Deformation Fabric in the Pan-African Granites from Shillong Meghalaya Plateau, NE India: Insights from Field and Microstructural Observations

ABSTRACT Shillong Meghalaya Plateau in NE India represents the eastern continuation of the Indian peninsular shield separated by Garo-Rajmahal graben. The plateau consists of basement granite gneisses, granites, migmatites and granulites of the Paleoproterozoic age and Shillong Group of rocks as the cover sequence. Granites of the Neoproterozoic and Cambrian ages (Pan-African) have intruded the basement gneisses and Shillong Group of rocks. These granites are equigranular to porphyritic and consist of microgranular enclaves with no significant evidence of deformation in the field. An attempt has been made to understand the deformation fabric of the macroscopically undeformed granitoids exposed within the Shillong Group of rocks from the field and microstructural observations. In this study we have carried out a detailed petrographic investigation of Pan-African Granites of the Shillong plateau. It is observed that the granites preserve magmatic, high-T solid-state as well as low-T solid-state fabrics. It is thus concluded that these granites are deformed.