Evolution of the Archean crust in Finland

Gaál, Gabor; Mikkola, Aimo K.; Söderholm, B.

doi:10.1016/0301-9268(78)90012-8

Cited by 55 publications

(14 citation statements)

References 12 publications

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“…The same problem is also encountered elsewhere in northern Finland, where many supracrustal rocks have been proposed Archean (Gaål et al 1978;Silvennoinen et al 1980). The majority of the radiometric datings have been made by U-Pb methods on zircons, titanites and monazites separated from various rocks.…”

Section: Chronostratigraphic Implicationsmentioning

confidence: 64%

“…It seems plausible that, as proposed by Gaål et al (1978), some zones of mafic to ultramafic rocks in the Tuntsa-Savukoski area (Fig. 1) …”

Section: Chronostratigraphic Implicationsmentioning

confidence: 68%

“…One of these is the Salla schist area, which Gaål et al (1978) have designated as an Archean (> 2500 Ma) greenstone belt. Their opinion was partly based (op.cit., p. 206) on the U-Pb age of zircons from the Hatajavaara granite, or, more properly, on the isotope ratios of the zircons from sample A126, reported in the GSF, Ann.…”

Section: Chronostratigraphic Implicationsmentioning

confidence: 99%

“…Simonen (1980 a, b) has designated it traditionally as Svecokarelian (i.e. Proterozoic), Silvennoinen et al (1980) as partly Archean (> 2600 Ma), partly Proterozoic, and Gaål et al (1978) as an Archean (> 2500 Ma) greenstone belt. As mentioned by Kulikov et al (1980), different interpretations have also been presented by Soviet researchers.…”

mentioning

confidence: 99%

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

Lauerma¹

1982

Bull Geol Soc Finland

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Section: Chronostratigraphic Implicationsmentioning

confidence: 64%

“…It seems plausible that, as proposed by Gaål et al (1978), some zones of mafic to ultramafic rocks in the Tuntsa-Savukoski area (Fig. 1) …”

Section: Chronostratigraphic Implicationsmentioning

confidence: 68%

Section: Chronostratigraphic Implicationsmentioning

confidence: 99%

mentioning

confidence: 99%

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

Lauerma¹

1982

Bull Geol Soc Finland

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“…The linear shape of the belt cannot therefore be entirely primary. This is corroborated by several small (from decimeters to kilometers in size) isolated outcrops of greenstone materials scattered over the gneissic basement on both sides of the belt itself (see Gaål et al 1976;Rybakov and Lobach-Zhuckenko 1981 a). This is evidence of (1) a larger, original extent of the belt and (2) the deposition of the greenstone belt over a preexisting sialic crust.…”

Section: Discussion and Modelmentioning

confidence: 80%

Origin and geodynamic evolution of the Archean crust of eastern Finland

Martin¹,

Auvray²,

Blais³

et al. 1984

Bull Geol Soc Finland

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The Archaean crust of eastern Finland is composed of three main lithological units: -Gneissic basement. It was originally composed of tonalites, trondhjemites and granodiorites emplaced at 2.86 G.a. and 2.62 G.a. and subsequently transformed into grey gneisses. The parental magmas originated from the mantle in a two-stage process: (i) formation of a basaltic crust, (ii) melting of this crust transformed into garnet-bearing amphibolite. Field, petrological and geochemical data argue in favour of a subduction-like process rather than an underplate accretion model. -Greenstone belt (Kuhmo-Suomussalmi). The lower volcanic sequence of this greenstone belt is composed of mafic and ultramafic lavas with komatiitic and tholeiitic affinities and was emplaced at about 2.65 G.a. The uprising of a mantle diapir initiated the breaking of the preexisting sialic crust (grey gneisses) and induced the emplacement of the greenstones in a proto-oceanic rift geodynamic environment. -Calc-alkaline magmatism. The calc-alkaline magmas were emplaced as volcanic rocks in the greenstone belt 2.5 G.a. ago (Luoma acid volcanics), or as K-feldspar phenocryst granodiorites in the immediate vicinity of the KuhmoSuomussalmi greenstone belt 2.5 G.a. ago (Suomussalmi and Arola augen gneisses). The younger plutons were emplaced as pink leucogranites 2.41 G.a. ago. The origin of this magmatism is thought to be correlated to the late tectonic evolution of the Kuhmo-Suomussalmi greenstone belt. The high density (d ~ 3.3) lavas of the lower volcanic sequence were emplaced over a low density (d -2.7) sialic crust. This created an inverse density gradient and generated a gravity instability that initiated the subsidence (sagduction) of the greenstone belt with respect to its basement. This later was carried down in the vicinity of the belt and underwent partial melting, thus generating the calc-alkaline magmas.It must be pointed out that, in the course of time, petrogenetic processes have changed from ensimatic to ensialic, implying a major reworking of the preexisting crustal materials.

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Metallogeny of gold in the Fennoscandian Shield

Gaál

Sundblad

1990

Mineral. Deposita

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Evolution of the Archean crust in Finland

Cited by 55 publications

References 12 publications

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

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

Origin and geodynamic evolution of the Archean crust of eastern Finland

Metallogeny of gold in the Fennoscandian Shield

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