The main Variscan deformation event in the Pyrenees; new data from the structural study of the Bielsa Granite

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doi: 10.1016/j.jsg.2003.09.001
Authors:Román-Berdiel, T.; Casas, A. M.; Oliva-Urcia, B.; Pueyo, E. L.; Rillo, C.
Author Affiliations:Primary:
Universidad de Zaragoza, Departamento de Ciencias de la Tierra, Saragossa, Spain
Other:
University of Leoben, Austria
Volume Title:Journal of Structural Geology
Source:Journal of Structural Geology, 26(4), p.659-677. Publisher: Elsevier, Oxford, International. ISSN: 0191-8141
Publication Date:2004
Note:In English. 49 refs.; illus., incl. 2 plates, 1 table, geol. sketch maps
Summary:A structural and magnetic fabric study of the Bielsa granite (Axial Zone of the Pyrenees) provides new data indicating that this pluton was emplaced during the main Variscan event recognized in the Pyrenees. We argue that the later post-Triassic deformation was localized along mylonitic bands reactivating earlier Variscan shear bands. The Bielsa granite intrudes Cambro-Ordovician metasediments at its northern border, and the pluton is unconformably overlain by sediments Triassic in age to the south and east. The main structures in the igneous body are magmatic foliations and lineations defined by feldspar phenocrysts and biotite and dextral shear bands with dominant WNW-ESE trends. The WNW-ESE striking magmatic foliations have variable dips, and the magmatic lineation a subhorizontal WNW-ESE trend. The zonation of low-field magnetic susceptibility, coarsely related to mineral content, indicates a layer arrangement of rock-types, with more basic compositions at the northern border. The magnetic ellipsoids are prolate along a WNW-ESE central band, and oblate at the pluton borders, where flattening is more important. All these data allow us to interpret the Bielsa intrusion as being caused by coeval NNE shortening and dextral shear. The presence of shear bands indicates that strain localization under dextral transpression continued during late-Variscan times. Abstract Copyright (2004) Elsevier, B.V.
Sections:Petrology
Subsections:Metamorphism: regional, dynamic
Subjects:Accelerator mass spectra; Cambrian; Deformation; Fabric; Faults; Foliation; Granites; Igneous rocks; Intrusions; Jurassic; Lineation; Magnetic minerals; Magnetic properties; Magnetic susceptibility; Magnetite; Mass spectra; Mesozoic; Metamorphic rocks; Metasedimentary rocks; Mineral composition; Mylonites; Orogeny; Oxides; Paleomagnetism; Paleozoic; Petrography; Phenocrysts; Plutonic rocks; Plutons; Preferred orientation; Shear zones; Spectra; Structural analysis; Tectonics; Textures; Variscan Orogeny; Aragon Spain; Europe; Huesca Spain; Iberian Peninsula; Pyrenees; Southern Europe; Spain; Spanish Pyrenees; Bielsa Massif; Bielsa Spain
Coordinates:N423000 N424500 E0014500 E0011500
Abstract Numbers:04M/1775
Record ID:2005071132
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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