Exploring the Ar isotope record of an early Miocene pseudotachylyte in an early Oligocene intrusion (Rieserferner pluton, eastern Alps)

Journal article


Publication Details

Author(s): Di Vincenzo G, Pennacchioni G, Bestmann M
Journal: Lithos
Publication year: 2019
Volume: 338-339
Pages range: 1-17
ISSN: 0024-4937


Abstract


We investigate the influence of unmelted clasts on the
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Ar[sbnd]
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Ar age record of a Miocene pseudotachylyte within the early Oligocene Riesenferner pluton (eastern Alps). This case study is ideal to investigate the effect of inherited Ar retained in survivor clasts because, although seismic faulting was only slightly younger (<20 Ma) than the igneous source rock, the pseudotachylyte includes layers with significant variations in K content, of either dominant plagioclase and biotite microlites or dominant submicrometric muscovite matrix. Numerical modeling, assuming pure diffusive loss and a short-lived thermal pulse due to frictional heating, indicates that unmelted plagioclase clasts represent the most critical issue in interpreting Ar data. Plagioclase clasts of only a few to tens micrometers in size are expected to retain most of radiogenic Ar accumulated before coseismic faulting. A comparable behavior is only predicted for much larger (ten to fifty times larger) K-feldspar clasts. In-situ
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Ar[sbnd]
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Ar laser analyses of low-K microlitic domains, free of discernable clasts, yield slightly, but significantly, older ages than those from the high-K matrix. Results suggest that older ages (up to ~4% on average) from low-K domains are due to contamination by plagioclase clasts and suggest an age of 17.12 ± 0.22 Ma for coseismic slip. This age dates the last stage of activity of the Giudicarie Fault during tectonic indentation of the Dolomites block of the southern Alps against the nappe stack of the eastern Alps.


FAU Authors / FAU Editors

Bestmann, Michel Dr.
Professur für Tektonik


External institutions with authors

Istituto di Geoscienze e Georisorse
University of Padova / Universita degli Studi di Padova


How to cite

APA:
Di Vincenzo, G., Pennacchioni, G., & Bestmann, M. (2019). Exploring the Ar isotope record of an early Miocene pseudotachylyte in an early Oligocene intrusion (Rieserferner pluton, eastern Alps). Lithos, 338-339, 1-17. https://dx.doi.org/10.1016/j.lithos.2019.04.009

MLA:
Di Vincenzo, Gianfranco, Giorgio Pennacchioni, and Michel Bestmann. "Exploring the Ar isotope record of an early Miocene pseudotachylyte in an early Oligocene intrusion (Rieserferner pluton, eastern Alps)." Lithos 338-339 (2019): 1-17.

BibTeX: 

Last updated on 2019-17-05 at 13:08