Geochemistry and tectonomagmatic affinities of the metavolcanic rocks of the early proterozoic tampere schist belt, Southern Finland

Kähkönen, Y.

doi:10.1016/0301-9268(87)90060-x

Cited by 33 publications

(28 citation statements)

References 28 publications

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“…1), is characterized by arc-type metavolcanic rocks and turbiditic metasedimentary rocks (Ojakangas 1986, Kähkönen 1987. Metamorphism culminated in low-pressure, lowtemperature amphibolite to transitional greenschist/amphibolite facies conditions (Kilpeläinen et al 1994).…”

Section: Introductionmentioning

confidence: 99%

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

Kähkönen¹

1999

Bull Geol Soc Finland

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Section: Introductionmentioning

confidence: 99%

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

Kähkönen¹

1999

Bull Geol Soc Finland

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“…Supracrustal rocks of southern Finland belong to the Svecofennian domain of the Svecokarelidic orogeny, 1.90-1.83 Ga in age (Huhma 1986, Kähkönen 1989. The Svecofennides are interpreted to have formed through sequential accretion of island arcs (e.g.…”

Section: Geological Settingmentioning

confidence: 99%

Metamorphic olivine in pictritic metavolcanics from southern Finland

Peltonen¹

1990

Bull Geol Soc Finland

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.%), mafic to ultramafic metapicritic rocks in the Early Proterozoic Svecofennian domain of Southern Finland. Relatively Fe 2 Si0 4 -rich porphyroblastic olivines formed in those rocks through decomposition of Fe-Mg chloritedominated phyllosilicates at uppermost amphibolite facies conditions. Forsterite contents are, to some extent, related to bulk rock composition and abundances of coexisting phases. However, complex interactions dependent on modal compositions of the phyllosilicate assemblages being dehydrated and alteration processes which modified the phyllosilicate compositions were also controlling factors. These same factors are responsible for negative OL Ni -Fo correlations observed in the metapicrites, opposite to those characteristic of olivines formed through fractional crystallization of magmas. Nickel contents of metamorphic olivines analyzed (290-3315 ppm) cover the whole spectrum characteristic of igneous olivines. This wide range in olivine nickel contents is not due to Ni partitioning into a sulfide phase because only a very small amount of sulfide is present. Manganese contents in these metamorphic olivines are similar to those in igneous olivines and the very low calcium levels are characteristic of plutonic olivines. Caution is emphasized when utilizing olivine compositions for exploration purposes in regionally metamorphosed terrains.Key words: metavolcanic rocks, picrite, olivine groups, petrography, electron probe data, Proterozoic, Rantasalmi, Western Uusimaa, Vammala, Finland Petri Peltonen: Geological Survey of Finland, SF-02150, Espoo, Finland IntroductionMetamorphic olivine is an important phase in medium to high grade assemblages of metamorphosed ultramafic rocks (e.g. Evans 1977). It is a common constituent of progressively metamorphosed serpentinites (Peretti et al. 1987, Kunugiza 1982, Vance and Duncan 1977, Tromsdorff and Evans 1974, Binns and Groves 1976 where it first forms through the metastable reaction crysotile = antigorite + forsterite + vapour (Peretti et al. 1987) and at slightly higher grade by antigorite + brucite = olivine + vapour (Evans 1977). Olivine is thereafter stable in all prograde assemblages. Metamorphic olivine formed through dehydration reactions of serpentine minerals is anomalously Fo-rich (Pincent and Hirst 1975, Evans 1977, Vance and Duncan 1977, Kunugiza 1980, Papunen and Idman 1982, Dymek et al. 1988. The growth of this olivine does not affect magnetite, formed in the serpentinization process, thus ignoring most of the iron previously present in the igneous olivine characteristic for that rock composition. Forsterite contents exceeding 95 mol.% are not uncommon for olivines formed through such a process (Evans 100 Petri Peltonen 1977). Magnetite is often seen as droplet-shaped inclusions or tracks in metamorphic olivine that are remnants from the serpentinite protolith and mimic original grain boundaries.Metamorphic olivine can also form from phyllosilicates other than serpentine. In WestAustralian metakomatiites, relatively Fe-rich porphyro...

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“…1 and 2) has been regarded as one of the key areas of the Finnish Precambrian since the times of Sederholm (1897) and has been subject to almost continuous geological study ever since (Neuvonen & Matisto 1948, Seitsaari 1951, Simonen & Kouvo 1951, Simonen 1952, 1953, Campbell 1980, Gaål et al 1981, Kähkönen 1989, Kähkönen & Leveinen 1994. This belt, more than 200 km long in an E-W direction, reaches locally maximum widths of about 20 km and comprises metasedimentary and metavolcanic rocks intruded by a variety of granitoids.…”

Section: Introductionmentioning

confidence: 99%

“…The basement of deposition for the belt has so far remained obscure. The regional metamorphism has commonly peaked under low-pressure amphibolite facies conditions, 10 km Simonen (1980b) and Kähkönen (1989). which has resulted in the preservation of a number of primary sedimentary and volcanic textures.…”

Section: Introductionmentioning

confidence: 99%

Lead and neodymium isotopic results from metabasalts of the Haveri Formation, southern Finland: Evidence for Palaeoproterozoic enriched mantle

Vaasjoki¹,

Huhma²

1999

Bull Geol Soc Finland

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Geochemistry and tectonomagmatic affinities of the metavolcanic rocks of the early proterozoic tampere schist belt, Southern Finland

Cited by 33 publications

References 28 publications

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

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

Metamorphic olivine in pictritic metavolcanics from southern Finland

Lead and neodymium isotopic results from metabasalts of the Haveri Formation, southern Finland: Evidence for Palaeoproterozoic enriched mantle

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