M Yousefi; A Kamkar-Rouhani; M Alipoor
Abstract
Study of geochemical stream sediments is an effective method for prospecting mineral deposits especially in preliminary exploration stages. In this regard, generally multivariate analysis, for example factor analysis, is used to elicit an indicator component of the mineralization type sought. There are ...
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Study of geochemical stream sediments is an effective method for prospecting mineral deposits especially in preliminary exploration stages. In this regard, generally multivariate analysis, for example factor analysis, is used to elicit an indicator component of the mineralization type sought. There are still several problems with regard to usage of factor analysis that have been discussed in several published papers. In this research, we have used the stepwise factor analysis, which is a new approach to create geochemical stream sediment evidential map. Using the stepwise factor analysis, we have succeeded in recognizing more effective indicator components, increasing the intensity of geochemical halos and explaining higher percentage of the total variance of the data. We have also improved the prediction rate of mineral occurrences and consequently, increasing the exploration success. In this research, we have successfully used the stepwise factor analysis to generate enhanced geochemical evidential map for prospecting two different deposit-types in two different areas of Iran for case studies. Using the stepwise factor analysis, the total variance relevant to the indicator component of porphyry copper mineralization has been increased from 13.43 to 20.05, and the prediction rate of mineral occurrences has been increased from 34.37% to 46.8% for cumulative percentile of 95% frequency. Hence, the exploration success has been increased up to 13% at least in the study area. Furthermore, using stepwise factor analysis, there are much simultaneous present of geochemical anomalies and geological indicative features.
E Eshaghi; A Kamkar-Rouhani; A Arab-Amiri
Abstract
Every geophysical method has its own advantages and disadvantages. The integration of the results obtained from surveys using various geophysical methods causes the weaknesses of a particular geophysical method to be covered by the other geophysical methods. For this, different exploration, engineering, ...
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Every geophysical method has its own advantages and disadvantages. The integration of the results obtained from surveys using various geophysical methods causes the weaknesses of a particular geophysical method to be covered by the other geophysical methods. For this, different exploration, engineering, environmental and other investigations using various geophysical methods usually provide more reliable results. In this research work, it is attempted to integrate the results of electrical resistivity tomography (ERT) and ground-penetrating radar (GPR)surveys in order to examine the advantages and weaknesses of each of the two methods, and finally, to present more accurate and more reliable interpretation as a result of this integration. The ERT method that is, in fact, one of optimal resistivity survey methods, renders acceptable results in complex geology areas. The GPR method as a high resolution non-destructive geophysical method, which is based on transmission of electromagnetic waves in the ground and recording the reflected waves from the interfaces of the subsurface layers, is used for shallow subsurface investigations. In this research work, a water qanat was selected as a suitable target for detection by these two geophysical methods, and the, ERT and GPR surveys were carried out in an area enclosing the target. The results obtained from processing, modeling and interpretation of the acquired data indicated that the GPR method, compared to the ERT method, had higher resolution than the ERT method. However, the ERT method, compared to the GPR method, had higher depth of penetration. The results of both methods were mainly in good agreement with each other in depicting features such as subsurface cavities, variation of the grain sizes of the subsurface sediments and water percolation from the qanat to its surroundings. Furthermore, following the integration of the results of these two methods, it was found that the accuracy and reliability of the interpretation were considerably enhanced.
