نشریه مهندسی منابع معدنی
سال چهارم شماره 1 (بهار 1398)

In regional exploration, various evidential exploration layers, i.e., remote sensing, geology, geochemistry and geophysics, are extracted, analyzed and integrated to delimit prospective areas for further exploration phases. In this paper, the evidential maps of host rock (elicited from Sentinel-2B satellite images), fault density and geochemical signature were fuzzified using the continuous (based on logistic function) and knowledge-driven (discretization of evidential data into classes and then assigning the same weight to the values in each class of evidential features based on expert judgment) approaches and then integrated using the fuzzy gamma and geometric average operators to generate mineral prospectivity mapping. The receiver operating characteristics (ROC) and prediction-area (P-A) plots were utilized to appraise the generated prospectivity models. The outcomes of this paper demonstrated that the prospectivity models generated with continuously-weighted spatial evidence values is superior to those of the prospectivity models generated with discretely-weighted exploration evidence data. Consequently, the former prospectivity models could be utilized to selecting target areas for further exploration of deposit-type sought in the study area.

Cu-Mo porphyry deposit of Aliabad Damak is located at 35 km southwest of Taft in Yazd province, Iran. A detailed exploration of this deposit has been carried out. The indications of mineralization on the surface can be seen as veins and contaminations of Malachite - Azurite with some Pyrite and Chalcopyrite, and rarely Chalcocite and Covellite. The mineralization took place as stockwork texture and scattered distribution. The hydrothermal solutions due to Aliabad's semi-deep intrusive body, in addition to copper mineralization, have caused severe alteration of granite and Cretaceous sedimentary-volcanic units. While the phyllic alteration has the largest extent, outcrop of potassic alteration has not been seen in the study area yet. Argillic and propylitic alteration zones are also seen in and around the phyllic alteration. According to the drilling wells in the area, potassic and propylitic alterations can be observed inside and around the phyllic alteration in depths. Magnetic and IP/RS (with rectangular and pole-dipole array) surveys have been performed in the studied area. In this research, we tried to adapt the different alteration zones with geophysical anomalies. In studied area phyllic alteration zones have weak magnetic anomaly, propylitic alteration zones are associated with mild magnetic anomaly and argillic zones have not any sign of magnetic anomaly. Relation between different alterations and chargeability and resistivity anomalies was investigated in this study. Phyllic alteration zones show low resistivity and high chargeability, potassic alteration show high resistivity and low chargeability and propylitic alteration zones represent moderate resistivity and chargeability.

The sweetening process with amine is widely used to remove acidic gases. However, this process requirement are cooling and heating energies. In addition, the reduction of energy requirements is limited by optimizing operational parameters. Therefore, changing the process parameters can lead to significant reductions in energy consumption, resulting in lower operating costs. In this study, parameters such as the amine temperature in entrance of the regeneration tower, the condenser heat load, the reboiler heat exchanger and the heat load of the rich / lean amine gas sweetening unit were investigated and the optimum temperature value to reduce operating costs and increase profitability achieved. Simulation analysis was performed using PRO II software. The comparison between the main process and the optimized process showed that the optimal temperature selection of the rich amine to the recovery tower has the ability to reduce operating costs to over $ 97704 per year, while also leading to the highest recovery of hydrogen sulfide.

The over-break and slough of walls and roof of stopes in underground mines leads to unplanned dilution and dropping in the grade. The complex mechanism of unplanned dilution resulting from the effect of different parameters and interaction between them makes it impossible to provide an unplanned dilution model with sufficient accuracy through non-system methods. In this paper, a high-precision model in which interactions between parameters are considered is presented using the rock engineering systems approach. For this purpose, after selecting 8 parameters, as the most important parameters for unplanned dilution, the steps of this method include the formation of interaction matrix, matrix coding and formation of the ranking table, the index of unplanned dilution of 24 stopes from the Venarch Manganese mines has been calculated. Subsequently, using the cavity monitoring system, the actual values of unplanned dilution of each stope were measured and from there the unplanned dilution prediction model was obtained based on the unplanned dilution index. The model, which is a power relationship, has a coefficient of 0.89, root mean square error of 0.034, mean absolute error of 0.089 and a percentage of variance of 87. In the end, using this model, unplanned dilution of 9 new stopes (other than the 24 workshops) was predicted and compared with the actual values measured. The coefficient of this prediction is equal to 0.95, which indicates the high efficiency of the model and system approach in predicting the unplanned dilution of underground mining stopes.

In many environments, rocks are usually exposed to continuous wetting and drying. The number wetting-drying cycles will exacerbate weathering and reduce the mechanical properties of the rock and due to that process, geological disasters occur. The effects of alternating wetting and drying cycles on rocks degradation have a greater impact than long-time soaking, which is a critical issue in the sustainability of rock mass engineering. In this research , sandstone specimens of Lalun Formation in Loshan area were used and the effect of wetting-drying cycles (0, 1, 4, 16 ) on physical properties including effective porosity, P-wave velocity, dry and saturated specific weight and mechanical properties including indirect tensile strength, uniaxial compressive strength, elasticity modulus, triaxial compressive strength, cohesion and internal friction angle was investigated. The results indicate that by increasing the wetting-drying cycles, Effective porosity increased but dry and saturated specific weight, P-wave velocity, tensile strength, uniaxial compressive strength, triaxial compressive strength, elasticity modulus, cohesion and internal friction angle decreased.

Experiments have indicated that the fracture properties of rocks change with variations of loading rate. In this study, the microstructural properties of two marbles are characterized by three different microscopic techniques including petrographic thin sections method, fluorescent replacement technique, and scanning electron microscopy (SEM). An experimental investigation is conducted to study the quasi-static fracture behavior in different microstructural features of crystalline rocks. The hollow center cracked disc (HCCD) method is employed to determine the fracture parameters with variations of loading rates using a hydraulic machine. Microscopic studies on microstructure deficits reveal that fractal dimension in Maroon marble is higher than in Baghat marble .Variations of toughness, crack propagation speed, and crack tip opening displacement (CTOD) with changes of loading rate are also investigated. The results indicate that toughness and crack propagation speed increase with loading rate, but the effect of microstructure in two marbles reduces the rate of growth. The fracture toughness in Baghat marbles is higher than in Maroon marble, and difference of fracture toughness is magnified with the loading rate.

In this research, the monitoring and modification of the 0-3 mm processing circuit of the Semirom fireclay factory, was investigated. The results of the identification of the samples showed that kaolinite was the main mineral, while hematite and goethite are the iron minerals. Study of the polished sections and liberation analysis showed that most of the hematite had been oxidized to goethite and specially expanded in kaolinite particles. This circuit was monitored by sampling from different streams. The effect of parameters on iron removal, including feed rate, separator speed and particle size were investigated by dry drum separator. Also experiments with a roller separator with a magnetic field intensity of 10 kilo-gauss were performed to measure the possibility of further iron removal. According to the results of the experiments and the monitoring of the circuit, a new flowsheet was proposed by adding the roller separators to process the tail of the first series of the plant separators as well as the final product, which allows the decrease of product Fe2O3 grade to less than 1% and a 5% increase in the overall yield.

Tumbling mill liners transfer the energy to the mill charge and have a significant effect on the load behavior. A plant audit at the Sarcheshmeh_copper complex indicted that due to the inappropriate design of ball mills liners the liners wear and tear increased and the grinding efficiency decreased. With the objective of investigating the design of initial, current and proposed liners, the simulation of charge trajectory was performed by the GMT and KMPCDEM software packages. It was observed that the charge impact point for the current liners design was above the toe and on the shell liners. By simulation it was found that increasing the liner lifter face angle from 0 to 15° and the lifter height from 18 to 21cm could decrease the difference between the impact point and the toe and direct balls impact to liners. Given the promising results, the new liners were designed, constructed and installed in the ball mill 4. The result of sampling for a period of one liner life indicated that the amount of particles smaller than 75 microns for ball mill 4 product (proposed design) compared with the ball mill 3 (current design) increased by 2.5% and the liners life of the first half and second half increased by 18% and 20%, respectively.