Recurrent mesoproterozoic continental magmatism in South-Central Norway

Abstract

We report U-Pb dates and Lu-Hf isotope data, obtained by LAM-ICPMS, for zircons from metamorphic rocks of the Setesdalen valley, situated in the Telemark block south of the classic Telemark region of southern Norway. The samples include infracrustal rocks from the metamorphic basement, metaigneous rocks and metasediments from the Byglandsfjorden supracrustal cover sequence, and metaigneous rocks which intruded the whole succession. The main crustal evolution took place from 1,550-1,020 Ma, beginning with the emplacement of juvenile tonalitic melts; the contribution of older crustal material increased with time. Around 1,320 Ma, further addition of juvenile material occurred, involving both mafic and felsic melts, metamorphism and deformation. Acid magmas with high FeO*/MgO were intruded at 1,215 Ma, coinciding with underplating elsewhere in South Norway. The period starting at 1,215 Ma is represented by supracrustal rocks, principally metarhyolites with minor mafic material and immature sediments of the Byglandsfjorden Group. The crust generation processes ended with the intrusion of diorites and granodiorites at 1,030 Ma, late in the Sveconorwegian orogeny. Regional processes of metamorphism and deformation (around 1,290 and 1,000 Ma) can be related to the assembly of Rodinia.

Intermontane basins and bimodal volcanism at the onset of the Sveconorwegian Orogeny, southern Norway

“…This implies that: (i) these two depocentres were receiving similar age detritus but derived from different source rocks via discrete drainage systems (see also Lamminen et al, 2011); and (ii) the average Hf isotopic composition of the Lake Vrådal region are more depleted than those north of Lake Bandak. However, the wide spread in published zircon Hf values from the Telemark region do not provide the resolution necessary to discriminate specific sources for the detrital zircons in this study (see Andersen et al, 2002;Andersen et al, 2007;Andersen et al, 2009;Pedersen et al, 2009;Lamminen and Köykkä, 2010;Bingen et al, 2011; A c c e p t e d M a n u s c r i p t 18 . Furthermore, oxygen isotopes in the Sveconorwegian-age zircons analyzed show that the host magmas were derived from a source that had assimilated an appreciable amount of supracrustal material driving their compositional trends to higher (Fig.…”

“…Dons, 1960;1972;Sigmond, 1978) that can be separated into several temporally distinct volcanic and sedimentary basins ranging from ~1.5 to 1.1 Ga in age (e.g. Bingen et al, 2002Bingen et al, , 2003Brewer et al, 2004;Laajoki et al, 2002;Bingen et al, 2008;Pedersen et al, 2009;Roberts et al, 2011). A number of terminologies and groupings have been proposed for this suite of supracrustal rocks, and here we follow the terminology of Laajoki et al (2002).…”

“…Several distinct phases of Mesoproterozoic intra-continental extension and associated bimodal volcanism are present in southern Norway: for example, the ~1.26-1.21 Ga Saesvatn-Valldal Group (Bingen et al, 2002;Brewer et al, 2004), ~1.23 Ga Grøssae-Totak belt (Sigmond, 1978;Roberts et al, 2011), < 1.12 Ga Ofte, Morgedal, and Gjuve formations (Brewer et al, 2002;Laajoki et al, 2002;Bingen et al, 2003, herein), and the <1.22 Ga Byglandsfjorden supracrustals (Pedersen et al, 2009) Brewer, et al, 2004;Roberts et al, 2011). This is consistent with geodynamic models that join the leading margins of Fennoscandia, Laurentia, and Amazonia as part of a long-lived (> 600 Ma) retreating accretionary margin (Zhao et al, 2004;Whitmeyer and Karlstrom, 2007;Johansson, 2009;Condie, 2013;Roberts, 2013).…”

Zircon U-Pb, Hf and O isotope constraints on growth versus reworking of continental crust in the subsurface Grenville orogen, Ohio, USA

“…the Baltic Shield (Pedersen et al, 2009;Petersson et al 2013), in Mexico (Weber et al, 2010) and in the Gardar Province of south Greenland (Blaxland et al, 1978;Upton et al, 2003). This event is roughly coeval with emplacement of the Harp (1271 ±1 Ma; Cadman et al, 1993), Mackenzie (1267 ±2 Ma; Le Cheminant & Heaman 1989) and Sudbury (1238 ±4 Ma; Krogh et al, 1987) dyke swarms.…”

Sedimentary recycling in arc magmas: geochemical and U–Pb–Hf–O constraints on the Mesoproterozoic Suldal Arc, SW Norway

“…The evolution of the ~1.7 to 1.5 Ga crust can be described by two end-member models: 1) Palaeoproterozoic crust underlies the entire region and has been recycled during younger magmatic episodes (Andersen et al, 2002b;2004a;2009b), or 2) the various terranes represent accreted juvenile arcs with limited contribution from older material (Brewer et al, 1998;Åhäll & Connelly, 2008). Various isotope data point to a contribution from Palaeoproterozoic crust to both Gothian aged (~1.7-1.55 Ga) and Sveconorwegian magmatism (1.2-0.93 Ga; Andersen, 1997;Andersen et al, 2001;2002b;2004a;2007b;2009b;Andersen & Griffin 2004;Pedersen et al, 2009). In the Hardangervidda-Rogaland and Telemark Blocks, ~1.5 Ga units are widespread and are the oldest exposed crust currently dated (Bingen et al, 2005;2008b;Pedersen et al, 2009), but are hitherto poorly understood.…”