Geophysics
Ghazal Janghorban; Seyed Mohammad Abtahi Forooshani; Keytash Moshtaghian; Hooshang Asadi Harooni; Hamzeh Sadeghi Sorkhani; Mohammad Hajheidari
Abstract
Kuh-e Lakht epithermal gold index is located on Urumieh-Dokhtar Volcanic Belt in Isfahan province. Geological studies indicate the presence of an epithermal gold mineralization system in the area. The geophysical exploration in the area includes magnetometry, resistivity, and induced polarization ...
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Kuh-e Lakht epithermal gold index is located on Urumieh-Dokhtar Volcanic Belt in Isfahan province. Geological studies indicate the presence of an epithermal gold mineralization system in the area. The geophysical exploration in the area includes magnetometry, resistivity, and induced polarization surveys. Then, we implemented Li and Oldenburg algorithm for 3D inversion of the magnetic data. The depth of the largest estimated magnetic susceptibility obtained from data inversion coincides with the average depth of the magnetic sources obtained from Euler deconvolution. Furthermore, we compared the estimated 2D resistivity and electrical changeability models and the estimated magnetic susceptibility. The comparison denotes the correlation of the estimated magnetic susceptibility variations with the reduction of resistivity, high electrical chargeability, and alteration zones. Combining the estimated magnetic susceptibility model with the geochemical analysis of the exploratory boreholes in the area indicates that the mineralization often occurred at the maximum variation of the magnetic susceptibility. Nonetheless, the results indicate the possibility of mineralization along the zones with large magnetic susceptibility variations.
F. Alahverdi Maygooni; M. Mohamadi Vizheh; A.R. Farrokhnia; E. Boostan; H. Nazari
Abstract
Undoubtedly, one of the evidence of tectonic activity in each region is earthquake, which has a major role in casualties and financial losses. The earthquake is usually caused by faults that sometimes extend to the depths of the earth's crust. In cases where no signs or complications of these faults ...
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Undoubtedly, one of the evidence of tectonic activity in each region is earthquake, which has a major role in casualties and financial losses. The earthquake is usually caused by faults that sometimes extend to the depths of the earth's crust. In cases where no signs or complications of these faults are observed on the surface of the earth, it is necessary to get a better understanding of these faults and its sub branches by combining geological knowledge as well as remote sensing and geophysical instruments. The Kazar fault in the study area is a fundamental fault that has been attributed to at least six historical earthquake events. Due to quaternary activities, recognition of this fault is very important in the region. Therefore, geological and geophysical studies were carried out on the historical site of Gohartepeh in Behshahr city to reveal its hidden parts. Specific resistive methods with bipolar bipolar arrangement at 10 and 20 meters intervals are used to provide sections and maps. By examining them and considering the position and depth of the anomalies obtained in the next stages, new profiles and networks were designed. In order to obtain more accurate results, the cesium magneto metric scanning was performed on 4 profiles. Data obtained from field operations and data acquisition as well as final processing of data in specialized software have been incorporated and clearly interpreted from sub-surface structures, especially faults and discontinuities in the study area, which indicate an impressive anomalous adaptation obtained with field evidence.
M.J Mohammadzadeh; A Nasseri; S Ansari
Abstract
Sahebdivan area is located at 20.km of Meshkinshahr in Ardebil province. The study area is comprises of volcanic rocks and intrusive masses consisting of quartz monzonite and granite along with several vast epithermal alterations. The main objective of this paper is to recognize the present ...
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Sahebdivan area is located at 20.km of Meshkinshahr in Ardebil province. The study area is comprises of volcanic rocks and intrusive masses consisting of quartz monzonite and granite along with several vast epithermal alterations. The main objective of this paper is to recognize the present alteration zones indicating metal promising areas using geophysical methods such as induced polarization (IP) surveying and resistivity (RS) in order to assess the presence of minerals and delineate the subsurface masses at depth. Therefore, IP/resistivity survey was carried out based on rectangular array in the area and their corresponding maps were prepared. Accordingly, their promising anomalous zones for mineralization were initially detected. Furthermore, a new IP survey was attempted based on a dipole-dipole electrode array for detailed potential mapping.
Considering IP/RS pseudo-sections, the position, depth, intensity and extent of mineralization was defined. Correlating the anomalous zones obtained from geophysical results with Lithology and alteration zones in the area indicate Cu mineralization along E-W trend in Sahebdivan which is associated with increase in chargeability and reduction in resistivity. Furthermore topographic corrections were attempted resulting in anomalous halos enhancement. Discriminating the important alteration zones in the area were carried out based on chargeability variations where higher chargeability indicate phyllic alteration with pyrite and in contrast the Potassic alteration with low chargeability that coincide with igneous intrusive.
It can be deduced from this study that the porphyry micro quartz monzonite - micro quartz diorite generator fluids was recognized as source of mineralization along with surrounding andesite–dacite andesite as source of the anomalous zones in Sahebdivan area. Summing all the evidences from field studies and their compliance with geophysical results, Lithology, alterations and ultimately considering the susceptible mineralization zones, the optimal drilling points was proposed with priority of SABH-1 according to the Potassic zone in terms of potential copper mineralization.
M. K. Hafizi; H. Ranjy Roodposhti
Abstract
In this paper, the results of recent archaeological studies in Neyshabour, Iran, by the application of Electrical Resistivity (ER) and Induced polarization (IP) methods have been presented. The aim of this study was to verify the effectiveness and suitability of these techniques in detecting of the buried ...
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In this paper, the results of recent archaeological studies in Neyshabour, Iran, by the application of Electrical Resistivity (ER) and Induced polarization (IP) methods have been presented. The aim of this study was to verify the effectiveness and suitability of these techniques in detecting of the buried archaeological structures and remains in Iran and other similar sites that were mostly constructed out of adobe, mud brick. Several geoelectrical profiles were conducted in addition to IP and ER experiments on the samples and the test profile. The test profile was performed over an adobe-made wall outcrop. This work shows that these methods are so effective and useful for investigating of structures like walls, furnaces and pavements which their materials contain a large amount of clay.
M. Farzamian; A. Kamkar Rouhani; M. Ziaiie; H. A. Faraji Sabokbar; K. Seif panahi
Abstract
Chichakloo Lead and Zinc ore deposit is one of mineral potential areas, located in Lead and Zinc belt limit of Takab zone and 25 km far from Anguran mine. This ore deposit has been prospected and explored in different scales several times within the last few decades. The last exploration activity over ...
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Chichakloo Lead and Zinc ore deposit is one of mineral potential areas, located in Lead and Zinc belt limit of Takab zone and 25 km far from Anguran mine. This ore deposit has been prospected and explored in different scales several times within the last few decades. The last exploration activity over the deposit is the detailed geophysical survey (using resistivity and induced polarization methods) and also geochemical survey for potential mapping of Lead and Zinc zones. In this paper, after modeling and interpretation of geophysical data and processing and interpretation of geochemical data, we have prepared suitable exploration maps in GIS environment. For this, we have taken a new fuzzy approach for exploration maps using trapezoidal membership function. Then, for integration of exploration fuzzy layers, we have used fuzzy operations. The results of investigation of the final integrated exploration map indicate lead and zinc zones having a fuzzy favorability of greater than 0.5 in southeast of the study area that is obtained from remarkable overlapping of geophysical and geochemical anomalies. The results of drilling boreholes in the area confirm the exploration results obtained in this research work.
M. Mohamadi Vizheh; A. Kamkar Rouhani
Abstract
Ground water, cavities, and isolate buried structures embedded at shallow depths are well detectable by resistivity and GPR methods because of distinct contrast in their electric and electromagnetic properties in comparison with their surrounding media. In this research work, 3 different profiles on ...
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Ground water, cavities, and isolate buried structures embedded at shallow depths are well detectable by resistivity and GPR methods because of distinct contrast in their electric and electromagnetic properties in comparison with their surrounding media. In this research work, 3 different profiles on such targets have been chosen, and their responses have been investigated. Using both resistivity and GPR methods together, it has also been possible to investigate capabilities and limitations of the methods in practice. The results obtained from this research work indicate that the GPR method, in addition to its speed and simplicity in data acquisition, is very successful in detection of interfaces or boundaries between different media in which electromagnetic properties at the boundaries change rapidly. The resistivity surveys, which have been carried out using Wenner array in this study, indicate low resistivity of the media under investigation. The low resistivity of the subsurface media caused the depth of penetration of the GPR method to be low, and as a result, made it impossible to investigate the targets buried at depths greater than 2 meters. Unlike the GPR method, the resistivity method has not been very successful in detection of multiple targets with high resistivity contrasts. Lower resolution of the resistivity method in comparison with GPR method has caused this problem. In this study, considerable information has been obtained by selecting two different processing algorithms and applying them on a series of raw GPR dataset. The obtained information from the resistivities of the subsurface structures as a result of the resistivity surveys has made it possible to choose and apply these processing algorithms. This research work well indicates that high conductive areas in resistivity sections coincide with the areas in the GPR sections having intensive attenuation. This characteristic can be used well in the interpretation of the GPR sections. Finally the resistivity method can be introduced as a suitable supplementary geophysical method to the GPR method.