Laser-probe 40Ar/39Ar investigation of a pseudotachylyte and its host rock from the Outer Isles thrust, Scotland

Abstract

Research Article| May 01, 1994 Laser-probe 40Ar/39Ar investigation of a pseudotachylyte and its host rock from the Outer Isles thrust, Scotland S. P. Kelley; S. P. Kelley 1Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Search for other works by this author on: GSW Google Scholar S. M. Reddy; S. M. Reddy 1Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Search for other works by this author on: GSW Google Scholar R. Maddock R. Maddock 230 Kingsway, Woking, Surrey, United Kingdom Search for other works by this author on: GSW Google Scholar Author and Article Information S. P. Kelley 1Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom S. M. Reddy 1Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom R. Maddock 230 Kingsway, Woking, Surrey, United Kingdom Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1994) 22 (5): 443–446. https://doi.org/10.1130/0091-7613(1994)022<0443:LPAAIO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation S. P. Kelley, S. M. Reddy, R. Maddock; Laser-probe 40Ar/39Ar investigation of a pseudotachylyte and its host rock from the Outer Isles thrust, Scotland. Geology 1994;; 22 (5): 443–446. doi: https://doi.org/10.1130/0091-7613(1994)022<0443:LPAAIO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search 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 40Ar/39Ar 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 beating event probably lasted less than 10 s, leading to temperatures >730°C in the host gneiss; these high temperatures may have caused catastrophic argon loss rather than loss by volume diffusion. An 40Ar/39Ar 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 ±6 Ma (2σ) obtained in the center corresponds closely to movement ages derived for the associated Moine thrust zone. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.