Strike-slip tectonics and granitoid emplacement: an AMS fabric study from the Odenwald Crystalline Complex, SW Germany

AMS fabric studies supported by field and microscopic work were applied to identify the internal structure and possible emplacement processes of the V ariscan late-tectonic granodiorite-granite intrusions of the Unit III in th e Odenwald Crystalline Complex. This Unit is bounded towards NW and NNE by steeply inclined shear zones, the southern part is unexposed. The magnetic susceptibility ranges between 10(-3) and 10(-6) SI units and is caused by p aramagnetic and subordinately by ferromagnetic components. AMS ellipsoids a re typically oblate with gently plunging long axes (lineations). AMS foliat ions and lineations trend mainly WSW-ENE and NNW-SSE, parallel with the NNW and ENE trending marginal shear zones of Unit III, respectively. As reveal ed by microstructural studies, a penetrative foliation in the plutons is re lated to emplacement processes. Therefore the observed AMS foliation and li neation are also interpreted as the result of syn-emplacement deformation w hich is dominantly strike-slip. Weakly inclined foliations around pluton ro of xenoliths point to a component of buoyant rise of magma. It is suggested that the granitoid magma was generated in a low level anatectic zone along a left-lateral transpressive shear zone during local extension at releasin g bends. During successive fault movements magma ascended through extension al parts of the shear zone. Local normal faults and the Otzberg zone at the eastern margin of Unit III document mostly brittle extension, which overpr inted the strike-slip fabrics after the emplacement of the plutons.