Dating fault reactivation by Ar/Ar laserprobe; an alternative view of apparently cogenetic mylonite-pseudotachylite assemblages

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doi: 10.1144/0016-764903-160
Authors:Sherlock, S. C.; Watts, L. M.; Holdsworth, R. E.; Roberts, D.
Author Affiliations:Primary:
Open University, Department of Earth Sciences, Milton Keynes, United Kingdom
Other:
University of Durham, United Kingdom
Geological Survey of Norway, Norway
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 161(3), p.335-338. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:2004
Note:In English. 29 refs.; illus., incl. 1 table, geol. sketch map
Summary:Apparently cogenetic mylonite-pseudotachylite assemblages are commonly reported in major fault zones. They represent two very incompatible modes of deformation, and complex formation mechanisms have been proposed to explain this paradox. We report here one such assemblage from Central Norway in which apparently synchronous mylonite and pseudotachylite formation is separated by 100 Ma-mean muscovite Ar/Ar laserprobe spot ages from mylonite, and pseudotachylite matrix, are 406±11 Ma and 290±10 Ma respectively. In preference to a complex cogenetic model we invoke fault reactivation as a viable alternative, and suggest that assumed contemporaneity in such assemblages may be invalid in many cases.
Sections:Age determination
Subjects:Absolute age; Ar/Ar; Dates; Experimental studies; Faults; Kinematics; Laser methods; Metamorphic rocks; Mica group; Muscovite; Mylonites; Paleozoic; Pseudotachylite; Reactivation; Sheet silicates; Silicates; Europe; Norway; Scandinavia; Trondelag; Western Europe; Central Norway; Fosen Peninsula; More-Trondelag Complex
Coordinates:N633000 N643000 E0120000 E0113000
Abstract Numbers:04M/1915
Record ID:2004051474
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
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