Application of K-means and PCA approaches to estimation of gold grade in Khooni district (central Iran)

Grade estimation is an important phase of mining projects, and one that is considered a challenge due in part to the structural complexities in mineral ore deposits. To overcome this challenge, various techniques have been used in the past. This paper introduces an approach for estimating Au ore grades within a mining deposit using k-means and principal component analysis (PCA). The Khooni district was selected as the case study. This region is interesting geologically, in part because it is considered an important gold source. The study area is situated approximately 60 km northeast of the Anarak city and 270 km from Esfahan. Through PCA, we sought to understand the relationship between the elements of gold, arsenic, and antimony. Then, by clustering, the behavior of these elements was investigated. One of the most famous and efficient clustering methods is k-means, based on minimizing the total Euclidean distance from each class center. Using the combined results and characteristics of the cluster centers, the gold grade was determined with a correlation coefficient of 91%. An estimation equation for gold grade was derived based on four parameters: arsenic and antimony content, and length and width of the sampling points. The results demonstrate that this approach is faster and more accurate than existing methodologies for ore grade estimation.     

Proposed algorithm for optimization of directional additional exploratory drill holes and computer coding

Block model estimated based on the drill hole information gathered during exploration stage is not appropriate for short- and medium-term mine planning. Additional information prior to mining is required for various purposes, that the source of this information is drill holes. In most situations, reducing the overall uncertainty on the estimation is the major objective of additional drilling and collecting samples from them. The topic of selecting the optimum location for additional exploratory drill holes has been of interest to mining engineers and geostatisticians in the second half of last century, but all of them are not able to optimize directional drill holes because they are based on the 2D space and do not consider the 3D extension of drill holes and block model. This study introduces a methodology to optimize the dip and location of additional exploratory drill holes based on the defined objective function with considering 3D extension of ore body and drill holes. Direct search simulated annealing used that is efficient and robust method for solving the nonlinear unconstrained global optimization problems. This method is very useful in the case that drilling the drill holes with different dips has been obligated due to topography condition and ore body situation. A case study in gold resource illustrates the method.     

Integration multisource data for mineral exploration by using fuzzy logic,case study: Taknar deposit,NE of Iran

The Taknar Zone is located at the northern margin of the eastern Iranian continental microplate, and it is host to the Taknar massive sulfide deposit. This study was conducted to find new exploration targets. We used multiple data sources (e.g., litho-geochemical and magnetic surveys) to produce more effective predictive maps. Principal component analysis and hierarchical cluster analysis methods were used to organize the new information into favorability maps and to determine multi-element correlations. We then employed fuzzy logic modeling to create favorability maps from geochemical and magnetic data. A concentration–area multifractal method was used to evaluate the final integrated favorability map for massive sulfide exploration. Our new map identifies previously unexploited sites in the eastern part of the study area, near the boundary of the Taknar formation, with intrusive and subvolcanic rocks, with potential for mineral exploration. The newly defined targets are attractive because old mined ore bodies are also identified in the favorability map.     

Application of a Modular Feedforward Neural Network for Grade Estimation

This article presents new neural network (NN) architecture to improve its ability for grade estimation. The main aim of this study is to use a specific NN which has a simpler architecture and consequently achieve a better solution. Most of the commonly used NNs have a fully established connection among their nodes, which necessitates a multivariable objective function to be optimized. Therefore, the more the number of variables in the objective function, the more the complexity of the NN. This leads the NN to trap in local minima. In this study, a new NN, in which the connections based on the final performance are eliminated, is used. Toward this aim, several network architectures were tested, and finally a network which yielded the minimum error was selected. This selected network has low complexity and connection among nodes which help the learning algorithm to converge rapidly and more accurately. Furthermore, this network has this ability to deal with the small number of data sets. For testing and evaluating this new method, a case study of an iron deposit was performed. Also, to compare the obtained results, some common techniques for grade estimation, e.g., geostatistics and multilayer perceptron (MLP) were used. According to the obtained results, this new NN architecture shows a better performance for grade estimation.     

Application of multifractal modeling technique in systematic geochemical stream sediment survey to identify copper anomalies: A case study from Ahar,Azarbaijan, Northwest Iran

This research is based on the application of stream sediments to mineral exploration. Identifying the geochemical anomalies from background is a fundamental task in exploration geochemistry. This paper applied the element concentration–area (C–A) model, to separating the geochemical anomalies from background based on a fractal approach and for the compilation of geochemical mapping from stream sediment samples (n = 620) of the Ahar region (Iran), where some Cu mineralization occurs. Comparisons of the known copper occurrences against the anomalous area created using thresholds from C–A method illustrate these hits. All of known Cu mineralizations and moreover defines two extra Cu anomaly districts. Additional sampling (n = 186) around new Cu anomaly confirms this anomaly within the district.     

The application of lithogeochemical and alteration index for copper mineralization in the Sonajil area, NW Iran

The Sonajil intrusive is located about 60 km southeast of Ahar, in Azarbaijan province in northwestern Iran, and is intruded into by andesitic trachytic Eocene pyroclastics and agglomerate. To the center, the stock is hydrothermally altered, that contains sub-economic copper mineralization. The 1,248 cells with 100?×?100 m grid were sampled, and measurement of elements by ICP-MS method and major oxides included by X-ray fluorescence method was performed. After statistical interpretations, geochemical anomalies and indices alteration (sericitization, alkali, Spitz–Darling, chloritization, Hashimoto, Hashiguchi) were calculated, and their map distribution was prepared. Based on these maps and other interpretations of data, our study indicated that despite the anomaly of copper and other elements such as gold, molybdenum, lead, arsenic and antimony of not being quite consistent, almost all of them are within the alteration zones.     

Multiple-point geostatistical modeling based on the cross-correlation functions

An important issue in reservoir modeling is accurate generation of complex structures. The problem is difficult because the connectivity of the flow paths must be preserved. Multiple-point geostatistics is one of the most effective methods that can model the spatial patterns of geological structures, which is based on an informative geological training image that contains the variability, connectivity, and structural properties of a reservoir. Several pixel- and pattern-based methods have been developed in the past. In particular, pattern-based algorithms have become popular due to their ability for honoring the connectivity and geological features of a reservoir. But a shortcoming of such methods is that they require a massive data base, which make them highly memory- and CPU-intensive. In this paper, we propose a novel methodology for which there is no need to construct pattern data base and small data event. A new function for the similarity of the generated pattern and the training image, based on a cross-correlation (CC) function, is proposed that can be used with both categorical and continuous training images. We combine the CC function with an overlap strategy and a new approach, adaptive recursive template splitting along a raster path, in order to develop an algorithm, which we call cross-correlation simulation (CCSIM), for generation of the realizations of a reservoir with accurate conditioning and continuity. The performance of CCSIM is tested for a variety of training images. The results, when compared with those of the previous methods, indicate significant improvement in the CPU and memory requirements.     

Optimally locating additional drill holes in three dimensions using grade and simulated annealing

Average kriging variance is a standard tool used in optimization of the location of additional drill holes. However, this tool cannot distinguish between areas with different priorities. This limitation could be eliminated by using weighted average kriging variance. This paper extends the problem of optimal location to three dimensional cases, use grade as a weight and search optimum locations by simulated annealing. Weighted average kriging variance is used as objective function. The method is applied to a copper deposit. Results have shown that weighting of the estimation variance with ??grade?? is effective only when the difference among the grades estimated for different blocks is considerable.     

Rocking vibration of a rigid circular disc in a transversely isotropic full‐space

In this paper, forced rocking vibration of a rigid circular disc placed in a transversely isotropic full‐space, where the axis of material symmetry of the full‐space is normal to the surface of the plate, is analytically investigated. Because of using the Fourier series and Hankel integral transforms, the mixed boundary‐value problem is transformed into two separate pairs of integral equations called dual integral equations. The dual integral equations involved in this paper are reduced to Fredholm integral equations of the second kind. With the aid of contour integration, the governing integral equation is numerically evaluated in the general dynamic case. The reduced static case of the dual integral equations is solved analytically and the vertical displacement, the contact pressure and the static impedance/compliance function are explicitly determined, and it is shown that the pressure in between the plate and the full‐space and the compliance function reduced for isotropic half‐space are identical to the previously published solutions. The dynamic contact pressure in between the disc and the space and also the related impedance function are numerically evaluated in general dynamic case and illustrated. It is shown that the singularity exists in the contact pressure at the edge of the disc is the same as the static case. To show the effect of material anisotropy, the numerical evaluations are given for some different transversely isotropic materials and compared. Copyright © 2010 John Wiley & Sons, Ltd.