GEOMAGNETIC DEPTH SOUNDING OVER THE SINGHBHUM AND THE SURROUNDING REGIONS OF EASTERN INDIA

Magnetovariational studies have been carried out in Singhbhum and surr ounding regions during 1987 and 1989. Three deep-seated linear conduct ors have been identified. One of them is located to the north of Ranch i, Bokaro and Purulia extending in E-W direction coinciding with high heat now region and Gondwana sediments. The trend of anomaly at Ranchi and Purulia at longer periods suggests a conductivity anomaly due to the mafic and ultramafic intrusions, considered to be responsible for the uplift of Chhotanagpur plateau. The second conductor is associated with the basin margin fault that Separates the Singhbhum craton and C hhotanagpur plateau from the West Bengal basin. This conductive zone a ppears to extend further south and join the high heat flow region of A ttri-Tarabalo, This conductor could be isolated only after eliminating the coast effect from the observed induction vectors. The third condu ctive zone follows the trend of Mahanadi valley located south of the S ukinda thrust.,Conductive anomaly associated with the Sukinda and Sing hbhum thrust zones could not be resolved due to the interference from neighbouring conductive structures. These two thrusts may not be very deep-seated structures. The Singhbhum granite batholith is found to be highly resistive and seems to extend to greater depths.