فصلنامه مهندسی معدن
پیاپی 47 (تابستان 1399)

Kordagan 1:100,000 sheet is located in the northern Lut structural block and in South Khorasan province. In this area, mineralogy is mainly a vein controlled by fault structures with a northwest-southeast trend. In order to improve the results of the exploration, three solutions were used. To eliminate interfering elements and obtain clean factors in the multivariate statistical technique of stepwise factor analysis (SFA) was used. In addition to eliminate ineffective elements in the calculations, the elements that were not related to vein-type copper mineralization were also excluded. Finally, using the GMPI method, the obtained anomalies were intense. During the exploratorion operations in the Kordgan region, 836 stream sediment and 30 duplicate samples were taken. The samples were analyzed by ICP method by the Geological Survey and Mineral Exploration of Iran. Through the SFA in three step, the elements Ag, Ni and Cd were omitted from factor analysis calculations. In the next step, the elements Co, Cr, Fe, Mn, Sc, Ti, V, Zn, Sr, and W, which did not correspond to vein-type copper mineralization, were removed and factor analysis was prformed again. The results classified the elements into three factors, which were integrated and classified by GMPI method. Based on the results, eight favorable exploration areas were detected. These area was entirely compatible with the former investigation and also faults and favorable geological units for veins reserves such as Andesite and Andesitic tuff with Eocene age. It seems that the applied methods, by using multi-elemental geochemical signatures and integrating them appropriately, can identify and deduce anomalies consistent with other exploratory evidence.

Improvement of the value chain of mining and mineral industries requires a lot of investment. Considering the current condition of the country, this cannot be achieved just by the public budget. One possibly effective approach in financing is the participation of public and private parties is Public-Private Participation (PPP). In order to apply this method to the mining projects, it is necessary to identify factors effective on success through studying and analyzing other countries' experiences and experts' solutions. In this manuscript, in order to identify and prioritize factors effective on PPP success in mining projects, previous researches and papers were studied, success-factors identified and several questionnaires prepared and were given to the experts in order to prioritize them. Then, the results were ranked using Friedman Test. The results of this research showed that through different factors, "defining the appropriate project" has the highest importance on the success of PPPs. Next important ones are payment mechanisms, proper contracts, appropriate political and social environment and legislating new laws, respectively.

One of the most important goals in minerals exploration is the identification of mineralization areas. Since gold is considered as the financial support of the countries, this is one of the important requirements in identifying and evaluating these types of deposits. Therefore, samplings and exploratory studies should be designed in such a way that the risk of exploratory operations is minimized. The mineralization of gold in the Kurdistan region of Iran, located in the Sanandaj-Sirjan zone, has been categorized as a shear zone gold type. In order to optimum separation of gold mineralized anomalous areas, it is necessary to carefully investigate the characteristics of the sub-population. In this research, for the purpose of a more accurate investigation of these characteristics and improvement of results, the discriminant analysis method was implemented on the probability plot modeling results. For this purpose, the stream sediment samples for 21 geochemical variables (Zn,W,...) was used. Initially, by modeling the probability diagram, four sub-population were identified among the data of the gold element, and by analyzing the model, were estimated approximate background and anomaly limits. Subsequently, each of these sub-population is allocated code. By the use of the discriminant analysis, DA, method was classified the data with three discriminant functions, DF, consisting of 6 variables (Ag, Au, Co, Mn, Mo, V) that have the greatest effect in classifying the samples. In order to validate functions in classifying the population, were used the original methods and cross-validation. With this validation the areas were categorized with the correctness 87% and 83%. The results of DFM on the probability model can be used to optimize the exploratory operations and classifying new exploratory data to the background or anomaly using the six geochemical parameters mentioned above and it can be an effective guide to the subsequent stages of exploratory operations.

Trucks are the main hauling machinery in open pit mines. High capital and operational cost requires accurate management and high efficiency of this equipment, this circumstance depends on the accurate understanding of the system and its behavior in different operating conditions. “Importance measure” approach is one of the useful methods that prioritizes system or implement it from different perspectives such as up and down time aiding the engineers for better decision making about management and resource allocating. Reliability, availability and maintainability (RAM) importance measure are combination of system behavior and importance, that by analyzing up and down time prioritizes and detection bottleneck of system. In this paper, a comprehensive approach based on availability importance measure for increase performance of a truck from Golgohar mine has been suggested. In this truck, transmission and body subsystem are identified as most and least important subsystem from availability point of view respectively. Also, transmission maintainability has major contribution for increasing system availability.

DTH drilling is a reliable method for drilling in medium to hard geological structures. Considering the country's need for different types of drilling bits in various industries, with development of knowledge and production of them, it can limit the vast importation of these products. In this study, process of bit/rock collision taking into account interaction between the insert/body and stresses resulting from interference fit is simulated to determine proper tolerance for fitting, which is the most important factor limiting the life of drilling bit. Simulations were carried out taking account rotary motion of bit in addition to impact in single-insert condition with different angles of collision and also in a 3.5 inch bit with 13 inserts. Mechanical properties of specimens made of DIN1.6580 steel, used for manufacturing of bit body, were obtained through experiments. Then, in order to validate and also obtain appropriate mesh size, results of pin-hub interference fit simulations with selected parameters were compared to Lame's analytical method. Results show that interference tolerance and speed and angle of impact have great influence on stresses and process forces. In case of 1.2% of interference, stresses in bit body are about to reach material strength. In the case of 0.9% and 0.6%, certain amount of plastic strain is also created in the body. The results of this study is greatly helpful in choosing fitting tolerance of inserts into bit body during manufacturing process.

In this study, the modeling of vanadium, nickel and copper bioleaching from fuel oil ash ash using artificial neural networks was investigated. In the obtained models, the extraction percentage of metals was investigated as a function of factors such as initial pH (from 1-2.5), initial Fe2+ concentration (from 0 – 9 g/l), initial bacterial inoculation (from 1 – 10%) and process time (from 0-15 day). Three neural network models were presented to estimate the extraction percentage of metals. The propagation error method and Levenberg–Marquardt algorithm were used for training. Furthermore, trial and error method was used to determine the optimal number of neurons. One quarter of the data were used to evaluate the model and were not used for training process. The Mean Relative Errors (MRE) were obtained 5.35%, 3.07% and 2.82% for V, Ni and Cu, respectively. Also the higher 0.99 of R2 indicates the validity of the obtained models.

Nugget effect is a common feature of many vein-style gold deposits. This style of mineralization results in complication in many exploitation stages including resource and average grade estimation, representative sample selection, ore characterization as well as processing. Accurate and reliable ore characterization is a vital stage in any mineral processing project. Ore characterization in high nugget effect gold ores is so complex due to uncertainties associated with representativity of the selected sample. The main challenge is to provide a representative sample for identification of each process mineralogy parameter such as average grade, liberation, grinding size, mineral association, floatability, etc. Here, different protocols are collected and compared to draw a comprehensive picture of the available methods. The results are examined on a high nugget effect gold ore from Northeast of Iran, Azghad mine. Processing experiments were conducted to develop a process suitable for Azghad gold mine. To investigate the feasibility of pre-concentration, gravity methods using a Nelson separator was applied on the oxide sample as the main gold vein. 43.3% of total gold was concentrated in the gravity concentrate with only 2% weight recovery, suggesting gravity concentration can be considered as an efficient method in this ore. Gold preg-robbing experiments were performed for Shale sample due to the organic matter, clay minerals and mica. Preg-robbing potential of the shale ore was determined to be 1.1 ppm. Optimization of operating parameters was performed by central composite design method for the combined oxide and shale samples.