Application of Fuzzy Weights of Evidence Method in Mineral Resource Assessment for Gold in Zhenyuan District, Yunnan Province, China
CHENG Qiu-ming1,2, CHEN Zhi-jun1, Ali Khaled21.State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China2.Department of Earth and Space Science and Engineering, York University, Toronto M3J1P3, Canada
The fuzzy weights of evidence method implemented in GeoDAS GIS was applied to delineate targets for exploration of gold mineral deposits in Zhenyuan mineral district, Yunnan Province, southwestern China. According to the mineral deposit model compiled by USGS, the mineral deposit type discovered in the area is determined as mesothermal gold deposit. Together with field observations the mineralization associated elements are determined, which include Au, As, Hg, Ag, Sb, Pb, and Cd. The singularity method and S-A methods provided in GeoDAS GIS were applied to delineate the weak anomalies and mixing anomalies related to gold mineral deposits. Principal component analysis method was utilized to analyze these elements to form two components (PC2 and PC3) which may reflect two different types of mineralization: PC2 dominated by Au-As-Hg-Co-Ni-Cu may be related to mesothermal deposits formed close to the contact of the ultramafic intrusions; whereas the PC3 dominated by Au-As-Hg-Ag-Pb may represent epithermal mineral deposits located in the sedimentary basin away from the ultramafic intrusions. The peaks of scores on these types of composite anomaly maps were delineated and used as training points for utilization of weights of evidence method and fuzzy weights of evidence method, respectively. 16 targeting areas were delineated using fuzzy weights of evidence method and were suggested for further exploration. The detailed comparison of fuzzy weights of evidence method with the ordinary weights of evidence method shows that the former can produce better results with less loss of useful information during construction of discrete evidential layers.