SEDIMENTARY AND GEOCHEMICAL CHARACTERISTICS OF OIL SHALE IN THE PERMIAN LUCAOGOU FORMATION IN THE SOUTHEASTERN JUNGGAR BASIN, NORTHWEST CHINA: IMPLICATIONS FOR SEDIMENTARY ENVIRONMENTS

In this study, the sedimentary and geochemical characteristics of oil shale in the Lower and the Upper Member of the Permian Lucaogou Formation in the southeastern Junggar Basin, Northwest China, were investigated. Mineral and bulk chemical compositions, sedimentary facies and distribution of oil shale show that in the Lower Member it is rich in organic matter, but in the Upper Member, organic-poor. The distribution area of deep lake subfacies and oil shale in the Lower Member is larger than that in the Upper Member. The sedimentary modes of these two members were estimated using geochemical parameters, such as Sr/Cu, the chemical index of alteration (CIA), Ni/Co, V/Sc and (C-27 + C-28 )/C-29 regular steranes. The organic-rich oil shale in the Lower Member of the Lucaogou Formation formed in the more humid climate and under oxidative conditions, its organic matter derived mainly from algae. On the other hand, the organic-poor oil shale in the formation's Upper Member formed in the humid climate and under more oxidative conditions, while the input of land plants to its organic matter was high and that of algae low.