Abstract:
The calc-gneiss and garnet-sillimanite-gneiss of Eastern Ghat Mobile Belt around Lathore bear the imprint of multiple phases of deformtion. The folds of the first generation, F-1, are isoclinal, intrafolial and vary in style from reclined to upright. This has developed a pervasive axial planar gneissosity. The second generation folds, F-2, which are coaxial with the F-1 are open to tight with a planar axial surface dipping moderately to SE and varied plunging axis. At places mesoscopic plane non-cylindrical F-2 sheath folds are noticed. Gentle upright folds, F-3, with NW-SE striking axial plane represent structure of third generation. Superimposition of F-2 on F-1 has resulted in Type 3 interference pattern and dome and basin structures are due to the interference of F-2 and F-3 folds. F-1 and F-2 folds are attributed to WNW-ESE buckling and F-3 is reported to be due to shortening across it, The 'sheath folds' are due to heterogeneous simple shear along the axial plane of the F-2 fold. The map shows a large scale southwesterly plunging overturned F-2 fold. Post-exhumation deformation has resulted in brittle shearing parallel to the axial plane of F-2 fold. The structure of the area points to a collisional tectonic setting like other granulite belts of Gondwanaland.