Analysis of the Occurrence of Platinum-Palladium and Precipitation Mechanism by SEM and EPMA in the Ni-Cu Sulphide Deposits from Yangliupin, Sichuan Province, China

The occurrence of Pt and Pd in Cu-Ni suphide deposits from Yangliupin, Sichuan Province has been studied successfully by Electron Probe Microscope (EPMA) and Scanning Electron Microscope (SEM) with energy analysis function. The result showed that Pt existing in the form of sperrylite and native platinium, and Pd was either mainly in the form of individual minerals such as testibiopalladite and hexatestibiopanickelite, or in the form of hexastibiopalladinite, michenerite and merenskyite. Pd was also found as isomorphism form in the Vavrinite (Pd 5%), sperrylite (Pd 1%-5%) and melonite (Pd 10%) which was initially found in the deposit. The precipitation of Pt and Pd was closely related to base metal sulfide (BMS) and altered minerals such as serpentine and calcite. The process can be described as follows: in the first stage with high temperature (1200-900℃), Pt and Pd was precipitated and then included in BMS; in the second stage with high-moderate temperature (650-250℃), Pt and Pd was precipitated on the side or in the crack of BMS with fractional crystallization or hydrothermal function respectively; and in the last stage with the temperature of 500-300℃, Pt and Pd was precipitated in the alteration minerals or in the crack of BMS by reason of alteration. The analysis results provide the scientic basis for other Ni-Cu sulfide of the same type.