Geochemistry of PGE in the regolith on Feihong ultramafic complex, western Yunnan, China

摘要

The geochemical behavior of platinum group elements (PGE) in weathering processes has been studied over the different parts of the world in recent years. As a first example in southwestern China, here an investigation is carried out in a lateritized regolith profile, which is developed over the bedrock of Feihong ultramafic complex in western Yunnan. The profile can be divided into four horizons: (1) topsoil zone, (2) ferruginous-clay zone, (3) saprolite zone and (4) semi-weatheredbedrock zone. Clay mineral assemblage shows that the lateritization of the regolith is at the red-clay stage without mature laterite. The PGE contents in the topsoil and ferruginous clay zones of the regolith (Ir, 8.67-16.02×10-9; Ru, 19.17-39.88×10-9;Rh, 1.90- 4.42×10-9; Pt, 11.83-35.83×10-9; Pd, 6.32-11.04×10-9) are higher than those of the bedrock (Ir,0.65-2.96×10-9; Ru, 0.30-2.41×10-9; Rh, 0.22-1.52×10-9; Pt, 3.69-12.21×10-9; Pd, 0.54-2.16×10-9).The fractionation of PGE is developed from Pt concentration type in the bedrock to Ru-Pt concentration type in the regolith during lateritization indicated by the changes of relative distribution and C1-chondrite normalized models of PGE. The enrichment degrees of Ru and Pd are relatively high, and Ir is moderate, while Pt and Rh are low.