Chapter 8 Svecofennian supracrustal rocks

Kähkönen, Y.

doi:10.1016/s0166-2635(05)80009-x

Cited by 34 publications

(22 citation statements)

References 59 publications

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“…Bergman et al 2004b;Hermansson et al 2007). Notably, the mafic Hedesunda rocks show overlapping geochemical signatures with similarly aged mafic intrusions (Vuori 1999;Peltonen 2005) and volcanites (Väisänen and Mänttäri 2002;Kähkönen 2005) occurring in the northern part of the Southern Svecofennian Arc Complex in Finland, which belong to an inferred suture zone between the alleged eastwards extension of the Bergslagen microcontinent in the south and the Keitele microcontinent in the north . After 1.85 Ga active margin magmatism ceased in the Ljusdal area in the north and moved to the south and west of Bergslagen (Figure 18).…”

Section: Palaeotectonic Implicationsmentioning

confidence: 96%

Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

Rutanen

Andersson

2008

Geological Journal

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Mafic intrusive rocks (1.79-1.78 Ga) of the Transscandinavian Igneous Belt (TIB) and the c. 1.87 Ga Hedesunda Igneous Complex in the Fennoscandian Shield of south-central Sweden were studied using whole-rock and isotope geochemistry.Rock types vary from gabbros/norites (and leucogabbros) to quartz diorites, with Mg# between 76 and 49, and wt% SiO 2 between 43.6 and 59.7, indicating some variation in evolutionary levels and variable cumulus components. Geochemical signatures are calc-alkaline to shoshonitic, large ion lithophile elements and light rare earth elements enriched and high-field strength elements depleted of continental-arc type.e Nd (t) ranges between þ1.0 and þ2.7, and 87 Sr/ 86 Sr(t) between 0.7020 and 0.7038. There is no systematic correlation between chemical parameters and isotope ratios. These isotopic data overlap with other mafic plutonic TIB rocks; samples from the Dala Province (DP) tend to overlap with the c. 1.7 Ga basic Dala lavas of TIB at slightly elevated relative Sr/Nd ratios.With two exceptions, the e Nd (t) of þ1 to þ2 conform to an isotopically 'mildly depleted' source, typical for mafic TIB rocks and many Svecofennian rocks in the region. Reported values above e Nd (t) þ2.0 are scarce in the TIB. Mantle sources represent depleted mantle wedge material that was enriched by fluids/melts not long before (T DM c. 2.0 Ga), that is during subduction in the preceding Svecofennian (2.0-1.87 Ga) and/or during the TIB-0&1 event (1.85-1.78 Ga). The palaeotectonic settings inferred are active continental margins; N-S-directed convergence at 1.87 Ga and E-W-directed at 1.79-1.78 Ga.

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Section: Palaeotectonic Implicationsmentioning

confidence: 96%

Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

Rutanen

Andersson

2008

Geological Journal

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“…1) where Precambrian crystalline rocks are exposed. Here, the tectonic pattern of the crust is mainly defined by Phanerozoic faults and Permo-Carboniferous mafic dykes, which are obvious from a system of linear magnetic anomalies (Erlström & Kornfält 2001, 2005Erlström et al 2004;Obst et al 2004). Nevertheless, older structures and rocks can still be recognized in many places.…”

Section: Geology Of the Bedrock In Southernmost Swedenmentioning

confidence: 99%

“…Recently, secondary ion mass spectrometry (SIMS) methods have been applied extensively to Paleoproterozoic metasedimentary and metavolcanic sequences in the Svecofennian domain of the Baltic/Fennoscandian Shield in Finland (Kähkönen, 2005;Lahtinen et al 2010) and central Sweden (Claesson et al 1993;Andersson et al 2006;Sultan & Plink-Bjorklund 2006;Bergman et al 2008;Williams et al 2008). The results indicate that sedimentation was related to the overall accretionary evolution of the Svecofennian domain between c. 1.95 and 1.8 Ga, which involved the formation of continental margin, forearc and backarc basins.…”

Section: Introductionmentioning

confidence: 99%

Danopolonian migmatization of Mesoproterozoic sedimentary rocks in southernmost Sweden: a SIMS zircon study

Bogdanova

Cecys

Bibikova

et al. 2014

GFF

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To assess the age and origin of the metasedimentary migmatites in southernmost Sweden and their relationships with the Mesoproterozoic granitoid magmatism in the area, we have dated migmatite zircon using the secondary ion mass spectrometry U -Pb method. The studied metasedimentary migmatites, here called the Nöteboda migmatites, occur along the southwestern boundary of the 1442 Ma Tåghusa granitoid intrusion in southeastern Skåne. They contain the mineral assemblage garnet þ biotite^muscovite þ cordierite þ sillimanite þ quartz þ plagioclase þ K-feldspar and were formed during a retrograde evolution from c. 750-7208C and 6 kbar (peak conditions) to c. 6758C and 4 kbar. Zircon is characterized by detrital cores surrounded by U-rich rims and overgrowths. Separate rounded metamorphic grains also exist. The age probability-density distribution peaks for detrital zircon are at c. 1700, 1670, 1650, 1610, 1570 and 1530 Ma. These ages suggest Gothian orogenic rocks in the present west as the most probable principal source. Sedimentation occurred after c. 1530 Ma, the age of the youngest detrital zircon, indicating the existence of a previously unknown period of Mesoproterozoic sedimentation in southernmost Sweden. A homogeneous zircon overgrowth yielded a concordant 207 Pb/ 206 Pb age of 1439^5 Ma, which dates the migmatization and is close to the age of the Tåghusa intrusion. We conclude that the burial of the sediments down to c. 20 km, their metamorphism and progressive migmatization took place concurrently with granitic magmatism, NE-SW compression, folding and shearing of the crust between 1460 and 1440 Ma during the Danopolonian orogeny.

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“…Continental deformation, metamorphism and crust forming magmatism occurred at approximately 1900–1800 Ma. The granitoids with biotite, hornblende, titanite, apatite, magnetite, and zircon (Kähkönen 2005) are predominant rocks in the CFGC together with schists and gneisses. Arc‐type volcanic rocks, which are metamorphosed at high‐T and low‐P amphibolite facies, characterize also this part of the Paleoproterozoic crust.…”

Section: Geological Settingmentioning

confidence: 99%

“…Arc‐type volcanic rocks, which are metamorphosed at high‐T and low‐P amphibolite facies, characterize also this part of the Paleoproterozoic crust. According to Kähkönen (2005), the Svecofennian granitic bedrock resulted from remelting of older approximately 2100 Ma crust of several microcontinents. Based on ε Nd (Nd isotopic ratio) values the Hirsilä belt, part of the Tampere schist belt, which reaches the southern parts of CFGC, includes an Archaean component as well as abundant approximately 2000 Ma detritus from the suggested microcontinents.…”

Section: Geological Settingmentioning

confidence: 99%

Rock magnetic and paleomagnetic study of the Keurusselkä impact structure, central Finland

Raiskila

Salminen

Elbra

et al. 2011

Meteorit & Planetary Scien

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Abstract-There are 31 proven impact structures in Fennoscandia-one of the most densely crater-populated areas of the Earth. The recently discovered Keurusselka¨impact structure (62°08¢ N, 24°37¢ E) is located within the Central Finland Granitoid Complex, which formed 1890-1860 Ma ago during the Svecofennian orogeny. It is a deeply eroded complex crater that yields in situ shatter cones with evidence of shock metamorphism, e.g., planar deformation features in quartz. New petrophysical and rock magnetic results of shocked and unshocked target rocks of various lithologies combined with paleomagnetic studies are presented. The suggested central uplift with shatter cones is characterized by increased magnetization and susceptibility. The presence of magnetite and pyrrhotite was observed as carriers for the remanent magnetization. Four different remanent magnetization directions were isolated: (1)

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Chapter 8 Svecofennian supracrustal rocks

Cited by 34 publications

References 59 publications

Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

Danopolonian migmatization of Mesoproterozoic sedimentary rocks in southernmost Sweden: a SIMS zircon study

Rock magnetic and paleomagnetic study of the Keurusselkä impact structure, central Finland

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