Structural and magnetic fabric study of the Marimanha granite (Axial Zone of the Pyrenees) |
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| Authors: | B Antolín-Tomás T Román-Berdiel A Casas-Sainz I Gil-Peña B Oliva R Soto |
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| Institution: | 1.Dpt. de Ciencias de la Tierra,Universidad de Zaragoza,Zaragoza,Spain;2.Unidad de Geología y Geofísica,Instituto Geológico y Minero de Espa?a,Madrid,Spain;3.Department of Geological Sciences,University of Michigan,Ann Arbor,USA;4.Laboratorio de Paleomagnetismo, Departamento de Física,Universidad de Burgos,Burgos,?Spain;5.Institut für Geologie,Universit?t Tübingen,Tübingen,Germany |
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| Abstract: | The structural and magnetic fabric study of the Marimanha granite, Axial Zone of the Pyrenees, provides new data to characterize
the zonation and the internal structure of the pluton. The Marimanha granite intrudes Cambro–Ordovician clastic rocks and
Silurian–Devonian limestones and slates. The zonation of the low field magnetic susceptibility, consistent with the petrological
zonation of the igneous body, indicates a concentric arrangement of rock types, with more basic compositions at the external
areas. This pluton is characterized by a low susceptibility, and rock–magnetic studies indicate a majority of “paramagnetic”
samples. Magnetic foliations strike parallel to petrographic contacts and to contours of zonation of magnetic susceptibility,
and show a dominant NE–SW strike, steeply dipping towards the North. Locally, in the northern border of the pluton foliation
directions become perpendicular to petrographic contacts and depict sigmoidal trajectories. Magnetic lineations are characterized
by the predominance of NE–SW trends with shallow plunges to the NE and SW. These foliations and lineations are parallel to
the slight elongation of internal petrographic zonation. Magnetic fabric within the granitoid body and internal elliptical
shape of petrographic zonation, suggest an intrusion contemporary with a transpressional regime and NNW–SSE shortening, syntectonic
with the late stages of the Variscan orogeny. These results are in accordance with anisotropy of magnetic susceptibility studies
of others plutons in the Pyrenees. To explain the origin of the Marimanha granite we propose magma ascent through faults at
depth and emplacement by ballooning in situ at the rheological boundary between Cambro–Ordovician and Siluro–Devonian metasediments. |
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| Keywords: | Granite Anisotropy of magnetic susceptibility Marimanha Variscan Pyrenees |
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