2D GRAVITY MODELLING OF ARAVALLI-DELHI FOLD BELT, WESTERN INDIA

Eight east-west trending 2D crustal sections are modelled by applying forward Bouguer gravity modelling across the Aravalli Delhi Fold Belt, north-west India in order to understand the geometrical behavior of tectonic domains comprising the fold belt. The central gravity high along the entire fold belt is modelled as a result of an underplated ultramafic body. A layer showing a gradual transition from mantle to lower crust has been modeled on the south-eastern side based on a deep seismic reflection profile. The gravity lows along the western and eastern margins of the central gravity high are modelled as deeply penetrating crustal scale thrusts, namely the South Delhi Thrust Fault, the Jahazpur Thrust Zone and the Great Boundary Fault. The steep gravity high along the western margin of each 2D crustal sections is modelled as high density mafic-ultramafic bodies, namely the Phulad Ophiolite Suite, the Basantgarh Ophiolite Suite and the Rakhabdev Ultramafic Suite. The lows in the residual gravity are modelled as granitic intrusions. The study shows that the high grade (amphibolite to granulite facies) Bhilwara domain is a tilted upthrusted crustal block along the Jahazpur Thust Zone, which has brought it in juxtaposition with the low grade (lower green schist metamorphism) Hindoli domain. The linearly disposed high gravity anomaly bisecting the Paleoproteroizoic metasedimentary rocks of the Aravalli supergroup is the result of fault-bounded ultramafic rocks originating in the lower crust.