Gravity Survey Over Bankura Anorthosite Complex, West Bengal

Results of Gravity surveys conducted over Bankura anorthosite complex lying between latitude 23°28.5' to 23°33'N and longitude 86°50' to 87°15'E are discussed. The area is characterised by a gravity high of the order of 20 mgals in the eastern part and decreases to 4-5 mgals in the western part. The gravity high is found to be unrelated to the anorthosite and extends beyond the outcrop of this exposure. It is attributed to the presence of a gabbroic body underlying the anorthosite and its adjacent areas. The thickness of anorthosite layer is found to be less than 200 meters. Assuming a density contrast of +0.23 gm/cc between the underlying gabbro and the surrounding Bengal gneisses, the maximum thickness of the gabbro is found to be 5.0 km in the eastern part near Rajarampur (23°29.7'N, 87°11'E). The causative body is found to be elongated along the strike of the anorthosite exposure. It appears to be faulted underneath the Damodar river along the northern as well as the northeastern sides.