『Abstract
　A case application of a hybrid method combining multilevel fuzzy comprehensive evaluation with asymmetric fuzzy relation analysis is demonstrated to map porphyry-copper prospectivity in the Gangdese district, Tibet, western China. Two-level binary geoscience variables including favorable rocks, intrusive rocks, faults and geochemical anomalies, are identified based on porphyry-copper mineral deposit model and ranked using asymmetric fuzzy relation analysis. The prospective target areas are identified by fuzzy membership values greater than 0.82 and corresponding uncertainty less than 0.36. The target areas occupy only 7.0％ of the study area but contain 52.4％ of the total number of known deposits. The prospectivity map illustrates that the targets are not only directly associated with the known deposits in the central part of the study area, but also with E-W and N-E oriented faults in the northern part of the study area. The targets can be used to guide further exploration for undiscovered porphyry copper in Gangdese district.

Keywords: Multilevel fuzzy comprehensive evaluation; Asymmetric fuzzy relation analysis; mineral potential mapping; Uncertainty; Porphyry copper; Tibet』

1. Introduction
2. Multilevel fuzzy comprehensive evaluation
3. Asymmetric fuzzy relation analysis
4. Application to mapping prospectivity for porphyry copper deposits, Gangdese belt
　4.1. Geological background and porphyry Cu deposits
　4.2. Calculation of the weights of two-level geoscience variables
　4.3. Mapping prospectivity for porphyry Cu deposits
　4.4. Comparison with the results obtained by weights of evidence
5. Conclusions
Acknowledgements
References