Application of SEM and EDS to Analyze the Occurrence of Platinum Group Elements and Characteristics of Platinum Group Minerals in the Pt-Pd Deposit from Huili, Sichuan Province, China

The Huili Pt-Pd deposit in Sichuan Province is an independent platinum element ore deposit. In some ore sections, the contents of Pt and Pd have reached industrial grade. It is necessary to understand the occurrence of platinum group elements and characteristics of platinum group minerals. However, due to the low-grade platinum group elements (PGEs) in raw ore, chemical analysis is an indirect research method for the occurrence of platinum group elements, and the conclusion is thus not complete. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) were used to observe the inbuilt state, particle size, morphology characteristics, and the occurrence of the platinum group minerals. Results show that the PGEs in the deposit are mainly composed of pure Pt and Pd. The contents of Rh, Ir, Ru, and Os are very low, and the independent minerals composed of these four elements are undetected. Pt and Pd can exist in the form of simple substance elements and compounds with As, Te, Sb, Bi. There were 17 kinds of platinum group minerals, including Pt, As-Pt, As-Pd-Pt/As-Pt-Pd, and Pd-Pt-Cu/Pt-Pd-Cu. The pure Pt and the remaining Pt group minerals are found locally. The platinum group minerals have two kinds of inbuilt states, wrapped (52.39%) and intergranular (47.62%). Crystals of platinum group minerals are mainly xenomorphic granular, 1.36-32.7 μm, with a large range of particle sizes. The micropore structure, grapy structure and girdle zone can be found in some mineral crystals. The contact mode is mainly curve contact, followed by linear contact. These results provide a scientific basis for the platinum group minerals in beneficiation-metallurgy and resource evaluation.