Deformation history of the NW salient of the Eastern Ghats Mobile Belt, India

The Eastern Ghats Mobile Belt of India displays fold-thrust belt structure with a prominent salient on its NW margin. The salient consists of Lathore nappe and Turekela klippe that have overthrust the craton to NW. The rocks of the nappes have undergone granulite facies metamorphism and multiple phases of folding corresponding to the Eastern Ghats orogeny, prior to thrusting. As a result the granulites along the thrust are retrograded to amphibolites and the axial traces of the folds have been truncated against the thrust plane. The basal decollement of the fold-thrust belt is represented by the Terrane Boundary Shear Zone that defines the tectonic margin between the craton and the mobile belt. It occurs as a ductile thrust affecting the cratonic basement as well as the mobile belt suggesting that the basement did not behave as a rigid body during thrusting. Thus the study area is comparable with the Caledonide fold-thrust belt. Further, two large lateral ramps namely Khariar and Paikamal lateral ramps have been developed on the decollement at the lithological contact between tonalite-trondhjemite gneisses/granite gneisses and the latetectonic potassic granites of the craton. Fault-bend folds associate with these ramps too. It is suggested that the salient structure of the fold-thrust belt is the combined result of (I) lateral ramps on the decollement and (2) differential displacement along the sole thrust due to lateral variation in detachment strength. (C) 2003 Published by Elsevier Science Ltd.