Extraction of High Chargeability Distribution using Joint Inversion of Direct Current Resistivity and Time Domain Induced Polarization Data: A Development and Test Results on Uranium Bearing Target Rock

Abstract

Induced polarization datasets, which assess the overvoltage characteristics of the subsurface, are becoming increasingly prevalent. These datasets are not limited to mineral resource exploration but are also gaining traction in various engineering applications. We present the result of joint inversion of direct current resistivity and induced polarization data. We have obtained two subsurface properties: electrical resistivity and chargeability, by minimizing the single objective function. For this purpose, we have computed the distorted apparent resistivity using the secondary voltage measure at each time gate. We compared our results with the conventional inversion of induced polarization on synthetic data with both high and low chargeable mineralized ore bodies. We noted that our approach provides a more reasonable model for high chargeable ore bodies. However, both joint inversion and nonlinear approaches give similar results for low-chargeable ore bodies. Nonlinear inversion of induced polarization was accomplished by solving two objective functions: One for resistivity and another one for induced polarization. Thus, error in the resistivity inversion propagates in the chargeability computation due to consequences. Further, the developed joint inversion algorithm is also applied to a field data set measured at the Beldih mine located in the West Bengal, India. We compared our final chargeability models with the local geology and geologic models obtained via other geophysical methods on the same profiles and found an excellent correlation in both models.