Hostname: page-component-78c5997874-94fs2 Total loading time: 0 Render date: 2024-11-13T06:49:37.843Z Has data issue: false hasContentIssue false
  • English
  • Français

Tectonic setting and origin of the Proterozoic rapakivi granites of southeastern Fennoscandia

Published online by Cambridge University Press:  03 November 2011

Ilmari Haapala  and
O. Tapani Rämö
Ilmari Haapala
Affiliation:
Ilmari Haapala and O. Tapani Rämö, Department of Geology, University of Helsinki, Box 115, SF-00171 Helsinki, Finland
Get access Rights & Permissions [Opens in a new window]

Abstract

The 1·65–1·54 Ga rapakivi granites of southeastern Fennoscandia represent the silicic members of a bimodal magmatic association in which the mafic members are tholeiitic diabase dykes and minor gabbroic-anorthositic bodies. They are metaluminous to slightly peraluminous A-type granites and occur as high-level batholiths and stocks in an E-W-trending belt extending from Soviet Karelia to southwestern Finland. The Soviet Karelian granites were emplaced into the contact zone between Archaean craton and Svecofennian juvenile 1·9Ga-old crust, while the Finnish granites were intruded into the Svecofennian crust. Deep seismic soundings show that the rapakivi granites and the contemporaneous, mainly WNW or NW-trending diabase dyke swarms are situated in a zone of relatively thin crust. Below the Wiborg Batholith there exists a domal structure in the lithosphere in which a transitional zone (mafic underplate) occurs between the crust and the mantle.

The Nd isotopic evolution of the rapakivi granites (εNd(T) −3·1—−0·2) corresponds to the evolution of the 1·9Ga-old Svecofennian crust, as do their Pb isotopic compositions. This implies that the Finnish granites represent anatectic melts of the Svecofennian crust. In contrast, the Soviet Karelian granites show isotopic composition indicative of substantial incorporation of Archaean lower crust material. Petrochemical modelling of one of the Finnish batholiths shows that its parental magma could have been generated by c. 20% melting of a granodioritic source and that fractional crystallisation was important during the subsequent evolution of this magma.

The rapakivi granites are redefined as A-type granites that show the rapakivi texture at least in larger batholiths. The field, geochemical, and seismic data indicate that the classical Finnish rapakivi granites were generated in an anorogenic extensional regime by partial melting of the lower/middle crust. The melting, and possibly also the extensional tectonics, were related to upwellings of hot mantle material which led to intrusion of mafic magmas at the base and into the crust.

Keywords

anorogenicA-typebimodaldiabaseextensionalFinlandisotopes (Nd, Pb)mantle upwellingpartial melting
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 83 , Issue 1-2: Second Hutton Symposium: The Origin of Granites and Related Rocks , 1992 , pp. 165 - 171
Copyright
Copyright © Royal Society of Edinburgh 1992

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

Babel Working Group 1991. Integrated seismic studies of the Baltic Shield using data in the Gulf of Bothnia region. GEOPHYS J INT (in press).Google Scholar
Beljaev, A., Larin, A. & Amelin, Yu. 1991. Geochemistry. In Haapala, I., Rämö, O. T. & Salonsaari, P. T. (eds) Salmi batholith and Pitkäranta ore field in Soviet Karelia, IGCP Project 315 Symposium Rapakivi Granites and Related Rocks, Excursion Guide. GEOL SURV FINLAND GUIDE 33, 11–9.Google Scholar
Bergman, L. 1981. Berggrunden inom Signilskär, Mariehamn och Geta kartblad—Signilskärin, Maarianhaminan ja Getan karttaalueiden kallioperä (in Swedish); English summary: Pre-Quaternary rocks of the Signilskär, Mariehamn and Geta mapsheet areas. Geological map of Finland 1:100,000, Explanation to the map of rocks, 0034 + 0043 Signilskär, 1012 Maarianhamina and 1021 Geta, Geological Survey of Finland.Google Scholar
DePaolo, D. J. 1981. Neodymium isotopes in the Colorado Front range and crust-mantle evolution in the Proterozoic. NATURE 291, 193–6.CrossRefGoogle Scholar
DePaolo, D. J. & Wasserburg, G. J. 1976. Nd isotopic variations and petrogenetic models. GEOPHYS RES LETT 3, 249–52.Google Scholar
Eklund, O. 1991. Betydelsen av magmamixing som magmatisk evolutionsprocess i tolkningen av post- och anorogena bergarters uppkomst, Åland SV Finland. Unpublished thesis, Abo Akademi University, Institute for Geology and Mineralogy (partly in English).Google Scholar
Emslie, R. F. 1991. Granitoids of rapakivi granite-anorthosite and related associations. In Haapala, I. & Condie, K. C. (eds) Precambrian granitoids—petrogenesis, geochemistry and metallogeny. PRECAMBRIAN RES 51, 173–92.CrossRefGoogle Scholar
Esipchuk, K. Ye. 1991. Rapakivi granites of the Ukrainian shield: phases and facies. In Haapala, I. & Rämö, O. T. (eds) Symposium on Rapakivi Granites and Related Rocks Abstract Volume. GEOL SURV FINLAND GUIDE 34, 16.Google Scholar
Front, K. & Nurmi, P. A. 1987. Characteristics and geological setting of synkinematic Svecokarelian granitoids in southern Finland. PRECAMBRIAN RES 35, 207–24.CrossRefGoogle Scholar
Haapala, I. 1977. Petrography and geochemistry of the Eurajoki stock, a rapakivi-granite complex with greisen-type mineralization in southwestern Finland. GEOL SURV FINLAND BULL 286.Google Scholar
Haapala, I. 1989. Suomen rapakivigraniiteista, Rapakivi granites of Finland. ACAD SCI FENNICA YEARB 1988–1989 (in Finnish with an English summary).Google Scholar
Haapala, I. & Rämö, O. T. 1990. Petrogenesis of the Proterozoic rapakivi granites of Finland. In Stein, H. J. & Hannah, J. L. (eds) Ore-bearing granite systems; Petrogenesis and mineralizing processes. GEOL SOC AM SPEC PAP 246, 275–86.Google Scholar
Hibbard, M. J. 1981. The magma mixing origin of mantled feldspars. CONTRIB MINERAL PETROL 76, 158–70.CrossRefGoogle Scholar
Hubbard, F. & Branigan, N. 1987. Late Svecofennian magmatism and tectonism, Åland, Southwest Finland. PRECAMBRIAN RES 35, 241–56.CrossRefGoogle Scholar
Huhma, H. 1986. Sm-Nd, U-Pb and Pb-Pb isotopic evidence for the origin of the Early Proterozoic Svecokarelian crust in Finland. GEOL SURV FINLAND BULL 337.Google Scholar
Huhma, H., Claesson, S., Kinny, P. D. & Williams, I. S. 1991. The growth of early Proterozoic crust: new evidence from Svecofennian detrital zircons. TERRA NOVA 3, 175–8.CrossRefGoogle Scholar
Irvine, T. N. & Baragar, W. R. A. 1971. A guide to the chemical classification of the common volcanic rocks. CAN AD J EARTH SCI 8, 523–48.CrossRefGoogle Scholar
Korja, A. 1991. Crustal and upper mantle structure of the Wiborg batholith, SE Finland. Institute of Seismology, University of Helsinki, Report S-25, 97–101.Google Scholar
Korja, A. & Elo, S. 1990. Crustal and upper mantle structure of the Wiborg batholith, SE Finland. Abstracts of the second symposium on the Baltic shield, Lund, Sweden, June 5–7, 1990, 57.Google Scholar
Larin, A., Beljaev, A. & Stepanov, K. 1991. Geological setting of the Salmi batholith. InHaapala, I., Rämö, O. T. & Salonsaari, P. T. (eds) Salmi batholith and Pitkäranta ore field in Soviet Karelia, IGCP Project 315 Symposium Rapakivi Granites and Related Rocks, Excursion Guide. GEOL SURV FINLAND GUIDE 33, 6–7.Google Scholar
Laurén, L. 1970. An interpretation of the negative gravity anomalies associated with the rapakivi granites and the Jotnian sandstone in southern Finland. GEOL FÖREN STOCKHOLM FÖRH 92, 21–34.CrossRefGoogle Scholar
Lindberg, L. & Eklund, O. 1988. Interactions between basaltic and granitic magmas in a Svecofennian postorogenic granitoid intrusion, Åland, southwest Finland. LITHOS 22, 13–23.CrossRefGoogle Scholar
Luosto, U. 1991. Moho depth maps of the Fennoscandian shield based on seismic refraction data. Institute of Seismology, University of Helsinki, Report S-25, 43–9.Google Scholar
Luosto, U., Tiira, T., Korhonen, H., Azbel, I., Burmin, V., Buyanov, A., Kosminskaya, I., Ionkis, V. & Sharov, N. 1990. Crust and upper mantle structure along the DSS Baltic profile in SE Finland. GEOPHY J INT 101, 89–110.CrossRefGoogle Scholar
Nekvasil, H. 1991. Ascent of felsic magma and formation of rapakivi. AM MINERAL 76, 1279–90.Google Scholar
Neymark, L. & Amelin, Yu. 1991. Isotope geochemistry. In Haapala, I., Rämö, O. T. & Salonsaari, P. T. (eds) Salmi batholith and Pitkäranta ore field in Soviet Karelia, IGCP Project 315 Symposium Rapakivi Granites and Related Rocks, Excursion Guide. GEOL SURV FINLAND GUIDE 33, 39–40.Google Scholar
Neymark, L., Amelin, Yu. & Larin, A. 1991. Geochronology of the rocks of the Salmi batholith. In Haapala, I., Rämö, O. T. & Salonsaari, P. T. (eds) Salmi batholith and Pitkäranta ore field in Soviet Karelia, IGCP Project 315 Symposium Rapakivi Granites and Related Rocks, Excursion Guide. GEOL SURV FINLAND GUIDE 33, 34–6.Google Scholar
Nurmi, P. A. & Haapala, I. 1986. The Proterozoic granitoids of Finland: granite types, metallogeny and relation to crustal evolution. BULL GEOL SOC FINLAND 58, 203–33.CrossRefGoogle Scholar
Patchett, J. & Kouvo, O. 1986. Origin of continental crust of 1·9–1·7 Ga age. Nd isotopes and U-Pb zircon ages in the Svecokarelian terrain of South Finland. CONTRIB MINERAL PETROL 92, 1–12.CrossRefGoogle Scholar
Pearce, J. A., Harris, N. B. W. & Tindle, A. G. 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J PETROL 25, 956–83.CrossRefGoogle Scholar
Pesonen, L. J., Torsvik, T. H., Elming, S.-Å. & Bylund, G. 1989. Crustal evolution of Fennoscandia-palaeomagnetic constraints. TECTONOPHYSICS 162, 27–49.CrossRefGoogle Scholar
Rämö, O. T. 1990. Diabase dyke swarms and silicic magmatism-evidence from the Proterozoic of Finland. In Parker, A. J., Rickwood, P. C. & Tucker, D. H. (eds) Mafic dykes and emplacement mechanisms, 185–99. Rotterdam: A.A. Balkema.Google Scholar
Rämö, O. T. 1991. Petrogenesis of the Proterozoic rapakivi granites and related basic rocks of southeastern Fennoscandia: Nd and Pb isotopic and general geochemical constraints. GEOL SURV FINLAND BULL 355.Google Scholar
Rämö, O. T. & Haapala, I. 1991. The rapakivi granites of eastern Fennoscandia: a review with insights into their origin in the light of new Sm-Nd isotopic data. In Gower, C. F., Rivers, T. & Ryan, B. (eds) Mid-Proterozoic Laurentia-Baltica. GEOL ASSOC CANAD SPEC PAP 38, 401–15.Google Scholar
Sahama, Th. G. 1945. On the chemistry of the east Fennoscandian rapakivi granites. BULL COMM GÉOL FINLANDE 136.Google Scholar
Salonsaari, P. T. & Haapala, I. 1991. The Jaala-Iitti rapakivi complex: an example of bimodal magmatism and hybridization in the Wiborg rapakivi batholith, Finland. In Haapala, I. & Rämö, O. T. (eds) Symposium on Rapakivi Granites and Related Rocks Abstract Volume. GEOL SURV FINLAND GUIDE 34, 45.Google Scholar
Sederholm, J. J. 1891. Ueber die finnländischen Rapakiwigesteine. TSCHERMAK'S MINERAL PETROGR MITT 12, 1–31.CrossRefGoogle Scholar
Sederholm, J. J. 1928. On orbicular granites, spotted and nodular granites etc. and on the rapakivi texture. BULL COMM GÉOL FINLANDE 83.Google Scholar
Stacey, J. S. & Kramers, J. D. 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. EARTH PLANET SCI LETT 26, 207–21.CrossRefGoogle Scholar
Suominen, V. 1991. The chronostratigraphy of SW Finland with special reference to the Postjotnian and Subjotnian diabases. GEOL SURV FINLAND BULL 356.Google Scholar
Törnroos, R. 1984. Petrography, mineral chemistry and petrochemistry of granite porphyry dykes from Sibbo, southern Finland. GEOL SURV FINLAND BULL 326.Google Scholar
Vaasjoki, M. 1977. Rapakivi granites and other postorogenic rocks in Finland; Their age and the lead isotopic composition of certain associated galena mineralizations. GEOL SURV FINLAND BULL 294.Google Scholar
Vaasjoki, M. 1981. The lead isotopic composition of some Finnish galenas. GEOL SURV FINLAND BULL 316.Google Scholar
Vaasjoki, M., Rämö, O. T. & Sakko, M. 1991. New U-Pb ages from the Wiborg rapakivi area: constraints on the temporal evolution of the rapakivi granite-anorthosite-diabase dyke association of southeastern Finland. In Haapala, I. & Condie, K. C. (eds) Precambrian granitoids-petrogenesis, geochemistry and metallogeny. PRECAMBRIAN RES 51, 227–43.CrossRefGoogle Scholar
Vorma, A. 1976. On the petrochemistry of rapakivi granites with special reference to the Laitila massif, southwestern Finland. GEOL SURV FINLAND BULL 285.Google Scholar
Wahl, W. 1925. Die Gesteine des wiborger Rapakiwigebietes. FENNIA 45 (20).Google Scholar
Wark, D. A. & Stimac, J. A. 1991. Experimental evidence for the origin of rapakivi texture by a dissolution- and diffusion-controlled mechanism. In Haapala, I. & Rämö, O. T. (eds) Symposium on Rapakivi Granites and Related Rocks Abstract Volume. GEOL SURV FINLAND GUIDE 34, 63.Google Scholar
Whalen, J. B., Currie, K. L. & Chappell, B. W. 1987. A-type granites; Geochemical characteristics, discrimination, and petrogenesis. CONTRIB MINERAL PETROL 95, 407–19.CrossRefGoogle Scholar
Whitney, J. A. 1975. The effects of pressure, temperature, and X on phase assemblages in four synthetic rock compositions. J GEOL 83, 1–31.Google Scholar
Windley, B. F. 1988. Mid-Proterozoic “anorogenic” magmatism: its pre-orogenic and post-orogenic environments in the Grenville, Ketilidian and Svecofennian collisional belts. Geological Association of Canada, Mineralogical Association of Canada, Canadian Society of Petroleum Geologists Joint Annual Meeting Program with Abstracts 13, A136.Google Scholar
Windley, B. F. 1991. Two groups of rapakivi granites and related “anorogenic” rocks: their evolution in a plate tectonic framework during the formation and during the breakup of a supercontinent. In Haapala, I. & Rämö, O. T. (eds) Symposium on Rapakivi Granites and Related Rocks Abstract Volume. GEOL SURV FINLAND GUIDE 34, 63.Google Scholar