ORIGINAL PAPER Sequential granite emplacement: a structural study of the late Variscan Strzelin intrusion, SW Poland Teresa Oberc-Dziedzic • Ryszard Kryza • Christian Pin • Stanislaw Madej Received: 27 June 2012 / Accepted: 24 January 2013 / Published online: 3 March 2013 Ó The Author(s) 2013. This article is published with open access at Springerlink.com Abstract The Strzelin Massif in SW Poland (Central European Variscides) records a protracted igneous evolu- tion, with three main magmatic stages: (1) tonalitic I, (2) granodioritic and (3) tonalitic II/granitic. In the northern part of this Massif, the Strzelin intrusion proper comprises three successively emplaced rock types: a medium-grained biotite granite (303 ± 2 Ma), a fine-grained biotite granite (283 ± 8 Ma) and a fine-grained biotite-muscovite granite; based on field evidence, the third variety postdates both types of the biotite granites. The structural data from the three granites, including their parallel, approximately E–W striking and steeply dipping lithological contacts and ENE– WSW trending subhorizontal magmatic lineations, suggest that the emplacement of all three successive granite vari- eties was controlled by an active, long-lived strike-slip fault, striking ESE–WNW, with a dextral sense of move- ment. After the emplacement of the youngest biotite- muscovite granite, the intrusion underwent brittle extension which produced ‘‘Q joints’’ striking NNW–SSE to N–S and dipping at 55–70° WSW to W, and showing evidence of broadly N–S directed sinistral displacements. The structural observations, supported by new geochronological data, indicate that the internal structure of the composite granitoid intrusion, including the faint magmatic foliation and lineation, formed in a long-lived strike-slip setting, different from the subsequent, post-emplacement exten- sional tectonics that controlled the development of brittle structures. Keywords Granite tectonics Á Variscan granitoids Á Strzelin Massif Á Hans Cloos Introduction Extensive granitoid plutonism is a distinct feature of the European Variscides (Fig. 1a). In the Bohemian Massif in the eastern part of the Variscan belt (Fig. 1b), the igneous activity continued from the late Devonian to early Permian and produced granitoid magmas generated from various sources and, consequently, differing in their petrographic and geochemical characteristics (Finger et al. 1997). The abundant granite plutons in Lower Silesia in the NE part of the Bohemian Massif were studied nearly a century ago by Hans Cloos, and it was where he developed his classical concept of ‘‘granite tectonics’’ (Cloos 1920, 1921, 1922a, b, 1925). Nearly one hundred years after Cloos’ basic works, the knowledge of the internal structures of granite intrusions and their interpretations have considerably developed, though Cloos’ main ideas seem to remain valid. The Strzelin intrusion in the Sudetes (Fig. 1c) was the site of Cloos’ original investigations in the early 1920s. Since that time, this intrusion has been intensely excavated in large quarries, making it more accessible for new investigations. In this paper, we present structural observations from the From 1920 to 1922, Hans Cloos published his pioneering studies on granite tectonics, based on his investigations initiated in the Strzelin Massif (NE part of the Bohemian Massif). The authors of this paper wish to commemorate the 90th anniversary of the prominent Hans Cloos’ publications, presenting results of their recent research in the Strzelin intrusion. T. Oberc-Dziedzic Á R. Kryza (&) Á S. Madej Institute of Geological Sciences, University of Wroclaw, Plac M. Borna 9, 50-204 Wroclaw, Poland e-mail: [email protected] C. Pin De ´partement de Ge ´ologie, CNRS, Universite ´ Blaise Pascal, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France 123 Int J Earth Sci (Geol Rundsch) (2013) 102:1289–1304 DOI 10.1007/s00531-013-0863-y
Sequential granite emplacement: a structural study of the late Variscan Strzelin intrusion, SW Poland
Jun 30, 2023
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