Mineral prospectivity mapping of porphyry Cu deposit using VIKOR method

Naysian Porphyry Cu District (NPCD) is situated at the northeast of Isfahan, in the center of Iran along the Urumia-Dokhtar Magmatic Assemblage (UDMA) belt. Mineral Potential Mapping (MPM) is an important issue in mining to reduce the exploration costs by proposing a layout of drilling over the most favorable regions in association with ore-bearing target. MPM can be defined as a multi-criterion decision-making (MCDM) problem. Out of many MCDM methods, the VIKOR is based on a compromise solution which evaluates issues with inappropriate and incompatible criteria. In this study, seven geospatial indicators related to the NPCD were extracted from geological, geochemical and geophysical criteria. According to the conceptual model of a porphyry copper mineralization system, the highest weight was allocated to the geochemical criterion with a value of 0.499 and to the sublayer of the copper concentration map (0.425). In addition, the lowest weight was allocated to the geophysical criterion (0.113). Two variants of the VIKOR method that are the conventional (C-VIKOR) and the adjusted (A-VIKOR) ones were examined in this study, and their outputs were compared with the index overlay (IO) method as a popular approach in MPM. Taking a threshold value of 0.6 into account for final synthesized indicators, the mineral favorability areas highlighted by the IO, A-VIKOR and C-VIKOR methods have occupied 49.5, 15.8 and 18.7 hectares, respectively. It is worth pointing out that the MPM derived from the A-VIKOR method has superiority over the outputs of the IO and C-VIKOR methods by introducing the lowest favorable area and 92% matching of high grade boreholes with the proposed areas. Comparing the mean grade of copper obtained from boreholes drilled in the area and the values of MPM, a significant correlation between boreholes and prospectivity map was also obtained.ABSTRACTNaysian Porphyry Cu District (NPCD) is situated northeast of Isfahan, in the center of Iran along the Urumia-Dokhtar Magmatic Assemblage (UDMA) belt. Mineral Potential Mapping (MPM) is an important issue in mining to reduce the exploration costs by proposing a layout of drilling over the most favorable regions in association with an ore-bearing target. MPM can be defined as a multi-criterion decision-making (MCDM) problem. Out of many MCDM methods, the VIKOR is based on a compromise solution which evaluates issues with inappropriate and incompatible criteria. In this study, seven geospatial indicators related to the NPCD were extracted from geological, geochemical, and geophysical criteria. According to the conceptual model of a porphyry copper mineralization system, the highest weight was allocated to the geochemical criterion with a value of 0.499 and the sublayer of the copper concentration map (0.425). In addition, the lowest weight was allocated to the geophysical criterion (0.113). Two variants of the VIKOR method that are the conventional (C-VIKOR) and the adjusted (A-VIKOR) ones were examined in this study, and their outputs were compared with the index overlay (IO) method as a popular approach in MPM. Taking a threshold value of 0.6 into account for final synthesized indicators, the mineral favorability areas highlighted by the  IO, A-VIKOR, and C-VIKOR methods have occupied 49.5, 15.8, and 18.7 hectares, respectively. It is worth pointing out that the MPM derived from the A-VIKOR method has superiority over the outputs of the IO and C-VIKOR methods by introducing the lowest favorable area and 92% matching of high-grade boreholes with the proposed areas. Comparing the mean grade of copper obtained from boreholes drilled in the area and the values of MPM, a significant correlation between boreholes and prospectivity map was also obtained.