Long-term convergence along SW fennoscandia: 330 m.y. of proterozoic crustal growth

Åhäll, Karl‐Inge; Connelly, James N.

doi:10.1016/j.precamres.2007.09.007

Cited by 70 publications

(7 citation statements)

References 71 publications

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“…The 1527 ± 23 Ma reverse dip-slip in DZ4:-549 is consistent with maximum compressive stress (σ 1 ) oriented WSW-ENE. This is roughly in line with NE-SW bulk crustal shortening during the Gothian orogeny affecting southwestern Sweden at 1.75-1.55 Ga 33,34 . However, in eastern Sweden and western Finland this period is commonly ascribed to NE-SW extensional tectonics 1,25 , which disagrees with the reverse dip-slip in DZ4:-549.…”

Section: Discussionsupporting

confidence: 81%

In situ Rb-Sr dating of slickenfibres in deep crystalline basement faults

Tillberg

Drake

Zack

et al. 2020

Sci Rep

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Establishing temporal constraints of faulting is of importance for tectonic and seismicity reconstructions and predictions. Conventional fault dating techniques commonly use bulk samples of syn-kinematic illite and other K-bearing minerals in fault gouges, which results in mixed ages of repeatedly reactivated faults as well as grain-size dependent age variations. Here we present a new approach to resolve fault reactivation histories by applying high-spatial resolution Rb-Sr dating to finegrained mineral slickenfibres in faults occurring in Paleoproterozoic crystalline rocks. Slickenfibre illite and/or K-feldspar together with co-genetic calcite and/or albite were targeted with 50 µm laser ablation triple quadrupole inductively coupled plasma mass spectrometry analyses (LA-ICP-MS/MS). The ages obtained disclose slickenfibre growth at several occasions spanning over 1 billion years, from at least 1527 Ma to 349 ± 9 Ma. The timing of these growth phases and the associated structural orientation information of the kinematic indicators on the fracture surfaces are linked to far-field tectonic events, including the Caledonian orogeny. Our approach links faulting to individual regional deformation events by minimizing age mixing through micro-scale analysis of individual grains and narrow crystal zones in common fault mineral assemblages.

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Section: Discussionsupporting

confidence: 81%

In situ Rb-Sr dating of slickenfibres in deep crystalline basement faults

Tillberg

Drake

Zack

et al. 2020

Sci Rep

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“…The 1.6-1.55 Ga calc-alkaline granitoids and gneisses of the Bamble-Lillesand and Kongsberg-Marstrand blocks have similar moderately juvenile isotopic signatures (Andersen et al, 2002b;2004a), and thus seem likely candidates for continental arc rocks formed via processes similar to that of the Suldal Arc. If an accretionary orogen is envisaged for the 1.65-1.45 Ga period in SW Fennoscandia, as has been suggested by Åhäll & Connelly (2008), then one can imagine a collage of various immature volcanic arcs, ribbon continents, and continental arcs; all forming within the vicinity of the SW Fennoscandian margin, all originating as rifted fragments, and all possessing varying volumes of older crustal substrate.…”

Section: The Origin Of the Hardangervidda-rogaland And Telemark Blocksmentioning

confidence: 90%

“…At ~1.85 Ga, a subduction zone initiated on the southwest margin (present-day position) of the continent, producing the Transcandinavian Igneous Belt (TIB; see Högdahl et al, 2004). The terranes to the southwest of the TIB that comprise the Southwest Scandinavian Domain (SSD), can be interpreted as forming in continental and island arcs along a long-lived subduction margin that progressively moved away from the Fennoscandian continent (Åhäll & Connelly, 2008) in a retreating accretionary orogen (Cawood et al, 2009). …”

Section: Geological Settingmentioning

confidence: 99%

“…Gaál & Gorbatschev, 1987;Bingen et al, 2008a). 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).…”

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confidence: 99%

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

Roberts

Slagstad

Parrish

et al. 2012

Contrib Mineral Petrol

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The Hardangervidda-Rogaland Block within southwest Norway is host to ~1.52-1.48 Ga continental building, and variable reworking during the ~1.1-0.9 Ga Sveconorwegian orogeny. Due to the lack of geochronological and geochemical data, the timing and tectonic setting of early Mesoproterozoic magmatism has long been ambiguous. This paper presents zircon U-Pb-Hf-O isotope data combined with whole-rock geochemistry to address the age and petrogenesis of basement units within the Suldal region, located in the centre of the Hardangervidda-Rogaland Block. The basement comprises variably deformed grey gneisses and granitoids that petrologically and geochemically resemble mature volcanic arc lithologies.U-Pb ages confirm that magmatism occurred from ~1521 to 1485 Ma, and conspicuously lack any xenocrystic inheritance of distinctly older crust. Hafnium isotope data range from εHf (initial) +1 to +11, suggesting a rather juvenile magmatic source, but with possible involvement of late Palaeoproterozoic crust. Oxygen isotope data range from mantle-like (δ 18 O ~5‰) to elevated (~10‰) suggesting involvement of low-temperature altered material (e.g. supracrustal rocks) in the magma source. The Hf-O isotope array is compatible with mixing between mantle-derived material with young low-temperature altered material (oceanic crust/sediments) and older low-temperature altered material (continent-derived sediments). This, combined with a lack of xenoliths and xenocrysts, exposed older crust, AFC trends and S-type geochemistry, all point to mixing within a deep-crustal magma-generation zone. A proposed model comprises accretion of altered oceanic crust and the overlying sediments to a pre-existing continental margin, underthrusting to the magma generation zone, and remobilisation during arc magmatism. The geodynamic setting for this arc magmatism is comparable to that seen in the Phanerozoic (e.g. the Sierra Nevada and Coast ranges batholiths), with compositions in the Suldal Sector reaching those of average upper continental crust. As within these younger examples, factors that drive magmatism towards the composition of the average continental crust include the addition of sedimentary material to magma source regions, and delamination of cumulate material. Underthrusting of sedimentary materials and their subsequent involvement in arc magmatism is perhaps a more widespread mechanism involved in continental growth than is currently recognized. Finally, the Suldal Arc magmatism represents a significant juvenile crustal addition to SW Fennoscandia.

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“… (A) The sketch map shows large‐scale tectonic situation and units in south‐central Scandinavia (compiled from Åhäll and Connelly, 2008; Bingen and Solli, 2009). WGR, Western Gneiss Region; TIB, Transscandinavian Igneous Belt; CDF, Caledonian deformation front; SDF, Sveconorwegian deformation front; SF, approximate boundary of Sveconorwegian overprint in the WGR; K‐Ba, Kongsberg‐Bamble terrane; OR, Oslo rift; SK, Mesozoic cover of Skåne.…”

Section: Introductionmentioning

confidence: 99%

The Ammarnäs Complex in the central Scandinavian Caledonides: an allochthonous basin fragment in the foreland of the Sveconorwegian orogen?

2011

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The Ammarnä s Complex is a tectonic unit in the Middle Allochthon of the central Scandinavian Caledonides and consists of several hundred metres of thick uniform meta-greywacke successions of greenschist metamorphic grade containing kilometre-scale lenses of pre-Caledonian crystalline basement rocks. Meta-greywacke samples were analysed for major and trace elements and U-Pb isotopes. Lithoclasts and geochemical data indicate that the greywackes were derived from granitic-granodioritic rocks. Detrital zircon dating yielded 7% Neoproterozoic, 52% Mesoproterozoic and 41% Palaeo-proterozoic 207 Pb ⁄ 206 Pb ages with two prominent age peaks at 1.64 and 1.5 Ga and a broad distribution of Sveconorwegian (1140-900 Ma) and 'pre-Sveconorwegian' (1340-1140 ages. We interpret the Ammarnä s Complex as a former Neoproterozoic basin in the foreland of the Sveconorwegian orogen, which escaped major pre-Caledonian magmatismmetamorphism and which was most likely deposited between c. 920 and 630 Ma.

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Long-term convergence along SW fennoscandia: 330 m.y. of proterozoic crustal growth

Cited by 70 publications

References 71 publications

In situ Rb-Sr dating of slickenfibres in deep crystalline basement faults

In situ Rb-Sr dating of slickenfibres in deep crystalline basement faults

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

The Ammarnäs Complex in the central Scandinavian Caledonides: an allochthonous basin fragment in the foreland of the Sveconorwegian orogen?

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