نشریه زمین شناسی کاربردی پیشرفته
سال دوازدهم شماره 45 (پاییز 1401)

The Zajkan base (± precious) metal deposit is located in the Tarom-e-Sofla part of the Qazvin province, and is part of the Tarom-Hashtjin metallogenic belt (THMB). The THMB has been documented as one of the most important epithermal metallogenic belts in Iran (Ghorbani, 2013; Kouhestani et al., 2018) that host numerous epithermal precious and base metal deposits (i.e., Rashtabad, Gulojeh, Aqkand, Aliabad–Khanchy, Chodarchay, Khalyfehlou, Chargar, Lubin-Zardeh, Marshoun, Abbasabad, Zehabad, and Shah Ali Beiglou).Mining at Zajkan started around 1970 and continued to the beginning of 1980s. Recent exploration work at the Zajkan deposit started from 2017 by Roy Godaz Company, and the deposit is still under exploration. In this paper, we present detailed geology and mineralization characteristics of the Zajkan deposit along with geochemical and fluid inclusions data to investigate ore genesis of the deposit. These results may have implication for the regional exploration of epithermal deposits in the THMB.

In this research biostratigraphy of the Eocene deposits of the Eastern margin of Lut Block based on calcareous nannofossils in Alanj stratigraphic section was investigated to determine the biozones and finally exact age of these deposits based on them.The Eocene deposits in this stratigraphic section are about 633 m thickness, and lithological composition mainly contain shale and marl with intercalations of sandstone and sandstone unites. According to taxonomical studies, 45 nannofossil species belong to 20 genera in Alanj stratigraphic section were identified and photographed. Based on the identified species, in north Alanj stratigraphic section biozones were divided as follows:Discoaster binodosus Zone (NP11), Tribrachiathus Orthostylus Zone (NP12), Dicoaster lodoensis Zone (NP13), Discoaster sublodoensis Zone (NP14), Nannotetrina fulgens Zone (NP15), Discoaster taniinodifer Zone (NP16), Discoaster saipanensis Zone (NP17), Chiasmolithus oamaroensis Zone (NP18), Isthmolithus recurvus ZONE (NP19) According to the identified biozons, the age of this sequence, Ypresian (early Eocene) to Periabonian (Late Eocene) is suggested for the studied thickness

Many researchers have studied subsurface stratigraphy by approaching three-dimensional geological models in recent decades to overcome the complex nature of the subsurface. In many urban areas, specific three-dimensional spatial models have been developed that are used to predict land conditions, reduce risk, and uncertainty in urban planning. In this study, geological, geotechnical and geophysical analyzes were used based on data collected from 20 geotechnical boreholes and 29 geoelectric soundings around Zarand wide. Having statistically geotechnical and geophysical parameters of the soil estimated (such as liquid limit LL%, plasticity index PI %, moisture content w%, dry density γd, soil shear strength parameters of C and ϕ◦, modified standard penetration resistance N (60) and electrical resistance of the ground Ωm) and using the weighted moving average interpolation method (kriging), two-dimensional maps and three-dimensional spatial distribution of soil properties were prepared by which the problematic soils were identified. The results of spatial distribution and trenches to a depth of 15 meters show that the soils of Zarand are of Cl, CL-ML, SC, SC-SM and ML. According to the classification maps of the dominant soil texture and density as well as ASTM regulation (2002), these soils are in the range of medium collapsibility. In addition, regarding classification map of soil corrosion obtained from moisture content and the same electrical resistance levels of the ground to an average depth of 4 meters, surface soils were mainly located in the range of moderate to high corrosive according to BS-7361 and ASTM STP 1013 standards.

The Qarkhotlou bauxite deposit occurs as a semi-continuous horizon situated along the parallel unconformity surfaces between Ruteh and Shemshak Formations. Based on color, facies and textural features, three distinct bauxitic facies are distinguished in the Qarkhotlou deposit, which is, from bottom to top include: (1) lower red-brown pisolitic bauxite, (2) middle red bauxite and (3) upper brick-yellow bauxite. Hematite, goethite, boehmite, diaspore, kaolinite, and pyrophillite are the major mineral components in the Qarkhotlou bauxite ores; muscovite-illite, anatase, rutile, and chlorite are minor minerals. Petrographic observations indicate that panidiomorphic, microgranular, pelitomorphic, pisolitic, and oolitic are the main texture-forming components in the Qarkhotlou ores. These ore textures suggest that the bauxite material has an authigenic origin. However, the existence of clastic assemblages in the pelitomorphic matrix, as well as flow and breccia textures of the ore indicate that the bauxite at Qarkhotlou was locally experienced transportation and re-deposition. Geochemical data indicate that the Qarkhotlou bauxite deposit has bauxite and bauxitic clay compositions, and suggests that trachy andesibasalt lavas are the main component of their parent material. This data reveals that the bauxite horizon at Qarkhotlou formed in pH of 4 to 7 and Eh of 0.4 to 0.6 and experienced a moderate degree of lateritization. The bauxite samples and trachy andesibasalt lava show similar chondrite-normalized REE patterns indicating that they are genetically related. The petrographical, textural and geochemical studies of the Qarkhotlou deposit indicate that this deposit can be classified as Mediterranean karst bauxite.

The study area is located in the central Alborz region, 36.5 to 37 north latitude and 50 to 51 east longitude of the Greenwich meridian. The objectives of this study is to identify the structural lineaments in the study area, using aerial magnetic data and investigate the tectonic relationship of magnetic lineaments with hidden faults. Aerial photographs, satellite images, existing maps including topographic maps and geological maps were studied to determine the main structures. The location of the previously identified faults was reviewed and using aerial geophysical maps, the structural lineaments of the area were visually extracted using the Geosoft software version 1.1 Oasis montaj 4.1 (Geosoft). The maps of magnetic lineaments, and the maps of the magnetic stress nodes were matched Using the Geographic Information System (GIS) and the overlap method, the maps of the surface epicenter. Two methods of combination and analysis of magnetic stress nodes and magnetic lineaments were used for identify the hidden faults in the region. The location of the lines or linear zones that common to all three maps indicates the location of new surface faults and old faults, and the rest of the lines are hidden faults. Based on this, structural hazards, hidden faults and seismic springs were identified.

In recent years, exploration methods based on studies of alterations due to hydrocarbon leakags from reservoir to the surface have been considered. Since these leaks occur as vertical chemnies upon the oil traps, these seeps have a relative adaptation to the position of hydrocarbon reservoirs. The purpose of this study was to process and interpret the geological, remote sensing, surface geochemical exploration data of Moghan sedimentary basin and then match the results of these data with possible hydrocarbon rich areas. In remote sensing studies, band ratio methods, RGB color composition and principal component analysis were used to identify ferrous iron, carbonate replacement by gypsum and clay minerals alterations. Also, surface magnetic anomalies were identified by applying analytical signal analysis, first derivative and continues highpass filter on ground magnetic data. Adaptation of concentration of positive geochemical anomalies first to the anticline layer and then to the combined faults and anticline layer showed that alteration of carbonate minerals and illite were the most significant altered zone observed upon the anticlines, and Ferrous iron and the surface magnetic anomalies are the least of them. Also, the concentration of positive geochemical anomalies on the anticline is higher than the area without anticline and if the faults are used, this concentration will almost double. It proves the possible leakage of hydrocarbons from the reservoirs to the surface and the creation of geochemical anomalies above them. This finding can help to locate the approximate location of underground reservoirs and significantly reduce the cost of drilling operations.

Shurab Kabir manganese deposit is located 60 km northeast of Shahrekord, the center part of Sanandaj-Sirjan zone. The oldest rocks include metamorphic shale, sandstone, limestone and dolomites of Permian. Permian units have been thrusted on the younger units (Jurassic shale, sandstone, and conglomerates with andesitic intercalation) by trust faults. Mineralization has occurred at sedimentary and metamorphic units as veins, masses and stockwork. The mineralization contains pyrolusite, psilomelane, manganite and goethite, hematite, magnetite with calcite and quartz. Alterations is carbonate and siliceous. The primitive mantle normalized pattern of REE indicates negative Ce anomaly due to oxidation and acidic environment, and a weak negative Eu anomaly due to the distance of hydrothermal fluid from the origin. also primitive mantle normalized pattern of elements of the studied samples show enrichment of Ba, La, Sr, Pb and depletion of Ti, Nb, Rb, Ce and Nb. All of data, field, microscopic and geochemical data indicate hydrothermal fluids for formation Shurab Kabir Mn deposit.

The Malayer-Esfahan metallogenic belt hosts large deposits of Zn-Pb with sedimentary host rocks. In addition to Zn-Pb mineralization, Cu, Cr, Au, Fe, Mn, W have been mineralized in this area with different host rocks. In the present study, using airborne magnetic data, promising mineral areas in Malayer-Esfahan metallogenic zone have been introduced. Using reduction to pole (RTP) filters, signal analytical and vertical derivative were processed and airborne magnetic data were interpreted. The map derived from the vertical derivative is considered as the final map to identify anomalies resulting from airborne magnetic data. Due to the sedimentary nature of the Malayer-Esfahan area and the fact that the minerals in the rocks of this area usually have low magnetic properties, the anomalies obtained from the airborne magnetic data showed a relative overlap with some the Zn-Pb deposits in the area; According to this case, the anomalies obtained in this study can be used to identify iron reserves other than Zn-Pb in this area. Anomalies resulting from the vertical derivative filter with iron deposits more than Zn-Pb deposits such as Shams-Abad and Akhtarchi Fe deposits, Astaneh and Muteh Au deposits, Rousht W deposit, Ghaleh-Arab Cu deposit, Ahangaran Zn-Pb deposits, Saleh-Payghambar, Ab-Bagh, Dardahaneh, Khan-Abad, Lakan and etc show overlap. In general, the results of this study showed that in the northwestern, central, and southeastern parts of the Malayer-Esfahan metallogenic zone, there are areas as new and hidden anomalies that can be used for sampling of promising mineral areas by sampling and spectroscopy.

In order to investigate sequential stratigraphy and its influence on the reservoir quality of the Sarvak Formation (Sarvak Formation), some 3 wells which were drilled in one of oil fields in the Abadan Plain have were in this work. On the basis of evidences like palaeosoil, brecciation, meteoric porosity and karstification, 4 discontinuities were identified in the wells as: Lower Cenomanian discontinuity, Middle Cenomanian discontinuity, Cenomanian-Turonian and Middle Turonian discontinuities. With respect to the identified facies, discontinuities, gamma log diagram and core samples, 4 sedimentary sequences of 3rd order were identified in the wells as: The 1st sequence of Upper Albian, Lower Cenomanian age, the 2nd sequences of Middle Cenomanian age, the 3rd sequences of Upper Cenomanian age, the 4th sequences of through Middle Turonian age. The entire sequential boundaries are of SBI type as per the identified discontinuities, exclusive of the lower boundary of the 1st sequence which is of SB2 type. The facies which belong with the TST portion of the 1st and 2nd sequences are of low reservoir quality, whilst the TST of the 3rd and 4th sequences have good to high reservoir quality (owing to the presence of grain-supported rudistic facies). The HST of the 3rd and 4th sequences has the greatest reservoir quality in the study formation. In sub-discontinuities, notably in those of Upper Cenomanian and Cenomanian-Turonian boundary, reservoir quality has markedly risen due to the development of meteoric diagenetic processes, viz. karstification, moldic porosity and widespread and large vuggy solutions.

The Hal Hal Chaldoran garnet amphibolites, one of the Mesozoic colored mélange components, are investigated for their geochemistry and crystal size distribution (CSD). These rocks are rich in (Fe-Mn rich) garnet and green/blue amphiboles and have less plagioclase, chlorite, epidote and opaque minerals have porphyroblastic texture and foliation due to regional metamorphism. The rocks are ortho-amphibolites which have a tholeiitic basalt protolith formed on an intra-plate setting with a high degree of crustal contamination. The garnet with considerable abundance (due to access to suitable materials and mechanism) show a linear CSD pattern with a slope of -3 for coarse-grain samples up to -7 for finer grain rocks. The ratio of nucleation to growth rates for these minerals is 4 to 7 times. Multiple nuclei were formed by a large degree of overstepping in the rocks and regular morphology of the grains indicates crystallization under crystal interface control (not fluid diffusion control).

In this study, the hydrocarbon potential and depositional environments of the Laffan Formation in the Binak Oilfield is investigated. Rock-Eval pyrolysis results indicate that the Laffan Formation contains a mixed type II/III kerogen. Based on the classification of the source rock in terms of total organic carbon (TOC) content, the Laffan Formation can be classified as a good to very good source rock. According to the plots of S1+S2 versus TOC, the Laffan Formation has weak to excellent hydrocarbon potential in the Binak Oilfield. However, organic petrographic inspections showed that the main components of the organic matter are inertinite, bituminite along subordinate amounts of amorphous organic matter. The predominance of Inertinites together with minor Liptinites confirms the type II and IV kerogen mixture in the studied formation. It is noteworthy that the presence of bituminite has a noticeable impact on the results of Rock-Eval pyrolysis. Therefore, in this study, the organic geochemistry of the Laffan Formation was evaluated using organic petrographic results. Accordingly, it is concluded that the organic matter in the Laffan Formation consists mainly of inertinite and bituminite with minor amounts of Liptinites. Therefore, significant hydrocarbon generation potential cannot be expected from this formation in the Binak Oilfield. Considering the public shape of the chromatograms obtained from PY-GC analysis, which show that the initial depositional environment of the Laffan Formation was predominantly oxic marine. The results of this study can be useful for better understanding the Cretaceous hydrocarbon system in the study area.

Jalal Abad iron deposit is located in 38 km northwest of Zarand city with about 200 million tons of iron ore reserves with an average grade of 46.2% iron, 0.98%, sulfur and 0.07% phosphorus. It is one of the seven important iron deposits of central Iran. The rock types of this area include low-sulfur oxide high-grade iron ore, sulfur-containing high-grade iron ores and low-grade silicate magnetite iron ores. Separation of mineralized zones based on the extent of ore and geological gangues is important for mine planning and drilling operation in mines. The main purpose of this study is the separation of mineralized zones based on the frequency and spatial expansion of mineral ores and gangues using fractal modeling in the deposit. The concentration-volume (C-V) fractal model was used for iron, sulfur and phosphorus in this deposit. These results showed that the main mineralized zones have a grading range as Fe ≥ 51, S ≤0.7 and P ≤0.4%. The fourth and fifth populations obtained by the iron block model are related as the main ores. Gangues and weakly mineralized zones also indicated at the first and second zones. Finally, optimal decisions can be made based on economic changes related to time and market conditions, for the third zone.