Geological setup, structure and metamorphism of south-eastern part of Sandur Schist Belt around Obulapuram area, Anantapur District, Andhra Pradesh

Geological mapping of over 50 km² area has been carried out in and around Obulapuram area, SE of Sandur Schist Belt. The Sandur Schist Belt (SSB), a part of Eastern Dharwar Craton (EDC) is a NW–SE trending lens-shaped late Archaean volcano-sedimentary belt. The litho-types exposed include peninsular gneiss of PGC, fuchsite quartzite, meta-basalt with intercalation of amphibolite, phyllite, metagabbro and quartzite, banded magnetite quartzite (BMQ), banded hematite quartzite (BHQ) belonging to the Donimalai Formation of Sandur Group. Granites, dolerite dykes, gabbro dykes and quartz veins are younger intrusives. Basement Peninsular Gneiss and intrusive granite are exposed towards the southern and eastern side of the study area. The area has undergone two phases of deformation, of which the earlier D₁ deformation is quite pronounced producing the NW–SE trending S₀∥S₁ regional structures of the area. D₁ deformation is responsible for the development of tight isoclinal and macroscopic (F₁) folds. D₂ deformation resulted in the development of open to close mesoscopic (F₂) folds and broad warps with axial traces along ENE-WSW direction and crenulation cleavage (S₂). The area is predominantly characterised by regional green schist facies of metamorphism, which increases to amphibolite facies near the contact of the schist belt with gneisses and intrusive granites.