Abstract
Mylonitic pegmatites from the Austroalpine basement north of the Deferregen-Antholz-Vals shear zone (DAV) in the Eastern Alps record episodic deformation at greenschist facies conditions after the Eoalpine tectonometamorphic event and before uplift in the Oligocene. Fluorapatite-allanite-epidote coronae around monazite formed at about 60 Ma. They postdate a main mylonitic foliation and predate a second shear band foliation. Deformation of quartz is controlled by crystallographic orientation: Dislocation glide in favourable orientation forms elongate high-aspect-ratio grains. Localised recrystallisation takes place at sites of increased dislocation densities in less favourable oriented quartz and distributed microcracking in unfavourable orientation. Distributed microcracking of quartz occurred quasi-instantaneously coeval with cataclastic deformation of garnet and tourmaline, indicating transient high stresses. During subsequently decreasing stresses, small isometric quartz grains precipitate within the shear band boundaries from the pore fluid, probably derived from recrystallisation of fluid-rich quartz porphyroclasts. Cataclasites with mylonitic components record a coeval or subsequent stage of transient deformation, reflecting the main activity of the DAV with uplift from greenschist facies conditions. The mylonitic pegmatites record systematically changing deformation mechanisms during episodic deformation at greenschist facies conditions dominantly governed by changing stresses and strain-rates, as opposed to changing temperatures.
| Dokumententyp: | Zeitschriftenartikel |
|---|---|
| Fakultät: | Geowissenschaften > Department für Geo- und Umweltwissenschaften |
| Themengebiete: | 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie |
| ISSN: | 0191-8141 |
| Sprache: | Englisch |
| Dokumenten ID: | 110760 |
| Datum der Veröffentlichung auf Open Access LMU: | 02. Apr. 2024, 07:20 |
| Letzte Änderungen: | 02. Apr. 2024, 07:20 |
- Dokument bearbeiten
