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Landslide, as a geohazard issue, causes enormous threats to human lives and properties. In order to characterize the subsurface prone to the landslide which is occurred on the Tehran-North freeway, Iran, a comprehensive study focused on geological field observations, and a geoelectrical survey as a cost-effective and fast, non-invasive geophysical measurement was conducted in the area. As a result of road construction, problems in this region have increased. The Vertical Electrical Sounding (VES) investigation in the landslide area has been carried out by the Schlumberger array for data acquisition, implementing eight survey profiles varying in length between 60 and 130 m. Based on the electrical resistivity models through a smoothness-constrained least-square inversion methodology, the landslide structure (i.e., depth of the mobilized material and potential sliding surface) is better defined. The inferred lithological units, accompanied by stratigraphical data from a borehole and geological investigations for the prone landslide region, consisted of a discontinuous slip surface, having a wide range of resistivity, observed to be characterized by tuff with silt. Electrical resistivity values above 150 Ωm indicate a basement of weathered marlstone and sand. Values between 15 and 150 Ωm illustrate a shale-content layer with outcrops in the area that is the reason for movement. The sliding surface is at a depth of about 12 m. The method used in this study is a good candidate to investigate the risk of landslides in this region and can be applied to other landslide areas where borehole exploration is inefficient and expensive due to local complications. [ABSTRACT FROM AUTHOR]

Potential field geophysical measurements were conducted in the west of Kifl region in central Iraq to image a plausible oil-trapping reservoir. Ground-based magnetometry and gravimetry surveys were conducted to investigate this region by covering an area of 16 × 24 km by designing a regular grid spacing of 250 m. After preprocessing potential field data, different filters were utilized to separate the residuals from the regional anomalies. The complicated tectonic setting of the studied area was imaged by recognition of the fault system through simulation of the magnetic and gravity anomalies, which facilitates the configuration display of the oil-trapping mechanism. The geometry of a fault system was derived from parametric inversion of gravity data. The magnetic anomalies were extended with the trends of NS, NW, and NE and reached a maximum value of 55 nT. However, the gravity anomalies appeared with the same extensions and values ranging from -3.3 to 1.5 mGal. The intense magnetic susceptibility amount of the reservoir rocks is arising from chemical processes and iron-oxide ion replacements, accompanied by the migration and accumulation of hydrocarbon. Incorporating the results from the Euler's depth estimation, parametric data modeling along with logging data assisted simultaneous modeling of the magnetic and gravity data. The 2D geological model of the subsurface layers at the Kifl area presents a graben-horst fault system within a thick sequence of sediment. Geological characteristics extracted from geophysical data modeling provided insightful information on the nature and essence of the hydrocarbon reservoirs in the Kifl area. It has formed through tectonic deformation and tension over the Arabian plate during the Permian - Paleocene cycle. Hence, it can be concluded that the aforementioned fault system has divided the hydrocarbon reservoirs. [ABSTRACT FROM AUTHOR]

Producing an accurate and valid mineral prospectivity map is one of the most significant parts of mineral exploration studies. For this purpose, it is needed to obtain valid evidential layers and integrate them with an accurate methodology. Knowledge and data‐driven methods are two primary techniques applied to combine various evidential layers for mineral prospectivity mapping, of which each of them includes a variety of analytical techniques. In this study, in the first step, satellite data, aeromagnetic and airborne radiometric data, stream sediment geochemical data and geological data were applied to create valid remote sensing, geophysical, geochemical, lineaments and lithological evidential layers of the study area that are an essential factor in recognition porphyry copper mineralization, then in the second step, based on the known mineralization occurrences data, the evidential layers were weighted. Finally, these layers were integrated using fuzzy logic and index overlay methods in a combination of knowledge and data‐driven way. Validation of each layer was done using available data in the second step. The final mineral prospectivity map was evaluated, and the confirmation of this layer detected that the final mineral prospectivity map obtained from data‐driven multi‐index overlay method has a higher ore prediction rate of 76%, which identifies 24% of the area as potential zones for further exploration. [ABSTRACT FROM AUTHOR]

This study serves the purpose of generating a geochemical Fe-bearing potential map. Stream sediment geochemical survey was employed by collecting 843 samples for analyzing 19 elements and oxides. Taking preprocessing of data (e.g. outlier correction and data normalization) into consideration, a Concentration-Number (C-N) fractal model was used to separate different geochemical populations of Fe2O3, TiO2, V, and the main multi-element factor in close spatial association with the Fe targeting. A prediction-area(P-A) plot was drawn for each variable to determine the weight of each geochemical indicator. Results indicate that the main geochemical factor with an ore prediction rate of 73%, has occupied 27% of the Esfordi area as favorable zones for further mining prospectivity. The Esfordias a favorable Fe-bearing zone is of special interest in the NE of the Bafq mining district that hosts important "Kiruna-type" Magnetite-Apatite deposits. In addition, a synthesized indicators map was prepared by implementing a data-driven multi-class index overlay in a similar fashion to the previous version of the method, upon which geochemical potential zones were mostly in the NE part of the Esfordi, intimately linked with intense fault density map. The significance of this study lies in localizing the most geochemical favorable zones through simultaneous consideration of the C-N and PA plots accompanied by the incorporation of known active mines and prospects to determine indicator weight. Of note is that the Mineral Potential Mapping(MPM) has higher efficiency over each geochemical indicator with an ore prediction rate of 78% and area occupation of 22%. [ABSTRACT FROM AUTHOR]

This paper describes an application of diverse geophysical methods to detect the geological contacts in the Tomelilla area, Sweden. Airborne magnetic data and the tipper and peaker maps derived from tensor very-low-frequency electromagnetic (TVLF-EM) data are interpreted in order to indicate most geological boundaries. The inverted airborne TVLF data along adjacent profiles over each contact show the resistivity variations at depth and laterally localize the geological contacts while delineating resistive bedrocks in all cases. To control the resistivity images across these profiles, the ground-based measurements of the radio magnetotelluric data combined with controlled-source magnetotelluric data (RMT/CSMT) have been performed to plot resistivity variations with higher resolution. The obtained resistivity images are in good agreement with the ones acquired from airborne TVLF data. A relatively conductive layer with an average thickness of 20 to 30 m of the Quaternary deposits, increasing in thickness from east to the west, and a resistive basement with much higher resistivity on the granites than the shales are resolved from the geoelectric sections. This paper confirms that the combined geophysical surveys (i.e., airborne magnetometry/TVLF along with ground-based RMT/CSMT) reduce the uncertainty arising from geological mapping. It is shown that the airborne TVLF data have high capability for image resistivity variation along geological contacts in the study area while its resolution has been confirmed by the ground-based RMT/CSMT survey. [ABSTRACT FROM AUTHOR]

This paper describes a general framework of incorporating magnetic data as prior information in the modeling of an iron deposit based on sparse drilling boreholes. Since multivariate kriging of a sparse pattern of drilling yields lower uncertainty in mineral deposit modeling, a model of magnetic susceptibility as a second variable which has an acceptable level of correlation with the first variable, iron, is used to make a model of iron grade. Before applying an inversion technique to recover a 3D model of magnetic susceptibility, the normalized full gradient (NFG) approach is used to generate an approximate visualization of probable magnetic anomaly. Based on the NFG result, we have acquired appropriate dimensions of composites to apply the geophysical inversion method. The subsurface of the desired area of the magnetic anomaly is divided into a mesh with a large number of rectangular prisms (composites) with unknown susceptibilities. The recovered magnetic susceptibility model which has a correlation equal to 0.543 with the iron grade is used as a second variable in order to apply a multivariate set of kriging equations. The collocated cokriging method as a modified version of the cokriging system is used to interpolate the iron grade based on a model of magnetic susceptibility. This method has been applied to a real case study in Zanjan Province of Iran, showing its effectiveness when we encounter with such lack of drilled boreholes in the study area. [ABSTRACT FROM AUTHOR]

In this paper, a set of airborne magnetic data and helicopter-borne frequency domain electromagnetic data are used in order to retrieve a joint model of magnetic susceptibility and electrical conductivity. The study area called Kalat-e-Reshm located in Semnan province of Iran consists of an arc-shaped porphyry andesite covered by sedimentary units which has high potential of mineral occurrences especially porphyry copper. Based upon Occam approach assuming a multilayered earth model with fixed thicknesses, a conductivity-depth plot from airborne electromagnetic data is generated to image the desired porphyry type geological structure. The 3D visualization of the 1D conductivity models along all flight lines provided a resistive geological unit which corresponds to the desired porphyry andesite. A multi-constraint method is also applied on the airborne magnetic data to recover a 3D distribution of magnetic susceptibility model which reveals extension of an arc-shaped porphyry andesite at depth. The high susceptibility, low conductivity porphyry andesite shows a thicker structure than what is shown on the geological map and extends to depth. [ABSTRACT FROM AUTHOR]