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The tourmaline-bearing granite pluton of Bodmin (Cornwall, UK); magnetic fabric study and regional inference

Jean Luc Bouchez, Thierry Mintsa Mi Nguema, Lionel Esteban, Roberto Siqueira and Richard Scrivener
The tourmaline-bearing granite pluton of Bodmin (Cornwall, UK); magnetic fabric study and regional inference
Journal of the Geological Society of London (July 2006) 163 (4): 607-616

Abstract

The magnetic fabrics and microstructures of the Variscan granite pluton of Bodmin (Cornwall) have been studied. Its low susceptibility magnitude, consistent with its lack of magnetite, comes from biotite and tourmaline. As the magneto-crystalline behaviour of tourmaline is "inverse" compared with that of the phyllosilicates, the magnetic fabric was remeasured after heating the specimens to enhance the biotite magnetic signal by the growth of mimetic magnetite. The roughly similar magnetic fabrics before and after heating demonstrate that the effect of tourmaline is not important as long as the tourmaline content does not exceed that of the phyllosilicates. Regionally, this study reveals a well-defined NNW trend of the magnetic lineations with opposite plunges on each side of a separation line crossing the pluton centre. This pattern, very similar to that documented in the nearby Carnmenellis pluton, is ascribed to unroofing during emplacement. It agrees with the late to post-magmatic NW stretch that characterizes the Devonian to Carboniferous formations located to the north of this region, the thrust-and-fold structure of which is attributed to southward compression. We conclude that syntectonic emplacement may have characterized the whole Cornubian batholith at the very end of the Variscan orogeny in Cornwall.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 163
Serial Issue: 4
Title: The tourmaline-bearing granite pluton of Bodmin (Cornwall, UK); magnetic fabric study and regional inference
Affiliation: CNRS, Laboratoire des Mecanismes de Transfert en Geologie, Toulouse, France
Pages: 607-616
Published: 200607
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 33
Accession Number: 2006-058834
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch maps
N50°28'00" - N50°28'00", W04°42'00" - W04°42'00"
Secondary Affiliation: British Geological Survey, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200632
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