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  • 1.
    Andersson, Joel
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lynch, Edward P.
    Department of Mineral Resources, Geological Survey of Sweden, Uppsala, Sweden.
    Evolution of structures and hydrothermal alteration in a Palaeoproterozoic supracrustal belt: Constraining paired deformation–fluid flow events in an Fe and Cu–Au prospective terrain in northern Sweden2020Inngår i: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 11, nr 2, s. 547-578Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An approximately 90 km long Palaeoproterozoic supracrustal belt in the northwestern Norrbotten ore province (northernmost Sweden) was investigated to characterize its structural components, assess hydrothermal alteration–structural geology correlations, and constrain a paired deformation–fluid flow evolution for the belt. New geological mapping of five key areas (Eustiljåkk, Ekströmsberg, Tjårrojåkka, Kaitum West, and Fjällåsen–Allavaara) indicates two major compressional events (D1 and D2) have affected the belt, with each associated with hydrothermal alteration types typical for iron oxide–apatite and iron oxide Cu–Au systems in the region. Early D1 generated a regionally distributed, penetrative S1 foliation and oblique reverse shear zones that show a southwest-block-up sense of shear that formed in response to NE–SW crustal shortening. Peak regional metamorphism at epidote–amphibolite facies broadly overlaps with this D1 event. Based on overprinting relationships, D1 is associated with regional scapolite ± albite, magnetite + amphibole, and late calcite alteration of mafic rock types. These hydrothermal mineral associations linked to D1 structures may form part of a regionally pervasive evolving fluid flow event but are separated in this study by crosscutting relationships.

    During D2 deformation, folding of S0–S1 structures generated F2 folds with steeply plunging fold axes in low-strain areas. NNW-trending D1 shear zones experienced reverse dip-slip reactivation and strike-slip-dominated movements along steep, E–W-trending D2 shear zones, producing brittle-plastic structures. Hydrothermal alteration linked to D2 structures is a predominantly potassic–ferroan association comprising K-feldspar ± epidote ± quartz ± biotite ± magnetite ± sericite ± sulfides. Locally, syn- or post-tectonic calcite is the main alteration mineral in D2 shear zones that intersect mafic rocks. Our results highlight the importance of combining structural geology with the study of hydrothermal alterations at regional to belt scales to understand the temporal–spatial relationship between mineralized systems. Based on the mapping results and microstructural investigations as well as a review of earlier tectonic models presented for adjacent areas, we suggest a new structural model for this part of the northern Fennoscandian Shield. The new model emphasizes the importance of reactivation of early structures, and the model harmonizes with tectonic models presented by earlier workers based mainly on petrology of the northern Norrbotten area.

  • 2.
    Logan, Leslie
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Veress, Ervin Csaba
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Andersson, Joel B. H.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias E.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Structural framework and timing of the Pahtohavare Cu ± Au deposits, Kiruna mining district, Sweden2023Inngår i: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 14, nr 7, s. 763-784Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As part of the larger mineral systems approach to Cu-bearing mineralization in northern Norrbotten, this study utilizes structural geology to set the classic Pahtohavare Cu ± Au deposits into an up-to-date tectonic framework. The Pahtohavare Cu ± Au deposits, situated only 5 km southwest of the Kiirunavaara world-class iron oxide–apatite (IOA) deposit, have a dubious timing, and their link to IOA formation is not constrained. The study area contains both epigenic Cu ± Au (Pahtohavare) and iron oxide–copper–gold (IOCG; Rakkurijärvi) mineral occurrences which are hosted in bedrock that has been folded and bound by two shear zones trending northeast to southwest and northwest to southeast to the east and southwest, respectively. Structural mapping and petrographic investigation of the area reveal a noncylindrical, SE-plunging anticline. The cleavage measurements mirror the fold geometry, which characterizes the fold as F2 associated with the late phase of the Svecokarelian orogeny. Porphyroclasts with pressure shadows, mylonitic fabrics, and foliation trails in porphyroblasts indicate S0/S1  is a tectonic fabric. The epigenetic Pahtohavare Cu ± Au mineralization sits in brittle–ductile structures that cross-cut an earlier foliation and the F2 fold, indicating that the timing of the deposits occurred syn- to post-F2 folding, at least ca. 80 Myr after the Kiirunavaara IOA formation. A 3D model and cross-sections of the Pahtohavare–Rakkurijärvi area and a new structural framework of the district are presented and used to suggest that the shear zones bounding the area are likely reactivated early structures that have played a critical role in ore formation in the Kiruna mining district.

    Fulltekst (pdf)
    fulltext
  • 3.
    Skyttä, Pietari
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Boliden Mineral AB, 93681 Boliden, Sweden.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hermansson, Tobias
    Boliden Mineral AB, 93681 Boliden, Sweden.
    Dehghannejad, Mahdieh
    Uppsala University, Department of Earth Sciences, Villavägen 16, 75236 Uppsala, Sweden.
    Juhlin, Christopher
    Uppsala University, Department of Earth Sciences, Villavägen 16, 75236 Uppsala, Sweden.
    García Juanatey, M.
    Uppsala University, Department of Earth Sciences, Villavägen 16, 75236 Uppsala, Sweden.
    Hübert, Juliane
    Uppsala University, Department of Earth Sciences, Villavägen 16, 75236 Uppsala, Sweden.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Crustal 3-D geometry of the Kristineberg area (Sweden) with implications on VMS deposits2013Inngår i: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 4, s. 387-404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Structural analysis of the Palaeoproterozoic volcanogenic massive sulfide (VMS) hosting Kristineberg area, Sweden, constrained by existing magnetotelluric (MT) and seismic reflection data, reveals that the complex geometry characterized by non-cylindrical antiformal structures is due to transpression along the termination of a major high-strain zone. Similar orientations of the host rock deformation fabrics and the VMS ore lenses indicate that the present-day geometry of the complex VMS deposits in the Kristineberg area may be attributed to tectonic transposition. The tectonic transposition was dominantly controlled by reverse shearing and related upright to overturned folding, with increasing contribution of strike-slip shearing and sub-horizontal flow towards greater crustal depths. Furthermore, the northerly dip of the previously recognized subsurface crustal reflector within the Kristineberg area is attributed to formation of crustal compartments with opposite polarities within the scale of the whole Skellefte district. The resulting structural framework of the main geological units is visualized in a 3-D model which is available as a 3-D PDF document through the publication website.

    Fulltekst (pdf)
    fulltext
  • 4.
    Skyttä, Pietari
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hermansson, Tobias
    Boliden Mineral AB.
    Andersson, Jenny
    Sveriges Geologiska Undersökning.
    Whitehouse, Martin
    Naturhistoriska Riksmuseet.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    New zircon data supporting models of short-lived igneous activity at 1.89 Ga in the western Skellefte District, central Fennoscandian Shield2011Inngår i: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 2, s. 205-217Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New U-Th-Pb zircon data (SIMS) from three intrusive phases of the Palaeoproterozoic Viterliden intrusion in the western Skellefte District, central Fennoscandian Shield, dates igneous emplacement in a narrow time interval at about 1.89 Ga. A locally occurring quartz-plagioclase porphyritic tonalite, here dated at 1889 ± 3 Ma, is considered the youngest of the intrusive units, based on the new age data and field evidence. This supports an existing interpretation of its fault-controlled emplacement after intrusion of the dominating hornblende-tonalite units, in this study dated at 1892 ± 3 Ma. The Viterliden magmatism was synchronous with the oldest units of the Jörn type early-orogenic intrusions in the eastern part of the district (1.89–1.88 Ga; cf. Gonzàles Roldán, 2010). A U-Pb zircon age for a felsic metavolcanic rock from the hanging-wall to the Kristineberg VMS deposit, immediately south of the Viterliden intrusion, is constrained at 1883 ± 6 Ma in this study. It provides a minimum age for the Kristineberg ore deposit and suggests contemporaneous igneous/volcanic activity throughout the Skellefte District. Furthermore, it supports the view that the Skellefte Group defines a laterally continuous belt throughout this "ore district". Tentative correlation of the 1889 ± 3 Ma quartz-plagioclase porphyritic tonalite with the Kristineberg "mine porphyry" suggests that these units are coeval at about 1.89 Ga. Based on the new age determinations, the Viterliden intrusion may equally well have intruded into or locally acted as a basement for the ore-hosting Skellefte Group volcanic rocks.

    Fulltekst (pdf)
    FULLTEXT01
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