Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

Kähkönen, Y.

doi:10.17741/bgsf/71.1.002

Cited by 16 publications

(6 citation statements)

References 13 publications

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“…The TIMS and SIMS datings of the rocks in the To rsholma area give us time constraints as follows. The emplacement age of the deformed orthogneiss, c. 1879±6 Ma, is comparable to the ages of the early gneissose granodioritic intrusions reported from southern Finland in this study (c. 1885 Ma,a nd summarised in Ta ble 3) and in neighbouring regions of the Ta mpere SchistB elt (c. 1900-1880 Ma)a nd elsewhere (Kähkönen, 1999;Nironen et al, 2002). The studied area forms a sub-horizontal sequence of multiply folded supracrustal rocks and gneisses with structures (refolded folds in Fig.…”

Section: 1timing Of the Imbrication And Overthrust In Torsholmasupporting

confidence: 86%

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Timing of Svecofennian crustal growth and collisional tectonics in Åland, SW Finland

Ehlers¹,

Skiöld²,

Vaasjoki³

2004

Bull Geol Soc Finland

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In an effort to quantify the time parameter in the tectonomagmatic evolution of what has been called the Southern Svecofennian Arc Complex (SSAC) of SW Finland, advanced radiometric dating techniques have here been applied to rock groups of key importance in that area. In this paper we report the results of 131 high-resolution ion microprobe spot analyses (SIMS) of zircons, and 33 measurements using isotope dilution mass spectrometry (ID-TIMS) on zircon, monazite and titanite,and employing both large-sample multi-grain as well as single-grain techniques.The To rsholma area of the Åland archipelago,situated between southern Finland and central Sweden, is a key structural area significant to resolve the time dimension in Svecofennian tectonics.There a collage of imbricated rock slabs was formed by tectonic shortening representing the culmination of large-scale penetrative Svecofennian deformation. Another structurally significant feature investigated is the South Finland Shear Zone (SFSZ) that transects the southwest-Finnish archipelago and further east follows the southern coast of Finland.This shear zone forms the southern limit of the c. 1830 Ma Late Svecofennian Granite and Migmatite Zone (LSGM) and also features deformations of a later stage when the considered region of Svecofennian crust was consolidated.The obtained age results and theirt ectonic analysis can be summarized as follows. The Enklinge volcanic sequence (1885±6 Ma) is within error limits coeval with the intrusion of abundant early-kinematic gneissose granodiorites whose average age of 1884±5 Ma marks the formation of new crust in this region.Some of these geisses contain a significant amount of 2000-2080 Ma zircon. Although many Svecofennian granitoids are known to contain heterogeneous zircon populations, mainly formed c. 1890 Ma ago but also containing an inherited component, the Kökar gneiss is, to the best of our knowledge,the first case where inheritance from c. 2030 Ma sources has been unequivocally demonstrated in a syntectonic Svecofennian intrusive rock.At To rsholma,granodiorites (1879±6 Ma) have similarly intruded the supracrustal series, but there they were later metamorphosed into granulite orthogneisses.The mesoscopic recumbent folds and subhorizontals chistosityo ft heseg neisses were transected by a set of steep amphibolitic dykes indicating an episode of extension. During a preceding stage,these gneisses had been sandwiched like an allochthonous slab unit between the supracrustal rocks. Yo unger sheet-like granodioritic intrusions (1861±19 Ma) with associated dykes (1865±7 Ma) reflect an even later stage of collisional thrusting. Altogether this tectonic evolution lasted for approximately 15 Ma (c. 1875-1860 and records a period of significant deformations during the Svecofennian orogeny. Monazites and zircon rims yield concordant U-Pb ages of c. 1830 Ma.This is in agreement with previously obtained ages of late Svecofennian granites and migmatites in the LSGM zone in S Finland.Weaklyd eformed pegmatites and even-grained granit...

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Section: 1timing Of the Imbrication And Overthrust In Torsholmasupporting

confidence: 86%

“…The oldest well-constrained age of early magmatism from the Ta mperer egion is c. 1904±4 Ma (Kähkönen, 1999). The rock interfingers surrounding supracrustals which sometimes haveb een paralleled with the Haveri, and Vammala belts (Kähkönen &N ironen, 1994).…”

Section: Regional Considerations Within the Svecofennian Domainmentioning

confidence: 99%

Timing of Svecofennian crustal growth and collisional tectonics in Åland, SW Finland

Ehlers¹,

Skiöld²,

Vaasjoki³

2004

Bull Geol Soc Finland

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“…Осадочно-вулканогенная толща прорвана телами гранитоидов, связанных с Центрально-Финляндским массивом. Основание тектоно-стратиграфического разреза в южной части пояса образовано турбидитами и глинистыми осадками, значительно обогащенными графитом и сульфидами, что нехарактерно для остальной части пояса [Kähkönen, 1999]. Пояс Пирканмаа протяженностью 175 км при максимальной ширине около 50 км можно рассматривать в качестве южного компонента пояса Тампере.…”

Section: геологический очеркunclassified

3d Model of the Deep Structure of the Svecofennian Accretionary Orogen Based on Data From CDP Seismic Reflection Method, Mt Sounding and Density Modeling

Минц¹,

Mekhdiev

Ladoga³

et al. 2018

Proceedings of KarRC of RAS

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“…According to Kähkönen (1989;1999;, Kähkönen and Leveinen (1994), Ojakangas (1986), and Nironen (1989a), the Tampere Belt is predominant-ly composed of turbiditic metasedimentary rocks, felsic-intermediate arc-type metavolcanic rocks and granitoids, and formed in an island-arc or continental arc setting. The absence of carbonate rocks and iron formations, the presence of turbidites and a mantle reflector dipping to the north indicate a steep convergent plate margin and northward subduction (Kähkönen, 1989;Kähkönen, 1999;Lahtinen et al, 2005). The metasedimentary rocks are mainly Ma old and the metavolcanic rocks 1904-1889 Ma old (Huhma et al, 1991;Kähkönen et al, 1989;Kähkönen et al, 2004).…”

Section: Tampere Beltmentioning

confidence: 99%

Geochemical and boron isotopic compositions of tourmalines from selected gold-mineralised and barren rocks in SW Finland

Talikka¹,

Vuori²

2010

Bull Geol Soc Finland

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Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

Cited by 16 publications

References 13 publications

Timing of Svecofennian crustal growth and collisional tectonics in Åland, SW Finland

Timing of Svecofennian crustal growth and collisional tectonics in Åland, SW Finland

3d Model of the Deep Structure of the Svecofennian Accretionary Orogen Based on Data From CDP Seismic Reflection Method, Mt Sounding and Density Modeling

Geochemical and boron isotopic compositions of tourmalines from selected gold-mineralised and barren rocks in SW Finland

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