Schenker, Filippo and Ambrosi, Christian and Scapozza, Cristian and Czerski, Dorota and Castelletti, Claudio and Maino, Matteo and Gouffon, Yves (2017) Combining in-situ U-Pb geochronology in zircons and geological data to investigate nappe formation in the Central Alps. In: Congresso congiunto di AIV, SGI, SIMP e SoGel 2017, Pisa, Italy. (Unpublished)
Full text not available from this repository.Abstract
The pre-Alpine Variscan gneissic crust was intensely intruded by several generations of granitoids forming laccoliths and dikes of different shapes and sizes within paragneisses, augengneisses and amphibolites. During the Alpine orogenic cycle this initial and complex geological architecture was reshaped into a fold and thrust belt. Nevertheless, distinguishing within a nappe pile of gneisses a major tectonic contact from a reactivated magmatic contact is not trivial. In the Lepontine dome (Central Alps), these gneissic nappes are subdivided into, from bottom-to-top, Leventina, Simano, Adula/Cima-Lunga and Maggia. In particular, the boundary between the Leventina and the Simano gneisses is not clear. The boundary was traced within leucogneisses by joining lenses of metasediments of unknown age but assumed to be Mesozoic. Magmatic Early Permian U-Pb SHRIMP zircon ages from a folded granitic dike discordant within paragneisses that separate the Leventina and the Simano units attest moderate deformation along the boundary during the Alpine orogen. Furthermore, Devonian-Silurian U-Pb SHRIMP ages in detrital zircon cores of the same paragneisses suggest that the deposition was older than Mesozoic. Hence, those sediments can not be used as Alpine nappe divider. Therefore, the combined geochronological and geological results bring evidence (i) of moderate strain localization between the Leventina and the Simano, questioning the allochthonous character of the Simano unit, (ii) of a top-to-the-foreland deformation gradient between the Leventina and the Adula/Cima-Lunga units and (iii) of non-coaxial ductile deformation along inherited rheological heterogeneities within the units, complicating the tectonic understanding.
| Item Type: | Article in conference proceedings or Presentation at a conference (Poster) |
|---|---|
| Subjects: | Physical sciences > Geology Physical sciences > Geology > Earth science Physical sciences > Geology > Earth science > Geoscience Physical sciences > Geology > Geochemistry |
| Department/unit: | Dipartimento ambiente costruzioni e design > Istituto scienze della Terra |
| Depositing User: | Filippo Schenker |
| Date Deposited: | 15 Jan 2018 08:52 |
| Last Modified: | 15 Jan 2018 08:52 |
| URI: | http://repository.supsi.ch/id/eprint/9112 |
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