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Abstract |
The studied migmatites correspond to the transition between initial gneissic facies and melted granite in rocks that were affected by high-grade metamorphism during the Paleoproterozoic. They present high susceptibility, mainly carried by magnetite. Their anisotropy is also mostly very high. In gneiss samples without strong deformation of the mesoscopic foliation, a good agreement in orientation exists between this foliation and the magnetic foliation. In partly melted gneiss with restites, a similar relation has been obtained. In granite from in situ melting, the magnetic foliation mostly also coincides with the magnetic foliation of the closest non-melted gneiss. In granitic dykes, the orientation of the magnetic foliation becomes in relation with that of the dyke plane. Most magnetic lineations have the same sub-horizontal orientation as a mineral lineation, only locally described in the studied area. Some gneissic sites however point out vertical magnetic lineation. In neighboring samples of gneiss and of granite from in situ melting, the magnetic lineation, contrary to the magnetic foliation, has often a different orientation. That is also the case for granite in dykes crossing the gneisses. |
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