Proterozoic tectonic evolution and late Svecokarelian plate deformation of the Central Baltic Shield

Gaál, Gabor

doi:10.1007/bf01825033

Cited by 45 publications

(10 citation statements)

References 24 publications

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“…Literature data on the tectonic environments of geologic complexes (Peive et al 1972, Piirainen et al 1974, Hain 1977, Archibald et al 1978, Condie 1980, Baragar and Scoates 1981, Barton and Key 1981, Jackson and Iannelli 1981, Gaal 1982, Sims et al 1982, Milanovskii 1983 and their comparison with the ones in nickeliferous epiarchean provinces, for which the geotectonic conditions can be determined with more confidence, confirm the above. The initial point of the paleotectonic analysis, the results of which are in Table 2, is the Sawkins' model (Sawkins 1972).…”

supporting

confidence: 70%

Peridotitic Komatiites and the Origin of Ores (Southeastern Part of the Baltic Shield)

Kochnev-Pervukhov

Zaskind

Proskuryakov³

1986

Special Publication No. 4 of the Society for Geology Applied to Mineral Deposits

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Komatiite magmatism of the Archean greenstone belts of the southeastern part of the Baltic shield is considered here. The conformable bedding and interbedding of bodies of komatiites with pillow basalts and horizons of tuffs, with breccias at their tops, pillows, amygdules, glass and spinifex textures permit the determination of these rocks as peridotite komatiite lavas. Plutonic analogs of these rocks are found in ultramafic effusion feeders. Nickel-copper ore mineralization is orthomagmatic and is associated with komatiitic intrusives. The nickel ore potential of units associated with komatiite magmatism seems .to be correlated with the appearance of island-arc basalts: the larger these are, the smaller the ore potential of the structures. And, in this sense, the nearest analogs of the belts in the Baltic shield are the Canadian greenstone belts, not the Western Australian. These may be considered geotectonically as nickeliferous provinces.The southeastern part of the Baltic shield is a region of wide spreading greenstone belts; these are filled with Archean series and form a complicated network of the narrow elongated structures within gneissose granite blocks (Fig. 1). The extension of the belts ranges from 1 -2 km to a few tens of kilometers. In a number of such structures, komatiitic series are found (Fig. 1). The authors studied the volcanic-plutonic komatiite complex in the Kenozero-Kozhozero greenstone belt.Komatiitic bodies have ~arious lengths and thicknesses and conform with basalt sheets. Deformational and metamorphic changes in such basalts and komatiites are much the same. The generalized section of the researched bodies consists of two parts (Fig. 2): the upper, less thick part, is composed of breccias and vitreous and spinifex rocks; the lower part of serpentinite after ordinary peridotite and dunite. The ratio of thicknesses of the upper and lower parts fluctuates from 1: 10 to 1: 50.The glass, the skeletal forms of magmatic minerals, and the spinifex textures are doubtless evidences of the crystallization of these rocks from a melt under high temperature-gradient conditions. The composition of the melt is determined from the composition of altered glass and rocks with spinifex textures (Table 1), and corresponds to that of peridotite komatiites (Arndt et al. 1979, Brooks and

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supporting

confidence: 70%

Peridotitic Komatiites and the Origin of Ores (Southeastern Part of the Baltic Shield)

Kochnev-Pervukhov

Zaskind

Proskuryakov³

1986

Special Publication No. 4 of the Society for Geology Applied to Mineral Deposits

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“…Many authors have modelled the evolution of the Archaean/Proterozoic boundary and presented different views on the direction of the possible subduction (e.g. Gaál, 1982Gaál, , 1986Gaál, , 1990Ward, 1987;Ekdahl, 1993;Lahtinen, 1994;Ruotoistenmäki, 1996;Nironen, 1997;Lahtinen et al, 2005). On the basis of the fact that Archaean influence (low ε Nd value) is controlled by the Archaean/ Proterozoic contact at the present erosion level and assuming that the magma conduit in the upper crust was vertical to subvertical, we can assume that the Archaean basement was not present further west at deeper levels during magma ascent at 1880 Ma.…”

Section: Tectonic Implicationsmentioning

confidence: 99%

Sm-Nd data for mafic-ultramafic intrusions in the Svecofennian (1.88 Ga) Kotalahti Nickel Belt, Finland - Implications for crustal contamination at the Archaean/Proterozoic boundary

Makkonen¹,

Huhma²

2007

Bull Geol Soc Finland

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Sm-Nd data were determined for eight mafic-ultramafic intrusions from the Svecofennian (1.88 Ga) Kotalahti Nickel Belt, Finland. The intrusions represent both mineralized and barren types and are located at varying distances from the Archaean/Proterozoic boundary. The samples for the 23 Sm-Nd isotope analyses were taken mostly from the ultramafic differentiates. Results show a range in initial ε Nd values at 1880 Ma from -2.4 to +2.0. No relaNo relationship can be found between the degree of Ni mineralization and initial ε Nd values, while a correlation with the geological domain and country rocks is evident. The Majasaari and Törmälä intrusions, which have positive ε Nd values, were emplaced within the Svecofennian domain in proximity to 1.92 Ga tonalitic gneisses, which have previously yielded initial ε Nd values of ca. +3. In contrast, the Luusniemi intrusion, which has an ε Nd value of -2.4 is situated close to exposed Archaean crust. Excluding two analyses from the Rytky intruArchaean crust. Excluding two analyses from the Rytky intru-. Excluding two analyses from the Rytky intrusion, all data from the Koirus N, Koirus S, Kotalahti, Rytky and Kylmälahti intrusions, within error limits, fall in the range -0.7 ± 0.3. The results support the concept of contamination by Archaean material in proximity to the currently exposed craton margin. The composition of the proposed parental magma for the intrusions is close to EMORB, with initial ε Nd values near +4.

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“…An Andino-type plate-tectonic model with subduction from the southwest beneath the Archean basement was first proposed to explain the genesis of the Svecokarelian crust by Hietanen (1975). Her view has since been endorsed by Barker et al (1981), Gaål (1982 a) and others. More complex models with several subduction zones have been proposed by Gaål (1982 b) and Bowes et al (1984).…”

Section: Synkinematic Granitoidsmentioning

confidence: 79%

“…Granitoids predominate in both the Svecokarelian and the Archean complexes. The supracrustal rocks in the Svecokarelian complex comprise a variety of sedimentary and mafic to felsic volcanic rocks that underwent low-to high-grade metamorphism and polyphase deformation (Simonen 1980;Gaål 1982 a).…”

Section: Classification Of the Granitoidsmentioning

confidence: 99%

The Proterozoic granitoids of Finland: Granite types, metallogeny and relation to crustal evolution

Nurmi¹,

Haapala²

1986

Bull Geol Soc Finland

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Proterozoic tectonic evolution and late Svecokarelian plate deformation of the Central Baltic Shield

Cited by 45 publications

References 24 publications

Peridotitic Komatiites and the Origin of Ores (Southeastern Part of the Baltic Shield)

Peridotitic Komatiites and the Origin of Ores (Southeastern Part of the Baltic Shield)

Sm-Nd data for mafic-ultramafic intrusions in the Svecofennian (1.88 Ga) Kotalahti Nickel Belt, Finland - Implications for crustal contamination at the Archaean/Proterozoic boundary

The Proterozoic granitoids of Finland: Granite types, metallogeny and relation to crustal evolution

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