1. 1National Center of Inspection and Testing on Quality of Gold and Silver Products, Nanjing Institute of Product Quality Inspection, Nanjing 210029, China
2. 2State Key Laboratory for Mineral Deposits Research, Institute of Geo-Fluids, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
3. 3Nanjing Center, China Geological Survey, Nanjing 210016, China
4. 4Development Research Center, China Geological Survey, Beijing 100037, China