Structure of a hypovolcanic acid complex inferred from magnetic susceptibility anisotropy measurements: the Western Red Hills granites (Skye,Scotland, Thulean Igneous Province) |
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Authors: | Geoffroy Laurent Olivier Philippe Rochette Pierre |
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Institution: | (1) Laboratoire de Géologie, URA 1316-CNRS & Ecole Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex, France, FR;(2) Laboratoire de Pétrophysique et Tectonique, UMR 5563-CNRS & Université Paul-Sabatier, 38 rue des Trente-Six Ponts, F-31400 Toulouse, France, FR;(3) CEREGE, Europole de l'Arbois, BP80, F-13545 Aix en Provence Cedex 4, France, FR |
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Abstract: | The geochemistry and the injection mechanism of hypovolcanic ring dykes have been extensively studied, but such is not the
case for their internal fabric. The Tertiary Western Red Hills epigranites of the Isle of Skye are a classic example of such
intrusions. Using anisotropy of magnetic susceptibility measurements, we present the first structural data of their internal
magmatic fabric. The magnetic foliations, equated with the magmatic flow planes, have strikes which roughly follow the walls
of the different intrusions. They dip steeply toward the convex wall of each intrusion. The lineations, or maximal magnetic
susceptibility axes, generally have shallow plunges, except in the latest granite intrusion. These structures appear to be
related to the compressional deformation of each intrusion toward the end of its crystallization. This shortening would be
a consequence of a radial and compressive stress field acting after each injection of magma. This radial stress field is interpreted
as the effect of high magma pressures originating from the acid magma chamber underlying the ring-dyke complex at a shallow
depth.
Received: 10 October 1995 / Accepted: 4 June 1997 |
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Keywords: | Ring dykes Granites AMS Ferromagnetic Skye Thulean Province |
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