Neoproterozoic Metamorphic Evolution of the Isbjørnhamna

Total Page:16

File Type:pdf, Size:1020Kb

Neoproterozoic Metamorphic Evolution of the Isbjørnhamna Neoproterozoic metamorphic evolution of the Isbjørnhamna Group rocks from south-western Svalbardpor_186 250..264 Jaroslaw Majka,1 Jerzy Czerny,2 Stanislaw Mazur,3 Daniel K. Holm4 & Maciej Manecki2 1 Department of Earth Sciences, Uppsala University, Villavägen 16, SE-75236 Uppsala, Sweden 2 Department of Mineralogy, Petrography and Geochemistry, AGH–University of Science and Technology, 30 Mickiewicza Av., PL-30059 Kraków, Poland 3 GETECH, Kitson House, Elmete Hall, Elmete Lane, Leeds, LS8 2LJ, UK 4 Department of Geology, Kent State University, Kent, OH 44242, USA Keywords Abstract Caledonides; geothermobarometry; metapelites; Neoproterozoic; Spitsbergen. A metamorphosed volcano-sedimentary complex constitutes the Caledonian basement in the south-western part of Wedel Jarlsberg Land, Svalbard. Field, Correspondence textural and previous thermochronologic data indicate a weak, localized meta- Jaroslaw Majka, Department of Earth morphic Caledonian overprint (M2). Deformed M1 isograds and variation in Sciences, Uppsala University, Villavägen 16, pressure–temperature estimates indicate a pervasive Neoproterozoic SE-75236 Uppsala, Sweden. E-mail: amphibolite-facies metamorphism that pre-dates large-scale Caledonian age [email protected] folding. Garnet–biotite and garnet–Al silicate–plagioclase (GASP) geother- doi:10.1111/j.1751-8369.2010.00186.x mobarometry of the Isbjørnhamna Group mica schists, and their comparison with the K2O–FeO–MgO–Al2O3–SiO2–H2O (KFMASH) petrogenetic grid, indi- cates a peak pressure of ca. 11 kbar, and a peak temperature of ca. 670°C during M1 metamorphism. A cooling rate of ca. 5°C My-1 is estimated on the basis of geothermobarometry and the available U–Th–total Pb and Ar–Ar data. Southern Wedel Jarlsberg Land (Fig. 1) uniquely pre- tectonic models proposed for this region. In this study we: serves a record of Neoproterozoic metamorphism on (1) quantify the peak pressure and temperature condi- Spitsbergen, Svalbard. In situ uranium–thorium–lead tions for Neoproterozoic metamorphism; (2) verify the electron microprobe (U–Th–Pb EMP) ages of metamor- correlation between the peak of metamorphism and the phic monazites from a Proterozoic volcano-sedimentary pervasive deformational fabric; (3) define zones of pro- complex date amphibolite-grade metamorphism at ca. gressive metamorphism and the relationship between 643 Mya (Majka et al. 2008). The northern extent of isograds and major tectonic structures; and (4) constrain this Neoproterozoic metamorphism is bounded by the the cooling history of this Neoproterozoic complex. Our Vimsodden–Kosibapasset zone (VKZ), which is a major study is based on extensive fieldwork supported by results strike–slip shear zone with sinistral kinematics (Fig. 2; of microstructural analysis and geothermobarometric Mazur et al. 2009). The VKZ separates the Neoproterozoic calculations. metamorphic complex from the remaining part of the south-western terranes of Svalbard, which were sub- Geological setting jected to younger, early Palaeozoic metamorphism (Gee & Tebenkov 2004; Czerny et al. 2010). The occurrence of The south-western part of Spitsbergen island exposes an a Neoproterozoic metamorphic domain in south-western elongate north–south trending metamorphic basement Spitsbergen has important bearing on terrane concepts exhumed within the axial zone of an Early Palaeogene for Svalbard construction in general, and specifically for fold-and-thrust belt (e.g., Lowell 1972; Dallmann et al. its proposed correlation with the Timanide metamorphic 1993; Braathen et al. 1995; Bergh et al. 1997). This belt of north-eastern Europe (Mazur et al. 2009). A better elevated basement high consists of Precambrian to understanding of the nature and extent of Neo- Early Palaeozoic rocks, the deformation and metamor- proterozoic metamorphism and associated pervasive phism of which were originally ascribed solely to the deformation, compared with earlier reports (Smulikowski Caledonian orogeny (e.g., Holtedahl 1926; Ohta 1982; 1965; Czerny et al. 1993; Majka et al. 2004), is an essen- Harland 1985; Harland et al. 1992). However, the occur- tial prerequisite for testing between, and refining, the rence of regionally extensive unconformities that are 250 Polar Research 29 2010 250–264 © 2010 the authors, journal compilation © 2010 Blackwell Publishing Ltd J. Majka et al. Neoproterozoic metamorphism in southern Svalbard Fig. 1 Geological sketch map of the Svalbard Archipelago (modified from Gee & Tebenkov 2004). associated with metamorphic and lithological contrasts western and south-western terranes (Fig. 1; Gee 1986; (e.g., Sandford 1956; Krasil’šcˇikov 1979; Birkenmajer Gee & Page 1994; Gee & Tebenkov 2004). 1975; Bjørnerud 1990) and geochronological studies North of Isfjorden, the south-western terranes of both provide evidence that the Caledonian basement Svalbard include a blueschist–eclogite allochthon known includes Proterozoic crustal domains juxtaposed by Early as the Vestgötabreen complex (e.g. Ohta 1979) that Palaeozoic tectonic events (e.g., Peucat et al. 1989; yielded argon-40 (40Ar)–argon-39 (39Ar) mineral cooling Balashov et al. 1995; Gee et al. 1995; Hellman et al. 1997; ages of ca. 460 My (Dallmeyer et al. 1990). The complex Johansson et al. 2004; Pettersson et al. 2009). These is non-conformably overlain by Middle Ordovician domains, together with their sedimentary cover, are conglomerates and limestones (Armstrong et al. 1986), interpreted to be individual tectonostratigraphic terranes succeeded by Late Ordovician to Early Silurian turbidites assembled during the Caledonian orogeny (e.g., Harland (Scrutton et al. 1976). The metamorphic basement, 1972; Harland & Gayer 1972; Gee & Page 1994). Based on together with its Early Palaeozoic cover, is thrust over a important contrasts in stratigraphy, structural develop- succession of diamictites of inferred Vendian age (Gee & ment and tectonothermal evolution, the Caledonian Tebenkov 2004). To the south of Isfjorden, the south- rocks of Svalbard have been divided into eastern, north- western terranes consist of a Meso- to Neoproterozoic Polar Research 29 2010 250–264 © 2010 the authors, journal compilation © 2010 Blackwell Publishing Ltd 251 Neoproterozoic metamorphism in southern Svalbard J. Majka et al. Fig. 2 Geological sketch map of the south- western part of Wedel Jarlsberg Land (modified from Czerny et al. 1993). metamorphic complex, which is divided into three and a metavolcanic succession of the Eimfjellet Group units: Isbjørnhamna, Eimfjellet and Deilegga groups (Birkenmajer 1958; Czerny et al. 1993). The Isbjørn- (Birkenmajer 1981, 1991). The latter is non-conformably hamna Group is composed of garnet–mica schists, overlain by the low-grade Neoproterozoic Sofiebogen paragneisses, calc-silicate rocks and marbles subjected Group, comprising a succession of conglomerates, lime- to amphibolite-grade Barrovian metamorphism, which stones and dolomites passing up into fine-grained was followed by greenschist facies metamorphism siliciclastic rocks (Bjørnerud 1990; Czerny et al. 1993; (Smulikowski 1965; Majka et al. 2004). The Eimfjellet Gee & Tebenkov 2004). The Sofiebogen Group is capped Group consists of quartzites, amphibolites and green- by Vendian tillites of the Kapp Lyell Group, and comprises schists, accompanied by minor metarhyolites and a thick series of diamictites (Bjørnerud 1990; Dallmann muscovite schists. These rocks were subjected to green- et al. 1990; Harland et al. 1993). The Cambro–Ordovician schist to lower amphibolite facies (Czerny et al. 1993). succession is tectonically emplaced atop the Proterozoic The contact between the two crustal blocks exposed in complexes (Dallmann et al. 1993; Mazur et al. 2009). the south-western part of Wedel Jarlsberg Land between Wedel Jarlsberg Land, located in the southern part of the Hornsund fjord and Torellbreen glacier is represented the south-western terranes (Fig. 2), consists of two Prot- by the ca. 2 km wide VKZ. The deformation zone is char- erozoic basement blocks with contrasting metamorphic acterized by a heterogeneous array of structures formed histories. The northern block comprises rocks of the during ductile shear deformation. Structural features of metasedimentary Deilegga and Sofiebogen groups, which the VKZ indicate bulk sinistral strike-slip to oblique-slip are separated by a Late Proterozoic angular unconformity shear strain formed under greenschist facies conditions. (Torellian unconformity; Birkenmajer 1975). The south- Thermochronologic data obtained from the Isbjørn- ern block corresponds to a stratified volcano-sedimentary hamna and Eimfjellet groups indicate a Neoproterozoic polymetamorphic complex that consists of a metasedi- age of metamorphism. 40Ar–39Ar step heating of mineral mentary sequence known as the Isbjørnhamna Group separates yielded a 616 My age for hornblende from the 252 Polar Research 29 2010 250–264 © 2010 the authors, journal compilation © 2010 Blackwell Publishing Ltd J. Majka et al. Neoproterozoic metamorphism in southern Svalbard Eimfjellet Group, and 585–575 My ages for muscovite consists of carbonate–mica schists, with irregular bands from the Isbjørnhamna Group (Manecki et al. 1998). of mica schists, paragneisses of the Skoddefjellet type Manecki et al. (1998) interpreted these ages as represent- and minor marble intercalations. A mineral assemblage ing a previously unrecognized episode of Neoproterozoic characteristic of carbonate-mica schists comprises Cal + reheating, probably connected with the opening of the Qtz + Bt + Grt +
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]
  • Assembly, Configuration, and Break-Up History of Rodinia
    Author's personal copy Available online at www.sciencedirect.com Precambrian Research 160 (2008) 179–210 Assembly, configuration, and break-up history of Rodinia: A synthesis Z.X. Li a,g,∗, S.V. Bogdanova b, A.S. Collins c, A. Davidson d, B. De Waele a, R.E. Ernst e,f, I.C.W. Fitzsimons g, R.A. Fuck h, D.P. Gladkochub i, J. Jacobs j, K.E. Karlstrom k, S. Lu l, L.M. Natapov m, V. Pease n, S.A. Pisarevsky a, K. Thrane o, V. Vernikovsky p a Tectonics Special Research Centre, School of Earth and Geographical Sciences, The University of Western Australia, Crawley, WA 6009, Australia b Department of Geology, Lund University, Solvegatan 12, 223 62 Lund, Sweden c Continental Evolution Research Group, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia d Geological Survey of Canada (retired), 601 Booth Street, Ottawa, Canada K1A 0E8 e Ernst Geosciences, 43 Margrave Avenue, Ottawa, Canada K1T 3Y2 f Department of Earth Sciences, Carleton U., Ottawa, Canada K1S 5B6 g Tectonics Special Research Centre, Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia h Universidade de Bras´ılia, 70910-000 Bras´ılia, Brazil i Institute of the Earth’s Crust SB RAS, Lermontova Street, 128, 664033 Irkutsk, Russia j Department of Earth Science, University of Bergen, Allegaten 41, N-5007 Bergen, Norway k Department of Earth and Planetary Sciences, Northrop Hall University of New Mexico, Albuquerque, NM 87131, USA l Tianjin Institute of Geology and Mineral Resources, CGS, No.
    [Show full text]
  • Balkatach Hypothesis: a New Model for the Evolution of the Pacific, Tethyan, and Paleo-Asian Oceanic Domains
    Research Paper GEOSPHERE Balkatach hypothesis: A new model for the evolution of the Pacific, Tethyan, and Paleo-Asian oceanic domains 1,2 2 GEOSPHERE, v. 13, no. 5 Andrew V. Zuza and An Yin 1Nevada Bureau of Mines and Geology, University of Nevada, Reno, Nevada 89557, USA 2Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095-1567, USA doi:10.1130/GES01463.1 18 figures; 2 tables; 1 supplemental file ABSTRACT suturing. (5) The closure of the Paleo-Asian Ocean in the early Permian was accompanied by a widespread magmatic flare up, which may have been CORRESPONDENCE: avz5818@gmail .com; The Phanerozoic history of the Paleo-Asian, Tethyan, and Pacific oceanic related to the avalanche of the subducted oceanic slabs of the Paleo-Asian azuza@unr .edu domains is important for unraveling the tectonic evolution of the Eurasian Ocean across the 660 km phase boundary in the mantle. (6) The closure of the and Laurentian continents. The validity of existing models that account for Paleo-Tethys against the southern margin of Balkatach proceeded diachro- CITATION: Zuza, A.V., and Yin, A., 2017, Balkatach hypothesis: A new model for the evolution of the the development and closure of the Paleo-Asian and Tethyan Oceans criti- nously, from west to east, in the Triassic–Jurassic. Pacific, Tethyan, and Paleo-Asian oceanic domains: cally depends on the assumed initial configuration and relative positions of Geosphere, v. 13, no. 5, p. 1664–1712, doi:10.1130 the Precambrian cratons that separate the two oceanic domains, including /GES01463.1. the North China, Tarim, Karakum, Turan, and southern Baltica cratons.
    [Show full text]
  • Sm–Nd and U–Pb Isotope Geochemistry of the Palaeoproterozoic Mafic Magmatism in Eastern and Northern Finland
    Geological Survey of Finland GeologicalGeological SurveySurvey ofof FinlandFinland 2018 Sm–Nd and U–Pb isotope geochemistry of the Palaeoproterozoic mafic magmatism in eastern and northern Finland Hannu Huhma, Eero Hanski, Asko Kontinen, Jouni Vuollo, Irmeli Mänttäri and Yann Lahaye Bulletin 405 • Monograph Geological Survey of Finland, Bulletin The Bulletin of the Geological Survey of Finland publishes the results of scientific research that is thematically or geographically connected to Finnish or Fennoscandian geology, or otherwise related to research and innovation at GTK. Articles by researchers outside GTK are also welcome. All manuscripts are peer reviewed. Editorial Board Prof. Pekka Nurmi, GTK, Chair Dr Stefan Bergman, SGU Dr Asko Käpyaho, GTK Dr Antti Ojala, GTK Dr Timo Tarvainen, GTK, Scientific Editor Instructions for authors available from the Scientific Editor. GEOLOGICAL SURVEY OF FINLAND Bulletin 405 Sm–Nd and U–Pb isotope geochemistry of the Palaeoproterozoic mafic magmatism in eastern and northern Finland by Hannu Huhma, Eero Hanski, Asko Kontinen, Jouni Vuollo, Irmeli Mänttäri and Yann Lahaye Unless otherwise indicated, the figures have been prepared by the authors of the publication. Layout: Elvi Turtiainen Oy Espoo 2018 Huhma, H.1) , Hanski, E.2), Kontinen, A.3), Vuollo, J.4), Mänttäri, I.1) & Lahaye, Y.1) 2018. Sm–Nd and U–Pb isotope geochemistry of the Palaeoproterozoic mafic magmatism in eastern and northern Finland. Geological Survey of Finland, Bulletin 405, 150 pages, 128 figures, 1 table and 11 appendices. The extensive isotopic studies performed at the Geological Survey of Finland (GTK) since the early 1970s have shown that mafic magmas in the Karelia province of the Fennoscandian Shield were emplaced in several stages, including ca.
    [Show full text]
  • Geochemical and Lu-Hf Isotope (LA-ICP-MS
    Arch & Anthropol Open Acc Archaeology Copyright& Anthropology: © Kuznetsov NB CRIMSON PUBLISHERS C Wings to the Research Open Access ISSN: 2577-1949 Research Article Geochemical and Lu-Hf Isotope Systematic of Detrital Zircons from the Ordovician Sandstones of the Sol-Iletsk Arch (Russia, Northern Caspian, Borehole Ordovician-2) Kuznetsov NB 1,2,3,4*, Belousova EA4, Romanyuk TV2,3,4 1Geological Institute, Russian Academy of Sciences, Russia 2Schmidt Institute of Physics of the Earth, Russian Academy of Science, Russia 3Gubkin Russian State University of Oil and Gas, National Research University, Russia 4Australian Research Council Centre of Excellence for Core to Crust Fluid Systems/GEMOC, Macquarie University, Australia *Corresponding author: Kuznetsov NB, Geological Institute, Russian Academy of Sciences, Gubkin Russian State University of Oil and Gas, Russia Submission: July 02, 2018; Published: September 20, 2018 Abstract The Sol-Iletsk arch is located at the south eastern edge of the East European platform (EEP), where EEP adjoins with the Southern Urals. The results of the integrated (U-Pb age, Lu-Hf isotopic system and trace-elements) study of detrital zircons (dZr) from the Ordovician sandstones (within Sol-Iletsk arch) reached by borehole Ordovician-2 are presented. The primary sources of Early Precambrian dZr were most likely the crystalline complexes of the Late Proterozoic Volgo-Sarmatian and Taratash orogens and Archean Volga-Uralia basement. However, for numerous dZr with ages younger 1.65Ga, it is not possible presently to unambiguously identify primary sources. Crystalline complexes with such ages are absolutely atypical for the south-eastern part of the EEP, but they occurred within parts EEP very remote from Sol-Iletsk arch and beyond EEP.
    [Show full text]
  • Ages of Detrital Zircons (U/Pb, LA-ICP-MS) from the Latest
    Precambrian Research 244 (2014) 288–305 Contents lists available at ScienceDirect Precambrian Research jo urnal homepage: www.elsevier.com/locate/precamres Ages of detrital zircons (U/Pb, LA-ICP-MS) from the Latest Neoproterozoic–Middle Cambrian(?) Asha Group and Early Devonian Takaty Formation, the Southwestern Urals: A test of an Australia-Baltica connection within Rodinia a,∗ b c Nikolay B. Kuznetsov , Joseph G. Meert , Tatiana V. Romanyuk a Geological Institute, Russian Academy of Sciences, Pyzhevsky Lane, 7, Moscow 119017, Russia b Department of Geological Sciences, University of Florida, 355 Williamson Hall, Gainesville, FL 32611, USA c Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya ul. 10, Moscow 123810, Russia a r t i c l e i n f o a b s t r a c t Article history: A study of U-Pb ages on detrital zircons derived from sedimentary sequences in the western flank of Received 5 February 2013 Urals (para-autochthonous or autochthonous with Baltica) was undertaken in order to ascertain/test Received in revised form source models and paleogeography of the region in the Neoproterozoic. Samples were collected from the 16 September 2013 Ediacaran-Cambrian(?) age Asha Group (Basu and Kukkarauk Formations) and the Early Devonian-aged Accepted 18 September 2013 Takaty Formation. Available online 19 October 2013 Ages of detrital zircons within the Basu Formation fall within the interval 2900–700 Ma; from the Kukkarauk Formation from 3200 to 620 Ma. Ages of detrital zircons from the Devonian age Takaty For- Keywords: Australia mation are confined to the Paleoproterozoic and Archean (3050–1850 Ma).
    [Show full text]
  • Crustal Structure of the Volgo-Uralian Subcraton Revealed by Inverse And
    https://doi.org/10.5194/se-2021-98 Preprint. Discussion started: 17 August 2021 c Author(s) 2021. CC BY 4.0 License. Crustal structure of the Volgo-Uralian subcraton revealed by inverse and forward gravity modeling Igor Ognev1, Jörg Ebbing2, Peter Haas2 1Institute of Geology and Petroleum Technologies, Kazan Federal University, 4/5 Kremlyovskaya street, Kazan 420008, 5 Russia 2 Department of Geosciences, Kiel University, Otto-Hahn Platz 1, Kiel, D-24118, Germany Correspondence to: Igor Ognev ([email protected]) Abstract. Volgo-Uralia is a Neoarchean easternmost part of the East European craton. Recent seismic studies of the Volgo- Uralian region provided new insights into the crustal structure of this area. In this study, we combine satellite gravity and 10 seismic data in a common workflow to perform a complex study of Volgo-Uralian crustal structure which is useful for further basin analysis of the area. In this light, a new crustal model of the Volgo-Uralian subcraton is presented from a step-wise approach: (1) inverse gravity modeling followed by (2) 3D forward gravity modeling. First, inversion of satellite gravity gradient data was applied to determine the Moho depth for the area. Density contrasts between crust and mantle were varied laterally according to the tectonic units present in the region, and the model is constrained 15 by the available active seismic data. The Moho discontinuity obtained from the gravity inversion was consequently modified and complemented in order to define a complete 3D crustal model by adding information on the sedimentary cover, upper crust, lower crust, and lithospheric mantle layers in the process of forward gravity modeling where both seismic and gravity constraints were respected.
    [Show full text]
  • Ediacaran–Middle Paleozoic Oceanic Voyage of Avalonia from Baltica Via Gondwana to Laurentia Paleomagnetic, Faunal and Geological Constraints J
    Document generated on 09/29/2021 6:04 a.m. Geoscience Canada Journal of the Geological Association of Canada Journal de l’Association Géologique du Canada Ediacaran–Middle Paleozoic Oceanic Voyage of Avalonia from Baltica via Gondwana to Laurentia Paleomagnetic, Faunal and Geological Constraints J. Duncan Keppie and D. Fraser Keppie Volume 41, Number 1, 2014 Article abstract Current Ediacaran–Cambrian, paleogeographic reconstructions place Avalonia, URI: https://id.erudit.org/iderudit/1023627ar Carolinia and Ganderia (Greater Avalonia) at high paleolatitudes off northwestern Gondwana (NW Africa and/or Amazonia), and locate NW See table of contents Gondwana at either high or low paleolatitudes. All of these reconstructions are incompatible with 550 Ma Avalonian paleomagnetic data, which indicate a paleolatitude of 20–30ºS for Greater Avalonia and oriented with the present- Publisher(s) day southeast margin on the northwest side. Ediacaran, Cambrian and Early Ordovician fauna in Avalonia are mainly endemic, which suggests that Greater The Geological Association of Canada Avalonia was an island microcontinent. Except for the degree of Ediacaran deformation, the Neoproterozoic geological records of mildly deformed ISSN Greater Avalonia and the intensely deformed Bolshezemel block in the Timanian orogen into eastern Baltica raise the possibility that they were 0315-0941 (print) originally along strike from one another, passing from an island 1911-4850 (digital) microcontinent to an arc-continent collisional zone, respectively. Such a location and orientation is consistent with: (i) Ediacaran (580–550 Ma) Explore this journal ridge-trench collision leading to transform motion along the backarc basin; (ii) the reversed, ocean-to-continent polarity of the Ediacaran cratonic island arc recorded in Greater Avalonia; (iii) derivation of 1–2 Ga and 760–590 Ma detrital Cite this article zircon grains in Greater Avalonia from Baltica and the Bolshezemel block (NE Timanides); and (iv) the similarity of 840–1760 Ma TDM model ages from Keppie, J.
    [Show full text]
  • 192016 94216 Rohr Et Al 2013
    ARTICLES Geochronology of Paleoproterozoic Augen Gneisses in the Western Gneiss Region, Norway: Evidence for Sveconorwegian Zircon Neocrystallization and Caledonian Zircon Deformation Torkil S. Røhr,1,* Bernard Bingen,1 Peter Robinson,1 and Steven M. Reddy2 1. Geological Survey of Norway, P.O. Box 6315 Sluppen, 7491 Trondheim, Norway; 2. Institute for Geoscience Research, Department of Applied Geology, Curtin University, G.P.O. Box U1987, Perth, Western Australia 6845, Australia ABSTRACT The Western Gneiss Region, western Norway, consists of Paleoproterozoic crust of Baltica ancestry (Baltican Base- ment), partly subducted to high- and ultrahigh-pressure (HP-UHP) conditions during the Scandian Orogeny between 415 and 395 Ma. The dominant felsic gneisses carry little evidence for the HP-UHP history but were affected by amphibolite-facies reworking during exhumation. Laser ablation–ICP-MS and secondary ion mass spectrometry (SIMS) zircon U-Pb data collected in augen gneiss samples constrain the magmatic and metamorphic geochronology in this crust. Five samples from the eclogite-bearing HP-UHP basement near Molde yield intrusion ages ranging from ע Ma. Two samples of the structurally underlying eclogite-free basement yield ages of 1685 10 ע 6to 1594 ע 1644 Ma, and a sample from the infolded Middle Allochthon Risberget Nappe yields an equivalent age 13 ע 18and 1644 Ma. Two samples of the eclogite-bearing basement contain low Th/U neocrystallized zircon with an 18 ע of1676 -Ma. This zircon provides the northernmost direct evidence for at least amphibolite-facies Sveco 26 ע age of950 norwegian metamorphism in unquestionable Baltica crust, close to the known “Sveconorwegian boundary” in the Western Gneiss Region.
    [Show full text]
  • Neoproterozoic and Post-Caledonian Exhumation and Shallow Faulting in NW Finnmark from K/Ar Dating and P/T Analysis of Fault-Rocks
    Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K/Ar dating and p/T analysis of fault-rocks Jean-Baptiste P. Koehl1,2, Steffen G. Bergh1,2, Klaus Wemmer3 6) Department of Geosciences, University of Tromsø, N-9037 Tromsø, Norway. 7) Research Center for Arctic Petroleum Exploration (ARCEx), University of Tromsø, N-9037 Tromsø, Norway. 8) Geoscience Centre, Georg-August-University Göttingen, Goldschmidtstraβe 3, 37077 Göttingen, Germany. Abstract. Well-preserved fault gouge along brittle faults in Paleoproterozoic, volcano-sedimentary rocks of the Raipas Group exposed in the Alta-Kvænangen tectonic window in northern Norway yielded latest Mesoproterozoic (ca. 1050 ± 15 Ma) to mid Neoproterozoic (ca. 825-810 ± 18 Ma) K/Ar ages. Pressure-temperature estimates from microtextural and mineralogy analyses of fault-rocks indicate that brittle faulting may have initiated at depth of 5-10 km during the opening of the Asgard Sea in the latest Mesoproterozoic-early Neoproterozoic (ca. 1050-945 Ma), and continued with a phase of shallow faulting during to the opening of the Iapetus Ocean-Ægir Sea and the initial breakup of Rodinia in the mid Neoproterozoic (ca. 825-810 Ma). The predominance and preservation of synkinematic smectite and subsidiary illite in cohesive and non-cohesive fault-rocks indicate that Paleoproterozoic basement rocks of the Alta-Kvænangen tectonic window remained at shallow crustal levels (< 3.5 km) and were not reactivated since mid Neoproterozoic times. Slow exhumation rate estimates for the early-mid Neoproterozoic (ca 10-75 m per Ma) suggest a period of tectonic quiescence between the opening of the Asgard Sea and the breakup of Rodinia.
    [Show full text]
  • COSC-1 – Drilling of a Subduction-Related Allochthon in the Palaeozoic Caledonide Orogen of Scandinavia
    Science Reports Sci. Dril., 19, 1–11, 2015 www.sci-dril.net/19/1/2015/ doi:10.5194/sd-19-1-2015 © Author(s) 2015. CC Attribution 3.0 License. COSC-1 – drilling of a subduction-related allochthon in the Palaeozoic Caledonide orogen of Scandinavia H. Lorenz1, J.-E. Rosberg2, C. Juhlin1, L. Bjelm2, B. S. G. Almqvist1, T. Berthet1, R. Conze3, D. G. Gee1, I. Klonowska1, C. Pascal4, K. Pedersen5, N. M. W. Roberts6, and C.-F. Tsang1,7 1Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden 2Engineering Geology, Lund University, John Ericssons väg 1, 221 00 Lund, Sweden 3GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany 4Institute of Geology, Mineralogy and Geophysics, Ruhr-University Bochum, Universitätsstraße 150, 44780 Bochum, Germany 5Department of Civil and Environmental Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden 6NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham, NG12 5GG, UK 7Lawrence Berkely National Laboratory, Earth Sciences Division, 1 Cyclotron Road, MS74R316C, Berkeley, CA 94720, USA Correspondence to: H. Lorenz ([email protected]) Received: 13 February 2015 – Revised: 24 April 2015 – Accepted: 5 May 2015 – Published: 29 May 2015 Abstract. The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project focuses on mountain building processes in a major mid-Palaeozoic orogen in western Scandinavia and its comparison with modern analogues. The project investigates the subduction-generated Seve Nape Complex. These in part un- der ultra-high-pressure conditions metamorphosed outer continental margin and continent–ocean transition zone assemblages were emplaced onto the Baltoscandian platform and there influenced the underlying allochthons and the basement.
    [Show full text]
  • Eastern Europe: the Timanian and Uralian Orogens Victoria Pease, Department of Geological Sciences, Stockholm University, Stockholm, Sweden
    Eastern Europe: The Timanian and Uralian Orogens Victoria Pease, Department of Geological Sciences, Stockholm University, Stockholm, Sweden © 2021 Elsevier Ltd. All rights reserved. Introduction 302 The Timanides 302 The Timanian foreland fold and thrust belt 303 The Pechora basin and Barents shelf 305 The Timanides within the Ural mountains 306 Tectonic evolution 306 The Uralides 307 Crustal structure 307 Tectonic evolution 308 Future Work 309 Further Reading 310 Glossary Orogenesis The mountain building process resulting from collision between two tectonic plates; can be ocean-continent or continent-continent collision. Supercontinent Assembly of much of Earth’s continental crust into a large single landmass, such as Pangea or Rodinia. Timanian orogen Latest Neoproterozoic through Cambrian mountain building event resulting from oceanic subduction beneath/accretion to NE Baltica. Uralian orogen Carboniferous through Permian mountain building event resulting from the subduction of oceanic crust associated with the Uralian ocean and ultimately the collision between eastern Europe and the Kazakhstan plus Siberian plates. Wilson cycle Divergence (rifting) of continental crust ultimately results in the formation of intervening ocean basin due to spreading; later motion reversal results in the closure of that ocean with associated collision leading to orogenesis. Introduction Eastern Europe as seen today is the result of multiple orogenic events, i.e., the mountain building processes associated with collision between tectonic plates. Orogens may be products of the supercontinent cycle: continental collision results in orogenesis and fewer but larger continents. Rifting, on the other hand, leads to basins and more, smaller continents. Multiple orogens occurring in the same general location over geological time are not uncommon and can be explained by the Wilson Cycle.
    [Show full text]