gold-rich deposits in the east (Finland), followed by IOCG (copper±gold) and more iron-dominant ore types near the Finnish-Swedish border and further west into Sweden.

  • 90.
    Billström, Kjell
    et al.
    Swedish Museum of Natural History.
    Weihed, Pär
    Age and provenance of host rocks and ores in the Paleoproterozoic Skellefte District, northern Sweden1996Ingår i: Economic geology and the bulletin of the Society of Economic Geologists, ISSN 0361-0128, E-ISSN 1554-0774, Vol. 91, nr 6, s. 1054-1072Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Skellefte district in northern Sweden is a ca. 1.9 Ga, extensively mineralized, mainly felsic, submarine volcanic belt. Within the district, the volcanic rocks (Skellefte Group) are overlain by turbiditic sedimentary rocks and coarser clastic rocks, as well as younger, mainly mafic, volcanic rocks (Vargfors Group). To the north, subaerial volcanic rocks of the Arvidsjaur Group are probably coeval with the Vargfors Group. The sedimentation in the Bothnian basin, south of the Skellefte district, appears to have started at ca. 2.0 Ga and continued until ca. 1.86 Ga, as indicated by the presence of granitoids spanning this time interval. The first main magmatic episode in the Skellefte district was a felsic stage at around 1.89 Ga as confirmed by two new U-Pb zircon ages from volcanic rocks situated in the central and eastern part of the district (Bjurvattnet, 1884 + or - 6 Ma; Melestj rn, 1889 + or - 4 Ma). No basement is known to the felsic magmatism, but granitoids occurring to the south of the district, which have been dated at 2.0 to 1.9 Ga, could constitute remnants of a basement which was destroyed by 1.89 Ga arc volcanism within the Skellefte district. The Vargfors Group overlies the Skellefte Group with no major unconformity, and one new age from an ignimbrite in the Vargfors Group (1875 + or - 4 Ma) confirms the temporal relationship with the deposition of subaerial volcanic rocks of the Arvidsjaur Group.An evaluation of age data for the early, synvolcanic (ca. 1890 Ma) Joern-type granitoids suggests that these should be further subdivided. Three different generations of Joern-type granitoids may exist. The GI phase has an age of about 1.89 Ga, the GII and GIII phases within the major Joern batholith probably formed at around 1.87 Ga, and the Siktr sk intrusion in the southern part of the district, has a crystallization age of ca. 1.86 Ga.A number of distinctive isotopic characteristics have been observed, e.g., significant data scatter for Sr whole-rock data, reversely discordant zircon data, and unusually young lower intercept ages for zircon discordia. These features seem to relate preferentially to volcanic rocks, and it is suggested that this behavior is due to Phanerozoic hydrothermal processes that have mobilized elements at different scales. Upper intercepts for zircon discordia, however, are with one exception thought to represent true crystallization ages. The 1847 + or - 3 Ma age for a mass flow at Petiktr sk, as defined by a three-point discordia, is for geologic reasons too young, but a considerably higher (super 207) Pb/ (super 206) Pb age at 1890 Ma for one zircon fraction is more consistent with the field relationships.Volcanic-hosted massive sulfide ores occur in the upper part of the volcanic sequence of the Skellefte Group and, in some cases, also in the lower part of the Vargfors Group. A good approximation of the age of massive ore formation is provided by the age of the host rocks. It is suggested that two main depositional stages of massive ore occurred at ca. 1885 to 1880 Ma and at ca. 1875 Ma. Gold occurs in two principal settings, as a constituent in the volcanic-hosted massive sulfide ores, and related to quartz veins found both in intrusive and supracrustal rocks. In the massive ores, gold was probably emplaced in connection with the hydrothermal processes which concentrated the base metals. Gold in some major intrusive-related Au deposits (e.g., Bjoerkdal) is likely to have concentrated at a premetamorphic stage, tentatively at 1.87 Ga, and still other Au ores (e.g., Boliden) may be epithermal in origin and were possibly formed at a relatively late stage at ca. 1.85 Ga. Later, during peak metamorphic conditions, some mesothermal Au-As vein deposits (e.g., Grundfors) formed at ca. 1.84 to 1.82 Ga.

  • 91.
    Björklund, Lennart
    et al.
    Gothenburg University.
    Weihed, Pär
    Geochemistry and tectonic setting of the Orvar Hill mafic volcanic rocks of the Tiveden area, south-central Sweden1997Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 119, nr 2, s. 127-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Orvar Hill formation in Tiveden, south-central Sweden, constitutes a unique low-strain window of well preserved Svecofennian mafic volcanic rocks on the southwestern border of the Svecokarelian orogen. The area can be considered as the southwestern border of the Bergslagen region of the Svecokarelian orogen. The Orvar Hill formation consists of coherent pillowed and non-pillowed basalts alternating with mafic volcaniclastic racks in the lower part of the Lindberga supracrustal succession. Only minor felsic volcanic rocks occur in the upper part. Quartz-bearing metagreywackes comprise the top part of the Lindberga supracrustal succession. Geochemistry of lavas and volcaniclastic rocks suggests that the Orvar Hill mafic volcanic rocks were emplaced in a volcanic-are setting. This demonstrates that the Tiveden supracrustal units probably formed in response to volcanism related to subduction. The Tiveden area may thus represent a 1.89 Ga primitive, sediment-starved volcanic are at the margin of the continental volcanic are of the Bergslagen district. The relationship between Tiveden and Bergslagen at the time of formation is not clear and Tiveden may represent a remnant of an are that accreted to a continent at c. 1.88-1.86 Ga.

  • 92.
    Boström, Kurt
    et al.
    Luleå tekniska universitet.
    Widenfalk, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    The origin of iron-rich muds at the Kameni Islands, Santorini, Greece1984Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 42, nr 1-4, s. 203-218Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrothermal sediments form in several places within the Santorini caldera. The sediments at the most active hot submarine spring (at SW Nea Kameni) consist of 40-48% Fe2O3 and 8-15% SiO2, but only little Al2O3 (0.5-1.6%), P (0.1-0.3%), Mn (100-450 ppm), Sr, Zr, Ba, Zn and V (∼30-200 ppm) and Cu, Ni and Y (∼ 1-30 ppm) are present. The sediments contain more Fe and P and less Si, Al, Mn and many trace elements than sediments formed at less active springs at Palaea Kameni; the differences probably being caused by faster deposition rates of Fe at Nea Kameni and less dilution by rock detritus, which delivers Al, Si and Mn. The Santorini sediments differ much from other exhalative sediments at present or old spreading centers, for example on the East Pacific Rise, in the Red Sea or at En Kafala, which are rich in Mn, Cu, Zn, Ni and Ba. Hydrothermal rock leaching probably occurs at much lower pH-values at Santorini than on the East Pacific Rise, causing a more complete breakdown of the leached rock at Santorini. The very low trace element to iron ratios in the rocks at Santorini, therefore, prevent the hydrothermal solutions there from being very rich in trace elements. The very acid leaching solutions at Santorini are created by extensive oxidation of hydrogen sulfide to sulfuric acid, a process that is readily possible due to the close proximity of the oxygen-rich atmosphere to the top of the magma chamber

  • 93.
    Brethes, Anais
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Geological Survey of Denmark and Greenland (GEUS), Department of Petrology and Economic Geology, Denmark.
    Guarnieri, Pierpaolo
    Geological Survey of Denmark and Greenland (GEUS), Department of Petrology and Economic Geology.
    Rasmussen, Thorkild Maack
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias Erich
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Interpretation of aeromagnetic data in the Jameson Land Basin, central East Greenland: Structures and related mineralized systems2018Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 724-725, s. 116-136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper provides a detailed interpretation of several aeromagnetic datasets over the Jameson Land Basin in central East Greenland. The interpretation is based on texture and lineament analysis of magnetic data and derivatives of these, in combination with geological field observations. Numerous faults and Cenozoic intrusions were identified and a chronological interpretation of the events responsible for the magnetic features is proposed built on crosscutting relationships and correlated with absolute ages. Lineaments identified in enhanced magnetic data are compared with structures controlling the mineralized systems occurring in the area and form the basis for the interpretations presented in this paper. Several structures associated with base metal mineralization systems that were known at a local scale are here delineated at a larger scale; allowing the identification of areas displaying favorable geological settings for mineralization. This study demonstrates the usefulness of high-resolution airborne magnetic data for detailed structural interpretation and mineral exploration in geological contexts such as the Jameson Land Basin.

  • 94.
    Brethes, Anais
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Rasmussen, Thorkild Maack
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Guarnieri, Pierpolo
    GEUS.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    3D modelling of the base-metal mineralized Jameson Land Basin (central East Greenland) using geologically constrained inversion of magnetic data2015Konferensbidrag (Övrigt vetenskapligt)
  • 95.
    Brethes, Anaïs
    et al.
    Geological Survey of Denmark and Greenland.
    Guarnieri, Pierpaolo
    Geological Survey of Denmark and Greenland.
    Rasmussen, Thorkild Maack
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    3D-Modelling of the Early Triassic Base-Metal Mineralized Syn-Rift Sequence in the Jameson Land Basin (East Greenland)2015Ingår i: Mineral Resources in a Sustainable World / [ed] A.S. Andre-Mayer; M. Cathelineau; P. Muchez; E. Pirard; S. Sindern, 2015, s. 1701-1704Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Jameson Land Basin in central East Greenland is mineralized in Pb, Zn and Cu. Mineralization occurs in several stratigraphic horizons and along structures in Upper Permian and Triassic sediments. A good understanding of the basin architecture and evolution is therefore essential for mineral exploration in this area. 3D-Photomapping from high resolution aerial photos along with a structural interpretation of aeromagnetic data, electromagnetic data, and results from fieldwork and drilling were integrated into a 3D-structural model. This data integration allowed modelling the rift architecture in the eastern margin of the Jameson Land Basin.

  • 96.
    Brethes, Anaïs
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Guarnieri, Pierpaolo
    GEUS.
    Rasmussen, Thorkild Maack
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Geological Analysis of Aeromagnetic Data over the Blyklippen Lead-zinc Mine at Mesters Vig, Central East Greenland2016Ingår i: First Conference on Geophysics for Mineral Exploration and Mining: Near Surface Geoscience 2016, Barcelona, Spain, 4-8 September 2016, Houten, 2016, artikel-id Mo MIN 05Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the Mesters Vig area epithermal Pb-Zn sulphide-bearing quartz veins are associated with the border faults of a NNW-SSE elongated graben down-faulting Carboniferous to Lower Triassic sediments. The analysis of the total magnetic field, tilt derivative, vertical derivative and analytic signal allowed to define subcropping magnetic domains and identify structural trends. Doleritic dykes, sills and faults were mapped and structural relationships were established between them. Finally, aeromagnetic data allowed here to delineate structural trends along and in the vicinity of which mineralized quartz veins are mapped.

  • 97.
    Brethes, Anaïs
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Rasmussen, Thorkild Maack
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Guarnieri, Pierpaolo
    GEUS.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mapping and characterization of Induced Polarization in airborne TEM data from central East Greenland: application of a Self-Organizing Map procedure2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    nduced Polarization (IP) effects were observed in airborne Time Domain EM (TEM) data acquired in central East Greenland in the context of exploration for disseminated sulphides in a sedimentary basin. Some of the IP anomalies were targeted by drilling which revealed the absence of mineralization. In order to understand the possible causes of the IP effects we first identified them in the TEM data. IP indicators were extracted from the shape of the transient curves at every measurement location and were analysed by using a Self-Organizing Map (SOM) procedure. Results from K-mean clustering of the SOM are visualized on a geographical map showing the transient curves’ characteristics. Some of the clusters are clearly correlated with the geology whereas others merely reflect recordings below the noise level. In order to interpret the cause of the IP anomalies the airborne TEM data were inverted for the Cole-Cole parameters.

  • 98.
    Brojerdi, Fatemeh Sharifi
    et al.
    Department of Earth Sciences, Uppsala University.
    Juhlin, Christopher
    Department of Earth Sciences, Uppsala University.
    Stephens, Michael
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Malehmir, Alireza
    Department of Earth Sciences, Uppsala University.
    Reflection seismic imaging of the deeper structures at the Forsmark spent nuclear fuel repository site, central Sweden2013Ingår i: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 89, s. 21-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Forsmark area belongs to the Paleoproterozoic Svecokarelian orogen (c. 1.9-1.8 Ga), the principal geological entity inside the Fennoscandian Shield, and is the site where Sweden has proposed to store its spent nuclear fuel. Three major sub-vertical (at the surface), composite ductile and brittle deformation zones that strike in a WNW or NW direction are present in the area. In between these zones the bedrock is less deformed and considered suitable for a repository. We present reprocessed reflection seismic data from seven profiles in which we have focused on improving the images in the depth range 1–5 km by passing lower frequencies through the processing flow at the cost of poorer resolution in the near-surface realm. The new images indicate that sub-horizontal to moderately dipping structures are possibly more extensive at depth than previously thought. Three main deeper reflective zones have been identified, one that is sub-horizontal and two that dip moderately to the southwest. The sub-horizontal reflective zone may represent a 1.27-1.26 Ga dolerite sill at about 3 km depth. One of the moderately dipping reflective zones may originate either from another dolerite sill or from a brittle fault system. The other moderately dipping structure may be present throughout most of the area and could cut all three sub-vertical deformation zones at depth. The new images and corresponding interpretation do not require a re-evaluation of the Forsmark site for storage of spent fuel, but they do influence how to interpret the deeper structures and, as a consequence, the tectonic evolution of the area.

  • 99.
    Broman, Curt
    et al.
    Stockholms Universitet.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Fluid inclusions in epigenetic Fe-Cu-Au ores in northern Norrbotten2000Ingår i: Abstract volume & Field trip guidebook / [ed] Pär Weihed; Olof Martinsson, Luleå: Luleå tekniska universitet, 2000, s. 7-Konferensbidrag (Övrigt vetenskapligt)
  • 100.
    Cabri, Louis J.
    et al.
    Cabri Consulting Inc, Ottawa, Canada.
    Aiglsperger, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    A review of hexaferrum based on new mineralogical data2018Ingår i: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 82, nr 3, s. 531-538Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hexaferrum, defined as an hcp Fe mineral containing varying amounts of Ru, Os, or Ir(Mochalov et al. 1998) was re-examined in the light of new analyses of similar alloys from the Loma Peguera and Loma Larga chromitites, in the central part of Loma Caribe peridotite, Cordillera Central of the Dominican Republic, together with a review of the phase chemistry inthe Fe-Ni-Ir and Fe-Ru-Ir systems. We conclude that the hcp (Fe,Ir) mineral corresponds to theε-phase of Raub et al. (1964) and should be differentiated from hexaferrum [(Fe,Os) and(Fe,Ru)] because it is separated by one to two miscibility gaps and therefore is not a continuous solid solution with Fe.

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