عنوان مقاله [English]
Principal Component Analysis (PCA) and Catchment Basin Analysis (CBA) methods have important role in investigation of stream sediment geochemical data and can have special contribution in prospecting programs and other exploration steps. In this study, the data of 843 stream sediment samples from Khoy 1:100,000 geological sheet area in West Azerbaijan, were investigated using PCA and CBA methods. At first, dimension of variables such as REEs as well as Cu, Pb, Zn, Cr, Au and Ag was decreased using principal component analysis (PCA) and the main principal components were selected for further investigation and finally the correlation of each parameter with achieved factors were given. Then, the background values were calculated and local anomalies were separated using catchment basin analysis on the basis of real area and upstream geological units of catchment. In addition, it is demonstrated that catchment basin analysis is able to better discriminate local anomalies. Consequently two mentioned methods obviously can validate each other.Briefly, in this research, the rare earth and other strategic elements in stream sediments samples of the Khoy 1:100,000 geological sheet area, have been investigated. The background values were calculated and local anomalies were separated using catchment basin analysis on the basis of real area and upstream geological units of catchment. Threshold level method was used for separation of anomalies from background. Also, by principal component analysis (PCA) method, the main factors were delineated. Results obtained from PCA method, were estimated using ordinary kriging and finally these two methods were compared. Consequently two mentioned methods obviously can validate each other.
Aggregation of elements in stream sediments depends on the stream network, area and topography slope of catchment and upstream lithological units. Investigation of these sediments using catchment basin analysis and principal component analysis methods, obviously introduces elements dispersion and prevents demonstrating unreal anomalies. The PCA method is useful in identification of complicated structure, indexing and reduction of data dimension. Because of existence of vast alluvial plains, alluvial fans, coasts and vast basins in Iran, geochemical data analysis by CBA method can lead us to explore the valuable mineral resources to reach sustainable development. The above mention methods will cause to find probable mineralization regions.
Methodology and Approaches
In this study, for investigation of stream sediments geochemical anomalies, different steps such as data processing, separation of basins, calculation of local anomaly using CBA and PCA methods have been used for REEs and some other trace elements. In CBA method, the basins were separated by ArcGIS software and Archydro tools extension and then, real area of geological units for all catchments were calculated. Finally, using real area and application of upstream lithologies in given equations, the background values were calculated and local anomalies were separated. In PCA method, the main component of each elements were delineated, using ordinary kriging, values of each main factors have been estimated in unsampled regions.
Results and Conclusions
Results and geochemical maps obtained by BCA and PCA methods demonstrate that catchment basin analysis is able to better discriminate local anomalies and these anomalies have been correlated with the ordinary kriging maps obtained from principal component analysis and these two mentioned methods, obviously can validate each other.