Geoelectrical and magnetic survey of Tatta Pani thermal spring: a case study from Kotli District, Jammu and Kashmir, Pakistan

This study presents resistivity and geomagnetic surveys to identify the subsurface structure of Tatta Pani geothermal spring, Kotli, Jammu & Kashmir, Pakistan. The flow, extension and subsurface structures were investigated using 1D resistivity survey by applying the technique of Vertical Electrical Sounding using Schlumberger electrode configuration. The data were then fed into iterative software to obtain the resistivity of each layer and corresponding lithology. The resistivity structure of the spring revealed four distinct lithology units based on the resistivity contrast. The high resistivity unit (> 300 Ω-m) represented weathered dolomite/limestone of Abbottabad Formation. The low to moderate resistivity unit (80–200 Ω-m) comprised clay and sandstone layers of Patala Formation, having a potential of surface meteoric water. The low resistivity unit (20–80 Ω-m) interpreted as shaley to clay lithology was related to moderately altered hydro-thermally rocks. The low resistivity unit (5–20 Ω-m) demarcate the geothermal spring having high dissolved minerals. The thermal spring was concentrated on the right bank of River Poonch at a depth of 30 m below the surface and increased its depth in the North-East direction. The magnetic survey was performed to portray the deep-seated tectonics, magnetic signature of the rock and depth of the hot spring and was in agreement with the resistivity data. The magnetic intensity and anomaly changes were abrupt and smooth with the intensity variation of 460 nT, while the anomaly of – 75 nT to 60 nT representing a fault in the sedimentary sequence. The magnetic data showed two contrasting promising magnetic signatures of Patala Formation and anticlinal Abbottabad Formation, in line with the geology and resistivity data. The results showed that the resistivity structure of Tatta Pani geothermal spring is concentrated at the contact of a low resistivity rock of Patala Formation above and weathered and altered high resistivity underlying rocks of the Abbottabad Formation.