Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
  Geological Magazine   Signup for GSW Email News
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Geological Magazine; July 2008; v. 145; no. 4; p. 537-551; DOI: 10.1017/S0016756808004573
© 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
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Google Scholar
Right arrow Articles by ZÁK, J.
Right arrow Articles by TYCOVÁ, P.
GeoRef
Right arrow GeoRef Citation

Multiple magmatic fabrics in plutons: an overlooked tool for exploring interactions between magmatic processes and regional deformation?

JIRÍ ZÁK*,{dagger},*, KRYSTOF VERNER{dagger},{ddagger} and PATRICIE TYCOVÁ§

* Institute of Geology and Paleontology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic
{dagger} Czech Geological Survey, Klárov 3, Prague, 11821, Czech Republic
{ddagger} Institute of Petrology and Structural Geology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic
§ Czech Geological Survey, Geologická 6, Prague, 152 00, Czech Republic

* Author for correspondence: jirizak{at}natur.cuni.cz

This paper elaborates on the concept of multiple magmatic fabrics in plutons. After a general overview of various types of multiple fabrics that may develop in magmatic rocks, two case examples of porphyritic granite and melasyenite plutons in the Bohemian Massif are examined. In the Jizera granite, complex variations in K-feldspar phenocryst shape-fabric revealed by image analysis of a 200 m long section of an underground tunnel are in contrast with homogeneously oriented magnetic (AMS) fabric carried by coaxial contributions of biotite, magnetite and maghemite. In the Knízecí Stolec melasyenite pluton, emplacement-related margin-parallel feldspar foliation was overprinted by flat-lying foliation; the latter is interpreted to record regional tectonic strain. At the two stations examined in detail, the crystallographic-preferred orientation of biotite and amphibole in the inter-phenocryst matrix (measured using electron back-scatter diffraction – EBSD) differed from both feldspar fabric and also from the AMS principal directions. Multiple magmatic fabrics in these two plutons are interpreted in terms of fabric superposition, where late weak strain is superposed onto a high-strength phenocryst framework, but is accommodated preferentially by small mineral grains (biotite, magnetite) in the melt-bearing matrix. This mechanism may explain the discrepancy between mesoscopic feldspar fabric and AMS. We conclude that multiple magmatic fabrics in plutons may thus result from accumulated strain caused by different processes during final crystallization and, as such, may serve as a sensitive indicator of the evolving interactions between magmatic and tectonic processes in the Earth’s crust.

Key Words: deformation • fabric • granite • magnetic susceptibility anisotropy • pluton






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2008 by Cambridge University Press (CUP)