میرصالح میرمحمدی

One of the most crucial steps in ore exploration is the recognition of geological patterns and features. These features contain mineralogy, lithology, alteration, rock texture, etc. This stage has always been associated with many challenges. Among the challenges of this stage, we can mention the time-consuming and costly nature of this stage and the need for high expertise and human resources to recognize these patterns and features. In recent years, deep learning and machine learning have been adopted in earth sciences. In this research, by using the architecture of U-net, ore and waste were separated, and the grade pattern was identified using the core box images. For this purpose, iron minerals were segmented using binary image segmentation, trial-and-error methods were used to optimize the network, and finally, the model's accuracy for identifying ore was 91%. The IoU metric was utilized for further evaluation; this metric is a suitable criterion for the final evaluation of the image segmentation model, which has reached 75% in recognition of iron ores. For the final evaluation of the obtained model, the grade outputs of the model and the XRF analysis results of one core were compared. The network error was evaluated at 9%, which shows the good accuracy of the obtained model according to the real data.

In this study, microbial leaching of nickel from two arsenide ores (low-and high-grade samples) was precisely investigated. The microbial leaching of nickeline was accomplished with the admixture of mesophilic (Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans) cultures in shake flasks with pulp densities of 0.5, 1, and 5% for low- and high grade samples. The nickel content was over 99% dissolved by mesophilic bacteria of low-grade and high-grade samples after 10 and 28 days respectively at two 0.5% and 1% pulp densities, while the nickel content of the chemical and abiotic control tests was much lower than biotic tests (about 6.9% and 26.7% for low-grade, 10.3% and 16.9% for high-grade). This study marks the inaugural utilization of heterotrophic bacteria in such dissolution processes. Evaluation of three bacterial strains, (Bacillus cereus, Glutamicibacter nicotianae, and Bacillus zhanghouensis), revealed their proficiency in nickel dissolution from nickeline samples across a range of solid percentages (0.5%, 0.8%, 1.1%, and 3%). Notably, Glutamicibacter nicotianae demonstrated superior dissolution capabilities compared to its counterparts, resulting in 100% nickel recovery from low-grade samples and 70% recovery from high-grade samples. Control leaching experiments corroborated these findings, albeit with notably inferior dissolution rates (0.33%). Characterization of remaining samples and microbial activity was conducted through various analytical techniques including SEM-EDS, FE-SEM, and XRD analysis. The catalytic effect and galvanic interaction of different additives on the dissolution of the samples were investigated so that for the solid density of 50 grams per liter of low and high-grade samples, a specific amount of pyrite (0.75 g/L), graphite (0.8 g/L), L-Cysteine (0.48 g/L) and silver nitrate (0.0504 g/L) were added to the medium. In the low-grade sample, the nickel dissolution, all four additives in both low-grade samples with iron (II) and sulfur additives and without iron (II) and sulfur additives showed a positive efficiency so that the dissolution rate exceeded 90% on day 28. In high-grade, three of the four additives (silver-pyrite and L-Cysteine) in the high-grade sample without iron (II) and sulfur additives had a positive effect on the dissolution of nickel, and were able to increase the recovery to over 90% after 28 days, in the sample with iron (II) and sulfur additives, three additives (pyrite, silver, and L-Cysteine) had the greatest, but in the presence of iron (II) and sulfur was not benefiting but also reduced the recovery below 90%. That can be due to the high concentration of elements in the culture and its negative effect on the preformation of bacteria. In this study, mesophilic bacteria, by forming and depositing secondary arsenic minerals such as scorodite and jarosite, prepared the environment for their continued activity, which was also confirmed in the XRD analysis results.

The reprocessing tailings of iron ore processing plants is important from economic (as a secondary source of iron) and environmental points of view. The aim of the present study is to determine the appropriate method for recovery iron from the tailings of Balestan iron ore processing plant (located in the northwest of Iran). For this purpose, after taking samples from the tail piles of this plant, a representative sample was selected, and chemical, mineralogical, size distribution, and bond’s work index analyses were performed on it. The total iron grade in the tailings was measured to be about 10%, of which 8.5% was identified as magnetite mineral (with a degree of liberation less than 40%). The d80 value of the sample was 7 mm, and the bond index was measured as 11.84 (kWh/ton). To determine the appropriate method for iron recovery, pre-processing with magnetic drum, grinding, and Davis tube tests were performed. With the magnetic pre-processing of tailings with a particle size of 0-10 mm, under a field of 2000 G and in a dry method, about 80% of the load entering the drum with a total iron grade of 5% was transferred to the tailings. 20% of the input load with an iron grade of approximately 24% was recovered to the concentrate. In order to remove the gangue minerals and enrich the pre-processed concentrate, stepwise grinding and separation had the best results. Comminution was done in two stages to produce products with smaller dimensions of 250 and 45 microns, respectively. Magnetic separation was also done in three stages with 3000 G, and two stages of separation with 1000 G, which finally resulted in a concentrate with a total iron grade of more than 66% and iron recovery of 44.88%.

There are important deposits such as Sari Gunay epithermal gold, Dalli porphyry copper-gold, and Zarshuran Carlin deposits with a few common exploration features in the Zagros metallogenic province of Iran. This study used geological maps, remote sensing, geochemical, geophysical, mineralogical, petrographic, fluid inclusion and age dating information to characterize and identify exploration criteria of these deposits. Mineralization at Sari Gunay gold deposit is epithermal, which was formed in association with an alkaline magma and brecciated, altered dacite porphyry about 11 Ma. Mineralization at Zatshuran is Cralin with black shale and carbonate sedimentary hosts, formed indirectly in association with a deep alkaline magma about 14 Ma. Mineralization at Dalli deposit is copper-gold porphyry with diorite host, formed in association with a chalk alkaline magma about 21 Ma. Despite different host rocks, mineralization at Zarhuran and Sari Gunay gold deposits reveals some similarities. Among the common exploration criteria in the two deposits are Oligo-Miocene alkaline magma, mineralization depth of more than 300 meters, northeast trending structures, gold, arsenic and antimony geochemical association, presence of iron oxides such as jarosite and hematite, vuggy breccia textures, and silica and phyllic alteration hosting gold minerlization. The most important exploration criteria at the Dalli deposit, however, are Miocene chalk alkaline magmatism, depth of mineralization of more than 500 meters, strong potassic and phyllic alterations, presence of specularite mineral, northeast trending structures and strong high magnetic anomalies, associated with potassic alteration.

Khoy ophiolitic complex in northwest of Iran have several chromitite bodies with various textures, different geochemical features and associated minerals. Based on Cr#, Khoy chromitites are divided into two groups: high-Cr (Cr# > 0.6) and high-Al (Cr#

Composition of the Kiyamaki dome has mostly dacite and granodiorite in rims, with SiO2 contents ranging from 64 to 73 wt% and Mg# values ranging from 27 to 57. These rocks are high-Si adakite. Geochemical characteristics and Sr and Nd isotopic rates indicate that the rocks of Kiyamaki dome are a post-collisional adakite. Combined geochemical and Sr–Nd isotope data suggest that the Kiyamaki adakitic magma derived from partial melting of mafic rocks in the lower part of a thickened crust. So, with attention to tectonic setting and source of derived adakitic magma, age of Eocene to Miocene for generation and closing time of Neo-Tethys (Middle Miocene), it is not possible that generation of Kiyamaki adakites be directly related to geodynamical evolution of Neo-Tethys. Here, with suppose of age information for generation of Kiyamaki dome and closing of Neo-Tethys,formation of domes in the northern part of Tabriz fault can be related to the collision of Sanandaj-Sirjan micro-continual with Alborz-Azarbaijan block in Paleogene that was happened due to subduction of oceanic crust of Khoy-Zanjan basin toward beneath of Alborz-Azarbaijan block.

Kahang porphyry copper deposit is located in Isfahan Province, in the middle of Urmia-Dokhtar Magmatic Belt. Based on field investigations and petrography of thin sections and core samples, igneous rocks in eastern part of the deposit are divided into three types of host-rocks, source and mineralizing rocks, and post-mineralizing barren dikes. Quartzdiorite has formed more than 70 percent of the main mineralizing stock. Geochemistry of volcanic and plutonic rocks shows that these rocks have formed from a single Calk-Alkaline magma that has produced various igneous rocks by differential crystallization. With increasing Si oxide, Na2O and K2O linearly increase, and FeO, MgO, CaO, P2O5, Al2O3 and TiO2 linearly decrease. Trace elements including Rb, Th, Ba and La, as well, with increasing SiO2, linearly increase, Sc, Yb, Ni and Y decrease, and Ce has a constant trend. The main alteration types in the deposit are Potassic, Phyllic, Quartz-Sericite, Propyllitic, and Argillic. Biotite is the major product of potassic alteration, and hydrothermal alkali feldspar could only be observed in depths greater than 730 meter. Fluid inclusion studies on mineralized quartz veins in Potassic zone confirm that Cl-bearing saline fluids have carried Cu, and porphyry mineralization has formed in a temperature, pressure and depth of about 415 ºC, 340 bars, and 1.3 km, respectively. Boiling and fluid cooling in A2 and B veins are the main controlling factors in precipitation of chalcopyrite in Kahang PCD.

The Heydarabad bauxite-laterite deposit is located in 63 km southeast of Urmia city.This ore deposit occurs as a concordant layer within the boundaries of Upper Permian and Lower Triassic carbonate units (limestone and dolomite), although it has been suffered some tectonic displacements along its direction. The studied horizon varies from 15-20 m in thickness and has an east-west trend with a length of 3.5 km. This deposit consists primarily of two parts of dark and light in color. The former is rich in hematite and corundum, (upper horizon) and the latter in phyllo-aluminosilicates (lower horizon) with an gradual boundary, respectively. Common textures are mostly pisolitic, nodular, oolitic and massive. Based on the microscopic studies and XRD analysis, the main mineral components are hematite, diaspore, chloritoid, and corundum.On the other hand, chlorite, rutile, magnetite and pyrite are found as accessory phases. The Heydarabad bauxite-laterite horizon is different from those occurred into the Iran-Himalayan belt based on the absence of boehmite, kaolinite and other clay minerals, and the abundance of corundum, chloritoid and chlorite. The geological and mineralogical evidences indicated that a thermal metamorphic event was responsible for the formation of this special mineralogical composition after bauxitization processes. Based on geological, mineralogical, and chemical characteristics, it can be proposed that the probable parent rocks for the Heydarabad bauxite are mafic sills and diabasic dykes. Due to considerable accumulation of minerals which their hardness is greater than 6, this ore deposit can be presented as a potential for abrasive applications.

The chromite deposits of Aland (Barajok and Kochak villages) and Gheshlagh area in the Khoy ophiolite occur as layered, lenticular or irregular masses, surrounded by dunitie and harzburgites. These chromites are compositionally similar to alpine-type chromites, characterized by nodular, massive, disseminated and banded textures. EMPA data show that they vary widely in term of Cr-number [100Cr/Cr+Al]. On average, Cr# of chromites in harzburgites is 45.13, in disseminate Gheshlagh and Barajok chromites are 40.58 and 58.12 respectively but in Barajok and Kochak Chromitites are 66.7 and 73.43 respectively. The chromite composition in terms of Cr#, Mg#, Cr2O3, Al2O3, Fe2O3, MgO and TiO2 contents as well as correlation coefficients between different oxides, these chromits are comparable to podiform chromitites. The compositions of chromitites from Aland area with Cr#>66% and Gheshlagh area with Cr# about 40 wt% fall within high-Cr and high-Al types respectively. According to TiO2, Cr2O3 and Al2O3 content of the samples, it seems that the Aland chromites were formed from boninitic magmas in a supra-subduction zone although the Gheshlagh chromites were formed from tholeiitic magma in a geotectonic setting similar to the MORB.

Qareaghaj mafic-ultramafic intrusion (QMUI) is located in northwest Iran, 36 km NW from Urmia city. The QUMI is composed mainly of non-mineralized mafic and Fe-Ti-P-rich ultramafic rocks (FTP). The mafic rocks, mainly coarse-grained gabbro, microgabbro, metagabbro and ortho-amphibolite, have simple mineral assemblage (plg + cpx + ilm). Based on field observations, petrography and geochemistry, they are directly related to each other (comagmatic). The FTP forms numerous layers and sill-like bodies, ranging in thickness from ~5cm to several meters. These rocks with high proportions of olivine, apatite, ilmenite and magnetite, show unusual bulk composition (e.g., SiO2~21-30 wt%, Fe2O3t ~ 26-42 wt%, TiO2~5-11 wt%, MgO~9-20 wt%, P2O5 up to 5.1 wt%, Cr~40-160 ppm, Ni~7-73ppm, ∑REE~10-340ppm). The FTP totally included by mafic rocks with sharp and concordant contact shows magmatic lamination and follows general NW-SE trend of the QMUI. Field relationship, petrography and geochemical data suggest that the FTP is not related to mafic host rocks and indeed intruded later into gabbros during plastic, high temperature deformation in local shear zone.

Detailed studies on micro-texture and microprobe analysis of Fe-Ti oxides from Qareaghaj mafic-ultramafic intrusion (QMUI) is the basis of this investigation. The QMUI is mainly composed of non-mineralized mafic and Fe-Ti-P-rich ultramafic rocks (FTP). The FTP with high proportion of ilmenite (~11-19 modal %) and magnetite (~2-13 modal %) show an unusual bulk composition. Fe-Ti oxides are divided into three distinct generations on the basis of their micro-texture: 1) small-sized rounded to ellipsoid-shape inclusion in olivine and clinopyroxene, 2) coarse interstitial grains and 3) late stage veinlets. The ilmenite grains (0. 1-2mm) commonly contain fine hematite lenses arranged in [0001] planes. Primary Ti-magnetites contain ilmenite lamellae along the [111] planes and exhibit wide variety of exsolution textures (e. g., trellis- and sandwich-types). Ilmenite in FTP show Xilm range from 0. 82-0. 91 and has high MgO (0. 82-2. 38 wt %). Most Ti-magnetites (bulk composition) have low Xusp (0. 03-0. 13) and therefore high Xmag (0. 79-0. 93). Two oxide geothermobarometer in the ILMAT program, resulted in re-equilibration temperature range of 450-700ْ C and ƒO2 (nearly -19±3) during subsolidus cooling for FTP rocks.