Self-potential Data Research Articles

Autonomous-underwater-vehicle-based marine multicomponent self-potential method: observation scheme and navigational correction

Abstract. Marine self-potential (SP) investigation is an effective method to study deep-sea hydrothermal vents and seafloor sulfide deposits. At present, one of the commonly used marine self-potential systems is a towed array of electrodes. Large noises are recorded when great changes in electrode distance and array attitude occur due to the complex seafloor topography. In this paper, a new multicomponent electrical field observation system based on an autonomous underwater vehicle (AUV) was introduced for the measurement of seafloor self-potential signals. The system was tested in a lake, and the multicomponent self-potential data were collected from there. Observed data involve the navigational information of the AUV, which could be corrected using a rotation transform. After navigational correction, measured data can recover the location of the artificial source using self-potential tomography. The experimental results showed that the new SP system can be applied to marine SP observations, providing an efficient and low-noise SP acquisition method for marine resources and environmental investigations.

Groundwater Flow Monitoring via Joint Time-lapse Electrical Resistivity and Self Potential Data Tomography

Revealing the dynamics of groundwater movement in the vadose zone is crucial to groundwater management and artificial recharge development. In this study, the groundwater flow characterization of the pumping process is monitored by the time-lapse electrical resistivity tomography (ERT) and self-potential (SP)data tomography. The ERT data invert the resistivity distribution. Then, we combine the SP data and resistivity result to invert the apparent current density and estimate the permeability based on the Poisson equation. A total of 24 hours of time-lapse surveys are taken during the pumping and recharge of groundwater. The results show a significant increase in in resistivity and permeability during pumping water, which suggests groundwater drawdown. Similarly, significant decrease resistivity and permeability are observed during the recovery indicating groundwater recharge. These results have a significant agreement with the groundwater table monitoring result. Our experiment test suggests that combine ERT and SP data could provide a reliable way in groundwater or other hydrogeological surveys.

A practical approach for self-potential data acquisition, processing, and visualization

We have developed a comprehensive methodology for the acquisition and processing of self-potential (SP) data, as well as some keys for the interpretation of the results. The wide applicability of the SP method and its low cost make it a popular method to use in a variety of natural environments. Despite its versatility and the fact that various published journal papers describe the method and its applications, we believe that there is an important need for a dedicated, peer-reviewed SP acquisition, processing, and visualization/interpretation paper in the scientific literature. We have identified great interest from the scientific community for such a journal paper as a guide for existing and new practitioners with their SP survey design, data acquisition, robust processing, and initial interpretation steps. We have developed a step-by-step methodology for SP data acquisition and processing, combined with practical guidance for the interpretation of collected and processed SP data, including an evaluation of common errors and typical sources of uncertainty. Our examples are based on studies in volcanic environments (e.g., hydrothermal systems); however, the processing steps and methodology are fully applicable and transferable across disciplines to SP data acquired in any environment, and for a wide variety of applications. We evaluated the field acquisition method and the low-cost equipment, the reference and closure corrections, their meaning for the SP signal, and their effect on the data set. The benefits of interpolating SP data in two steps are examined. Combining map visualization, SP versus distance, and SP versus elevation graphs appears to be a highly effective strategy to interpret the signal in terms of hydrogeologic and hydrothermal domains and to highlight structural limits in volcanic contexts as well as in other environments.

Correction to: Model parameter estimation and its uncertainty for 2-D inclined sheet structure in self-potential data using crow search algorithm

Correction to: Model parameter estimation and its uncertainty for 2-D inclined sheet structure in self-potential data using crow search algorithm

Mapping leachate distribution based on the self-potential method in Manggar Landfill, Balikpapan Indonesia

TPA Manggar is a landfill in Balikpapan City. During the rainy season, the leachate discharge entering the processing plant is so large that the collection tub will not be able to withstand the leachate flow rate. To find out the direction of the distribution of leachate waste and the extent to which it has spread and to map the areas at high risk of being contaminated, measurements were taken using the Geophysical method, namely the Self Potential Method (SP). The SP method is based on measuring the self-potential of rocks in the earth’s crust without having to inject an electric current into the soil. Based on this, research will be carried out to determine the mapping of the distribution of leachate flow in the TPA Mangaar area. The results of measurement and processing of self-potential data can be showing beneath the surface in the form of leachate distribution in the study area based on isopotential contour. Based on the results of contour and isopotential map data processing. The highest potential value of this study was 60 mV, while the lowest potential value of this study was -40 mV.

Model parameter estimation and its uncertainty for 2-D inclined sheet structure in self-potential data using crow search algorithm

Fracture or fault can control several geological or geophysical events and exploration, where the fault associated with mineralization or fluid flow can be used as a source for Self-Potential (SP) anomaly. The 2-D inclined sheet can be used for modeling for fault interpretation using SP data. In this paper, the improved crow search algorithm (ICSA) using Levy flight is proposed for SP data inversion in determining SP model parameters. In order to evaluate ICSA, the ICSA is compared with standard crow search algorithm (CSA) for determining synthetic SP data that contains multiple anomalies with inclined sheet type structures. It was found that CSA is more explorative than ICSA, and both algorithms can estimate the posterior distribution model (PDM) of SP data. Using uncertainty analysis within the applied threshold in the objective function, both algorithms are reliable to determine PDM. Furthermore, ICSA is tested and implemented to both synthetic and field of SP anomalies for providing the posterior distribution model of SP parameters. The experimental results demonstrate that the ICSA is feasible and effective for determining model parameters and its uncertainty of mono- and multi-SP anomalies. Furthermore, estimating both model parameter and its uncertainty are sufficient for validation with previous researchers. Finally, the interpretation of multiple anomalies in SP anomaly crossing the Grindulu Fault in Pacitan, East Java, Indonesia, is analyzed.

Geophysical investigation of a weathered terrain for groundwater exploitation: a case study from Huidong County, China

2D electrical resistivity tomography (ERT) coupled with electrical resistivity profiling, induced polarisation, and self-potential (ER-IP-SP) measurements and pumping-test data has been used to acquire subsurface electrical properties for the assessment of groundwater reserves in weathered terrains of Huidong County, China. In this investigation, ERT was performed using a pole-dipole array with 305 measurements, and ER-IP-SP with 127 stations, both along three profiles. A least-squares inversion technique is used for the post processing of the ERT data to generate 2D models of the subsurface geologic units. The following deductions are made based on the 2D ERT modelling. The average depth of fresh basement is generally 10–30 m. Three distinct layers were interpreted, i.e. 5–10 m thick topsoil cover with resistivity <1800 Ωm (above the water table), 5–25 m thick weathered layer with resistivity <900 Ωm (below the water table), and fresh bedrock with resistivity >900 Ωm (below the water table). These layers comprise the 50 m thick overburden revealed by the inverted sections. The ERT models were incorporated with ER-IP-SP to delineate various discontinuities. Groundwater resources enclosed in the weathered/fractured zones were estimated by hydraulic conductivity (K) and transmissivity (T) into three different aquifer zones with specific ranges of T and K (i.e. high, medium, and low yield aquifer). The results suggest that the best potential groundwater resources are contained within fractures/discontinuous zones. The results are well in line with the hydrogeological information available for the investigated area. This geophysical approach is useful to assess the groundwater potential where the weathering has hydrogeological significance.

Self-Potential Method to Assess Embankment Stability: A Study related to the Sidoarjo Mud Flow

The stability of an embankment is generally influenced by a number of factors, such as deformation, fractures, overtopping, seepage, etc. Fractures and seepage are commonly found in the LUSI (Sidoarjo mud flow) embankment. In this study, analysis of self-potential (SP) data was applied to identify fractures and seepage in the LUSI embankment. Noise-Assisted Multivariate Empirical Mode Decomposition (NA-MEMD) and Continuous Wavelet Transform (CWT) were applied to determine the location of seepage and fractures in the subsurface based on SP data. The results were correlated with the 2D direct current resistivity (DCR) method, which showed that both methods worked well and were compatible in detecting and localizing fracture and seepage in the LUSI embankment.

An efficient global optimization method for self-potential data inversion using micro-differential evolution

Self-potential (SP) method has many applications, where the interpretation of SP data can be used for qualitative and quantitative interpretation. However, inversion of SP data in this paper is of quantitative interpretation and consists of highly non-linear, multimodal data and deploys global optimum method (GOM). Micro-differential evolution (MDE) is a GOM with small or micro-population size (5–8 populations) for each iteration. Consequently, this approach involves small numbers of forward computation in the inversion process. Two MDE variants, including adaptive MDE ( $$ \mu $$ JADE) and vectorized random mutation factor (MVDE) were tested first for different level of noises containing synthetic SP data with single anomaly and applied to synthetic SP data of multiple anomalies. The MDE variants are reliable and effective for inverting noisy SP data. Furthermore, in order to check the rationality of MDE variants, the algorithm is applied to seven field data from different applications, including groundwater exploration, shear zone tracing, water accumulation in landslides and embankment stability assessment. The model parameters revealed by MDE variants are accurate and show good agreement with the previous results estimated using other approaches. In addition, MDE variants also require fewer forward modelling calculations than other optimization approaches.

Geophysical survey of earthen dam using the electrical prospecting methods

The hydraulic structures for the land reclamation needs and their operation are the objects of careful attention. The water-bearing earth dams of small height pose an extra danger, where the accident occurs the most often. Such facilities should be constantly monitored to prevent the dangerous incidents. The article discusses an alternative method for studying the filtration properties of earth dams by the electrical parameters – resistivity, induced polarization and self-potential. The relative polarizability was used to exclude the influence of electrical resistivity to the induced polarization data. A study of advanced technology to identify the filter zones was carried out on an earthen dam in the Almaty region, Kazakhstan. The measurement data for three profiles are presented as the sections form in the parameters of resistivity and relative polarizability. Their complex interpretation with the respect of self-potential data, is given as a diagram of probable filtration paths. This is possibly due to the local increased watering in the dam loamy body. Then, the electric and self-potential parameters were evaluated to determine the filtering zones. The study results of above parameters have identified several water-saturated zones in the dam body. This technology could be used to estimate the condition of such objects and their engineering-geological monitoring.

Interpretation of Airborne Magnetic and Geo-electric Data: Resource Potential and Basement Morphology of the Ikom–Mamfe Embayment and Environs, Southeastern Nigeria

The Ikom–Mamfe Embayment, which cuts across southeastern Nigeria and southwestern Cameroon, is a bifurcation of the Benue Trough and the NW–SE splay component of the NE–SW trending trough. The Nigerian sector of the embayment, a sedimentary province bounded to the north and south by basement terrains, is considered a relatively frontier basin with little information about its resource potential. Here, airborne magnetic, resistivity and self-potential (SP) data were integrated in studying the Nigerian sector of the embayment and its surrounding localities. This study aimed to delineate (possible) mineral-bearing lineament structures and their corresponding trend orientations, to evaluate their relationship to tectonic fabric, to estimate depth of perturbing causative sources, to map ore bodies, and to identify probable locations for detailed petroleum system analysis. For the first time, 2D electrical resistivity and SP methods were deployed in the sub-surface characterization of the embayment. Results of aero-magnetic data analysis revealed the presence of high magnetic intensities predominantly in the western and northeastern parts of the study area. The high intensities observed at the western part are due to mineral ore bodies present within a sedimentary host. In addition to the presence of mineral ores, the noticeable high magnetic signatures at the northeastern part are associated with the presence of outcropping units of basement complex rocks that comprise mainly of migmatitic metasediments. The large variation in magnetic intensities within the embayment is attributed to the combined effect of igneous intrusives and mineral-bearing lineaments emplaced within the overlying sediments. Analysis of structural lineaments depicts E–W and ENE–WSW as the dominant orientations with minor NW–SE, NE–SW and NNE–SSW trends. The NE–SW and ENE–WSW structures are aligned parallel to the Benue Trough and the Cameroon Volcanic Ranges, and are genetically related. These lineaments occur in the form of faults, fractures and veins, and they are densely distributed within some areas of moderate to high intensities and analytical amplitudes. This suggests a possible relationship between structural lineaments and metalliferous deposits. These lineaments were marked for ground geophysical surveys. The geophysical traces derived from these areas reveal numerous underlying mineral bodies of contrasting resistivity and potential with their host formation. These bodies are shallow magnetic sources exposed in the first and second vertical derivative images. These show remarkable agreement between the geo-electric data and the aero-magnetic data. The results of quantitative assessment show shallow basement depth and, hence, thin sedimentary layer (0.2–2.4 km) within and around the embayment, which is insufficient for the concealment of hydrocarbon resource. In addition, the presence of numerous intrusive rocks implies a high temperature environment favorable for “cooking” of potential source rocks beyond the hydrocarbon generating window. This renders the area disadvantageous for hydrocarbon exploration. However, we discover that the sedimentary thickness (ranging between 3 and 4 km) mapped at the southwestern part of the area could favor the formation and accumulation of hydrocarbon fluids. This area, characterized by moderate igneous intrusion, lies approximately northeast of the prolific Niger Delta oil province and shows fair to good sub-surface structural conditions required for hydrocarbon entrapment. The basement morphology, sedimentary thickness and structural disposition call for a detailed petroleum system analysis within this area.

A time-lapse study using self-potential and electrical resistivity tomography methods for mapping of old mine working across railway-tracks in a part of Raniganj coalfield, India

The first coal mining in India was started in the seventeenth century with an unplanned way in Raniganj coalfield, the coal capital of India. The coalfield was possessed by several small private companies which were nationalized in 1973. A part plan of Chanch/Victoria Area, Victoria West Colliery, BCCL, Raniganj Coalfield, India, indicates an underground coal mine gallery/goaf in the Begunia Coal-seam that connects to a Light Casting Factory. It was established as “Barakar Iron Works” in the year 1881 by the government at that time. It is understood that the approaching gallery was used for coal supply to the “Light Casting Factory” by the mining of “Begunia Coal-Seam”. Mostly, these are uncharted and very poorly documented with scarce mine plans. So, the present study attempts to explore the location, depth, extension, and condition of the old working gallery through time-lapse monitoring using a combined study comprising of Self-Potential (SP) and Electrical Resistivity Tomography (ERT) techniques. Four SP profiles data along a line and thirteen ERT profiles data in four different lines were collected across the expected site with different station/electrode spacing covering different profile length in four seasons, viz., Summer (May 2016), Monsoon (August 2016), Post-Monsoon (October 2016) and Summer (April 2017). SP data were analysed using simulated annealing (SA) optimization technique for the evaluation of model parameters. The ERT data were acquired using Wenner, Dipole–Dipole and Schlumberger arrays and inversion of the combined data set was performed using the 2.5D ZZRESINV inversion software. Prominent negative SP signature with equivalent low resistivity anomaly have been delineated that possibly indicate the presence of the old mine working/mine gallery. However, the overall results of time-lapse study inferred that the ground is stable. All results are corroborated with available lithology and field photographs.

Global Optimization for Delineation of Self-potential Anomaly of a 2D Inclined Plate

A fast and efficient technique for explanation of self-potential anomalies is of immense importance for exploration, engineering, and environmental problems. Estimation of model parameters of ore bodies in the subsurface is the primary concern in mineral exploration. In most cases, self-potential data are delineated considering various simple or idealized structures for the interpretation of lateral and vertical variations of subsurface ore bodies. In this context, we developed an inversion algorithm to determine the different parameters associated with a 2D inclined plate-type structure, which does not require any a priori information. The developed algorithm can interpret appropriately every parameter with minimum uncertainty. The position of causative source body (x0), its half-width (w) and its depth (z) were the parameters interpreted using the developed algorithm. It was found that these parameters were well resolved within the estimated uncertainty, although solutions for w showed wide variability. The technique was verified with synthetic data without noise and with different degrees of Gaussian noise. The technique was also confirmed with three field datasets for mineral exploration, and the interpreted parameters were in fair agreement with those reported in earlier works.

A Novel Approach to Self-potential Data Interpretation in Support of Mineral Resource Development

A new efficient technique has been developed to interpret self-potential data from different mineralized sources (horizontal cylinder, vertical cylinder, sphere, and 2-D inclined sheet). This technique is based on the first horizontal gradient filter and particle swarm optimization algorithm. This suggested method can be used for single-source and multiple-source interpretation. In this study, the developed technique was applied to five different synthetic examples (vertical cylinder model, horizontal cylinder model, sphere model, 2-D inclined sheet model, and multi-source model), using a real case from Canada—the multi-source field example—and two real cases from India. The results obtained from the synthetic and real data show that the method is fast, accurate, and effective in removing the regional background and does not require information regarding body shape. The results of the real data cases match well with the results obtained from other published methods.

Groundwater Flow Monitoring by Fusion Probability Tomography of Self-Potential Data

Groundwater flow could produce an observable self-potential (SP) signal; it is, therefore, useful to use SP signal to investigate the condition of water flow, which is meaningful to the processes to which the water flow is critical, such as landslide warning, contaminant transport, and volcanic eruption. Most of the SP data inversion methods are based on prior in situ electrical resistivity information, which is difficult to be accurately obtained in the continuous monitoring of the vadose zone. We suggest a fusion scheme of integrating the electric charge occurrence probability (ECOP) tomography and the continuous complex wavelet transform (CCWT) method to process and interpret SP data when it lacks prior electrical structure information on the background media. A model of fracture flow with precipitation recharge is used to testify our proposed method. The results indicate that the combination scheme can locate the source of SP anomalies with improved accuracy. The proposed fusion probability tomography can locate the fracture flow with an explicit region of probability anomaly and suppress the irrelevant noises.

Underground Coal fire Mapping Using Analysis of Self-potential (SP) Data Collected from Akashkinaree Colliery, Jharia Coalfield, India

Abstract Sub-surface coal mine fires burn valuable resources and give rise to great threat in the local environs and people’s health. Jharia coal field is one of utmost fire affected coal fields in India. This paper deals with the study of sub-surface coal fire using self-potential (SP) method, a cost-effective and non-invasive passive geophysical technique. SP method in coal fire mapping works based on redox potential generated by oxidation of coal and also on Thomson potential due to temperature gradient. Initially, SP anomaly map generated using electrode drift corrected field data. The SP anomalies in the present study area vary from ~95 to ~ -40mV. SP anomaly map has been continued to a height of 10m from the ground to remove the possible shallow surface noises. The upward continued anomaly map has been enhanced using first vertical derivative. Further, Euler’s depth solutions have been estimated to understand possible geometry and source depth of sub-surface coal fires. The local geological map and field photograph corroborate well with the results for the characterization of coal seam fires.

Identification of subsurface fluid flow using the 2D geoelectric method in Marunda, North Jakarta

Jakarta is the most densely populated province in Indonesia and it will grow over time. This overwhelming population causes a decrease in the quality and supply of groundwater. Brines has been discovered in several areas in Jakarta. Several studies conducted by earth science researchers conclude that brine in Jakarta appears from either seawater intrusion or trapped connate water. This study focuses on the use of the geoelectric method to evaluate the groundwater quality problem in Kelurahan Marunda. Methods used in this study are resistivity, self-potential, and groundwater sampling. Conductivity, Salinity, pH and water table elevation are the parameters used in this study. These methods are done to observe subsurface groundwater quality, fluid flow and how far the seawater infiltrated. Based on the result of groundwater data of 40 wells, high conductivity and high salinity zones are found. High conductivity in this area affected mostly by the saline factor indicated by high salinity and neutral pH. The subsoil has low resistivity values showed by 2D resistivity data. Also, self-potential data displays a North-South groundwater subsurface fluid flow 1, 20 km from the coastline. Altogether, these data indicate seawater intrusion in Kelurahan Marunda, North Jakarta.

Self-potential Data Interpretation for Two Co-axial Structures Utilizing the RMS Parameter

We have developed an algorithm to obtain the model parameters for two co-axial structures from self-potential data. The method uses the first numerical horizontal derivatives calculated from the observed self-potential anomaly employing filters of sequential window lengths (s-values) so as to gauge the model constraints for the shallow and deep structures. In addition, this algorithm uses a standard inversion method for solving a non-linear equation based on the lowest root-mean-square (RMS) error of the estimated model parameters. The body constraints are the depth, polarization angle and electric dipole moment of each structure. Our approach models the self-potential dataset as an aggregation of spheres, horizontal cylinders, and vertical cylinders. These simple bodies are used to approximate, without a priori expectations, the furthermost plausible position and/or area of intersection. In other words, the bodies are used to estimate the true values of the source parameters for the two-co-axial bodies at different s-values. Minimizing the RMS error has the advantage of optimizing all model factors. The proposed technique is tested using a numerical model with and without noise and on self-potential field data acquired at a site in Germany. In all cases, the assessed body parameters are reasonable approximations of the known values.

Advancing quantitative understanding of self-potential signatures in the critical zone through long-term monitoring

The self-potential (SP) method is a passive geophysical technique, which may offer insights about water and ionic fluxes in the vadose zone. The main obstacles presently prohibiting its routine use in quantitative vadose zone hydrology are the superposition of signals arising from various source mechanisms, difficult-to-predict electrode polarization effects that depend on electrode design and age, as well as incomplete knowledge on water saturation, pore water chemistry, clay content, and temperature in the immediate vicinity of the electrodes. We present a unique long-term SP monitoring experiment focusing on the first four years of data acquired at different depths in the vadose zone within the HOBE hydrological observatory in Denmark. Using state-of-the-art SP theory combined with flow and transport simulations, we attempt to replicate the observed data and suggest reasons for observed discrepancies. The predictions are overall satisfactory during the first six months of monitoring after which both the patterns and magnitudes of the observed data change drastically. Our main observations are (1) that predicted SP magnitudes are strongly sensitive to how the effective excess charge (or alternatively, the voltage coupling coefficient) scales with water saturation implying that continued research is needed to build more accurate models of electrokinetic phenomena in unsaturated conditions, (2) that significant changes in electrode polarization occur in the shallowest electrodes at time scales of a year, most likely due to desaturation by capillarity of the fluids filling the electrodes, suggesting that electrode effects cannot be ignored and that explicit electrode modeling should be considered in future monitoring studies, and (3) that multi-rate mass transfer and reactive transport modeling, with specific emphasis on fluid-mineral interactions, are needed to better predict salinity and pore water conductivity. We hope to stimulate other researchers to test new SP modeling approaches and interpretation strategies against these data by making the SP and complimentary (temperature, dielectric constant, potential/actual evapotranspiration, precipitation) data time-series available.

Combined self-potential, electrical resistivity tomography and induced polarisation for mapping of gold prospective zones over a part of Babaikundi-Birgaon Axis, North Singhbhum Mobile Belt, India

The Palaeo- to Meso-Proterozoic (1.0–2.4 Ga) North Singhbhum Mobile Belt (NSMB) is an assembly of multiphase folded, low- to medium-grade meta-sedimentary and meta-igneous rocks, lying within the north Singhbhum crustal province. The mobile belt is situated between the Archean Singhbhum craton in the south and the Meso/Neo-Proterozoic (0.9–1.7 Ga) Chotanagpur Gneissic Complex in the north. Gold mineralisation of moderate concentration is reported from different parts of NSMB along shear /fracture zones within the volcano-sedimentary and meta-sedimentary rocks sequence. The mineralisation is structurally controlled and is associated with higher order shear zones. Gold occurs in association with sulfides like pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, etc. This work attempts to map the auriferous shear/fracture zone along the Babaikundi-Birgaon axis (BBA), which lies within the NSMB. In the present study, combined geophysical approach comprising self-potential (SP), electrical resistivity tomography (ERT) and induced polarisation (IP) methods were used for mapping of subsurface gold prospects. SP data were collected along 7 profiles at 10 m station interval with approximate profile separation of 100 m. The anomalies of possible ore bodies were found at depth of about 18–25 m using Euler deconvolution of SP data. The ERT and IP data were collected along four profiles at 10 m electrode spacing with approximate profile separation of 100 m. The inverted resistivity sections indicate very low resistivity value in the depth range of ∼20 m inferring highly conducting, while relatively high chargeability are also observed at the depth range of ∼25 m. The possible existence of Babaikundi-Birgaon lineation and the occurrences of sulfide minerals in quartz reef associated with gold mineralisation were mapped based on the horizontal locations and extensions of negative anomaly in SP data, low resistivity in 2-dimensional (2D)-inverted resistivity section and high chargeability in 2D-inverted IP section. Previous studies based on electron probe micro-analyzer (EPMA) and scanning electron microscope (SEM) analysis over the study area substantiate our combined geophysical interpretations for the presence of gold prospective zones along the BBA. Highlights Integrated geophysical approach comprising SP, ERT and IP methods Delineation of BBA Mapping of subsurface gold prospects/ mineralisation Validation of results using borehole data, EPMA and SEM–SED analysis of rock samples (a) Map showing profiles AA/, BB/, CC/ and DD/across the Babaikundi-Birgaon Axis (BBA). (b) Upward continued (60 m) self-potential (SP) anomaly map showing possible extension of a part of BBA. Schematic resistivity (c) and chargeability (d) distribution models showing possible extension of a part of the BBA. (e) mineralised sample with sulfide hosted quartz reef in BBA. The possible existence of BBA and the occurrences of gold-bearing sulfide minerals in quartz reef are mapped based on the horizontal locations and extensions of negative SP, high conducting / low resistivity in electrical resistivity tomography (ERT) and high chargeability in Induced Polarization (IP). Note that profiles C-C/ and D-D/ are not parallel to each other; their field orientation is shown in Figure 1(c) and Figure 2.