in hard rock terrain, identification of groundwater potential is targeted in the weathered, fractured, fissured zones, etc. Electrical resistivity survey method is useful to delineate the weathered zone and its thickness. An attempt has been made to delineate the subsurface weathered zone and fracture pattern by using geoelectrical resistivity method. The chosen study area Lakkur sub basin falls in Mangalur block, Cuddalore district, Tamil Nadu. The basin consist charnockite and charnockitic gneiss rocks. Electrical resistivity profiling and vertical electrical soundings have been conducted at every 2 km interval in a grid pattern. Totally 36 VES were conducted and six profiles were carried out. The profile traverse is in N-S direction and the profile interval is 2 km. The resistivity data have been qualitatively and quantitatively analysed. A low resistivity anomaly at VES. 21 (Alambadi) has been observed in all the profiles and contour maps indicating a weaker and weathered zone. The qualitative approach is very essential before going in for quantitative approach.