Granite emplacement and its relation with regional deformation in the Aravalli Mountain Belt (India)—inferences from magnetic fabric

摘要

This contribution presents field, microstructural and anisotropy of magnetic susceptibility (AMS) data from the Godhra Granite, a ca. 1 Ga pluton at the southern margin of the Aravalli Mountain Belt (western India) that lies near the Central Indian Tectonic Zone (CITZ). The northern and southern margins of the granite are high strain zones with north dipping, E-W striking foliations, and NW plunging stretching lineations. The presence of preferentially oriented feldspars suggests that the granite was subjected to magmatic deformation during its emplacement. High temperature solid-state deformation fabrics are recorded from microstructural studies, which imply that the granite is deformed. AMS data show magnetic foliations and magnetic lineations in the granite with orientations similar to the field data. The magnetic foliation in the granite is parallel to the D_3 foliation in the gneissic host-rock. Both the stretching lineations and the magnetic lineations at the granite margin high strain zones are parallel with the axes of D_3 reclined folds in the gneiss. Therefore, the emplacement of the Godhra Granite is inferred to have taken place syntectonically, while the gneiss was undergoing the D_3 phase of deformation. The orientation and character of these lineations and the vergence of the D_3 folds imply oblique simple shear, which is inferred to have controlled the emplacement of the granite. The magnetic fabric data are compared with the regional structural trends of the metasedimentary rocks of the southern Aravalli region and the available geochronological data from rocks of the southern Aravalli region are summarised. Based on this information, it is suggested that the emplacement of Godhra Granite, deformation of the southern parts of Aravalli Mountain Belt and, tectonothermal events along the CITZ and Rodinia Supercontinent assembly were related events.