Articles written in Journal of Earth System Science

    • Electrical resistivity tomography of Mesoarchaean chromitite bands from Katpal in Sukinda Ultramafic Complex, Odisha


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      Katpal in Mesoarchaean Sukinda Ultramafic Complex (SUC) hosts chromitites within the ultramafic rocks emplaced in the Tomka–Daitari–Mahagiri greenstone belt, Singhbhum Craton. Chromite deposits occur as seams, lenses or pockets in ultramafic–mafic rocks mainly comprising serpentinised dunite, peridotite and gabbro. Chromite deposits at Kalrangi, Kaliapani and its precincts in SUC are currently being exploited by M/s. Odisha Mining Corporation (OMC), whereas their continuity is elusive in the subsurface in the Katpal area, Sukinda, Odisha. High-resolution electrical resistivity tomography (ERT) was carried out in quarry-G of M/s. OMC in Katpal on four profiles each with a profile length 400 m and each of them is separated at an interval of ${\sim}$100 m to capture and visualise a maximum anomaly variation within the host rock. The objectives of this study are to understand the behaviour of chromite seams vis-à-vis with a high-resolution electric potential signal with depths and to evolve a method to discriminate chromitites from the host rock both in horizontal and vertical directions with depths, which can be used to locate the extension of chromite seams around the study area. The interpretation of the ERT models revealed interesting resistivity anomalies, which is inferred as chromite associated with the ultramafic host rock in the area. Exploratory borehole data of the area confirmed the subsurface occurrence of chromitites within 22–40 m depths as lensoidal bodies within the mafic–ultramafic rocks. The chromite ore is mapped as low-resistive zones with a resistivity of ${\sim}$35–200 ${\Omega}$ m and extended up to a depth of 170 m within the high-resistive (${\ge}$500 ${\Omega}$ m) host rocks. Two distinct chromite bands were identified at different depths: 20–40 and 90–110 m based on the specific resistivity contrast and were validated using the existing shallow borehole data. The second band is highly folded whereas the first band resembles sill-like feature within the host rock. The electrical tomography technique can be aptly applied in an unknown area in SUC to establish the extension of the chromite ore body, its resistive signature and their variation with depths within the host rock for future resource prospecting and exploitation in the given geological setting of the area.


      $\bullet$ The chromite ore is mapped as a low-resistivity signature and its extension is delineated as a low-resistivity anomaly of ~35–200 Ω m.

      $\bullet$ The electrical resistivity models indicate low resistivity as chromite and high-resistivity as ultramafic rock (~500–10,000 Ω m) up to a depth of 170 m.

      $\bullet$ The light green up to yellow bands in the inverted resistivity models characterise various grades of mineralisation within the host rock setting.

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