Geopersia
Volume:12 Issue: 2, Summer-Autumn 2022

Landslides are deceitful natural disasters, resulting in the loss of human life, collapse of engineering structures, and the natural environment on the earth. Therefore, the aims of this study to assess, predict and mapping of susceptible landslide hazard map using GIS based software. Six landslide causative factors including aspect, distance from stream, lithology, plan curvature, slope and elevation selected as influencing factor for landslide occurrences. The landslide frequency ratio calculated using the probability technique. The controlling elements graded using a statistical and frequency ratio methodology based on GIS. The landslide hazard map shows 27% (4.8 km2) is no-danger zone, with 588 (41%) families living there. A medium to landslide danger zone covers 29% (5.2 km2), with 555 families (38.7%) living. A low-risk landslide zone covers 23% (4.1 km2), with 228 (16%) families living. A high-risk landslide zone covers 21% (3.8 km2), with 61 (4.3%) families living. The prediction rate of all factors revealed that, the highest landslide occurrence associated with Lithology and plan curvature. When these are added with high rainfall intensity, the magnitude of the landslide increases. The highest prediction accuracy of 89.58% found from combination of all causative factors which depicts how well the model and factors accurately forecast landslides.

In this study, soil samples with different weight percentages of silica colloids were subjected to uniaxial compression strength (UCS) tests in a parking lot in Anzali port (northern Iran) to estimate the suitable amount of these colloids to prevent soil liquefaction (10 wt.%). Next, by performing triaxial cyclic tests, the behavior of native sand and the one stabilized with optimal silica colloidal content (10 wt.%) was studied to ensure the occurrence of liquefaction with this content. Afterward, the soil of the study site was improved through a straightforward method, which includes driving screened pipes and injecting silica nanocolloids into the soil by these pipes with appropriate injection pressure. Key parameters in this method include accurate determination of injection pressure, gelation time, grain-size distribution of soil, and proper distribution of silica colloids at the site. In the next step, the effectiveness of the proposed improvement method was assessed by performing standard penetration tests and measuring the hydraulic conductivity. Overall, the results revealed that the proposed improvement method significantly enhanced the standard penetration number, and the formation of colloidal silica gel lowered the hydraulic conductivity of the study site. For instance, the average permeability in the first layer of unstabilized soil was 2.1 × 10-2 cm/s, which reaches 1.6 × 10-8 cm/s by performing the grouting operation. Finally, the relationship quF = 0.68 × quL was obtained between laboratory and field UCS values of the study site by sampling the soil stabilized in situ and performing UCS tests on them.

Structural analyses in the SE Alborz Mountains show that deformation style changes in different parts of the area. In the southwestern parts, presence of a thick succession of low competent middle-upper Eocene to Pliocene layers that include marl and evaporitic rocks have facilitated the occurrence of open to gentle upright folds. However, to northeast, where a thinner succession of low competent layer is observed, high-angle reverse faults has occurred. The low competent units seem to have deposited in a shallow-water marine basin formed as a result of a regional uplift in response to onset of reverse kinematics on the Bashm Fault during the late Eocene time. The onset of this reverse kinematics is contributed by the collision between the Arabian and Eurasian Plates. As a consequence, our data mainly agrees with the studies proposing the late Eocene-early Oligocene as the time of commencement of the Arabia-Eurasia collision. Additionally, since the SE Alborz Mountains seem to have experienced a prolonged extensional setting during the middle Eocene, the above-mentioned reverse kinematics may indicate inversion of a middle Eocene basin. Our data also revealed that the late Miocene-late Pliocene was a critical time in the study area, when regional surface uplift took place and substantial clastic materials were shed upon the already folded rock units. A significant episode of deformation may have occurred at this time.

The sedimentological analysis of the lower Cretaceous red deposits in the Boumalne Dades region (Central High Atlas) presented in this article is based on field observations associated with sedimentological methods (morphoscopy, exoscopy, and mineralogy determination of clays) conducted to investigate the paleo-environment of this study area. The analysis of the surface of the quartz grains with a binocular magnifier and scanning electron microscopy (SEM), allowed us to reconstruct their formation environment. Exoscopic analysis allowed the characterization of a mixture of quartz morphotypes. The results obtained reveal numerous indications of short- and long-distance transport, which reflect different environments (continental to marine environment). The paleo environments of the units revealed by sedimentology are essentially continental with marine influences. Specifically, an alluvial fin is recorded at the base of the Ifezouane Formation at unit 1 and a fluvial meandering medium (unit 2) at the top of the same formation; the deposits of the Ifezouane Formation correspond to a floodplain at the base (unit 3) and a playa at the top (unit 4).

The Gohar-Zamin mine is located in the southwest of Sirjan city in Kerman province, Iran. Geology condition showed that two fault categories played an important role in the formation of crushed and weathered regions in the southern part of the pit. The spatial analysis of the Lugeon variable indicated that the hydraulic conductivity in the rock mass is very low and the groundwater flow is concentrated only in a limited number of high-transmission main gaps. The mine needs to the designing a proper system for dewatering. Hence, a Gaussian simulation method was used to determine the suitable location of the dewatering wells in the vicinity of the pit. Exploratory spatial data analysis (ESDA) was used to examine location maps, histograms, correlations, and variogram of the Lugeon and RQD data. The relationship between Lugeon and RQD with depth demonstrated that the minimum of RQD and maximum of Lugeon were concentrated in certain elevations. The calculated variograms of RQD and Lugeon showed good spatial continuity. Variograms of the normalized values were performed to carry out the Gaussian simulation of the RQD and Lugeonn variables. Probability and uncertainty maps of RQD and Lugeon indicated that the south-eastern parts of the pit play an important role in permeability.

The study area is located in the Zard-Darreh village nearby Damavand city in the eastern part of Tehran province. Late Cretaceous strata are well-exposed in the Zard-Darreh village, comprising siliciclastic sediments with limestone stringers, which are overlain by red conglomerate deposits of the Fajan Formation. This study was carried out on a 96 m interval of the K3 and Fajan Formation to determine the precise age of the sampling interval. Eighty-nine surface samples were collected and treated for calcareous nannofossils. 53 species (27 genera) and 15 families were identified and nine biozones were established. Biozone CC20/UC15bTP occurs in the lowermost part of the K3 and represents the Late Cretaceous (Campanian) age. The NP1 to NP8 biozones are present the rest of the study interval, suggesting Early Paleocene (Danian-Thanetian) age. Based on calcareous nannofossils the Early Paleocene is recorded for the first time in the Zard-Darreh village in the Alborz Mountains. Likewise, a hiatus exists between the Late Cretaceous (CC20/UC15bTP )  and Early Paleocene (NP1), which encompasses the Maastrichtian stage and part of Early Paleocene. Finally, some small size calcareous nannofossils such as Biantholithus sparsus, Cruciplacolithus primus, Cruciplacolithus intermedius, and Cruciplacolithus asymmetricus are present in the NP1 biozone of Early Paleocene, which may indicate the effect of various environmental factors. Furthermore, some calcareous nannofossils such as Sphenolithus spp. and Discoaster mohleri are present in NP6 and NP7 biozones of the study area that may indicate a warning climatic condition toward the Eocene.

This paper focuses on metamorphic rock-hosted gold mineralization in Lakhshak gold-antimony deposit, lies along the southwestern margin of the Sistan suture zone. The area is occupied by metamorphosed Eocene volcano-sedimentary rocks, Oligocene granitoid intrusion, dikes, and quartz veins/veinlets. At Lakhshak, gold-bearing quartz-veins are hosted by the Eocene metamorphic complex. At least two generations of quartz veins are identified in Lakhshak deposit. The first is parallel to the foliation of the host rock, the second crosscuts the first generation of veins as well as the foliation. Gold grades in the first-stage veins are on average higher than that in the second veins. Ore mineral comprises pyrite, stibnite, arsenopyrite, chalcopyrite, pyrrhotite, sphalerite, native gold, and electrum. The mineralized- alteration zone controlled by NE-SW-trending ductile-brittle shear zone. Fluid inclusions in parallel quartz vein types consist of 4 phases including V-rich, L-rich, L-V-rich and L1-L2-V (CO2)-rich phases. Homogenization temperatures and salinities vary from 200 to 330 ºC and 8 to 13 wt. % NaCl eq., respectively. Microthermometric and Laser Raman Spectroscopy studies of fluid inclusions indicate abundant N2, CH4 ± CO2 fluids. Crush-leach analysis of fluid inclusions suggests that the halogen fluid chemistry is not identical to sea water, magmatic or epithermal related fluids, but tends to be similar to fluids in orogenic-type gold deposits. Based on those key features, gold mineralization in Lakhshak deposit tends to meet the characteristics of orogenic, mesothermal types of gold deposit. Metamorphic rock-hosted gold deposits could represent the new targets for gold exploration particularly in Sistan suture zone.

Brittleness is an important parameter that controls the mechanical behavior and fractures characteristics of rocks in drilling and rock bursting. Lack of accurate evaluation assessing rock brittleness can lead to many risks related to rock mechanics. In this paper, the relationship between brittleness with the ratio of point load index and porosity (PMP), was investigated for Hamedan limestone. Besides, the existing estimation methods for the brittleness index of the rock have been summarized and their application was briefly discussed. In order to estimate brittleness indices and the ratio of point load index to porosity, 18 blocks of Abshineh and Sarab Gyan limestone rocks have been chosen. Abshineh limestone rocks with the Oligo-Miocene age and Sarab Gyan limestones are extracted from Cretaceous rocks. In the following, at first, thin sections of limestone were investigated. Then the physical (porosity (n)) and mechanical properties of limestones were determined. The samples were exposed to point load index (Is 50), uniaxial compressive strength (UCS), and Brazilian tensile strength (BTS) tests, and the ratio of their point load to porosity (PMP) was calculated. Then, the relationship between brittleness indices and PMP (univariate regression) was checked. Also, the relationship between brittleness indices was determined with two-variable regression (input variables including porosity and point load index). Finally, the results of different types of relationships were compared. The results illustrate that using the PMP parameter, to predict the values of brittleness indices, obtains more reliable results compared to two-variable regression (n and Is 50). Also, the results of experiments showed that the highest agreement between brittleness parameters B3 and B4 with PMP parameter and the coefficient of determination (r 2) are 0.89 and 0.90, respectively.

Recently, many infrastructures, such as buildings, highways, petrochemical, and refinery facilities have been constructed on seaboards of the Persian Gulf region. In this area, for many geotechnical projects, the improvement of the engineering properties of soft and loose soils is necessary. In the area, the use of freshwater to obtain the required properties of soils for structures such as roads and highways is costly and not economically feasible. Therefore, the idea of using sea/saltwater instead of freshwater has significant benefits to the community, as it decreases the amount of freshwater being used which is of high importance. In this study, Saline water has replaced fresh water. Compaction, unconfined compression, and California bearing ratio (CBR) tests have been performed on sand samples with different fine contents. In addition to major changes in soil microstructure, the results showed that the stabilization of samples with saline water causes more bearing capacity and strength. The CBR and unconfined compressive strength (UCS) have been improved up to 11.3% and 12.2%, respectively. With increasing in salinity of water, the maximum dry density (MDD) of the soil samples increased up to 4.4% but optimum moisture content (OMC), liquid limit (LL), and plastic limit (PL) decreased up to 36.2%, 4.0%, and 6.6%, respectively. The results displayed that the lower the percentage of fine content, the higher the value of CBR and UCS.

Groundwater is basically known to be an essential source for drinking and agricultural uses. Therefore, the study of water resources is of great significance to manage its quality and control related pollutions. There are various ways to survey the quality of groundwater among which the statistical methods like cluster analysis and principal component analysis (PCA) are widely used. In this paper, a new method is introduced to determine aquifer hydrochemistry in the areas with similar quality characterization. After analyzing water samples in the laboratory, as the first step, the factor analysis was performed to determine the main factors controlling hydrochemistry. For example, the weathering of the carbonic rocks was determined as the primary factor to be used in the suggested statistical method in Asadabad study area. Then, the parameters were changed by rating them in new classes from 1 to 3. Finally, all samples with the new quantitative rates are plotted on a four-dimensional graph to differentiate hydrochemical zones. All samples in each hydro-chemical area were compared based on ionic ratios to ensure reliability of the results. The results showed that the new statistical method has the capability for zoning samples with comparable hydrochemistry features. These findings will help in the efficient use of water sources for various human activities, saving money and time.

The main goal of this present study is to apply an improved zonality index to epithermal gold ores based on staged factor and number-size (N-S) fractal analysis. This technique was utilized in Bardaskan district, NE Iran, which is epithermal gold mineralization. An improved zonality index is a proportion of factors including ore and pathfinder elements based on rock samples. Consequently, two factors were selected after four stages of the staged factor analysis which consist on F-4 (As-Fe-Mo-S) and F 3-4 (Au-Ag). Based on these factors, (F1-4)/(F3-4) is determined as an improved zonality index. In addition, the improved zonality index was categorized by fractal modeling. The N-S model demonstrates that the major anomalies of this improved zonality index are associated with silicification as main alteration zone and the intersections of faults, particularly in the NE and northern parts of the Bardaskan region. Additionally, additional rock samples with Au higher than 100 ppb are located in anomalous parts of the improved zonality index and marginal parts of this area with high values of this index contain pathfinders of gold mineralization, especially As based on this methodology. This methodology could be strongly considered in the exploration of different types of mineral deposits and the classification of the target anomalies.

In the Zagros Region, alternative karst and non-karst formations have been folded into a series of cylindrical synclines and anticlines. Some of folds are dissected by rivers oriented approximately perpendicular to the axes, forming excellent deep valleys for dam construction. Due to an ineffective site detection and inappropriate design and construction of grout curtain, some of the dams constructed on the folds in Zagros are facing with leakage problem or have been remediated. At this research, six schematic models for probable leakage route from the reservoirs constructed in synclines and anticlines are presented by considering fold characters and dam location. Results show that in synclines, the most important leakage controlling factors are thickness and permeability of the non-karst formations located at the floor or/and abutments of the reservoir. In case of anticlines, hydraulic relation between the limbs is the most important controlling factor. It was concluded that the precise problem appears at dam sites in which the anticline limbs are hydraulically connected and karst rocks are directly exposed on the surface or covered by a thin layer of permeable sediments at the floor or abutments of the reservoir. This kind of geological setting involves a high risk of leakage problem and reservoir needs an extended water-tightening system.