An AMS study of magma transport and emplacement mechanisms in mafic dykes from the Etendeka Province, Namibia

The other case anomalous fabric is rotation of the AMS axes by shear within the magma, producing symmetric imbrication of AMS fabric on opposite dyke walls; or more commonly, asymmetric magnetic fabrics, which we relate to tectonic shear at the dyke walls during emplacement. Field support for syn-emplacement shear is given by dyke segmentation geometries including locally curved segment tips, en-echelon arrangements and left/right-stepping displacements. Regionally, syn-emplacement shear is consistent with the observed reactivation during Gondwana breakup of transcrustal shear zones in the Damara mobile belt.