The use of spontaneous potential (SP) anomalies is well known in the geophysical literatures because of its effectiveness and significance in solving many complex problems in mineral exploration. The inverse problem of self-potential data interpretation is generally ill-posed and nonlinear. Methods based on derivative analysis usually fail to reach the optimal solution (global minimum) and trapped in a local minimum. A new simple heuristic solution to SP anomalies due to 2D inclined sheet of infinite horizontal length is investigated in this study to solve these problems. This method is based on utilizing whale optimization algorithm (WOA) as an effective heuristic solution to the inverse problem of self-potential field due to a 2D inclined sheet. In this context, the WOA was applied first to synthetic example, where the effect of the random noise was examined and the method revealed good results using proper MATLAB code. The technique was then applied on several real field profiles from different localities aiming to determine the parameters of mineralized zones or the associated shear zones. The inversion parameters revealed that WOA detected accurately the unknown parameters and showed a good validation when compared with the published inversion methods.
Magnetic and seismic methods have been used in this study as complementary methods to each other to construct a geologic hazard map for Wadi Thuwal area. Magnetic interpretation for deep-seated geologic structures has involved reduction to pole algorithm and downward continuation techniques. It showed that there are three major fault trends: NE-SW and NNE-SSW, NW-SE, and N-S. Furthermore, shear zone has been found close to Harrat Thuwal, which was confirmed by the seismic method. Seismic method revealed three lithologic layers where the depth of the bedrock was found to be ranging between 9?m at the southeastern part of the study area and 24?m at its northern part. It showed also five major fault trends: NW-SE, ENE-WSW, NE-SW, and nearly E-W. Supported by the surface geology, magnetic and seismic results showed that the Wadi Thuwal area can be divided into three zones on the basis of geologic hazards, depending on the presence of geologic features such as faults. It is recommended that before any development plan in Wadi Thuwal area, the delineated hazard zonation should be taken into account. 相似文献
Geophysical and geological studies play a fundamental role in the strategic and sustainable utilization of natural resources, especially that of fossil groundwater, in arid regions. The geophysical exploration of shallow groundwater aquifers is common in arid regions. In this work, a feasibility study of future development plans in the Siwa Oasis, Egypt, was carried out. A land electric resistivity survey was conducted, and approximately 14 vertical electric soundings were measured covering the Siwa Oasis, northwestern desert, Egypt. A detailed surface geology study was also conducted to study the underground water aquifer. Digital filters were applied to the reduced to pole-available magnetic data covering the area. The normalized source strength transformation and tilt depth were calculated and applied to delineate the possible structures that may control the shallow and deep aquifers in the area. The integrated interpretation showed the presence of four main geoelectric layers forming the shallow section of the Siwa Oasis down to 220 m. These layers varied in their resistivity and rock constituents from very low (0.2 Ω m) to very high (6200 Ω m) values. The calculated hydraulic parameters showed that the uppermost central area and the eastern area were the most promising areas for the required water development. Finally, based on the integrated interpretation and the estimated shallow aquifer potentiality, a land use map for the Siwa Oasis was produced to assist future strategic development of the region.
In the present study, Al Ji’lani layered intrusion was subjected to integrated field, petrographic, processing of ASTER data, and geophysical investigations to delineate its subsurface extension and to determine the chronological order of the exposed rocks. The intrusion is surrounded by foliated granodiorite and both were intruded by younger granite. Processing of ASTER data revealed that the intrusion incorporated foliated granodiorite masses along its NE corner indicating its younger age (postorogenic) setting contrary to what have been proposed by previous authors. Also, this is further confirmed by the presence of an offshoot from the intrusion in the South-East corner as well as freshness and undeformed nature of the gabbroic rocks. Petrographically, the gabbroic rocks are characterized by the presence of kelyphytic coronas around olivine in contact with plagioclase, magnetite-orthopyroxene symplectites after olivine, and symplectites between plagioclase and magnetite/ilmenite. These textures are explained in terms of interaction with late deuteric magmatic fluids and not to metamorphism as believed before. The extensive geophysical analyses of the Al Ji’lani prospect using aeromagnetic data suggest complicated combination of magnetic bodies composed mainly of gabbroic rocks intruding the foliated granodiorite with variable magnetic susceptibilities. Gradient analysis, tilt angle and edge detection techniques extracted the shallow subsurface magnetic boundaries and a probable multiple bodies in the subsurface are detected. The 3-dimensional constraint inversion using parametrized trust region algorithm revealed the deep subsurface distribution of magnetic susceptibilities of the bodies. Two resolved bodies are clear, a northern more shallow body, and a southern, deeper and laterally extend to the south and southwest. The calculated volume from the inverted model representing the Al Ji’lani layered intrusion is approximately 518.7 km3 as calculated to 6.0 km depth. The body could be extended to a deeper depth if a different proposed model geometry is adjusted. The surface area of the exposed body is only 42.39 km2. Several magnetic anomalies are defined within the intrusion and are considered potential sites of mineralization. The south east corner of the gabbroic intrusion is traversed by a shear zone trending ENE-WSW which hosts sulfide-bearing quartz veins with high silver content (Samrah Prospect) associated with an offshoot from the layered gabbro. The shear zone should be followed to the west where the intrusion extends for a distance of about 10 km in the subsurface to the southwest of the exposed part of the intrusion. 相似文献
