Resistivity Anomalies Research Articles

Mapping saltwater intrusion with an airborne electromagnetic method in the offshore coastal environment, Monterey Bay, California

Study RegionThe northern coast of the Monterey Bay, California, USA, extending from the coastline to 3.5 km offshore. Study FocusThree-hundred and twenty line-kilometers of airborne electromagnetic (AEM) data were acquired offshore. These data spanned 20 km of coastline, extending up to 3.5 km offshore in water up to 18 m in depth. Inversion of these data resulted in resistivity models extending to depths between 50 and 200 m below sea level. The data were interpreted in conjunction with onshore monitoring well data, hydrologic and geologic reports, and electrical resistivity tomography (ERT) data to locate the freshwater/saltwater interfaces throughout the region. A resistivity-to-water-quality transform was established using well-based water quality and resistivity logging measurements. For resistivity values that could not be converted to water quality with this transform, local auxiliary information was used on a case-by-case basis to interpret the observed features. Some low resistivity anomalies were identified near the shore at depth, which were interpreted to be artifacts of the 1D assumption in the inversion scheme used for these AEM data. New Hydrogeological Insights for this RegionWe found that the acquisition of AEM data provided valuable information about water quality in the offshore extents of the aquifers, a region inaccessible to traditional monitoring methods, but one that plays an important role in the modeling, prediction, and management of saltwater intrusion.

A four-point electrical resistivity method for detecting wood decay and hollows in living trees

An accurate method of detecting wood decay and hollows or cavities in living trees is useful for risk assessment and maintenance of both forest and urban trees. This study presents the implementation of the four-point electrical resistivity method for the early detection of the presence, location and extent of wood decay and hollows in living acacia trees (Senna alata L.). Electrical resistivity measurement of randomly selected living acacia trees and a freshly-cut acacia tree with decay and hollows were taken to obtain electrical resistivity profiles for sound, decayed and hollowed trees. A laboratory experiment was set up to replicate the resistivity profiles. Wood decay and hollows were replicated at different depths in the laboratory prototype using good electrical conductors and insulators respectively. Resistivity profiles for the sound, decayed and hollowed trees were obtained from the experimental and field results. The resistivity profiles were applied to detect decay and hollows of similar dimensions in living trees through resistivity curve matching. The electrical resistivity of the decayed acacia tree was markedly lowered by an average factor of 5 compared to that of the sound acacia tree. Likewise, the electrical resistivity of the hollowed acacia tree was noticeably greater than that of the sound acacia tree by an average factor of 4. Wood decay and hollows modelled into the laboratory prototype were detected with relatively lower and higher resistivity anomalies respectively. The method indicated that 80% of the randomly selected living trees were sound, healthy trees, whilst 20% had decay and hollow at the time of measurements. This method is suitable for early detection of decay and hollows in hardwood trees.

Complex gas hydrate system in a gas chimney, South China Sea

Abstract Gas hydrates and deep-sea cold seeps are of interest to industry and academia for several reasons, including their implications for offshore geohazards and unconventional resources, and for global climate change and carbon cycling. Guangzhou Marine Geological Survey (GMGS) implemented its fifth gas hydrate drilling expedition in the QiongDongNan Sea Area (QDN-SA) of the northern South China Sea (SCS) from June to September 2018. Multidisciplinary investigations, including Logging While Drilling (LWD), pressure and non-pressure coring, gas composition analyses, in situ temperature and permeability measurements, pore water geochemical analyses, and a regional seismic survey, reveal a complex distribution of gas hydrate within a vertical chimney structure. LWD profiles record high resistivity anomalies and high P-wave velocity variations at 9–174 mbsf, suggesting the coexistence of free gas and gas hydrate in the sediment column throughout the investigated gas chimney. Hydrate-bound and void gas is an admixture of methane (70.1%–98.3%) and heavier hydrocarbons (C2H6: 0.16%–17.59%, C3H8: 0.05%–9.88%, i-C4H10:

Integrated geophysical methods to characterize urban subsidence in Butte, Montana, U.S.A.

Geophysical investigations, designed to characterize unique subsidence features of unknown natural origin, provide imaging analysis of potential causes of subsidence. Recent subsidence in the alluvial plain in Butte, Montana is unrelated to historic mining in the area. This study aims to utilize a combined application of shallow electrical resistivity imaging (ERI), self-potential (SP), and frequency-domain electromagnetic (FDEM) methods in order to develop a better understanding of the particular set of hydrogeological and environmental conditions that contribute to this unique phenomenon. Geophysical measurements provide lateral and vertical variations of electrical resistivity in the subsurface to a depth of 6 m while also contouring the streaming potential to help characterize the site-specific groundwater flow components. Least-squares inversion resistivity models and conductivity from electromagnetic data are compared to known well lithologic information to identify general variations of sediments with depth as well as delineate the extent of the known subsidence features. Site investigations indicate that the subsidence features in basin fill sediments are spatially associated with electrical and electromagnetic signatures of water seepage and sharp contacts between resistive and conductive sediment layers. ERI results showed a circular resistive anomaly in place of known subsidence locations and delineated lithologic heterogeneity in each site, suggesting a clay contact at shallow depth. The FDEM results complemented ERI and further characterized the depth and thickness of the clay. The SP results indicated surficial seepage associated with subsidence locations. A borehole was hand-augered. We did a sieve test, atterberg limits test, and ASD Terraspec Halo shortwave-infrared (SWIR) mineral analysis. The findings showed a fines ration from 36.1% to 38.1%, and clays are dominantly kaolinite PX, montmorillinite, and some ferryhydrite. This work sets a baseline site characterization and analysis on the origin of these subsidence features, where the subsidence is expected to be associated with volumetric changes in clay and porous media during surficial seepage.

Proxies for Basement Structure and Its Implications for Mesoproterozoic Metallogenic Provinces in the Gawler Craton

AbstractThe link between mineral resources and crustal‐rooted structures has been proposed for many of the world's most significant mineral provinces. Here we utilize a new approach by interpreting potential field data, including satellite gravity data, and high‐resolution continental‐scale magnetotelluric data, constrained with aeromagnetic, and seismic tomography and reflection data, to determine the distribution of crustal‐scale faults in the Archean to Proterozoic Gawler Craton (South Australia). The eastern flank of the craton hosts the supergiant Olympic Dam iron oxide‐copper‐gold (IOCG) deposit within a larger Olympic IOCG province. The central part of the craton contains gold‐only deposits, which define the Central Gawler Gold province. Both of these provinces are part of a Mesoproterozoic mineral system with an extensive hydrothermal alteration footprint, which formed during complicated tectonic mode switches. We show that both types of mineralization are located in proximity to crustal‐scale structures that appear to connect deep crustal fragments, which likely record the amalgamation of the Archean nucleus of the craton during the Neoarchean with subsequent reworking during the Mesoproterozoic. Many of these structures do not have a surface expression but coincide with gradients in magnetism, gravity, and electric resistivity anomalies, the latter data set suggesting they acted as fluid pathways extending to the lower crust. The results indicate that the first‐order controls on the distribution of IOCG and Central Gawler Gold metallogenic provinces are inherited from earlier tectonic events, which formed major crustal boundaries and related structures that are prone to reworking during later tectonism.

Investigation of soil moisture content over a cultivated farmland in Abeokuta Nigeria using electrical resistivity methods and soil analysis

A combined 1D and 2D electrical resistivity surveys as well as laboratory determination of soil moisture contents of topsoil in a University cultivated farmland is presented. Apparent resistivity data were measured along six traverses using Schlumberger and Wenner arrays while soil samples were collected from all traverses at depths of 0.5, 1.0, 1.5 and 2.0 m respectively. The ranges of resistivity and thickness of the topsoil, clayey sand and weathered layers are 78.0–1094.0 Ωm, 0.5–1.9 m; 110.0–275.0 Ωm, 1.1–11.9 m; and 19.0–274.0 Ωm, 1.1–14.0 m respectively. 2D resistivity inverted sections revealed three zones of resistivity anomalies: topsoil with resistivity 78.0–600.0 Ωm for traverses within the farmland and that of two traverses along the entrances to the farm. The second resistivity zone represents a clay region of high moisture content with resistivity values less than 25.0 Ωm. The third layer represents weathered/fractured layer with relatively high resistivity values ranging from 116 to 600 Ωm. The 1D resistivity models showed effective depths of more than 30.0 cm while the 2D image lines revealed that active water uptake zone extends to about 3.0 m depth. All the collected soil samples belong to sandy loam while the soil moisture content values ranged from 45 to 74% at different soil depths of 0.5–2.0 m. The study has shown that the integrated methods provide important methods for better management of soil water reserves for improved agricultural production.

Interpreting CSEM data in complex resistivity regime

CSEM has been applied as a risk mitigation tool in the Krishna-Godavari Basin, East Coast India. A workflow for application of CSEM in a portfolio ranking process is described, ranging from feasibility assessment to interpretation and post-drilling analysis. Data interpretation was based on relative response analysis, unconstrained inversion and 3D modelling. A major challenge, encountered in the data interpretation was the lack of suitable calibration areas for the interpretation model. Nevertheless, several robust resistivity anomalies were identified, which were then prioritised for drilling. The drilling of a CSEM positive prospect yielded commercial hydrocarbons. This additional calibration information, obtained from the well, was then fed back into the integration work-flow and robustness analysis for the previously lower-ranked resistors. Even using this more complex model, the presence of the resistors was confirmed. This motivated Reliance to review the seismic to upgrade the CSEM leads to prospects.

Airborne Geophysics over the Dolly Varden VMS and Low Sulphidation Epithermal Silver Deposits, Northwestern BC, Canada

Results from helicopter VTEM time-domain electromagnetics that include aeromagnetics and gamma ray spectrometries and later ZTEM natural field helicopter electromagnetics are compared over the Dolly Varden Mine region that hosts both potential VMS Pb-Zn base metal and low sulphidation epithermal silver mineralization, beyond the known vein-type Ag deposits and showings.There are few well-defined discrete targets within the VTEM data set. The magnetic data have defined a network of older fault structures trending NNE, ENE, WNW, and NW. These structures are interpreted to be related to extensional basin formation. Prominent in the radiometrics is a potassium anomaly over the Red Point area, consistent with a quartz-K-feldspar-chlorite-pyrite zone, interpreted as a VMS feeder. ZTEM resistivity and magnetic geophysical anomalies suggest the presence of broad, generally flat lying resistive and magnetic units at depth. At Red Point and along the Tiger-Evindsen Corridor, ZTEM displays moderate to high resistivity and low magnetics, which suggest the presence of strong potassic-silicic alteration, related to low sulphidation epithermal systems.The airborne geophysical results over the Dolly Varden mine region provide valuable insights on the detectability of similar Ag rich Eskay Creek type HS VMS and Brucejack style LS epithermal deposits. The principal VMS deposits seem immune to clear or discrete identification as EM conductors using VTEM, likely due to their Pb-Zn rich/Cu poor mineralogy; whereas, unlike VTEM, the ZTEM seems to clearly define high resistivity regions surrounding the known deposits that would seem to be consistent with their K-Si-altered low sulphidation epithermal origin.

Three dimensional inversion of magnetotelluric (MT) resistivity data from Reykjanes high temperature field in SW Iceland

The resistivity structure of Reykjanes is presented, derived from a three dimensional (3D) model developed in 2016. The model is the final results of a 3D inversion of MT data, corrected for static shift by joint inversion with TEM soundings at the same location as the MT soundings. In the model presented here (REYSAND), a total of 136 sounding pairs are used for the inversion. The model covers Reykjanes area and Sandvík potential geothermal area. The resistivity structure of a high enthalpy system reflects the thermal alteration of the rock. The Reykjanes models reveal a conventional resistivity structure for a high enthalpy geothermal system, i.e. a low resistivity cap underlain by a high resistivity core. The low resistivity cap reaches surface in the hot spring area, Gunnuhver, and dips down in all directions forming an elongated area of 2.5 km × 3 km in strike direction down to 1 km depth bounded by the low resistivity. The resistivity of the low resistivity cap is less 3 Ωm and is underlain by a high resistivity core with resistivity of 10–30 Ωm down to 3 km depth. At greater depth, high resistivity anomalies are prominent with a zone of lower resistivity, in strike direction, under the main field. This zone coincides with an aseismic zone at depth and may indicate a fracture zone with higher temperature and/or permeability within the geothermal system. Comparison to data from the IDDP-2 drilling as well as seismic monitoring confirms that suggestion.

Detection of decay and hollows in living almond trees (Terminalia catappa L. Roxb.) using electrical resistivity method

A precise and cost-efficient diagnostic technique for detecting decay and other structural defects in living trees is indispensable for the risk assessment and conservation of urban and forest trees. A study was carried out to detect the location and extent of decay and hollows (or cavities) in almond trees (Terminalia catappa L. Roxb.) using the four-point electrical resistivity method. Electrical resistivity measurements (ERm) of randomly selected living almond trees were taken using an earth resistivity meter, four probes and a modified form of Schlumberger electrode configuration. The ERm were used to obtain resistivity profiles (RP) of the trees. The RP of freshly cut healthy, decayed and hollowed trees were also obtained. A laboratory experiment was set up to replicate the RP of healthy, decayed and hollowed trees. Wood decay and cavities in trees were detected through RP matching. In comparison to healthy trees, wood decay and cavities in tree stems were detected with relatively sharp decrease and increase in electrical resistivity values, respectively. The extent of the resistivity anomalies corresponds to the extent of wood decay and cavities in trees. This method is applicable to early detection of decay and cavities in hardwood trees.

Electrical Survey Results in a Sub-Seabed Co2 Release Experiment (QICS)

A controlled sub-seabed CO2 release experiment was carried out during May–October 2012 in Ardmucknish Bay in Scotland, UK. A total of 4.2 tons of CO2 gas was released for 37 days from May to June at a maximum flow rate of 80 L/min (210 kg/d) at a depth of 11 m beneath 12 m deep sea floor. During and after the CO2 release experiment, electrical resistivity and self-potential (SP) surveys were conducted to monitor CO2 migration under the seabed. Three electrical survey lines with a length of 45 m were completed on the seabed. The electrical resistivity surveys were conducted September 23, 2012 and May 27, 2016. The resistivity survey data were acquired with a pole-pole electrode configuration. Two-imensional analysis was performed in the three lines. The determined resistivity structures showed that positive anomalies of the resistivity structure of 2012 compared with the structure of 2016 distributed 10-20 m south-west of the CO2 released point. In this area CO2 bubbles was seen escaping from the seabed by divers and video cameras. CO2 migration under the seabed was estimated in this area by the seismic survey. The SP survey results measured during the CO2 release experiment showed that positive SP anomaly of a maximum of 0.05 V was observed when CO2 flow rate increased from 60L/min to 80 L/min. The positive anomalies distributed south-west of CO2 released point. This area is almost same as the positive electrical resistivity anomaly area in 2012. These results show that the CO2 migration under the seabed caused positive electrical resistivity anomalies and also positive SP anomalies.

Phase Transitions and Resistivity Anomaly of Layered MoO3 at High Pressure

MoO3 has large electronic and mechanical anisotropy arising from diverse chemical bonding in its layered structure. Here, we report high-pressure structural and electronic transitions in MoO3 to 10...

A generalized image and boundaries of the Bazhenov Formation: constraints from well log data for Salym-type sections (West Siberia)

A technique akin to Galton’s composite portraiture is suggested for creating a generalized image of a stratigraphic unit based on well log data from a group of well sections. The procedure begins with superimposing stratigraphically equivalent section points according to pairwise correlation models followed by weighted summation of similar logs. The superimposition highlights persistent common features of the sections, while their minor individual details become suppressed. A generalized model of the Bazhenov Formation in the Salym area has been constructed from gamma-ray, apparent resistivity, and self-potential logs. Radioactivity and resistivity anomalies, which are often used as constraints on the Bazhenov Formation boundaries, show a significant spatial discrepancy. According to the correlation, the formation volume in each well depends on the depth interval corresponding to the hypostratotype. The results were used to map the Bazhenov Formation thickness and its standard deviation, as well as average values of different logs.

A diverted submarine channel of Early Cretaceous age revealed by high-resolution seismic data, SW Barents Sea

Abstract Mud-rich prograding sediment lobes make for most of the Barremian – Albian stratigraphic record in the SW Barents Sea. Submarine canyons and channels potentially represent key components of sediment transport from shelf to basin floor but geological evidences are lacking. We present high-resolution seismic data and scrutinize an elongated, ∼150-km long bright seismic amplitude and resistive anomaly located alongslope of a NW-sourced Barremian delta in the SW Barents Sea. Seismic interpretation is performed on a comprehensive database comprising 3D/2D high-resolution P-Cable and conventional seismic data, tied to three exploration wells to provide age-control on key horizons. Our results highlight that the elongated geophysical anomaly originates from a soft layer deposited over a harder, erosional surface. The erosive morphology displays three narrow, V-shaped incisions to the NE of the Hoop area which develop into a single, ∼6 km-wide, U-shaped channel towards the transition to the Fingerdjupet Subbasin. The geological feature is named Ceres and interpreted as a submarine channel carved in Aptian, a period of marked sea level rise and sediment starvation in the Hoop area. An evolutionary model of a diverted submarine channel is proposed where a flooded delta lobe acted as a topographic barrier, funneling bottom currents and thereby carving an alongslope, possibly contouritic channel. This is the first documented case of a submarine channel pathway – delta lobe interaction on the Norwegian continental shelf. To account for the geophysical expression of Ceres, two competing explanations are discussed: (1) hydrocarbon-bearing sands, and (2) organic-rich source rock. Both scenarios have important implications for petroleum prospectivity: a faulted stratigraphic trap holding large volumes of hydrocarbons or alternatively the channel-controlled distribution of mature Aptian source rock in the SW Barents Sea.

The Application of Resistivity and Induced Polarization Methods in Identification of Skarn Alteration Haloes: A Case Study in the Qale-Alimoradkhan Area

This paper investigates the capability of the resistivity and induced polarization (IP) methods to delineate skarn alteration haloes within the Qale-Alimoradkhan skarn copper deposit. This deposit is located in the Sanandaj-Sirjan geological and structural zone, Hamedan province, Iran. It is understood that fresh limestone and metamorphosed limy units including skarns represent high resistivity anomalies whereas granodiorite intrusions represent medium to low resistivity responses. Four profiles were selected to explore the sulfide-rich zones within the deposit using the Combined Resistivity Sounding and Profiling (CRSP) array. After the appropriate selection of inversion parameters, the inverted models were in good agreement with the known geological features. The resistivity response of the intrusive rocks were found to be alteration dependent. Furthermore, IP targets likely represent sulfide-rich zones. Our study suggests that if preexisting knowledge regarding the geological setting is available, then resistivity and IP can be helpful in the exploration of skarn mineralization.

Characterizing Near-Surface Fractured-Rock Aquifers: Insights Provided by the Numerical Analysis of Electrical Resistivity Experiments

Fractured-rock aquifers represent an important part of the groundwater that is used for domestic, agricultural, and industrial purposes. In these natural systems, the presence and properties of fractures control both the quantity and quality of water extracted, meaning that knowledge about the fractures is critical for effective water resource management. Here, we explore through numerical modeling whether electrical resistivity (ER) geophysical measurements, acquired from the Earth’s surface, may potentially be used to identify and provide information about shallow bedrock fractures. To this end, we conduct a systematic numerical modeling study whereby we evaluate the effect of a single buried fracture on ER-profiling data, examining how the corresponding anomaly changes as a function of the fracture and domain characteristics. Two standard electrode configurations, the Wenner-Schlumberger (WS) and dipole-dipole (DD) arrays, are considered in our analysis, with three different spacing factors. Depending on the considered electrode array, we find that the fracture dip angle and length will impact the resistivity anomaly curves differently, with the WS array being better adapted for distinguishing between sub-horizontal and sub-vertical fractures, but the DD array leading to larger overall anomaly magnitudes. We also find that, unsurprisingly, the magnitude of the resistivity anomaly, and thus fracture detectability, is strongly affected by the depth of overburden and its electrical resistivity, as well as the fracture aperture and contrast between the fracture and bedrock resistivities. Further research into the electrical properties of fractures, both above and below the water table, is deemed necessary.

A pilot study to test the reliability of the ERT method in the identification of mixed sulphides bearing dykes: The example of Sidi Flah mine (Anti-Atlas, Morocco)

A multidisciplinary study, comprising geological, petrographical and geophysical methods, was carried out for the identification and the geometrical and volumetric assess of the main mineralized bodies (mixed sulphides, Zn-Pb and Fe-Cu) in the area of the Anti-Atlas chain, located at SW of the town of Sidi Flah (Ouarzazate, Morocco). The initial phase of exploration involved an extensive fieldwork (structural investigations and sampling) and a detailed survey for verifying the effectiveness and reliability of the Electrical Resistivity Method (ERT). Geological fieldworks and laboratory analyses played a fundamental role in identifying the resistivity anomalies and constraining tomographic results. Main issues we focused on are: i) mineralized bodies imaging according to the electrodic step; ii) consistency with geometry of mineralized bodies; iii) contrast of electrical resistivity between mineralized dykes and host rocks; iv) possible correlations between the type and amount of sulphides and electrical resistivity.

The Use of Electrical Resistivity Tomography to Investigate Basaltic Lava Tunnel Based on the Case Study of Al-Badia Cave in Jordan

DOI: 10.17014/ijog.5.2.161-177Electrical Resistivity Tomography (ERT) was employed to conduct a geoelectrical survey near the Al-Badia lava tunnel located close to the Al-Bishyrria Village in Jordan. The technique enabled the mapping of the subsurface tunnel extension and description of its inner structure. To assess the quality of data and resistivity models, Schlumberger and Reciprocal Schlumberger electrode configurations were used to produce eight ERT profiles. As revealed by the examination of received potential, the implemented configurations exhibited a strong signal, producing an approximated reciprocal error of up to 6%. The findings of ERT models showed that the lava tunnel had a clearly outlined structure with an elliptical to rectangular shape. The modelled resistivity of the lava tunnel was obtained in proximity to 1000 Ω-m, with a better characterization being possible at resistivity exceeding 8000 Ω-m in 200 Ω-m of Fahda Vesicular Basalt medium. An exploration depth of 50 m revealed that the lava tunnel was 10 m deep and 5 m in diameter on the average. Furthermore, potential means of groundwater recharging were reported by the simultaneous detection of a number of resistivity anomalies of less than 50 Ω-m and lava tunnel. In addition, the lava tunnel was observed to extend and ramify beyond the area under investigation, indicating at the potential existence of multiple lava tunnel extensions in both the investigation area and in the basaltic flows, which could have adverse implications for future urban projects.

Revealing the electrical properties of a gneiss dome using three-dimensional magnetotellurics: Burial and exhumation cycles associated with faulting in Central Anatolia, Turkey

The Niğde Massif is a small-scale exhumed lithospheric entity in Central Anatolia formed as a result of metamorphism driven by crustal thickening and migmatization. Its thermal and structural history records two burial and unroofing episodes induced by oblique tectonics related to an adjacent wrench zone of the Ecemiş Fault. To show the complex tectonic history of the events of this area, its electrical resistivity structure was determined using three-dimensional magnetotellurics. Forty-seven high-quality soundings within a frequency range of 320 Hz–5000 s were utilized for this purpose. The dimensionality of the data was investigated via phase tensor analyses and induction vectors. A hydrothermal system that might be related to Mt. Hasan was delineated as a widespread conductive zone. In addition, interpretation of the electrical resistivity models found a rheology-seismicity relationship in the study area. The Niğde Massif was depicted as a highly resistive dome-like anomaly bounded by low-angle detachment faults as indicated by the resistivity contrast between the massif and the adjacent features. The lower boundary of the massif is defined by a resistive to conductive transition situated at ∼25–30 km depth. Beneath this transition, a widespread low-resistivity zone was interpreted as a partially melting lower crust. This crustal feature is connected to a shallower anomaly beneath the Ecemiş Fault Zone, which may infer the ascension of fluids that may be contributing to earthquake generation. Seismicity along the Ecemiş Fault is overtly heterogeneous in that it tends to form a step approaching south along the fault where the lower crustal conductor is absent. Relevance between the seismicity and resistivity pattern denotes the presence of a fault configuration that is necessary for the yo-yo tectonics.

Three-dimensional magnetotelluric imaging of the geothermal system beneath the Gonghe Basin, Northeast Tibetan Plateau

To explore the geothermal system in the Gonghe basin located between Kunlun and Qinlin Orogen in northeast Tibetan Plateau, 310 Magnetotelluric (MT) sites were deployed in the basin. The MT sites have an average spacing of 1∼2 km and almost cover the whole basin with an area of ∼100 km by 100 km. We first analyzed the MT data using phase tensor analysis to qualitatively estimate the dimensionality of the subsurface resistivity structure and the resistivity anomalies. We then determined a 3D resistivity model from the surface to the depth of ∼50 km through a 3D MT inversion of MT data at the 272 sites with relatively higher quality. Overall, the inverted resistivity model fits the MT data very well. Our 3D resistivity model reveals significantly conductive anomalies at depths above ∼3 km, which are interpreted as widespread hot dry rocks or hydrothermal reservoirs. Furthermore, the 3D resistivity model shows pronounced low resistivity zones in the middle crust (∼15-35 km). These anomalies trend a NW-SE direction, consistent with the Kunlun Fault strike. Between the near-surface conductive zone and the middle crust conductive zone, lie several vertical narrow conductive zones, which are generally associated with hidden faults identified in the basin. Synthetic tests are used to validate the resolution of large low resistivity anomalies in the middle crust and the vertically elongated low resistivity anomalies in the model. These faults may serve as the channels for transporting heat from the heat source in the middle crust to the shallow zone around the depth of 3 km. Our 3D MT imaging results characterize for the first time the 3D distribution of the geothermal system in the Gonghe Basin.