On the ages of some granitoid and schist complexes in northern Finland

Lauerma, R.

doi:10.17741/bgsf/54.1-2.009

Cited by 29 publications

(10 citation statements)

References 8 publications

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“…The Sodankylä area is bordered on the west by the ophiolite-bearing, allochthonous Kittilä Greenstone belt , to the north and northwest by Belomorian Archaean basement, and to the south by autochthonous and allochthonous units of the Central Lapland Greenstone belt which are intruded by the c. 1.8 Ga (Lauerma, 1982) Central Lapland granitoids (Fig. 1a).…”

Section: Geological Setting Of the Sodankylä Areasupporting

confidence: 72%

Early Proterozoic nappe formation: an example from Sodankylä, Finland, Northern Baltic Shield

Evins

Laajoki

2002

Geol. Mag.

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The Central Lapland Greenstone belt comprises rift-related metavolcanic and metasedimentary rocks representing one of the largest supracrustal belts in the Baltic Shield. The Sodankylä area in the central part of the belt represents a complex thrust duplex within a nappe overlying Belomorian Archaean basement and autocthonous Luirojoki calc-silicate rocks. Here, an early D 1 schistosity is axial planar to at least three coaxial generations of southward-verging, subhorizontal, E-W-plunging D 1 folds associated with major southwards thrusting. D 2 is represented by broad, mapscale, upright, NE-trending folds in the south and crenulations in the north. Staurolite-grade metamorphism represented by post-tectonic andalusite + staurolite + kyanite assemblages occurred after D 2 folding. Later D 3 deformation was limited to local NW-trending folds and sinistral faults. The internal nappe-like structure of the Central Lapland Greenstone belt suggests that it represents the foreland of a large collisional complex cored by the Lapland Granulite belt.

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Section: Geological Setting Of the Sodankylä Areasupporting

confidence: 72%

Early Proterozoic nappe formation: an example from Sodankylä, Finland, Northern Baltic Shield

Evins

Laajoki

2002

Geol. Mag.

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“…1800 Ma granitoids of the Central Lapland Granitoid Complex . Lauerma (1982) has published a U-Pb zircon age of 1770±8 Ma for a porphyritic granite sampled near the northern margin of the Peräpohja Schist Belt, ca. 50 km west of the Misi region.…”

Section: Regional Geological Settingmentioning

confidence: 99%

General geology, alteration, and iron deposits in the Palaeoproterozoic Misi region, northern Finland

Niiranen¹,

Hanski²,

Eilu³

2003

Bull Geol Soc Finland

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The Paleoproterozoic Misi region forms the northeastern part of the Peräpohja Schist Belt in northern Finland. The area comprises mafi c volcanic and sedimentary rocks, differentiated gabbros, and late-orogenic granitoids.Three geochemically different mafi c volcanic units were recognised: LREE-depleted amygdaloidal lavas, slightly LREE-enriched lavas, and mafi c tuffs that have a fl at REE pattern. Sedimentary rocks include arkosites, mica gneisses, dolomitic marbles, quartzites, tuffi tes, mica schists, calc-silicate rocks and graphite-bearing schists. Two types of gabbros were identifi ed: one with a LREE-enriched pattern and another with fl at REE pattern. The age of the former is according to Perttunen and Vaasjoki (2001) 2117±4 Ma, whereas there is no age determination for the latter. The granitoid intrusions belong to the ca. 1800 Ma late-orogenic group of the Central Lapland Granitoid Complex. The geochemistry and the stable isotope data on mafi c lavas and dolomitic marbles show similarities with the mafi c volcanic rocks and marbles of the lower part of the Kivalo group in the western part of Peräpohja Schist Belt.Peak metamorphic conditions in the region vary from upper-greenschist to upper-amphibolite facies. Three major stages of deformation were distinguished: N-S compressional D 1 with ductile deformation, NE-SW compressional D 2 with ductile to brittle-ductile deformation, and E-W compressional D 3 with brittle deformation.Several magnetite occurrences are known in the region and four of those have been mined for iron. The ores are mainly composed of magnetite with minor haematite, pyrite, chalcopyrite and bornite. Besides iron, the ores contain small amounts of P, S and V as well as trace amounts of Cu, Co, Te and Au. The magnetite bodies are hosted by skarnoids within the ca. 2220-2120 Ma dolomitic marble-quartzite sequence, and highly differentiated, intensely albitised, LREE-enriched gabbro.Multistage and -type alteration is characteristic for the entire region. The styles of alteration in the region are: scapolitisation, regional and local albitisation, sericitisation and silicifi cation associated with a major shear zone, and late carbonatisation and carbonate veining associated with brecciation of the ores and their wall rocks.Local intense albitisation and formation of skarnoids and magnetite ores took place during the pre-D 1 or D 1 faulting or shearing which postdate the intrusion of 2120 Ma gabbros. The iron was mobilized from the mafi c to intermediate country rocks and/or marble sequence which possibly contained sedimentary iron formation. Regional alteration with the local intense albitisation and ore formation show similar features to the iron oxide-copper-gold type deposits, although the known deposits in the Misi region only contain trace amounts of gold and copper.

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“…These include the extensive Central-Lapland granitoid complex (Lauerma 1982) and Nat-tanen (Patchett et al 1981) and Hetta (Meriläinen 1976) granites in northern Finland. Interestingly, this is also the approximate age of the epigenetic Au-mineralisations in northern Finland as recorded by monazite from the Saattopora Au-deposit and by the Pb-Pb ages of several other Au-occurrences over a wide area (Mänttäri 1995).…”

Section: Discussionmentioning

confidence: 99%

An ion microprobe U-Th-Pb study of zircon xenocrysts from the Lahtojoki kimberlite pipe, eastern Finland

Peltonen¹,

Mänttäri²

2001

Bull Geol Soc Finland

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On the ages of some granitoid and schist complexes in northern Finland

Cited by 29 publications

References 8 publications

Early Proterozoic nappe formation: an example from Sodankylä, Finland, Northern Baltic Shield

Early Proterozoic nappe formation: an example from Sodankylä, Finland, Northern Baltic Shield

General geology, alteration, and iron deposits in the Palaeoproterozoic Misi region, northern Finland

An ion microprobe U-Th-Pb study of zircon xenocrysts from the Lahtojoki kimberlite pipe, eastern Finland

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