فصلنامه زمین شناسی ایران
پیاپی 57 (بهار 1400)

The Khoshnameh altered area is located about 20 km south of Khalkhal (Ardebil province) and lies in the Hashjin metallogenic district. The formation of extensive serictic, argillic, silicic, chloritic and iron oxides alterations in the Chenar, Mahmudabad and east of Khoshnameh, as well as the copper-lead-zinc mineralization events (e.g. Senjedeh, Shalvali and Ommabad) appears to be intimately affiliated to the fluids derived from upper Oligocene granodiorite intrusions which were emplaced within the Eocene trachy-basalt, andesite and pyroclastic rocks. The key point of this research is to investigate the preference of the Stage Factor Analysis (SFA) to evaluate the geochemical dispersion of mineralization and the visualization of real anomalies throughout the Khoshnameh area. Since the concentration of rock forming elements that are not related to mineralization has a negative effect on the factor privilege of elements, then the number of factors to increase the severity of anomalies must be reduce. For this purpose, initially nine factors were calculated based on the chemical composition of the samples. At this stage, non-representative elements and elements that did not participate in any of the factors were identified and removed from the data set and factor analysis was re-applied. After applying three stages of analysis on the data, the most effective predictive and important factors in terms of mineralization were deduced. Consequently, the number of factors decreased to 5. Therefore, using this method increases the prediction rate and success of the exploration, compared to the typical factor analysis method. Thus, the probable anomalies of Ba, Sn, Pb and Mo mineralization from the first factor and As, Cd and Sb mineralization from the fourth factor are predicted and introduced.

Estimating recharge is important in groundwater studies, especially in budget calculation to properly manage groundwater withdrawals. In this research, recharge value into the alluvial aquifer of Sarakhs, which is the only source of water for drinking, agricultural and industrial uses in Sarakhs Plain (NE Iran and adjacent to Iran-Turkmenistan border), was estimated using MODFLOW model in FREEWAT Software. After preparing the conceptual model of the aquifer and transforming it into a numerical model, the model was calibrated in unsteady states during a two-year period (water-year 2015-2016 and 2016-2017) and verified. The sensitivity process confirmed validity of the numerical model in estimation of the aquifer recharge. Accordingly, the annual surface recharge was estimated at 80 million cubic meters (Mcm), occurring from rainfall (32 Mcm/year) and irrigation return flows (48 Mcm/year). In this regard, rainfall recharge coefficient was estimated about 20% of the annual rainfall and irrigation return flow coefficient was calculated about 15% of the annual discharge rates of the discharging wells. Simulated temporal variations of the groundwater recharge indicates occurrence of the rainfall recharge during January to June and irrigation return flows from November to April each year. The estimated recharge coefficients can be used in budget studies to properly manage the Sarakhs aquifer, as well as the same aquifers in Iran.

One of the main concerns in the aquifers adjacent to oil facilities is the leakage of LNAPLs. Since remediation processes costly and time consuming, so the first step in these systems is determining design goals. Often the most important goal of these systems is to maximize pollutant removal and minimize the cost. Identifying the thickness of LNAPL and its fluctuations can determine the type of recovery method and thus can be effective on the amount of removal and the cost of the implementation. In this study, three methods of gene expression programming (GEP), adaptive neuro-fuzzy inference system (ANFIS) and multivariate linear regression (MLR) were used to estimate and predict the LNAPL level. Input variables are groundwater level elevation and discharge rate of LNAPL and the output variable is the LNAPL level elevation. The results of the three models were analyzed by statistical parameters and it was determined that GEP technique has better results and could be used successfully in predicting LNAPL level fluctuations in recovery processes.  Also, the GEP model provides an equation for predicting the LNAPL level that can be used in the field to predict the elevation of the LNAPL level.

The studied zone is in the Northern part of  Zagros Suture Zone (Kermanshah). The presence of deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rocks of active margin and carbonate sequence of passive margin that are assembled in the studied area show a compressional tectonic regime from the late Cretaceous up to the present. As a result of convergent regime, a very complicated structural zone is developed. The main purpose of this study is stress characteristic analysis in Zagros Suture Zone (Kermanshah).To recognize and study the arrangement of stress axes a great amount of data were gathered from the folds axial surface and the faults which are appeared within the rocks specially the radiolaritic rocks. The data includes characteristics of fault surface geometry, fault slip and lineation slip. The stress recording patterns for data in this study is Multiple Inverse Method and comparison with stress position by using folds axial surface.  By studying folds it was obtained the situation of main stress σ1, σ2 and σ3 respectively as 029, 127, 234 and by using the method Multiple Inverse Method, the situation of main stress is obtained as 059, 304, 194. Based on the investigations in the study area and measurements on Cretaceous rocks, the results show that the main stress direction since Cretaceous up to the present is northeastern with minor changes. The estimations of stress direction were the same in both folds and faults. As a result, the shortening direction has been constant, so the shortening faults all show one direction of stress.

The whole rock chemistry of the Garmichay metapelites located in the north of Miyaneh, NW Iran, is investigated to reveal the provenance and metamorphic conditions of the rocks. Petrofabric observations have revealed the syn-tectonic nature of regional metamorphic cordierite porphyroblasts in the metapelites. C' shear band structure is another feature that is observed in the rocks. Two regional metamorphic phases (RMP1, RMP2), one contact metamorphic phase (CMP) and two deformation (D1, D2) phases are identified. The major oxide geochemistry implies two sedimentary shale and greywacke parent rocks. Based on major, rare earth and trace elements (Ti, Ni, TiO2, Zr and K2O) the igneous source rock has been an andesite to dacite/rhyodacite. The CIA (chemical index of alteration) and CIW (chemical index of weathering) parameters imply a medium degree of alteration in the igneous source area. The Garmichay metapelites, in comparison with the PAAS and UCC, are enriched in Cs, La and Ce and depleted in Sr, Nb and Ta. The representative samples lie inside the paragenetic triangles of the compatibility diagrams that imply their thermodynamically stable conditions. Finally, based on the standard pseudosections, the maximum temperature and pressure range has been determined as 535-635 °C and 1-3 kb, respectively.

The Lakhshak Sb index is located in the northwest of Zahedan in the Sistan suture zone. The geological units of the area include metamorphosed flysch (garnet schist, actinolite schist, phylite, mylonite), granitoid pluton, acidic and basic dikes, mineralized and un-mineralized silicic veins. According to the geochemical studies, Lakhshak igneous rocks are calc-alkaline, high-K calc-alkaline and shoshonitic, metaaluminous rocks which are belong to the volcanic arc, and collisional and post-collisional tectonic settings. The studied igneous rocks are characterized by LREE and LILE enrichment relative to HREE and HFSE. Enrichment of Pb and depletion of Zr, Nb and Y are more consistent with melts generated from the lower crust. In the Lakhshak area, the Sb mineralization mainly occurs as quartz-stibnite veins in type-like rocks and is associated with silicic, argillic and phyllic alterations.

The Akhtarchi gold deposit with carbonate host is located in southeast Mahallat, Markazi province, and Sanandaj-Sirjan structural zone. Host rock includes impure carbonated rocks with Permian age which is affected by dissolution (decarbonatization) and brecciation in mineralized zones. Mineralization is controlled structurally and there is spatial relation between faults and mineralization. The most important alterations include silicification, hematization, dolomitization, decarbonatization and argillic. Gold occurrence is seen as three forms, associated with iron oxides, siliceous (jasperoid) and placer. There are five types of mineralized veins in the area including gold bearing iron oxide, gold bearing siliceous -iron oxide, copper bearing siliceous-iron oxide, siliceous-pyritic and milky quartz veins. Microscopic studies and microprobe analyses show that gold exists in this deposit as microscopic grains inside iron oxides and as submicroscopic in iron oxides, iron-manganese oxides, carbonates, copper bearing secondary minerals and sulfides. Based on geological, structural, alteration, mineralography and microprobe studies, properties of Akhtarchi deposit have the most similarity with Carlin type gold deposit.

In order to study biostratigraphy of the Tirgan Formation in western Kopet Dagh, two surface sections including Navia – Robat Eshgh and Ghezelghan, were selected and 230 samples were collected. The Tirgan Formation was measured with a total thickness of 237 and 192 meters in Navia and Ghezelghan sections respectively and was represented by thick and sometimes medium bedded, grey and weathered cream colored limestones in two localities. In Navia section, the Tirgan Formation conformably overlies the Zard – Shurijeh Formation with sharp lithological changes. However, as a result of being located in the core of an anticline, this boundary is not determined in Ghezelghan section. The Tirgan Formation disconformably underlies the Abderaz Formation in Navia section while conformably underlies the Sarcheshme Formation at Ghezelghan section.
As a result of biostratigraphical investigations, 58 species belonging to 68 genera of foraminifera were identified in the Tirgan Formation. Based on benthic foraminifera two biozones were determined as follows: 
1. Palorbitolina lenticularis Taxon Range Zone
2. Novalesia producta – Orbitolina spp. assemblage zone
 According to the determined biozones and fossils associations, the age of the Tirgan Formation is Barremian – Early Aptian in both sections. The comparison of the Tirgan Formation, in two-mentioned sections, shows some differences. In terms of biostratigraphy, there is not any significant distinctions, except for thickness difference in biozones.