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GEOREF RECORD

Laser-probe (super 40) Ar/ (super 39) Ar investigation of a pseudotachylyte and its host rock from the Outer Isles Thrust, Scotland; with Suppl. Data 9424

S. P. Kelley, S. M. Reddy and R. Maddock
Laser-probe (super 40) Ar/ (super 39) Ar investigation of a pseudotachylyte and its host rock from the Outer Isles Thrust, Scotland; with Suppl. Data 9424
Geology (Boulder) (May 1994) 22 (5): 443-446

Abstract

The formation of a friction melt or pseudotachylyte in the footwall of the Outer Isles thrust, Scotland, during thrust movement in the early Paleozoic Caledonian orogeny caused argon loss from biotites in the host gneiss. Mean (super 40) Ar/ (super 39) Ar ages for biotite grains decrease from 1450 to 923 Ma in a zone <2 mm wide, approaching the pseudotachylyte boundary. However, the laser-microprobe age traverses of the individual grains do not exhibit typical diffusive argon loss profiles. The heating event probably lasted less than 10 s, leading to temperatures >730 degrees C in the host gneiss; these high temperatures may have caused catastrophic argon loss rather than loss by volume diffusion. An (super 40) Ar/ (super 39) Ar age traverse across the pseudotachylyte vein revealed old ages adjacent to the margin, reflecting the incorporation of partially outgassed host-rock clasts. Apparent ages for the pseudotachylyte decrease unevenly toward the center of the vein. A weighted mean age of 430 + or -6 Ma (2) obtained in the center corresponds closely to movement ages derived for the associated Moine thrust zone.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 22
Serial Issue: 5
Title: Laser-probe (super 40) Ar/ (super 39) Ar investigation of a pseudotachylyte and its host rock from the Outer Isles Thrust, Scotland; with Suppl. Data 9424
Affiliation: Open University, Department of Earth Sciences, Milton Keynes, United Kingdom
Pages: 443-446
Published: 199405
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 20
Accession Number: 1994-026289
Categories: GeochronologyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N57°19'60" - N57°40'00", W07°49'60" - W07°00'00"
Secondary Affiliation: 30 Kingsway, Woking, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 199412
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