Geochemistry of Platinum Group Elements of the Late Permian Kaixinling Coal from North Qiangtang Basin, Tibetan Plateau: Implications for Modes of Occurrence and Origins

Abstract

The Kaixinling coal is located in the eastern part of the North Qiangtang Basin, which were the important coal resources in Tibetan Plateau. A total of thirty coal samples were collected from the Kaixinling area to determine the concentrations, distribution patterns, occurrences and origins of platinum group elements (PGEs) in the Permian coal. The total contents of PGEs are low ranging from 0.56 to 1.89 ng/g with a weighed mean value of 1.21 ng/g. The contents in Os exhibit considerably positive anomaly compare to the Upper Continental Crust and the ordinary Chinese coal. The individual PGEs in coal samples from the Kaixinling area exhibit various modes of occurrence. Pd and Pt are mainly concentrated in clay minerals and P-bearing minerals. Ir is probably present in clay minerals and partly controlled by other Fe-bearing and P-bearing minerals. Os is associated with organic matter and partly related to calcite. Three possible origins of PGEs were identified in coal seams in the Kaixinling area. Pd, Pt and Ir are mainly terrigenous inputs. Rh and Ru are derived from mixed sources (seawater and terrigenous supply), while Os is mainly derived from seawater.