Origin and mode of occurrence of trace elements in marine oil shale from the Shengli River area, northern Tibet, China

Abstract

With the aim of better understanding of geochemistry of marine oil shale, 25 samples from the Shengli River area were studied. The concentrations of Sr, U, Rb, Pb, and Th were 1.22 to 3.66 times higher compared to the average concentrations in the crust (Clarke values), while the concentrations of other elements were slightly higher/lower compared to the respective Clarke values. Trace elements including U, Pb and Th are important from the environmental point of view. The elements in the Shengli River oil shale may be divided into three groups according to their modes of occurrence, i.e. group A, B, and C. Group A exhibits a relatively high affinity with organic matter. Group B has weakly positive or slightly negative correlation coefficients with ash yield, while Group C shows high positive correlation coefficients with ash yield and possibly has an inorganic affinity. Elements related to terrigenous origin in the oil shale seams in the Shengli River oil shale have originated from two sources: the Nadi Kangri Formation felsic volcanic rocks and the Suowa Formation limestone. © 2011 Estonian Academy Publishers.