Pseudotachylyte as field evidence for lower crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.5194/se-2017-123.

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Authors

Friedrich Hawemann , Neil S. Mancktelow, Sebastian Wex, Alfredo Camacho, Giorgio Pennacchioni

Abstract

Geophysical evidence for lower continental crustal earthquakes in almost all collisional orogens is in conflict with the widely accepted notion that rocks, under high grade conditions, should flow rather than fracture. Pseudotachylytes are remnants of frictional melts generated during seismic slip and can therefore be used as an indicator of former seismogenic fault zones. The Fregon Domain in Central Australia, was deformed under dry sub-eclogitic conditions during the intracontinental Petermann Orogeny (ca. 550 Ma) and contains abundant pseudotachylyte. These pseudotachylytes are commonly foliated, recrystallized, and crosscut by other pseudotachylytes, reflecting repeated generation during ongoing ductile deformation under generally dry conditions. This interplay is interpreted as a cycle of seismic brittle failure and post- to inter seismic creep under dry lower crustal conditions. Thermodynamic modelling of the pseudotachylyte bulk composition gives conditions of shearing of 600-700 °C and 1.0-1.2 GPa, the same as in surrounding mylonites. We conclude that pseudotachylytes in the Fregon Domain are a direct analogue of current seismicity in dry lower continental crust.

DOI

https://doi.org/10.31223/osf.io/c3s5g

Subjects

Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure

Keywords

earthquake, rheology, Fracture, brittle, ductile, lower crust, eclogite, jelly sandwich, pseudotachylyte, XMapTools

Dates

Published: 2017-11-09 08:23

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License

CC BY Attribution 4.0 International

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