Magnetic anomalies and basement structure around Vizianagaram, Visakhapatnam and Srikakulam districts of Andhra Pradesh, India

A systematic regional magnetic survey was carried out in the districts of V izianagaram, Visakhaptnam and Srikakulam in Andhra pradesh, India comprisin g an area of 15,000 sq. km of eastern migmatite zone of Eastern Ghat Mobile Belt. The magnetic anomalies are very noisy, varying between -1300 nT and +700 nT in amplitude and correlate very poorly with the surface geology Upw ard continuation of these anomalies brought out distinct magnetic anomaly t rends, running along NE-SW on the south and turning later to E-W on the nor th, consistent with the folding pattern of Eastern Ghats. Based on the term ination of anomaly closures and displacement of anomaly trends, five faults , all striking approximately in the N-S direction, were inferred. From inve rsion of anomaly profiles, it is established that the anomalies are produce d by structures in the magnetic basement composed of charnockites.