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| Titel |
The Strudengau Shear Zone; a new Late Variscan low-angled ductile shear zone in the S Moldanubian Zone (Austria) |
| VerfasserIn |
Helga Zeitlhofer, Konstantin Petrakakis, Christoph Iglseder |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042740
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| Schlagwörter |
Geologie, Tektonik, Störung, Scherzone, Strudengau Scherzone, Duktile Scherzone, Kinematik, Extensionstektonik, Monotone Serie, Moldanubikum, Böhmische Masse |
| Geograf. Schlagwort |
Österreich, Niederösterreich, Amstetten (Bezirk), Melk (Bezirk), Strudengau, Amstettener Bergland |
| Blattnummer |
53 [Amstetten], 54 [Melk an der Donau] |
| Blattnummer (UTM) |
4321 [Grein], 4322 [Pöchlarn], 4327 [Amstetten], 4328 [Scheibbs] |
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| Zusammenfassung |
| The Variscan Moldanubian Zone in Austria is divided from E to W into three lithological units: Gföhl, Variegated and Monotonous units. In the Amstettener Bergland and Strudengau area (Lower Austria), important new late- to post-Variscan deformation has been observed. Between Persenbeug and Weins, a low-angled mylonitic shear-zone (Strudengau Shear Zone) has been mapped for over 2 km, with a thickness of 0.3 – 1.5 m. Shear-sense criteria, observed in both the field and thin-sections (shear-zone asymmetry, clast geometry, and quartz CPO) indicate a top NW sense of shear. The Strudengau Shear Zone lies in the Monotonous Unit and cross-cuts older structural pattern in the HT/LP metamorphic rocks and dykes which intruded the metamorphic nappe stack. The HT/LP metamorphic rocks, mainly ortho- and paragneisses, have steeply dipping foliation planes with SE-NW trending lineations, showing top SE kinematics. Dykes with variable mineralogies and chemical compositions have pre- and post-mylonitic cross-cutting relationships to the Strudengau Shear Zone. The shear zone mylonites have parageneses indicative of the lower amphibolite facies (Pl + Kfs + Bt + Ms + Qtz), with relict Ky/Sil. Syn- to post-tectonic chlorite grew parallel to the mylonitic foliation; this is interpreted as a greenschist-facies overprint during ongoing mylonitisation and exhumation in a regional W-E extensional system. In addition, brittle-ductile to brittle high-angle fault-patterns around the mylonites display an essentially NW-SE trending maximum compressive stress. Quartz shear bands indicate a lower temperature deformation, towards the brittle-ductile transition. Reactivation of the brittle structures during Alpine orogeny is likely. |
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