نشریه مهندسی منابع معدنی
سال دهم شماره 1 (بهار 1404)

The Zafarghand area is located as a porphyry Cu deposit in the northeast of Isfahan and the southeast of Ardestan, which is a part of the Iran-Central structural zone; More precisely, it is located in the Urmia-Dokhtar volcanic belt. In the porphyry Cu deposits exploration, identifying and determining the alteration zones is of special importance. The aim of the present study is to identify and highlight the alteration zones of Zafarghand area, with the help of fractal geometry in the processing of ASTER sensor satellite images. Accordingly, considering the raster nature and digital form of satellite images, the digital number values of each pixel from the image matrices were considered as samples in a systematic network. Finally, the algorithm of the Concentration-Area (C-A) fractal model was implemented as an efficient method for determining anomaly samples in the set of digital number (DN) values of ASTER satellite image pixels. The alteration zones identified with the help of the aforementioned technique based on their expansion in the region represent the very effective performance of this method. So that, especially in the case of phyllic and propylitic alterations, there is a very high correspondence between the results of satellite image processing and the spread of alterations in field studies. The non-identification of potassic and argillic alterations in the obtained results is also directly related to their limited expansion in the study area. Finally, it could be acknowledged that the application of the fractal C-A method (considering its structural nature) in decision-making has been successful and has proven to be very effective in determining the alteration zones in the Zafarghand area.

This study aims to use the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) remote sensing data to identify promising areas and design a targeted preliminary survey in the Karijgan area located in Khosuf-Birjand. Therefore, at first, necessary pre-processing, such as atmospheric and topographic corrections, was applied to the data. Then, from conventional processing methods on multispectral data, including band ratio, principal component analysis (PCA), and its improved type, the selective principal component analysis method (CROSTA), promising areas were identified. In this case, by using the band ratio method, index areas prone to iron oxides, silica, carbonate, chlorite and epidote, alunite, kaolinite and pyrophyllite, sericite, muscovite, illite, and smectite were identified. Also, with the Crosta method, various types of main alterations (propylitic, argillic, and phyllic) were determined. Finally, by combining the results, promising areas were identified for preliminary surveys. A check field and sampling of the identified areas were done to validate the processing results. The results of the sample analysis by ICP-OES and X-ray diffraction (XRD) showed good agreement and accuracy with the results obtained from the remote sensing processing of the Karijgan area.

In longwall mining, after extracting each slice from the coal seam and advancing the face, a severe stress concentration is formed in the vicinity of the roof and coalface due to the stress disturbance and also the caving of the immediate roof, which resulted in roof displacement, cracks propagation, and roof failure. Due to the caving of the immediate roof and the displacement of the overburden layers by face advancement, there is a possibility of propagating the fractures and instability of the roof in the coalface. The roof failure in a longwall face will bring adverse consequences such as the stoppage of mining operations, damage to equipment, injuries, and fatalities. In this research, the critical events that are effective on the roof failure in the E3 panel at the Tabas coal mine were identified, and the risk of roof failure was evaluated using the fuzzy event tree analysis approach through filling out the questionnaire by the mining experts and faculties. In this way, ten scenarios were examined to analyze the risk of roof failure by checking the roof failure or non-failure, and then the probability of critical events was calculated. Based on the results, the probabilities of roof failure in the fourth, tenth, and seventh scenarios are respectively 5.68, 4.21, and 1.70 percent, and the risk values in these three scenarios are respectively 28.42, 21.05, and 8.51. Therefore, the most critical scenario in this research is the fourth one, in which the preventive measures should be taken through the timely control of critical events to reduce or prevent the risk of roof failure.

In this research, the possibility of producing building bricks from the shale reserves of Lorestan province has been investigated. Sampling was done in six different areas, and after conducting XRF tests, one sample was selected for brick production. 10 different combinations of bricks with different percentages of shale were made from the selected sample. Compressive and bending strength and water absorption tests were performed on the manufactured samples. The results of the tests showed that with the increase in the percentage of shale, the amount of water absorption increased, so that the samples consisting of 90 to 100% shale had 14.8% water absorption. The sample containing 10% shale has a water absorption rate of 11.1%. Also, the results showed that increasing the percentage of shale decreased the compressive and bending strengths of bricks. The sample with the highest compressive strength, with a value of 27.2 MPa, corresponds to the sample containing 10% shale, while the compressive strength of the sample containing 100% shale is only 11.2 MPa. Based on the INSO-7 (Iranian national standard), the manufactured bricks are of good quality and can be used as building bricks and facing bricks in buildings.

As the main resource of zinc metal production, zinc sulfide mineral has poor sulfuric acid dissolution due to an inactive sulfur layer. This research has done a comparative study on the mechanism and kinetics of acid leaching of sphalerite concentrate in the presence of iron salts such as nitrate, chloride, and iron sulfate. For this purpose, studies were done on a sphalerite concentrate containing 41.23% Zn, 26.15% S, and 6.06% Fe. The investigated parameters include ferric ion concentration, sulfuric acid concentration, temperature, time, solid-to-liquid ratio, and oxygen injection rate, each evaluated at 5 levels. The results indicate that the parameters of temperature, solid-liquid ratio, and ferric ion concentration had the greatest effect on the sphalerite dissolution rate. In the optimal conditions of sulfuric acid concentration 0.51 M, ferric iron 0.9 M, oxygen injection rate 2 L/min, reaction temperature 90°C, time 12 h, and the solid-to-liquid ratio of 50 g/L, recovery of zinc was obtained to be 94.85%. Kinetic investigations showed that, based on the shrinking core model, the sphalerite leaching rate control is based on the diffusion mechanism due to the high correlation coefficient compared to the chemical reaction mechanism.

Today, the reprocessing of mineral processing plant tailings is important from an economic point of view (as a secondary source of valuable elements) as well as environmental issues. The purpose of this research is to characterize the flotation tailings of iron concentrate lines 5, 6, and 7 in Golgohar and their pre-processing in order to maximally separate copper and iron minerals and increase their grade. Therefore, after preparing representative samples from flotation tailings, instrumental chemical analysis, particle size analysis, and microscopic studies were performed on them. Then, using magnetic separation and classification methods, iron and copper separation and enrichment were done. The characterization results of the tailings showed that its main minerals are pyrite, magnetite, and talc, and the iron and copper grades are about 30% and 0.11%, respectively. The results of the pre-processing tests showed that by performing magnetic separation at a field intensity of 2000 Gauss, the grade of iron in concentrate and copper in the tailings increased to 47.8 and 0.18%, respectively. By adding a classification step before magnetic separation and discarding the coarse-grained part of the sample and then performing magnetic separation on the fine-grained part (-38 microns) in the field intensity of 2000 Gauss, the grade of iron and copper in the concentrate and tailings, respectively, is 53.6 and improved by 0.21 percent. Therefore, pre-processing can return the iron in the flotation tailings as an intermediate product to the iron concentrate production circuit and prevent its wastage. On the other hand, by discarding more than half of the flotation tailings, increasing the copper grade, and reducing iron in the rest, this operation created many technical and economic benefits for the copper extraction process in the next stages. Classification and magnetic separation methods are operationally simple and cost-effective and can be implemented in lines 5, 6, and 7 of Golgohar with minimal changes and costs.