Mineralogy, major and trace element geochemistry of Shichanggou oil shales, Jimusaer, Southern Junggar Basin, China: Implications for provenance, palaeoenvironment and tectonic setting

• Oil shales in the Lucaogou Formation have oil prone source rock potentiality.
• Oil shales are rich in SiO2, Al2O3, Fe2O3, and especially enriched in P.
• Shichanggou oil shales were developed in a back-arc foreland basin.
• Oil shales were deposited in a warm-humid climate, anoxic deep-water environment.

The Shichanggou oil shale, located in the northern Bogda Mountain, on the southern margin of the Junggar Basin, was deposited in a Late Permian lacustrine environment. The concentrations of minerals and trace elements in selected oil shale samples from the Shichanggou area were measured by X-ray fluorescence (XRF) and inductively-coupled plasma mass spectrometer (ICP-MS). Analyzed oil shale samples are characterized by high total organic carbon (TOC) contents (7.76–22.15%) and ash yields (49.35–70.73%) with oil yields from 3.92% to 13.8%.Shichanggou oil shale samples are rich in SiO2 (64.77%), followed by Al2O3 (9.14%) and Fe2O3 (4.19%). Compared with average shale composition (ASC) from Clarke and North American Shale Composite (NASC), analyzed oil shale samples are enriched in Ca (4.04%) and Mg (3.14%), especially P (0.69%). Al2O3 correlates quite well with Fe2O3, K2O, Na2O, MnO, TiO2, Cu, Ba, Co, and Ni for their association with clay minerals. Besides, the significant correlations between Fe2O3 and MnO, Co, Ni, Ti, Cr are considered to result from their similarity on geochemical behavior. All selected oil shales are characterized by distinctly sloping light rare earth elements (LREE) trends ((LaN/SmN =2.33–3.61) accompanied by flat heavy rare earth elements (HREE) trends, with distinct Eu negative anomalies (0.58–0.74).Discrimination diagrams based on geochemistry and some ratios of elements indicate that Shichanggou oil shales were deposited in deep water environments with warm-humid climates and anoxic conditions, and we believe the original sediments were consisted of felsic rocks from the west orogenic belt. Geochemical data for oil shales suggest a continental island arc setting. Together with regional geological evidence, the Shichanggou oil shales were deposited in a back-arc intracontinental basin.