Gravity Field, Structure and Tectonics of the Raniganj Coalfield - Three Dimensional Model

A residual Bouguer gravity anomaly map of the Raniganj Coalfield, West Bengal, India, has been prepared using graphical method of regional and residual separation. The gravity anomaly map reveals a minimum residual gravity of the order of -27 mgal in the central part of the coalfield. The residual gravity field over the basin has been interpreted in terms of the Gondwana sediments overlying the crystalline metamorphic rocks, using a three dimensional model with the help of computer programme given by Strange and Woollard (1969). A density contrast of -0.37 gm/cm³ between Gondwana sediments and metamorphic rocks has been used for calculations. The maximum thickness of sediments filling the basin is estimated to be 2.9 km in the central part of the basin. The basement depths obtained by three dimensional analysis are correlated with available borehole data in the coalfield and are found to give a good indication of the reliability of the model constructed.