## 6 Discussion  
The results of our geophysical studies are discussed here to obtain a clear picture of the resistivity structure and existence of geothermal potential in the study area. The 3D resistivity model showed that the conductive structure strikes W-E, which indicates the presence of the Gorontalo graben zone. This is consistent with the low CBA values that extend nearly W-E. These two features frequently occur in the fault zones of geothermal systems [60]. The contrast between the conductive and resistive zones, based on the 3D resistivity model, also characterized the presence of faults and fractures that are dominant in the NW-SE direction. The boundaries of these faults and fractures were clearly visible on the CBA and residual anomaly maps, which showed contrasts between low and high anomalies. The history of volcanism in the Limboto Lake--Pentado area is related to the regional tectonic system in the Gorontalo area through rifting and uplift after the Sula Platform collision and the appearance of the North Sulawesi Trench subduction pathway during the Late Miocene to the Quaternary periods. The appearance of the Pilomba and Lompotoo volcanoes in the Gorontalo graben zone was interpreted as the youngest Pleistocene volcanism controlled by the fracture system in the depression zone. The two volcanoes formed through the dyke system in the Gorontalo Depression Zone. The increasing values of the vertical anomaly gradient indicated the presence of high-density rock at a depth near the graben zone fill material, as shown in Figure 10c. This could be related to the situation in which a high-density body representing an intrusive rock or dyke system appears beneath the graben zone. Furthermore, the SVD analysis of gravity showed localized high-value features in the southern and northern sections, indicating the boundaries of the intrusive body or dyke system (Figure 10f). This condition agrees with the 3D MT inversion results, which yielded high resistivity contrasts at the boundaries of the Gorontalo graben zone, where geothermal surface manifestations were located. The high resistivity contrasts located at the boundaries of the Gorontalo graben zone were related to the elongated heat source, according to the geological analysis. The reservoir of the geothermal system beneath the study area belongs to the Gorontalo graben system. This reservoir is situated in a fracture zone that resulted from the rifting and uplift described in the previous section. Reservoir and clay cap zones can be seen in the resistivity model profile shown in Figure 9 (P3, P4, and P5). Conductive body C2, found near the surface, could be associated with the clay cap, whereas the reservoir was indicated by moderate resistivity values ranging from 60 to 100 \(\Omega\)m underlain by the conductive body. Two-dimensional (2D) gravity forward modeling was performed by incorporating the MT and geological results to reduce the possible ambiguity in the resulting 2D density model. We used the CBA as the observed data for the forward modeling scheme. The subsurface density models were developed such that the observed data were fitted using the calculated data generated by certain models. Figure 9a depicts the 2D density model. The model consisted of three layers with different density values. These three density values were determined according to [61]. The associated rock units were obtained from the geological map shown in Figure 1. The lowermost layer of density was bedrock, constituted by granitic rock with a density of 2.67 g/cm\({}^{3}\). The overlying bedrock was a low-density rock with a density of 2.4 g/cm\({}^{3}\) and was associated with andesitic lava. The topmost layer, with a density of 2.2 g/cm\({}^{3}\), corresponded to alluvium deposits filling the graben zone. The density profile confirmed the presence of graben structures in the study area.