A. R Shafeii; M. R. Ghassemi
Abstract
The present research is aimed at investigation of geometry and kinematics of joints, relationships and temporal and spatial distribution of the joints regarding the two deformational events within the Purkan-Vardij thrust sheet. We also studied the relationships between development of different joint ...
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The present research is aimed at investigation of geometry and kinematics of joints, relationships and temporal and spatial distribution of the joints regarding the two deformational events within the Purkan-Vardij thrust sheet. We also studied the relationships between development of different joint sets and the lithological characteristics of layers of the Karaj Formation. Considering outcrops of volcaniclastic and igneous rocks of variable lithology, we have divided them into five different rock units including thick-bedded to massive tuffs, thin- to medium-bedded tuffs, tuff-shale-sandstone sequence, shale, and igneous units. Joint study was carried out using selection method, and in part using listing method, which are useful for quick survey and statistical purposes. Joint classification was carried out using concentrations of pole to joint planes. We have used the fracture spacing index (FSI), which is an important parameter in controlling morphology and erodibility of the rock units; it is also useful for prediction of joint spacing in other layers and in surrounding areas. These characteristics are useful in road construction, tunneling and other engineering projects. A comparison of the FSI in different rock units indicates that the intrusive bodies and thick-bedded units develop a highly variable FSI with a wide range of spacings, which in most cases due to lower concentration of the joints show lower erodibility as compared to the other rock units, and therefore have more relief in their outcrops. Two major joint sets, J1 and J2, show the highest frequency within the classified joint sets. Both of these sets are of extension joint type, and their strikes indicate the s1 direction during their development. Our study in this research confirms that amount of the strain produced by the joints is very small.
F. Ghaemi; F. Ghaemi
Abstract
The Northern Khorasan is one of important active tectonics area. The main faults are strike slip (dextral and sinistral) and minor faults are thrust faults. Many of thrust faults are older than strike- slip faults and some of them are younger and are active now. It is because of bending of strike-slip ...
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The Northern Khorasan is one of important active tectonics area. The main faults are strike slip (dextral and sinistral) and minor faults are thrust faults. Many of thrust faults are older than strike- slip faults and some of them are younger and are active now. It is because of bending of strike-slip faults that converts, them into thrust faults. We recognized active faults based on their characteristics. In this area we have two series of tensile joints and two series of shear joints. Principal stresses have the fallowing attitudes :() - ((
)- ). Strikeslip faults can be sympathetic. For example the 1997 Bojnurd earthquake on the Yekke-shakh fault affects Baba- aman and Gharlegh faults
Z. Hosseinmardi; M. Ghorashi; M. R. Ghassemi; M. Talebian
Abstract
The outcrop of northern part of North Eshtehard Thrust has been selected for study of structural evolution and geological processes. The study area includes folding structures with different scales from regional to outcrop which belong to fault related folding category. Analysis of joints in the region ...
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The outcrop of northern part of North Eshtehard Thrust has been selected for study of structural evolution and geological processes. The study area includes folding structures with different scales from regional to outcrop which belong to fault related folding category. Analysis of joints in the region among upper red formation strata shows two main sets which are usually tensional (j1 & j2). These joints are visible in sandstone units of upper red formation and most of them are filled with gypsum. It is obvious that the j1 joints are younger than j2. j1 and j2 joints are related to folding processes. The local stress field which could be measured from the joint study is σ1=337/75, σ2=189/13 and σ3=077/03 and corresponds with the given paleostress direction for southern part of central Alborz.
R. Arfania
Abstract
The study area, located in 40 km southeast of Eghlid town, is a metamorphozed terrain situated between the Eghlid fault and the Zagros Main Thrust and is a part of the southeastern Sanandaj-Sirjan Zone. The area consists of the highly deformed rocks which have been emerging clearly in dextral ...
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The study area, located in 40 km southeast of Eghlid town, is a metamorphozed terrain situated between the Eghlid fault and the Zagros Main Thrust and is a part of the southeastern Sanandaj-Sirjan Zone. The area consists of the highly deformed rocks which have been emerging clearly in dextral shear zones. Mesoscopic scale analysis carried out for determining the paleostress directions and deformation history of the area. Thus mesoscopic faults, joints and veins were measured and analyzed based on the field measurements and statistical methods. Then fitting structural models were presented for each of them. Furthermore, formation ages of the structures were considered based on relative time scale. According to the results, it can be concluded that two different deformation phases were effective in formation of the analyzed structures.
B. Tokhmechi; H. Memarian; H. Ahmadi Noubari; B. Moshiri
Abstract
Joint study is one of the primary jobs in many geological, mining, geotechnical and petroleum exploration projects. Up to 10 features of joints are gathered during each field survey, while only two of them (dip and dip direction) are normally used to classify these complex features. This paper proposes ...
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Joint study is one of the primary jobs in many geological, mining, geotechnical and petroleum exploration projects. Up to 10 features of joints are gathered during each field survey, while only two of them (dip and dip direction) are normally used to classify these complex features. This paper proposes a new method for joint set classification which can use more than two surveyed features. A synthetic set of 8 joint set, each joint defined with 4 features (dip, dip direction, type of infilling and amount of infilling), created in a way that with two features (dip and dip direction) sets could not be differentiated. Necessary program developed to use Bayesian classifier to sort 8 synthetic joint sets in 4D space. Present study showed that all 8 sets can be successfully differentiated by using Bayesian method.
H. Mohseni; S. Khodabakhsh; A. H. Sadr; F. Aliani
Abstract
Bisotun inscription located on the mid-way of Hamedan- Kermanshah road (40 km to Kermanshah city), is carved on limestone cliffs exposed in the area. Dissolution of the inscription caused serious damage to the most important heritage of the country. The area comprises massive gray limestones of the Lower ...
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Bisotun inscription located on the mid-way of Hamedan- Kermanshah road (40 km to Kermanshah city), is carved on limestone cliffs exposed in the area. Dissolution of the inscription caused serious damage to the most important heritage of the country. The area comprises massive gray limestones of the Lower Cretaceous as a part of high Zagros thrust belt. Accordingly, the limestones are extensively tectonized and two main joint sets are developed in the area. Joint study was performed in an area of one km around the inscription. Thereby, it is revealed that these joint sets had impact on the dissolution of limestones. Limestone beds containing inscription are composed of mudstone to bioclastic algal wackestones. Original mineralogy of these algal bioclasts was aragonite. A few foraminifers and pellet also occur in some samples. Extensive jointing and unstable original mineralogy of limestone components lead to the dissolution of limestones in a meteoric condition. Evidences such as moldic, vuggy, canal, and cavern porosity suggest a meteoric diagenetic environment. Vugs up to centimeter scale in the field observations are evidences of karstification in the area. Jointing and dip direction of the bedding plane cut across the middle part of the inscription; conduct the corrosive rainfall precipitation toward the inscription surface. Consequently dissolution pit and holes were developed on it. Apparently the only practical way for remediation is to keep the inscription surface away from these corrosive waters. Considering the dip direction of the bedding plane, jointing on limestones and karstification in the area, it is recommended to drain the waters from bedding plane through a canal in a considerable distance from the inscription surface.
