THE PHONOLITIC BODY OF PETIT GERBIER (EASTERN VELAY, FRENCH MASSIF-CENTRAL, FRANCE) - MAGNETIC AND MAGMATIC STRUCTURES

Research areas:
Year:
1993
Authors:
Journal:
COMPTES RENDUS DE L ACADEMIE DES SCIENCES SERIE II
Volume:
316
Number:
11
Pages:
1603-1610
Month:
JUN 3
ISSN:
1251-8069
BibTex:
Abstract:
The magnetic structures of the Petit Gerbier phonolitic neck have been
studied by the Anisotropy of Magnetic Susceptibility (AMS), revealing
its internal organization (foliations and lineations). Results of the
AMS are microstructurally checked by studies of shape preferred
orientations of minerals, and image analysis using the intercept method.
The results point to a process of fabric acquisition involving
superposition of two main events: (1) a magmatic fabric sensu stricto
was responsible for a penetrative foliation and a lineation; (2) this
first structure was locally disorganized by microshear bands due to
strain localization at the end of emplacement. This evolution.from
magmatic to viscous-brittle, is a witness of the rheological evolution
during a superficial protrusion-type emplacement.