Emplacement Mechanism of the Panj-Kuh Granitoid Pluton Using Magnetic Fabric Method

Panj-Kuh granitoid intrusion with an area of 15 Km2 is intruded into the Eocene volcano-sedimentary sequence, in south-east of Damghan city. Syenite is the main composition of the pluton. It has converted to monzonite ver subjected to sodic-calcic alteration. The presence of albite-scapolite veins (mm to some hundred meters in width) are the main evidences of the Na-Ca alteration in the mentioned pluton. Present study investigates the result of magnetic fabric in the Panj-Kuh pluton and defines the emplacement mechanism according to the lineation and foliation patterns and microstructural observations. The pluton belongs to the ferromagnetic granites due to high mean bulk magnetic susceptibility (Km>400mSI) and presence of magnetite. The highest anisotropy values were observed in the regions with high deformation. High plunging lineation and foliations associated with negative value of shape parameter show the magma feeder zones. According to the present study, it seems that the pluton has two different types of fabric patterns. The first pattern belongs to the magmatic liniation and foliation that are arranged parallel to the long axis of the pluton with NE-SW trend. The second fabric is related to the regions that were subjected to Na-Ca alteration and cross cutting the first pattern as three parallel corridors. This fact is confirmed by magmatic to low temperature solid state microstructures as well. Compiling all data implies that the mentioned pluton was emplaced in a sinistral shear zone.