Integrated use of multispectral remote sensing and GIS for primary gold favorability mapping in Lahroud Region (NW Iran)

In this study, the reliability of the primary gold mineralization exploration using multispectral ETM⁺ imagery was investigated in Lahroud region, northwest Iran, which was conducted by integration of alteration and structural indicators. Co-occurrence of the clay minerals and iron oxides is an important criterion in gold deposit exploration; therefore, their alteration zones were mapped using Landsat 7 Enhanced Thematic Mapper Plus (ETM⁺) data analysis by feature oriented component analysis (FPCS) and band ratio techniques considering their applicability and simplicity. The structural data layers including lithological units and faults maps were also utilized to enhance the accuracy of the results. The gold favorability map of the study area was then created by the combination of the aforementioned resultant alteration and structural data layers in ArcGIS based on the weights assigned by the analytic hierarchy process method (AHP) considering the main role of the alteration zones in gold mineralization exploration. The final primary gold favorability map was evaluated through the known Au indices and ore bodies in the study area. Quantitative assessment of the results was carried out by means of the frequency ratio coefficient (FRC) that normalizes the total number of Au signatures in each potential zone with the relevant area measurement. Approximately 16% of the study area was categorized as the most favorable zone for primary gold mineralization which involves 50% of the Au signatures. Accordingly, the high potential zone which represents the highest FRC value (3.14) confirms the efficiency and reliability of the applied procedure. Therefore, the application of multispectral remote sensing techniques alongside the structural analysis is a reliable, rapid and cost effective method for mineral exploration.