Hostname: page-component-cd9895bd7-dzt6s Total loading time: 0 Render date: 2024-12-25T06:41:02.878Z Has data issue: false hasContentIssue false
  • English
  • Français

Structural and U–Pb isotopic study of late Archaean migmatitic gneisses of the Presvecokarelides, Lylyvaara, eastern Finland

Published online by Cambridge University Press:  03 November 2011

Erkki J. Luukkonen
Erkki J. Luukkonen
Affiliation:
Geological Survey of Finland, Box 237, SF 70101 Kuopio 10, Finland.
Get access Rights & Permissions [Opens in a new window]

Abstract

The migmatitic gneiss complex of Lylyvaara in the eastern part of Finnish Presvecokarelides of the Baltic Shield shows evidence of a polyphase deformational and metamorphic history and of the emplacement of a number of mafic and felsic igneous intrusions at various stages during this history. Sequential structural development has been established on the bases of refolding and cross-cutting relationships. U–Pb zircon and sphene isotopic data combined with structural studies indicate that the first six deformational phases took place in late Archaean (=Presvecokarelian) times. The seventh deformational phase is constrained as being early Proterozoic (=Svecokarelian) from regional considerations.

The gneissic foliation in the dominant tonalitic to trondhjemitic palaeosome is parallel to lithological layering (So). Mostly it is composite S1–S2; only in F2 fold hinges can separate S1 and S2 be unequivocally distinguished. There, both of these fabrics, which were formed in amphibolite facies conditions of metamorphism during D1 and D2 have retained their identity despite extensive tectonic overprinting. Further tonalitic or granodioritic material was intruded during D3 or between D2 and D3. Effects of the third deformational phase (D3) ar6e expressed only locally as asymmetrical and polyclinal folds, which deform S1–S2 and F2. These folds now have a northeasterly axial trend and they show considerable variations in the style of their parasitic structures. F4 folds are common. They are dextral and asymmetrical, have NW—NNW-trending axes and show complex interference patterns with F2 and F3 folds. During D4, much aplogranitic neosome material was emplaced in NW—SE-trending movement zones, which correspond to the axial planes of F4 folds. Superimposition of F5 and F6 structures on previously formed patterns add to the structural complexity although they only result in minor modifications. Both are open and upright and locally have associated cleavages or healed fractures (S5, S6). D7 is expressed throughout the migmatitic complex as narrow NW—SE-trending shear zones which reactivate the S4 trend.

U–Pb zircon isotopic data indicate that the metamorphism associated with gneiss formation took place 2843 ± 18 Ma ago. U–Pb sphene ages of c. 2660 Ma and 2620 Ma indicate that metamorphic conditions prevailed for a very considerable time. An aplogranitic neosome related to F4 axial planes gave a 2657 ± 32 Ma U–Pb zircon age, while granodiorite and pegmatite dykes related to D6 yielded U–Pb zircon ages of c 2670 Ma and 2640 Ma, respectively.

Keywords

amphibolitegranitegranodioritemetamorphismneosomeoverprintingpalaeosomepegmatitepolyphase deformationrefoldingshear zonespheneSvecokarelideszircon.
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 76 , Issue 4 , 1985 , pp. 401 - 410
Copyright
Copyright © Royal Society of Edinburgh 1985

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Auvray, B., Blais, S., Jahn, B. M. & Piquet, D. 1982. Komatiites and the komatiitic series of the Finnish greenstone belts. In Arndt, N. T. & Nisbet, E. G. (eds) Komatiites, 131–46. London: Allen & Unwin.Google Scholar
Bertrand, J. M., Blais, S. & Capdevila, R. 1978. Précisions sur 1'évolution structurale de l'Archéen de Karélie (Finlande) C R ACAD SCI PARIS 287, Serie D, 683–6.Google Scholar
Blais, S., Auvray, B., Capdevila, R., Jahn, B. M., Hameurt, J. & Bertrand, J. M. 1978. The Archaean greenstone belts of Karelia (eastern Finland) and their komatiitic and tholeiitic series. In Windley, B. F. & Naqvi, S. M. (eds) Archaean Geochemistry, 87–107. Amsterdam: Elsevier.CrossRefGoogle Scholar
Bowes, D. R. 1976. Archaean crustal history in the Baltic shield. In Windley, B. F. (ed.) The Early History of the Earth, 481–8. London: Wiley.Google Scholar
Bowes, D. R. 1980. Structural sequence in the gneissose complex of eastern Finland as a basis for correlation in the Presvecokarelides. ACTA GEOL POL 30, 15–26.Google Scholar
Doe, B. R. & Stacey, J. S. 1974. The application of lead isotopes to the problems of ore genesis and ore prospect evaluation: a review. ECON GEOL 69, 757–76.CrossRefGoogle Scholar
Gaál, G., Mikkola, A. & Söderholm, B. 1978. Evolution of the Archean crust in Finland. PRECAMBRIAN RES 6, 199–215.Google Scholar
Hanski, E. 1980. Komatiitic and tholeiitic metavolcanics of the Siivikkovaara area in the Archaean Kuhmo greenstone belt, eastern Finland. BULL GEOL SOC FINL 52, 67–100.CrossRefGoogle Scholar
Hopgood, A. M. 1971. Correlation by tectonic sequence in Precambrian gneiss terrains. GEOL SOC AUST SPEC PUBL 3, 367–76.Google Scholar
Hopgood, A. M. 1980. Polyphase fold analysis of gneisses and migmatites. TRANS R SOC EDINBURGH EARTH SCI 71, 55–68.CrossRefGoogle Scholar
Hopgood, A. M. & Bowes, D. R. 1972. Application of structural sequence to the correlation of Precambrian gneisses, Outer Hebrides, Scotland. BULL GEOL SOC AM 83, 107–28.CrossRefGoogle Scholar
Hyppönen, V. 1983. Kallioperäkarttojen selitykset, 4411 Ontojoki, 4412 Hiisijärvi ja 4413 Kuhmo. English summary: Pre-Quaternary rocks of the Ontojoki, Hiisijarvi and Kuhmo map sheet areas. Geological map of Finland 1: 100000. Espoo: Geological Survey of Finland.Google Scholar
Jaffey, A. H., Flynn, K. F., Glendenin, L. E., Bentley, W. C. & Essling, A. M. 1971. Precision measurement of half-lives and specific activities of 235U and238U. PHYS REV C4, 1889–906.Google Scholar
Jahn, B. M., Auvrey, B., Blais, S., Capdevila, R., Cornichet, J., Vidal, F. & Hameurt, J. 1980. Trace element geochemistry and petrogenesis of Finnish greenstone belts. J. PETROL 21, 201–44.CrossRefGoogle Scholar
Krogh, T. E. 1973. A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determination. GEOCHIM COSMOCHIM ACTA 37, 487–94.CrossRefGoogle Scholar
Martin, H., Chauvel, C. & Jahn, B. M. 1983. Major and trace element geochemistry and crustal evolution of Archaean granodioritic rocks from eastern Finland. PRECAMBRIAN RES 21, 159–80.CrossRefGoogle Scholar
Martin, H., Chauvel, C., Jahn, B. M. & Vidal, P. 1983. Rb–Sr and Sm–Nd ages and isotopic geochemistry of Archaean granodioritic gneisses from eastern Finland. PRECAMBRIAN RES 20, 79–91.CrossRefGoogle Scholar
Mattinson, J. M. 1982. —Pb “blocking temperatures” and Pb loss characteristics in young zircon, sphene, and apatite. ABSTR PROGRAM GEOL SOC AM 14, 558.Google Scholar
Mutanen, T. 1976. Komatiites and komatiite provinces in Finland. GEOLOGI 28, 49–56.Google Scholar
Park, A. F. & Bowes, D. R. 1983. Basement-cover relationships during polyphase deformation in the Svecokarelides of the Kaavi district, eastern Finland. TRANS R SOC EDINBURGH EARTH SCI 74, 95–118.CrossRefGoogle Scholar
Pekkarinen, L. J. 1979. The Karelian formations and their depositional basement in the Kiihtelysvaara-Värtsilä area, East Finland. BULL GEOL SURV FINL 301.Google Scholar
Sakko, M. 1971. Varhais-Karjalaisten metadiabaasien radiometrisiä zirkoni-ikiä. Summary: Radiometric zircon ages of the Early-Karelian metadiabases. GEOLOGI 23, 117–8.Google Scholar
Simonen, A. 1971. Das finnische Grundgebirge. GEOL RUNDSCH 60, 1406–21.CrossRefGoogle Scholar
Simonen, A. 1980a. Pre-Quaternary rocks of Finland 1:1000000. Espoo: Geological Survey of Finland.Google Scholar
Simonen, A. 1980b. The Precambrian in Finland. BULL GEOL SURV FINL 304.Google Scholar
Taipale, K. 1983. The geology and geochemistry of the Archaean Kuhmo greenstone-granite terrain in the Tipasjärvi area, eastern Finland. ACTA UNIVERSITATIS OULUENSIS, SERIES A, SCIENTIAE RERUM NATURALIUM No 151, GEOLOGICA No 5.Google Scholar
Vidal, Ph., Blais, S.Jahn, B. M., Capdevila, R. & Tilton, G. R. 1980. U—Pb and Rb–Sr systematics of the Suomussalmi Archaean greenstone belt (eastern Finland). GEOCHIM COSMOCHIM ACTA 44, 2033–44.CrossRefGoogle Scholar