Nature of Crustal Tri-Junction Between the Eastern Ghats Mobile belt, Singhbhum Craton and Bastar Craton Around Paikmal, Western Orissa: Structural Evidence of Oblique Collision

The Eastern Ghats Mobile belt skirting the east coast of India records a prolonged history of mountain building and orogenic activity continuing at least up to the Pan-African times. This granulite belt is bounded by the granite-greenstone belts of the Singhbhum-Orissa craton to the north and Bastar craton to the west. Around Paikmal in western Orissa, where the three crustal provinces meet, structural data in the boundary region provide important clues pertaining to the juxtaposition of the high-grade belt against the two granite-greenstone belts. etailed structural studies in several sectors, the Eastern Ghats granulite belt could be described as a convergent orogen that evolved under a NW-SE directed sub horizontal compression. Rotation of tectonic trends in both the northern and western boundary regions and the occurrence of strike-slip shear zones indicate oblique collisional juxtaposition of the Eastern Ghats granulite belt against both the cratons. The orientations of the palaeo-stress axes in the shear zone around Paikmal indicate a NW directed tectonic transport and is consistent with the NW-SE compression in the Eastern Ghats granulite belt. Thus, the Eastern Ghats Mobile Belt may be considered as a convergent orogen that collided against an ‘irregular’ continental margin: roughly E-W margin of Singhbhum and roughly N-S margin of Bastar. The tectonic transport being oblique to both the margins, strike-slip shear zones developed in both the boundary regions.