نشریه مهندسی منابع معدنی
سال ششم شماره 1 (بهار 1400)

The aim of this study was to separate the different mineralized zones consisting of supergene enrichment and hypogene zones in Milloieh porphyry Cu deposit (SE Iran) based on subsurface data and using the Staged Factor Analysis (SFA) and Concentration-Number (C-N) fractal modelling. Results obtained by SFA indicate that Cu and Mo were situated in a factor as F2-2 which was modelled by the C-N fractal method for separation of the mineralized zones. The supergene enrichment zone derived via the SFA and C-N fractal analysis contains 0.86% for Cu and 5.3 ppm for Mo. Moreover, the hypogene zone obtained by this modelling has Cu and Mo average values of 0.59% and 1.88 ppm, respectively. These mineralized zones were correlated with mineralographical data obtained by the polished section microscopic studies which indicate that the obtained zones based on the SFA and C-N fractal model are consistent with the geological and mineralization data.

Since most of the geochemical data analysis procedures require preliminary assumptions that lead to constraint and errors in the true nature of the data causing reduction in the effectiveness of the adopted methods. Therefore, a model-based clustering method as self-organizing map (SOM) were employed with the aim of recognizing Cu-Au mineralized zones by establishing an optimized exploration tool in Valezir area, NW of Iran. SOM as a dimension reduction method was introduced to recognize geochemical distribution patterns of Cu-Au with higher certainty while preserving the originality of the data. Subsequent to data preprocessing and testing different SOM architectures, an appropriate structure with a pattern containing six clusters was selected. Accordingly, the related elements distribution model was extracted and interpretation of the geochemical system represents two significant sets of elements in clusters (i.e. 1st, 2nd and 6th clusters) to anticipate the mechanism of distribution: 1- Copper and pertaining trace elements formation from intermediate to acidic hydrothermal solutions, which are localized in the northern part of the area and emplaced in the quartz monzo-dioritd intrusive body. 2- Au Anomalies and its associated elements As, Hg and Bi depicted in 2nd cluster. The Au anomalies follow geochemical pattern with Bi, Sb, As, and W that are mostly elongated from NW to SW of the area. It seems relatively the low enrichment of gold has occurred during the intrusion of the igneous body into older volcanic units that caused extensive alterations, remobilization and localization of Au and related elements. To assess the SOM results, a comparative study was carried out with the results obtained from hierarchical clustering analysis (HCA). The results illustrated higher performance by SOM approach in characterizing geochemical system and detecting the elements paragenetic sequence in the area for locating the exploration targets.

In this paper a hybrid approach of Sequential Gaussian Simulation (SGSIM) and Concentration-Volume (C-V) fractal method was applied to boreholes data for classification of major geochemical parameters and associated features with alteration zones of the Haftcheshmeh Cu deposit in NW of Iran. Thereupon, Cu parameters were detected with higher efficiency and lower uncertainty. The purpose is also extended to delineate the alteration zones pertinent to Cu mineralization. Firstly, the most straightforward simulation (SGSIM) was utilized for projecting different lithogeochemical parameters of Cu. Then the C-V fractal model was used to discriminate these parameters by thresholds, obtained from the C-V Log-Log plot. The Fractal based resulting maps of 10 realizations and their E-type indicate their association with potassic alteration that has imposed on porphyry granodiorite. Moreover, these maps illustrate that the boreholes (1, 9, 23, and 31) at about longitudes of 643400 to 643800 are more promising than others. This fact explicitly had been correlated with reality of the studied area and denoted in its primary surface map. The results based on SGSIM, C-V confirmed enhanced mineralization in three-dimensional maps of the Haftcheshmeh deposit as a powerful combined method that can be used to detect the similar ore zones in continuation of the ore roots in adjacent areas.

One of the most important issues in geotechnical studies is bearing capacity. It is also defined as the resistance when the maximum pressure is exerted from the footing to the foundation without creating shear failure therein. Since earing capacity is highly correlated with the stability of surface and subsurface structures, researchers have become interested in this subject. The area and geometry impacts on the footing are considered as the two important issues in this regard. In this research, a numerical model based on particle flow code was used in PFC3D software. To do experiments in numerical models, two triple-facet footings were utilized in square, rectangular and circular geometric shapes. Furthermore, these footings held a total area of 64 cm2 and other series included a full area of 49 cm2. In the modeling, the mechanical properties of granite were put into practice and the results of the numerical tests were scrutinized, as well. As a result, it was ascertained that the bearing capacity depends on both the footing geometry and the footing area.

In the case of explosions and fires, the rocks undergo a cycle of heating and cooling. For that, first, they are exposed to considerable heat and then cooled after extinguishing the fire. Temperature variations and subsequent contraction and expansion affect the physical and mechanical properties of rocks. Through two series of tests, the effects of temperature and the number of heating-cooling cycles on the mode I, mode II and the effective mixed-mode I-II fracture toughness of Lushan sandstone were investigated. In the first series, the effect of temperature was studied in a heating–cooling cycle at ambient temperature (25°C) and 60, 150, 200, 300, 500, and 700°C. The highest and lowest mode I, mode II and the effective mixed-mode I-II fracture toughness were, observed at 150 and 700°C, respectively. In the second series of tests, the effect of the number of heating–cooling cycles was investigated on the mode I, mode II and the effective mixed-mode I-II fracture toughness of sandstone specimens at 150°C (for hydraulic fracturing modeling) and a crack inclination angle of 45°. According to the results, the mode I, mode II and the effective mixed-mode I-II fracture toughness increased in the first cycle and decreased with increasing the number of heating–cooling cycles. As the crack inclination increased, the effective mixed-mode I-II fracture toughness of the sandstone specimens increased. The mode II fracture toughness increased up to a crack inclination angle of 45° and then decreased. Moreover, the mode of fracture changes from opening mode (mode I) at the crack inclination angle of zero degree to mixed mode (tension-shear) at the crack inclination angle of less than 28.8°. The mode of fracture changes from tensile-shear to compression-shear at the crack inclination angle of greater than 28.8°.

In this study, the effect of recycled water on the grade and recovery of lead and zinc sulfide flotation in comparison with Tap water has been investigated. The ore sample was prepared from Anguran lead and zinc mine, and the process water sample was prepared from KZG (Kimia Zanjan Gostaran) lead and zinc flotation plant. The results showed that when process water is used compared to Tap water, the recovery and grade of Galena and Sphalerite decreased. In Galena flotation, the recovery using Tap water was 3% higher than process water, and the grade with Tap water was significantly higher (8%). In Sphalerite flotation with Tap water, the recovery and grade were significantly increased (11% of recovery and 10% of grade). Investigation of the oxides in Galena and Sphalerite concentrates revealed that the number of oxides that were non-selective activated in the presence of process water is higher. This result is due to flotation reactant residues in these waters and their Precipitation on Galena and Sphalerite ores and non-selective activation of other minerals.