Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
  Geological Magazine   Don't get GSW? Talk to your librarian.
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Geological Magazine; November 2008; v. 145; no. 6; p. 858-867; DOI: 10.1017/S0016756808004962
© 2008 Cambridge University Press (CUP)
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by BATCHELOR, R. A.
Right arrow Articles by RAEBURN, A. S.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Petrogenesis of albite-rich mid- to late Proterozoic tephra-fall deposits (‘brown beds’)

RICHARD A. BATCHELOR*,{dagger}, ANTHONY R. PRAVE*, GRAHAME J. H. OLIVER* and ANDREW S. RAEBURN*,{ddagger}

* School of Geography & Geosciences, University of St Andrews, St Andrews, Fife KY16 9AL, Scotland, UK
{ddagger} 40 Main Street, Methven, Perthshire PH1 3PU, Scotland, UK

{dagger} Author for correspondence: rab{at}st-andrews.ac.uk

The discovery of volcanogenic ‘brown beds’ in Dalradian and Torridonian (Sleat Group and Diabaig Group) sequences in Scotland has raised questions about their origin and provenance. New discoveries of a grey facies cognate to the ‘brown beds’ have led to an hypothesis which proposes that these beds originated as tephra-fall deposits of intermediate to mafic composition. Subsequent prehnite–pumpellyite- and greenschist-facies metamorphism generated an albite–chlorite–muscovite–quartz–calcite assemblage. Recent sub-aerial weathering selectively dissolved interstitial calcite and oxidized iron, which left an albite-rich ‘brown bed’ with a porous saccharoidal texture. Field relationships and mineralogy support their origin as tephra-fall deposits and their widespread occurrence suggests they are not localized phenomena. Crucially, the weathered ‘brown beds’ point to the existence of otherwise cryptic grey metamorphosed tuffs which tend to blend in with their host metasediments.

Key Words: Proterozoic • tuffs • volcaniclastic • metamorphism






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Cambridge University Press (CUP)