International Journal of Mining & Geo-Engineering
Volume:57 Issue: 3, Summer 2023

One of the operating costs of exploiting underground mines is related to ventilation operations. The development of the underground network during the mine life and new excavations will cause a redesign of the ventilation plan over and over again. Excavating the waste pass in the Anguran underground lead and zinc mine and developing new access for the transfer of cement filling requirements from the surface will make it necessary to review the ventilation network plan. The present research aims to analyze the efficiency of the mine ventilation network through simulation with considering the effects of waste pass based on the consequences of natural ventilation. For this purpose, based on the estimation of the needs of the underground development plan, the required airflow intensity of this mine was 57.5 m3/sec and the air pressure drop was estimated to be 116.79 millimeters of the water column. The underground mine network was imported into the software by using Ventsim software, and the simulation and specifications of each branch have also been entered. Then, different positions of the main fan were examined according to the location of mine opening and airways the advantage of mine natural ventilation in different seasons, and finally, the most suitable design for ventilation was presented. Modeling natural ventilation was investigated in two parts before waste/ore pass excavation and after excavation in Ventsim software at temperature, pressure, and different humidity. According to the simulation, it was found that the minimum natural ventilation flow to the mining network is 14 m3/sec in winter, its use saves 16.02 Kwh of energy.

Based on magnetic susceptibility and density contrast models, the final purpose of analyzing potential field data is to estimate the parameters of the sought source, such as depth, structural index, horizontal location, and physical characteristics. Meanwhile, when conducting geophysical explorations, it is critical to ascertain the exact depth of the underground source as accurately as possible. In this study, the potential field is interpreted using the depth from extreme points “DEXP” automatic transformation technique, founded on the accurate processing of the local wavenumber at various scales and the extreme points of the DEXP field to extract the depth, horizontal position and structural index of the source. This highly stable method demonstrates low sensitivity to noise-contaminated data since it employs an upward continuation filter and a potential field derivative operator. In addition, the findings are more dependable than those of alternative techniques. Furthermore, the procedure is entirely automatic and does not require any basic information from the data collection area. In other words, DEXP can be considered a fast imaging method. Since multiscale methods are less reliant on the magnetic induction field, nowadays, they are utilized more frequently in magnetic field computations. At the beginning of this research, synthetic scenarios are simulated, and then the depth extension of the postulated models was demonstrated by implementing the DEXP technique to the synthetic gravity and magnetic data. Subsequently, this method has been implemented on data from the Ghareh-Aghaj potash exploratory area in Zanjan Province, North of Iran. By summarizing this method's results, it can be seen that the potash mass exhibits a minimal transverse expansion and has extended more in the depth dimension. Compared to the findings obtained via exploratory boreholes, these findings demonstrate a level of agreement that can be considered satisfactory.

Magnetic data play a significant role in the interpretation of various geologic structures using depth estimation methods and edge detection filters. In this study, we applied methods based on directional derivatives such as tilt-depth (TD), signum transform (ST), source distance (SD) and classical Euler deconvolution (ED) to estimate the depth of the magnetic sources. Moreover, to enhance the edges of magnetic field anomalies, we utilize the total horizontal derivative (THD), analytical signal (AS), tilt angle (TA), theta map (TM), hyperbolic tilt angle (HTA), the tilt angle of horizontal derivative (TAHG), and logistic function of total horizontal gradient (LTHD). These algorithms are tested on a synthetic magnetic model with noise and free noise to understand their performance. Since the edge detection filters are sensitive to noise, we carry out an upward continuation (UC) filter before the reduction of data to magnetic the pole to reduce the noise effect. After comparing the efficiency of the approaches in estimating the depth and horizontal lateral boundaries, these methods were applied to the data surveyed from the Aji-Chai salt dome in East Azerbaijan Province, Iran. The results obtained by the depth determination methods were compared with the drilling report of Iran’s geological survey and three-dimensional classical Euler deconvolution method.

Magnetic and gravity anomalies have spatially overlapping fingerprints from many buried sources that differ in shape, depth, density contrast, magnetization intensity, and direction. Geophysicists have developed a suite of image enhancement filter algorithms that accurately represent the geometry and detail of subsurface features. Edge enhancement filters are high-pass filters that emphasize potential field anomalies, horizontal lateral edges, and the horizontal location of buried sources, i.e., specific combinations of directional derivatives of gravity and magnetic fields. Lateral edge enhancement filters (e.g., THG, AS, TA, TM, LTHG, IL, and ILTHG) were investigated using Gaussian noise on synthetic magnetic and gravity field data. The results show that LTHG and IL perform better than the other procedures. The ILTHG filter defined with the logistic function does not have the required accuracy and capability to determine the lateral boundaries. In addition, the filters were examined using real gravity field data from the Western Carpathians area in Slovakia. The primary and secondary faults in the western and southern Tribeč Mountains and the secondary faults and geological formations in the Pohronský Inovec Mountains are recognizable in the LTHG and IL images. The results of the LTHG and IL maps will allow us to improve the qualitative interpretation of gravity anomalies in studying the structural and tectonic geology of the Slovak Tribeč and Pohronský Inovec Mountains.

Malawi’s geology has not been mapped in detail and there is no detailed geological and structural assessment in relation to gold mineralization. Mangochi-Makanjira area in southern Malawi is endowed with abundant gold mineral resources but there is a scarcity of precise knowledge on the structures that control primary mineralization. This study used aeromagnetic data to provide a structural framework of the Makanjira area and delineated potential areas for further gold exploration. Many analytic approaches were applied to the aeromagnetic data, including reduction to the pole, Euler deconvolution, Tilt, and Vertical Derivatives filtering. Euler deconvolution was used to determine the depth of magnetic sources. Geophysical data interpretations identify the dominant linear trends present in the area to be faults, dykes and deep level basement shear zones as structures responsible for fluid flow and gold mineralization in the area.  Gold in this area is structurally controlled by N-S structures that were derived during the Pan African orogeny and it is during in this event that the area got mineralized. These fractures and faults served as channel ways for hydrothermal solutions, resulting in the emplacement of gold mineralization within the fractures. Mineralization occurs from the surface and goes deep and ranges in depth from 0.5 km to 2.4 km.  Exploration for gold should focus on these structures.

The study area is located 12 km south of Zahedan city in Sistan-Baluchestan province. This area includes the northern part of Sistan and Baluchestan province, which has a similar geological history as the Chagai belt beyond the Iranian border in Pakistan. The porphyry prospect south of Zahedan is located in the fertile belt of the Sistan suture zone, which includes the Janja, Siastragi, Chahuk and Kuh-e-Lar mineral structures, then leading to the Sindak Pakistan Molybdenum Porphyry Mine. Based on the results of the geological mapping of 1: 5,000 areas, a series of subvolcanic masses with intermediate chemical composition (related to the Zahedan granitoid) have been intruded into the sedimentary host rocks with flysch facies. The zoning of alteration occurrence in the region are concentric and with the center of phyllic and potassic alteration. Pyrite is the most abundant sulfide and chalcopyrite the main copper ore mineral. Mo and Cu mineralization in this area mainly occurred as veinlets in stockwork and dissemination texture. Based on scanning electron microscopy (SEM) studies and using EDS analysis, the presence of molybdenite, copper sulfide minerals were detected along with electrum and gold inclusions in the collected samples. Most of the detected fluid inclusions in study area are of the two, three, and multiphase types, including liquid, vapor, and solid. Due to the trend of salinity changes versus homogenization temperature, the effective fluid densities in the mineralization systems of the region are between 0.8 and more than 1.2 gr / cm3. Based on the salinity percentage (30 to 60 wt% NaCl equivalent) and homogenization temperature (200 to 500°C), the fluid inclusions of the region are in the porphyry range. Fluid δ34S values in the study samples are in the range of 3.4 to 4.6 per thousand. Sulfur isotope analyses indicate a magmatic origin of hydrothermal fluid. In general, based on the geology, mineralization, fluid inclusion, and sulfur stable Isotope studies it can be proposed that probably south Zahedan area is a copper, gold and molybdenum-type porphyry deposit.

To date, there has been limited research conducted comparing the effects of various grinding media shapes on milling kinetics, load behavior, and mill power draw. However, no research has been conducted on their effects on a lifter. This study aims to fill the gap in knowledge. An investigation into the effect of grinding media shape on the lateral movement of the charge (grinding media and material), by analyzing specific breakage rate parameters in a laboratory dry rod mill, has shown how grinding media can act as a lifter. Two grinding media (simple and grooved rods) were compared. The specific breakage rate parameters were determined using the Austin model. The values related to the μ parameter, whose increase means a decrease in the specific rate of breakage and an increase in the lifting of the grinding media, were equal to 3758.76 and 4144.63 for simple and grooved rods, respectively. Results proved that although the grooved rods have a lower specific breakage rate than simple rods, they can perform well as a lifter. They had the highest cataracting effect of the charge.

This study presents an analysis of aeromagnetic and aero-radiometric data from the Chitipa area in northern Malawi to delineate structures, hydrothermal alteration areas, and gold mineral potential zones, as well as to identify prospective regions for further mineral exploration.  Airborne geophysical data, specifically aeromagnetic and aero-radiometric data, were utilized. We applied several enhancements and filters to the geophysical data, including reduction to the pole, the first vertical derivatives, analytical signal, tilt angle derivative enhancements, Centre for Exploration Targeting (CET) grid analysis, Euler deconvolution, and radiometric data ratios. The results of the analysis provided detailed information on the subsurface geology and indicate that the area is characterized by faulting and shearing with structures predominantly trending in a northwest direction, and minor trends in the northeast-southwest, east-west, and north-south directions. Zones with hydrothermal alteration were found to coincide with structural associations in the NW part of the study area, indicating that the structures served as channel ways for migrating hydrothermal fluids that reacted with the rock formation, resulting in alteration. The northwest area is a promising mineralization zone, and further exploration should focus on this area.

In this research, the effect of the high-voltage electric pulse (HVEP) crushing on the flotation of high-sulfur iron ore concentrate in the coarse particle fraction was studied compared to mechanical (conventional) crushing. A jaw crusher, a cone crusher, and a high-voltage electric pulse crushing device with a voltage level of 50 kV were used to investigate the effect of mechanical and electrical crushing. The results showed that a coarser particle product was produced with less slime in primary crushing with electric pulses compared to primary mechanical crushing. It was due to the crushing mechanism, which is based on separating minerals with a different dielectric constant from their connection boundaries and also encompasses a selective separation process. The effect of the mentioned method on coarser fractions led to the creation of cracks/microcracks in particle structures that made grinding easier and faster. In investigating the effect of particle size on pyrite flotation and desulfurization at -300 µm (d80=300µm), the sulfur grade of flotation iron concentrate samples using primary crushing was 0.86% and 0.36%, respectively, and at -150 µm (d80=150µm) fraction, the sulfur grade was found to be 0.33% and 0.19% respectively for mechanical and electrical methods. Also, the sulfur removal (recovery) of the sample with primary electrical crushing was 73.7% at a -300 µm fraction, almost equal to 73.2% at the size range of -150 µm with applying the mechanical method. These results indicated the flotation possibility of coarser particles using electrical crushing and desulfurization similarity to the samples with primary mechanical crushing in finer fractions.

Fractures are one of the most important geological features that affect production from most carbonate reservoirs. A large amount of the world’s hydrocarbon resources are located in fractured reservoirs and the identification of fractures is one of the important steps in reservoir development. Due to the high cost of tools that are used in the petroleum industry to identify fractures such as image logs, and their inaccessibility in most of the studied areas, it is often tried to use other available data to identify fractures. Due to the ever-increasing progress of data-driven methods such as neural networks and machine learning, this study has tried to apply a 1D-Convolutional Neural Network (1D-CNN) which is one of the deep learning algorithms on well-logging data and seismic attributes in a carbonate reservoir to identify the existing fractures in the investigating area. The approach used in this research is a binary classification which is applied first in the well location. To validate the method, results are compared with the reports obtained from image logs. Finally, the fracture density map is drawn in the entire reservoir area.

Electrical resistance tomography (ERT) provides images of the electrical properties of subsurface materials leading to the distinction of different Earth’s interior structures. The accuracy of electrical resistance imaging is strongly affected by the topographical variations so that the lack of incorporation of topography information into the inversion process may produce erroneous anomalies in the resistivity section. Owing to the significance of the topography effects on the resistivity measurements, we use a Schwarz-Christoffel transformation approach to incorporate the irregular surface into the 2.5-dimensional forward solution in the framework of the finite difference method. This approach is implemented on synthetic cases to illustrate how the resistivity measurements are dependent on the topographic irregularities. Numerical experiments demonstrate that in the presence of topographic features between current and potential electrodes, the resistivity response does not reflect the realistic resistivity values of the subsurface even in the case of a homogeneous resistivity distribution.

Optimum mud weight estimation in wellbore is one of the most important steps to prevent instability. In wellbore stability studies, media (rock) is usually assumed to be isotropic but errors occur when weak bedding planes cause the rocks to be anisotropic. In this study the effect of weak bedding plane in stability of wellbore was studied. Also, the effect of bedding plane parameters on stability of vertical and horizontal wellbore was investigated. Through the use of the geometric relations of bedding plane and wellbore, new equations were presented to calculate the attack angle. Sensitivity analysis on the dip and dip direction of weak bedding plane in the vertical and horizontal wellbore were also performed. On the basis of the porous elasticity theory and Jaeger theories, an analytical model was proposed to analyze the wellbore stability with regard to the dip and dip direction of the weak bedding plane. A code in MATLAB was written based on an analytical model and the effect of the dip and dip direction of the weak bedding plane can be reviewed. By using real data from a wellbore, a comparative analysis was carried out between the new analytical model and the intact rock failure model. Minimum drilling mud weight was calculated in two phases, without weak bedding planes, and with weak bedding planes. Results show that the existence of weak bedding planes causes more instability in the wellbore in some azimuths and deviations. The dip and dip direction of weak bedding planes have a significant impact on the wellbore stability and in the horizontal wellbore according to dip and dip direction, the optimum wellbore trajectory is different. By applying the code, geomechanical engineers can calculate the amount of mud weight based on the dip and dip direction of the weak bedding plane.