Features of platinum-group elements in different mineral assemblages in the Lower Cambrian black rock series in Hunan and Guizhou

Abstract：The mineral assemblages are very complex in the Lower Cambrian black shale in Zhangjiajie of Hunan and Zunyi of Guizhou. X- ray diffraction analysis combined with previous research results shows that the contents of sulfide minerals, clay minerals and organic matter are relatively high. After crushing and separation of the samples, the ICP-MS method was used to determine the PGE contents of the black shale and separated samples, and in addition, the mode of occurrence of PGE in the black shale in the study areas was studied. Study shows that the content of PGE in the area is high and stable. The chemical activity of PGE is high enough to enable them to be remobilized to a considerable extent under low-temperature, oxidizing conditions and precipitated and concentrated under low-temperature, reducing conditions. The PGE contents of black shale in the primary C/MoS2 mixed-layer mineral-rich black shale decreased to varying extent after strong weathering and leaching. The greater majority of the PGE are concentrated in organic matter and pyrite. The PGE distribution patterns show certain regularity. The remarkable differentiation of PGE demonstrates that the distribution pattern of the black shale does not have the characteristics of extraterrestrial material.