Single-zircon Pb-evaporation and 40Ar/39Ar dating of the metamorphic and granitic rocks in north-west Spitsbergen

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Ohta, Yoshihide ; Larionov, Alexander N. ; Tebenkov, Alexander M. ; Lepvrier, Claude ; Maluski, Henri ; Lange, Michael ; Hellebrandt, Barbara (2002)

North-west Spitsbergen consists of a complex of Caledonian and Grenvillian crystalline rocks, situated at the north-west corner of the Barents Shelf. The aim of this study is to understand the extent of pre-Caledonian basement rocks and their protoliths. Micas and zircon grains from six rocks from north-west Spitsbergen have been dated by the 40Ar/39Ar and single-zircon Pb-evaporation methods. Two grey granites yielded Late Caledonian mica 40Ar/39Ar and zircon ages of ca. 420-430 My, with inherited zircon grains as old as 1725 My. Zircon grains from a gneissose granite xenolith in a grey granites gave crystallization ages of ca. 960 My; some grains from a migmatite neosome show similar ages. Zircon grains yielding Archean and late Palaeoproterozoic ages (1600-1800 My) are interpreted as xenocrysts of detrital origin. The youngest ages obtained from detrital zircon grains from a greenschist facies quartzite of the Signehamna unit are ca. 1800 My. Similar schists are included as xenoliths in the 960 My old gneissose granite; therefore, the sedimentary protoliths of the unit are Mesoproterozoic. The dating results suggest a significant tectonothermal event during Grenvillian time; subsequent Caledonian events had less extensive thermal effects. However, it is still a matter of debate whether Grenvillian or Caledonian metamorphism produced the majority of the migmatites. A large population of zircon grains with Late Palaeoproterozoic ages suggests a wide surface exposure of rocks of this age in the source area, with some Archean zircons.
  • References (55)
    55 references, page 1 of 6

    Abakumov, S. A. 1979: Peculiar features of regional metamorphism of northwestern Spitsbergen. The geological development of Svalbard during the Precambrian, Lower Palaeozoic, and Devonian. Nor. Polarinst. Skr. 167, 29-36.

    Balašov, Ju. A., Tebenkov, A. M., Ohta, Y., Larionov, A. N., Sirotkin, A. N., Gannibal, L. F. & Ruyngenen, G. I. 1995: Grenvillian U-Pb zircon ages of quartz porphyry and rhyolite clasts in a metaconglomerate at Vimsodden, southwestern Spitsbergen. Polar Res. 14, 291-302.

    Balašov, Ju. A., Peucat, J. J., Tebenkov, A. M., Ohta, Y. & Sirotkin, A. N. 1996a: Additional Rb-Sr and single-zircon datings of Caledonian granitoid rocks from Albert I Land, northwest Spitsbergen. Polar Res. 15, 153-165.

    Balašov, Ju. A., Peucat, J. J., Tebenkov, A. M., Ohta, Y., Larionov, A. N., Sirotkin, A. N. & Bjørnerud, M. 1996b: Rb-Sr whole rock and U-Pb zircon datings of the graniticgabbroic rocks from the Skålfjellet Subgroup, southwest Spitsbergen. Polar Res. 15, 167-181.

    Brouand, M., Banzet, G. & Barbey, P. 1990: Zircon behaviour during crustal anatexis. Evidence from the Tibetan Slab migmatites (Nepal). J. Volcan. Geotherm. Res. 44, 143- 161.

    Bucher-Nurminen, K. 1981: Petrology of chlorite-spinel marbles from NW Spitsbergen (Svalbard). Lithos 14, 203- 213.

    Cornell, D., Åberg, A., Schersten, A. & Armstrong, R. 1998: The CANUTE model for Ion-probe U-Pb zircon dating and its application to the Borås mafic intrusion. 23rd Nordic Geological Winter Meeting, Århus, 1998. Abstract volume, p. 53.

    Dallmeyer, R. D., Peucat, J. J., Hirajima, T. & Ohta, Y. 1990a: Tectothermal chronology within a blueschist-eclogite complex, west-central Spitsbergen, Svalbard: evidence from 40Ar/39Ar and Rb-Sr mineral ages. Lithos 24, 291- 304.

    Dallmeyer, R. D., Peucat, J. J. & Ohta, Y. 1990b: Tectonothermal evolution of contrasting metamorphic complexes in northwest Spitsbergen (Biskayerhalvøya): evidence from 40Ar/39Ar and Rb-Sr mineral ages. Geol. Soc. Am. Bull. 102, 653-663.

    Dalziel, I. W. D. 1997: Neoproterozoic-Paleozoic geography and tectonics: review, hypothesis, environmental speculation. Geol. Soc. Am. Bull. 109, 16-42.

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