Exploration and Mining
Meysam Yazdani; Firouz Alinia
Abstract
Sehezar area is located in southern city of Tonokabon in Mazandaran province in north of Iran, and near the Tarom – Hashtjin belt. The existence of granitoid masses in the region can be important in terms of the potential of mineralization. The kriging geostatistical technique is used to predict ...
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Sehezar area is located in southern city of Tonokabon in Mazandaran province in north of Iran, and near the Tarom – Hashtjin belt. The existence of granitoid masses in the region can be important in terms of the potential of mineralization. The kriging geostatistical technique is used to predict the grade distribution, by using existing data and spatial correlation between them, which is described by the variogram. To identify the anomalous area, 50 stream sediment samples were collected from the area and analyzed by the ICP-MS method, and then interpreted. At first, the data were normalized and then the geostatistical analysis was used. Variogram studies showed that the spherical model is the best fitted model, and the spatial correlation range for the three elements of Au, Cu and Fe are approximately 350 m and for W is approximately 700 m. Finally, the estimation and estimation variance maps of the studied elements were prepared by using ordinary kriging geostatistical method with the spherical model on the GS+ software. Evaluating the results by calculating the root mean square error (RMSE) and calculating the mean absolute error (MAE) indicates the acceptable accuracy of variogram model. By studying the kriging estimation and kriging estimation variance maps, the anomal regions were introduced for the elements of Au, Cu, Fe and W in the case study. Due to the spatial correlation of the elements, it is concluded that this mass can be associated with iron-gold-copper deposits.
Y. Sharghi; F. Alinia; H. R. Siahkoohi
Abstract
Seismic travel time tomography uses seismic waves to image velocity distribution inside the ground. This method has been widely applied to practical applications in many fields including earth sciences. In this method, first-arrival times of seismic waves due to artificial sources, observed at receivers ...
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Seismic travel time tomography uses seismic waves to image velocity distribution inside the ground. This method has been widely applied to practical applications in many fields including earth sciences. In this method, first-arrival times of seismic waves due to artificial sources, observed at receivers in the vicinity of the exploration target are analyzed to obtain the velocity distribution within the propagation area. This paper describes the seismic tomography investigation performed at the abutments of Bakhtyari Dam site. The study aimed to find the low-velocity zones that may correspond to jointed media where seepage most likely happens. We performed 3-D tomographic inversion on Bakhtiari dam seismic data. To perform ray tracing and travel-time computation at each iteration, we used Um and Thurber (1987) method and for inversion step we used SIRT method. In most of the tomograms, average velocity was 3km/s. According to the Barton relation (2006) the seepage potential in dam sit abutments, is low. A low velocity zone has been detected above the 690 m level in right abutment. It shows that the weak zones extended from surface down to this level. Despite the presence of some weak zones, the rock mass quality is good, and the design of the grout curtain could help to bypass the reservoir water away from these seepage paths