DOCSLIB.ORG

Geophysical Studies of the Upper Crust of the Central Swedish Caledonides in Relation to the COSC Scientific Drilling Project

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Geophysical Studies of the Upper Crust of the Central Swedish Caledonides in Relation to the COSC Scientific Drilling Project Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1281 Geophysical studies of the upper crust of the central Swedish Caledonides in relation to the COSC scientific drilling project PETER HEDIN ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6214 ISBN 978-91-554-9320-2 UPPSALA urn:nbn:se:uu:diva-261112 2015 Dissertation presented at Uppsala University to be publicly examined in Hambergsalen, Geocentrum, Villavägen 16, Uppsala, Friday, 16 October 2015 at 10:00 for the degree of Doctor of Philosophy. The examination will be conducted in English. Faculty examiner: Associate Professor Charles Hurich (Department of Earth Sciences, Memorial University of Newfoundland, St. Johns, Canada). Abstract Hedin, P. 2015. Geophysical studies of the upper crust of the central Swedish Caledonides in relation to the COSC scientific drilling project. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1281. 87 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-554-9320-2. The Collisional Orogeny in the Scandinavian Caledonides (COSC) project aims to provide a deeper understanding of mountain belt dynamics through scientific deep drilling in the central parts of the mountain belt of western Sweden. The main targets include a subduction related allochthon, the basal orogenic detachment and the underlying partially subducted Precambrian basement. Research covered by this thesis, focusing primarily on reflection seismic data, was done within the framework of the COSC project. The 55 km long composite COSC Seismic Profile (CSP) images the upper crust in high resolution and established the basis for the selection of the optimum location for the two 2.5 km deep COSC boreholes. Together with potential field and magnetotelluric data, these profiles allowed the construction of a constrained regional interpretation of the major tectonic units. Non-conventional pseudo 3D processing techniques were applied to the 2D data prior to the drilling of the first borehole, COSC#1, to provide predictions about the 3D geometry of subsurface structures and potential zones of interest for the sampling programs. COSC-1 was drilled in 2014 and reached the targeted depth with nearly complete core recovery. A continuous geological section and a wealth of information from on-site and off- site scientific investigations were obtained. A major post-drilling seismic survey was conducted in and around the borehole and included a 3D reflection seismic experiment. The structurally and lithologically complex Lower Seve Nappe proved difficult to image in detail using standard processing techniques, but its basal mylonite zone and underlying structures are well resolved. The 3D data, from the surface down to the total drilled depth, show good correlation with the initial mapping of the COSC-1 core as well as with preliminary results from on-core and downhole logging. Good correlation is also observed between the 2D and 3D reflection seismic datasets. These will provide a strong link between the two boreholes and a means to extrapolate the results from the cores and boreholes into the surrounding rock. Ultimately, they will contribute to the deeper understanding of the tectonic evolution of the region, the Scandinavian Caledonides and the formation of major orogens. Keywords: reflection seismic, collisional orogeny, Scandinavian Caledonides, COSC, scientific drilling, geophysical logging, gravity, magnetics Peter Hedin, Department of Earth Sciences, Geophysics, Villav. 16, Uppsala University, SE-75236 Uppsala, Sweden. © Peter Hedin 2015 ISSN 1651-6214 ISBN 978-91-554-9320-2 urn:nbn:se:uu:diva-261112 (http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-261112) Dedicated to my beloved Marilyn and wonderful son Samuel Supervisors & Committee Supervisor Professor Christopher Juhlin Department of Earth Sciences – Geophysics, Uppsala University, Uppsala, Sweden Assistant Supervisor Associate Professor Alireza Malehmir Department of Earth Sciences – Geophysics, Uppsala University, Uppsala, Sweden Dr. Bjarne Almqvist Department of Earth Sciences – Geophysics, Uppsala University, Uppsala, Sweden Faculty Opponent Associate Professor Charles Hurich Department of Earth Sciences, Memorial University of Newfoundland, St. Johns, Canada Examination Committee Dr. Joaquina Álvarez Marrón Department of Earth’s Structure and Dynamics and Crystallography – Earth’s structure and Dynamics, Institute of Earth Sciences Jaume Almera, Barcelona, Spain Dr. Cédric Schmelzbach Department of Earth Sciences – Geophysics, ETH Zürich, Zürich, Switzer- land Dr. Ari Tryggvason Department of Earth Sciences – Geophysics, Uppsala University, Uppsala, Sweden List of Papers This thesis is based on the following papers, which are referred to in the text by their Roman numerals. I Hedin, P., Juhlin, C., Gee, D. G. (2012) Seismic imaging of the Scandinavian Caledonides to define ICDP drilling sites. Tectonophysics, 554-557:30–41 II Hedin, P., Malehmir, A., Gee, D. G., Juhlin, C., Dyrelius, D. (2013) 3D interpretation by integrating seismic and potential field data in the vicinity of the proposed COSC-1 drill site, cen- tral Swedish Caledonides. Geological Society, London, Special Publications, 390:301–319 III Hedin, P., Almqvist, B., Berthet, T., Juhlin, C., Buske, S., Si- mon, H., Giese, R., Krauß, F., Rosberg, J-E., Alm, P-G. (2015) 3D reflection seismic imaging at the 2.5 km deep COSC-1 sci- entific borehole, central Scandinavian Caledonides. Tectonophysics, manuscript under review IV Juhlin, C., Hedin, P., Gee, D. G. (2015) Seismic imaging of the eastern Scandinavian Caledonides: Siting the 2.5 km deep COSC-2 borehole. Solid Earth, manuscript to be submitted Reprints were made with permission from the respective publishers. Additional contributions to conference proceeding written during my Ph. D. which are not included in this thesis: Hedin, P., Malehmir, A., Gee, D. G., Juhlin, C., Dyrelius, D. (2013) COSC geophysical and geological site investigations. 75th EAGE Con- ference & Exhibition, London, UK, Extended Abstract 16529, TuSP1- 07, doi: 10.3997/2214-4609.20131097 Ahmadi, O., Hedin, P., Malehmir, A., Juhlin. C. (2013) 3D Seismic In- terpretation and Forward Modeling – an approach to providing reliable results from 2D seismic data. In: Johnson, E. (Ed.), Mineral Deposit Re- search for a High-Tech World, vols 1-4, p 50-53, 12th SGA Biennial Meeting, Uppsala, Sweden. Juhlin, C., Hedin, P. (2014) 3D Seismic Processing of Crooked Line 2D Data in the Vicinity of the COSC 2.5 Km Deep Scientific borehole. 76th EAGE Conference & Exhibition, Amsterdam, The Netherlands, Extend- ed Abstract 21889, WS5-P11, doi: 10.3997/2214-4609.20140522 Contributions The papers included in this thesis are the result of collaboration with several authors. The individual contributions of the author of this thesis are summa- rized below. I I participated in the seismic acquisition and performed the data decoding, processing and analysis. I participated in the discus- sion and interpretation and then wrote the first draft, with input from co-authors on geology. Worked with the co-authors to re- fine the manuscript. II I constructed the 3D geological model. Participated in the dis- cussion and interpretation and wrote a draft of the manuscript, with input from co-authors on the inverse modeling. I then made improvements to the manuscript based on feedback and guidance from the co-authors. III I participated in the acquisition, processing and analysis of core logging data as well as the processing and analysis of downhole logging data. I participated in the seismic acquisi- tion and performed the decoding, processing and analysis. I wrote the first draft, with input from co-authors on geology, and then improved the manuscript after helpful feedback. IV I participated in the seismic acquisition in 2010 and 2011 and processed the data from these two surveys. Participated in the discussion and interpretation of the full seismic profile and contributed with some parts of the draft as well as refinement of the final manuscript. Contents 1 Introduction ......................................................................................... 13 2 Collisional Orogeny in the Scandinavian Caledonides ........................ 16 2.1 The Caledonian geology of central Sweden .................................... 17 2.2 The Seve Nappe Complex ............................................................... 21 2.3 Geophysical Background ................................................................ 23 2.4 Scientific Drilling in the Scandinavian Caledonides ....................... 26 3 Methods ............................................................................................... 29 3.1 The reflection seismic method and data acquisition ....................... 29 3.1.1 2D crooked line acquisition ................................................... 30 3.1.2 Limited 3D acquisition .......................................................... 31 3.2 Reflection seismic processing ......................................................... 32 3.2.1 Crossdip analysis ................................................................... 33 3.2.2 Swath 3D imaging ................................................................. 37 3.3 Drilling of COSC-1 scientific borehole and logging of geophysical rock parameters .................................................................... 42 4 Summary of Papers .............................................................................
Load more

Recommended publications
  • From the Early Paleozoic Platforms of Baltica and Laurentia to the Caledonide Orogen of Scandinavia and Greenland
    44 by David G. Gee1, Haakon Fossen2, Niels Henriksen3, and Anthony K. Higgins3 From the Early Paleozoic Platforms of Baltica and Laurentia to the Caledonide Orogen of Scandinavia and Greenland 1 Department of Earth Sciences, Uppsala University, Villavagen Villavägen 16, Uppsala, SE-752 36, Sweden. E-mail: [email protected] 2 Department of Earth Science, University of Bergen, Allégaten 41, N-5007, Bergen, Norway. E-mail: [email protected] 3 The Geological Survey of Denmark and Greenland, Øster Voldgade 10, Dk 1350 Copenhagen, Denmark. E-mail: [email protected], [email protected] The Caledonide Orogen in the Nordic countries is exposed in Norway, western Sweden, westernmost Fin- Introduction land, on Svalbard and in northeast Greenland. In the The Caledonide Orogen is preserved on both sides of the North mountains of western Scandinavia, the structure is dom- Atlantic Ocean, in the mountains of western Scandinavia and north- inated by E-vergent thrusts with allochthons derived eastern Greenland; it continues northwards from northern Norway, across the Barents Shelf and Svalbard to the edge of the Eurasian from the Baltoscandian platform and margin, from out- Basin (Figure 1). The orogen is notable for its thrust systems, board oceanic (Iapetus) terranes and with the highest E-vergent in Scandinavia and W-vergent in Greenland. The width of the orogen, prior to Cenozoic opening of the North Atlantic, was in thrust sheets having Laurentian affinities. The other the order of at least 700–800 km, the deformation fronts on both side of this bivergent orogen is well exposed in north- sides of the orogen being defined by thrusts that, in the Devonian, eastern Greenland, where W-vergent thrust sheets probably reached substantially further onto the foreland platforms than they do today.
    [Show full text]
  • The Terrane Concept and the Scandinavian Caledonides: a Synthesis
    The terrane concept and the Scandinavian Caledonides: a synthesis DAVID ROBERTS Roberts , D. 1988: The terrane concept and the Scandinavian Caledonides: a synthesis. Nor. geol . unders . Bull. 413. 93-99. A revised terrane map is presented for the Scandinavian Caledcnldes. and an outline is given of the principal suspect and exot ic terranes and terrane-complexe s identified outboa rd from the Baltoscand ian miogeocline. The outermost part of the Baltoscandian continental margin is itself suspect , in the terrane sense. since the true palaeogeographical location s of rocks now represented in the Seve and serey-seuano Nappes, while inferred, are not known. The orogen -internal exotic terranes embrace the oceanic/eugeoclinal elements of the Caledonides, represented by the mag­ matosed imentary assemblages of the Koli Nappes, including ophiolite fragments and island arc products. Even more exot ic terranes occur in the highest parts of the tectonostratigraphy, inclu­ ding units which are thought possibly to derive from the Laurentian side of lapetus . D. Roberts. Norges geologiske uruierseketse, Postboks 3006. Lade, N-7002 Trondbeim , Norway . Introduction Project 233 has been to prepare a preliminary Earlier in this decade much of the research terrane map' at 1:5 M scale (Roberts et al. effort in the Caledonides of Scandinavia was 1986) for a larger, circum-Atlantic compilation. channelled through the highly successfu l IGCP This map, much simplified, is really one of Project 27 The Caledonide Orogen ' (Gee & palaeo-environments (marginal basins, vol­ Sturt 1985). An important aspect of the collabo­ canic arc comp lexes, overstep sequences , rative work in this project was that of map etc.), and not of terranes in the true sense.
    [Show full text]
  • Tectonic Regimes in the Baltic Shield During the Last 1200 Ma • a Review
    Tectonic regimes in the Baltic Shield during the last 1200 Ma • A review Sven Åke Larsson ' ', Bva-L^na Tuliborq- 1 Department of Geology Chalmers University of Technology/Göteborij U^vjrsivy 2 Terralogica AB November 1993 TECTONIC REGIMES IN THE BALTIC SHIELD DURING THE LAST 1200 Ma - A REVIEW Sven Åke Larsson12, Eva-Lena Tullborg2 1 Department of Geology, Chalmers University of Technology/Göteborg University 2 Terralogica AB November 1993 This report concerns a study which was conducted for SKB. The conclusions and viewpoints presented in the report are those of the author(s) and do not necessarily coincide with those of the client. Information on SKB technical reports from 1977-1978 (TR 121), 1979 (TR 79-28), 1980 (TR 80-26), 1981 (TR 81-17), 1982 (TR 82-28), 1983 (TR 83-77), 1984 (TR 85-01), 1985 (TR 85-20), 1986 (TR 86-31), 1987 (TR 87-33), 1988 (TR 88-32),. 1989 (TR 89-40), 1990 (TR 90-46), 1991 (TR 91-64) and 1992 (TR 92-46) is available through SKB. ) TECTONIC REGIMES IN THE BALTIC SHIELD DURING THE LAST 1200 Ma - A REVIEW by Sven Åke Larson and Eva-Lena Tullborg Department of Geology, Chalmers University of Technology / Göteborg University & Terralogica AB Gråbo, November, 1993 Keywords: Baltic shield, Tectonicregimes. Upper Protero/.oic, Phanerozoic, Mag- matism. Sedimentation. Erosion. Metamorphism, Continental drift. Stress regimes. , ABSTRACT 1 his report is a review about tectonic regimes in the Baltic (Fennoscandian) Shield from the Sveeonorwegian (1.2 Ga ago) to the present. It also covers what is known about palaeostress during this period, which was chosen to include both orogenic and anorogenic events.
    [Show full text]
  • Geochronology and Geochemistry of Zircon from the Northern Western Gneiss Region: Insights Into the Caledonian Tectonic History of Western Norway
    Lithos 246–247 (2016) 134–148 Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Geochronology and geochemistry of zircon from the northern Western Gneiss Region: Insights into the Caledonian tectonic history of western Norway Stacia M. Gordon a,⁎, Donna L. Whitney b, Christian Teyssier b, Haakon Fossen c, Andrew Kylander-Clark d a Department of Geological Sciences, University of Nevada, Reno, NV 89557, USA b Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA c Department of Earth Science and Museum of Natural History, University of Bergen, N-5020 Bergen, Norway d Department of Earth Science, University of California, Santa Barbara, CA 93106, USA article info abstract Article history: The Western Gneiss Region (WGR) of Norway is divided by the Møre-Trøndelag shear zone (MTSZ) into a south- Received 6 September 2015 ern region that contains domains of Caledonian ultrahigh-pressure (UHP) metamorphic rocks (N2.5 GPa) and a Accepted 25 November 2015 northern area of similar Caledonian-aged rocks that record a maximum pressure reported thus far of ~1.5 GPa. Available online 17 December 2015 Although both regions contain similar lithologies (primarily migmatitic quartzofeldspathic gneiss containing mafic lenses) and structural relationship of basement rocks to infolded nappes, this difference in maximum pres- Keywords: sure implies a difference in tectonic history (continental subduction south of the shear zone, none to the north) Western Gneiss Region Zircon and raises questions about the role of the MTSZ in the metamorphic history (including exhumation) of the WGR. Split-stream Previous geochronology results indicated a difference in timing of peak metamorphism (older in north, younger LA-ICPMS in south).
    [Show full text]
  • Early Caledonian Tectonothermal Evolution in Outboard Terranes, Central Scandinavian Caledonides: New Constraints from U-Pb Zircon Dates
    Journal of the Geological Society, London, Vol. 150, 1993, pp. 51-56, 4 figs, 1 table. Printed in Northern Ireland Early Caledonian tectonothermal evolution in outboard terranes, central Scandinavian Caledonides: new constraints from U-Pb zircon dates M. B. STEPHENS l,K. KULLERUD 2'3&S.CLAESSON 2 ~Geological Survey of Sweden, Box 670, S-751 28 Uppsala, Sweden 2Museum of Natural History, Laboratory of Isotope Geology, Box 50007, S-104 05 Stockholm, Sweden 3present address: Department of Geology, University of Oslo, Box 1047, N-0316 Oslo 3, Norway Abstract: Early Caledonian deformation in an outboard terrane (Stort]fillet) in the central Scandinavian Caledonides is constrained to the time-period Arenig to Caradoc on the basis of U-Pb zircon age determin- ations. A trondhjemite clast in a conglomerate belonging to a supracrustal sequence that was affected by the early deformational event yields an age of 489_+10 5 Ma. A granite intruded after this event defines an age of 44 J-6~ + 24 Ma. The clast is similar in age to a trondhjemite intrusion in a contiguous terrane (Gjersvik) dated at 483+~Ma and the granite age is in agreement with a Rb-Sr whole-rock isochron of 438 5= 6 Ma determined in a previous study. The three new ages provide further evidence for the separation of igneous events in outboard terranes in the Scandinavian Caledonides into older (Tremadoc to Arenig) and younger (Late Ordovician to Early Silurian) episodes. More critically, they argue against simple correlation of early Caledonian deformational events in outboard terranes with the Late Cambrian to Early Ordovician tectonometamorphic history along the margin of the continent Baltica (the so-called Finnmarkian orogenic phase).
    [Show full text]
  • The Scandinavian Caledonides—Scientific Drilling at Mid-Crustal Level in a Palaeozoic Major Collisional Orogen
    Workshop Reports The Scandinavian Caledonides—Scientific Drilling at Mid-Crustal Level in a Palaeozoic Major Collisional Orogen by Henning Lorenz, David Gee, and Christopher Juhlin doi:10.2204/iodp.sd.11.10.2011 Introduction emplacement of allochthons have been demonstrated, E-directed in the Scandes and W-directed in Greenland. The Caledonides of western Scandinavia and eastern Greenland have long been recognized to have been part of a In Scandinavia, major allochthons (Fig. 1) were derived collisional orogen of Alpine-Himalayan dimensions, essen- from Baltica’s outer shelf, dyke-intruded continent-ocean tially the result of the closure of the Iapetus Ocean during transition zone (COT), Iapetus oceanic domains and (upper- the Ordovician, with development of island-arc systems, and most) from the Laurentian margin. On the western side of subsequent underthrusting of continent Laurentia by Baltica the North Atlantic, exposed along the eastern edge of the in the Silurian and Early Devonian during Scandian colli- Greenland ice cap, there are major thrust sheets, all derived sional orogeny. Several hundreds of kilometers of thrust from the Laurentian continental margin and transported at least two hundred kilometers westwards onto the platform. In the Scandinavian and Greenland Caledonides, the major allochthons that were derived from the outer parts of the con- tinent margins have been subject to high-grade metamor- phism and apparently were emplaced hot onto the adjacent platforms. The International Continental Scientific Drilling Program (ICDP) workshop in Sweden provided an opportunity to examine the evidence for Caledonian collisional orogeny in Scandinavia and to discuss its relevance for understanding other orogens, particularly Himalaya-Tibet, and also the sub- duction systems along the margin of the western Pacific.
    [Show full text]
  • Thermal Evidence of Caledonide Foreland, Molasse Sedimentation In
    TECHNICAL REPORT Thermal evidence of Caledonide foreland, molasse sedimentation in Fennoscandia Eva-Lena Tullborg1, Sven Åke Larson1, Lennart Björklund1, Lennart Samuelsson2, Jimmy Stigh1 1 Department of Geology, Earth Sciences Centre, Göteborg University, Göteborg, Sweden 2 Geological Survey of Sweden, Earth Sciences Centre, Göteborg, Sweden November 1995 SVENSK KÄRNBRÄNSLEHANTERING AB SWEDISH NUCLEAR FUEL AND WASTE MANAGEMENT CO P.O.BOX 5864 S-102 40 STOCKHOLM SWEDEN PHONE + 46 8 665 28 00 TELEX 13108 SKB FAX+46 8 661 57 19 . $? i Li THERMAL EVIDENCE OF CALEDONIDE FORELAND, MOLASSE SEDIMENTATION IN FENNOSCANDIA Eva-Lena Tullborg1, Sven Åke Larson1, Lennart Björklund1, Lennart Samuelsson2, Jimmy Stigh1 1 Department of Geology, Earth Sciences Centre, Göteborg University, Göteborg, Sweden 2 Geological Survey of Sweden, Earth Sciences Centre, Göteborg, Sweden November 1995 This report concerns a study which was conducted for SKB. The conclusions and viewpoints presented in the report are those of the author(s) and do not necessarily coincide with those of the client. Information on SKB technical reports from 1977-197 8 (TR 121), 1979 (TR 79-28), 1980 (TR 80-26), 1981 (TR 81-17), 1982 (TR 82-28), 1983 (TR 83-77), 1984 (TR 85-01), 1985 (TR 85-20), 1986 (TR 86-31), 1987 (TR 87-33), 1988 (TR 88-32), 1989 (TR 89-40), 1990 (TR 90-46), 1991 (TR 91-64), 1992 (TR 92-46), 1993 (TR 93-34) and 1994 (TR 94-33) is available through SKB. THERMAL EVIDENCE OF CALEDONIDE FORELAND, MOLASSE SEDIMENTATION IN FENNOSCANDIA. Eva-Lena Tullborg, Sven Ake Larson, Lennart Björklund, Lennart Samuelsson1 and Jimmy Stigh.
    [Show full text]
  • Balticasiberia Connection Challenges Traditional Tectonics Notions
    Eos, Vol. 75, No. 40, October 4, 1994 At the same time, drilling can contribute its increasing vulnerability to natural haz­ curred in an ocean-continent transition zone to a number of problems related to obtaining ards, and in finding solutions to problems that was marginal to Baltica but faced north­ a better understanding of the structure, evolu­ associated with remediation of existing envi­ ern Siberia rather than Laurentia. tion, and dynamics of the lithosphere. These ronmental damage and prevention of include problems related to petrochemical additional environmental degradation. At An Alternate View of Early and structural evolution of Earth's crust in­ the same time, Earth scientists are motivated Landmass Positions cluding lithospheric rheology and strength, by an inexorable need to better understand and the distribution of plate driving forces; planet Earth. This report contains the scien­ A reconciliation of the paleomagnetic, pa­ and heat and mass transfer through the litho­ tific rationale for establishment of an leoclimatic, and biogeographic data (Figure sphere and thermal structure of the crust and International Continental Drilling Program to 1) indicates that Avalonia and the European upper mantle. enable the international geoscientific com­ Massifs (Armorica) were located close to Gondwana in high southerly latitudes during There is a broad consensus that any ICDP munity to meet the challenges they face by Early Ordovician times. Laurentia was posi­ to be established should carry out fundamen­ complementing ongoing field, laboratory tioned in equatorial latitudes during most of tal science covering as broad a spectrum of and theoretical studies with critical observa­ the Ordovician. Conversely, Baltica was first Earth science research as possible.
    [Show full text]
  • Metallic Mineral Deposits in the Nordic Countries
    125 by Pär Weihed1, Pasi Eilu2, Rune B. Larsen3, Henrik Stendal4, and Mikko Tontti2 Metallic mineral deposits in the Nordic countries 1 Division of Ore Geology and Applied Geophysics, Luleå University of Technology, SE-971 87 Luleå, Sweden. E-mail: [email protected] 2 Geological Survey of Finland, PO Box 96, FI-02151 Espoo, Finland. 3 NTNU, NO-7491 Trondheim, Norway. 4 Geological Survey of Denmark and Greenland, Ø. Voldgade 10, DK-1350 Cph., Denmark. The Nordic countries, including Green- land, have a long tradition in mining. Doc- umented mining dates back to the 8th cen- tury AD. Today this region is the most important metallic mining district of the European Union. Metals are produced from active mines in all countries except Iceland and related industries are thriving in all countries. Important ore deposit types include: volcanogenic massive sulphide deposits (Cu, Zn, Pb, Au, Ag), orogenic gold deposits (Au), layered intrusions (Ni, PGE, Ti±V), intrusive hosted Cu-Au, apatite-Fe deposits, Cr- and anorthosite hosted Ti deposits. Besides these well- documented deposits, new kinds of deposits are being explored, e.g., iron oxide-copper-gold (IOCG), shale-hosted Ni-Zn-Cu and different types of uranium deposits. Introduction The Fennoscandian Shield, which forms a large part of the Nordic countries (see descriptions else- where in this volume), has historically been one of the most active mining areas in Europe. For exam- ple, archaeological evidence shows that copper was produced from the Falun mine in the Bergslagen province, Sweden, early in the 8th century AD (Eriksson and Qvarfort, 1996).
    [Show full text]
  • Crustal Stretching in the Scandinavian Caledonides As Revealed by Deep Seismic Data
    Crustal stretching in the Scandinavian Caledonides as revealed by deep seismic data Haakon Fossen1*, Roy H. Gabrielsen2, Jan Inge Faleide2, and Charles A. Hurich3 1Department of Earth Science and Museum of Natural History, University of Bergen, Postboks 7803, 5007 Bergen, Norway 2Department of Geosciences, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway 3Department of Earth Sciences, Memorial University, St. John’s, Newfoundland A1B 3X5, Canada ABSTRACT micas that grew during the two phases suggests that the switch occurred The normalization of overthickened orogenic crust after a shortly before 400 Ma (Fossen and Dunlap, 1998). continent-continent collision typically involves several different Extensional reactivation of the low-angle Caledonian basal décolle- processes, including erosion, plate divergence, gravity-driven col- ment implies a reversal of the motion of Baltica; i.e., eduction (Duretz et lapse of the orogenic wedge, and viscous flow of the lower crust. As a al., 2012). However, this mode of extension transitioned into the formation contribution to this discussion, we here utilize reprocessed deep seis- of hinterland-dipping shear zones, shown as green lines in Figure 1. This mic data to image the Scandinavian part of the major Caledonian system of extensional shear zones extended to the surface, giving rise to continent-continent collision zone where we identify a double set of Devonian supra-detachment basins, of which remnants are preserved in extensional shear zones: one in the upper to middle crust (Hardan- the hanging wall of the Nordfjord-Sogn detachment (Séranne and Séguret, gerfjord shear zone) and a major oppositely dipping Moho-offset- 1987; Vetti and Fossen, 2012).
    [Show full text]
  • Large Meta-Eclogite Massifs Within the Western Gneiss Region, Scandinavian Caledonides: Subducted Ocean-Continent Transition?
    EGU21-16336 https://doi.org/10.5194/egusphere-egu21-16336 EGU General Assembly 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Large meta-eclogite massifs within the Western Gneiss Region, Scandinavian Caledonides: Subducted ocean-continent transition? Simon Cuthbert AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Kraków, Poland The northern part of the Western Gneiss Region (WGR) has distinctive belts of allochthonous metasediments and mafic rocks lying within tight infolds into the Baltica basement. They outcrop from the Grong-Olden Window to the Norwegian coast, possibly as far SW as Sørøyane, predominantly comprising metapelite and amphibolite with psammite, marble, calc-silicate, local large eclogite (>4km) lenses and ultramafites. These supracrustal lithotectonic units are attributed to the Blåhø Nappe, correlated with the Seve Nappe Complex (SNC) in its main outcrop in Sweden, which is considered to represent the pre-Caledonian continent-ocean transition (COT) of Baltica. They closely resemble the Lower Seve Nappe in northern Sweden where large amphibolite massifs with marbles are common, along with local eclogites. At least some have geochemical characteristics of spilitised extrusive MORB basalt in contrast to the better known, Neoproterozoic Baltoscandian Dyke Swarm in the SNC. In the WGR near Molde a >10km long massif of such “amphibolite” at Tverrfjella commonly exhibits a relict high-P granulite precursor that has, in turn, overprinted eclogite. It encloses marble, scapolite-bearing calc-silicate, garnet peridotite (harzburgite) and Cu ores. Marble and meta-eclogite are intermixed which, along with its high Na spilitic character, suggests that the protolith was extrusive.
    [Show full text]
  • Cave Development in Central Scandinavia
    13th International Congress of Speleology 4th Speleological Congress of Latin América and Caribbean 26th Brazilian Congress of Speleology Brasília DF, 15-22 de julho de 2001 Cave Development in Central Scandinavia Trevor FAULKNER Limestone Research Group, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK Abstract Metacarbonate outcrops occur in most nappes of the central Scandinavian Caledonides, but their numbers, lengths, areas and foliation dip-angles decline to the east. Caves of all complexities occur in the higher metalimestone-bearing nappes, from valley shoulder positions down to valley floors, and in (commonly homoclinal) Vertical, Angled, and Non Stripe karst types that guide internal morphologies. Total cave dimensions show no systematic trend when normalised against the length of outcrops, and are not related to catchment areas. Vertical distributions of outcrops and cave entrances are essentially random. Cave depth is always much smaller than the outcrop vertical range: caves in stripe karst have formed entirely within an upper 50m-thick zone of fractured rock. Similar cave inception, development and removal processes may have operated across the whole area from the time of the Caledonian Orogeny, and under the direct, and indirect, influences of the many glaciations since the late Miocene. Introduction The author is studying the caves in the Caledonian nappes of central Scandinavia in a region based on the Helgeland Nappe Complex (HNC). The study area extends eastwards from the Atlantic coast via stratigraphically
    [Show full text]