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The Qingbulake mafic complex hosting a copper-nickel sulfide deposit, Tekesi County, West Tianshan (Xinjiang Uygur Autonomous Region) consists of pyroxene diorite-gabbro, olivine gabbro-pyroxenite, pyroxenite-olivine gabbro, and clinopyroxene peridotite. The geochemical study presented in this paper indicates that the complex is characterised by low Ti, depletion in Nb and Ta, enrichment in LILEs and slight enrichment in light REEs. These geochemical characteristics, combined with isotope systematics, suggest that the formation of the complex may be related to the subduction of the South Tianshan oceanic plate beneath the Central Tianshan plate and their collision and that the magma could be derived from a depleted MORB-source mantle. The magma underwent weak hybridisation with the crust and country rocks during its emplacement. SHRIMP U-Pb dating of zircons in pyroxene diorite samples from the Qingbulake complex yielded a concordia age of 434.4 ± 6.2 Ma, indicating that the complex was emplaced in the early Silurian (Llandovery). The features of island-arc magma shown by the Qingbulake complex were probably induced by the subduction of oceanic crust beneath the depleted mantle. [ABSTRACT FROM AUTHOR]

The Permian Lucaogou oil shales in the eastern Junggar Basin have long been regarded as important source rocks and reservoirs for tight oil exploration. The oil shales can also be used to assess the provenance and tectonic setting of the East Junggar region using major, trace and rare earth element geochemistry. The low chemical index of alteration ratios (37.36–64.18, 45.54 on average), low plagioclase index of alteration ratios (26.99–62.95, 42.99 on average), and high index of compositional variability ratios (0.64–1.66, 1.10 on average) suggest that the Permian Lucaogou oil shales mostly consist of immature sediments that have experienced a weak weathering intensity. The samples have low TiO2/Al2O3 and TiO2/Zr ratios that indicate a felsic origin with minor intermediate igneous rocks. The high Th/Sc and Zr/Sc ratios suggest a felsic origin without sediment recycling. The samples show fractionated light rare earth elements and relatively flat heavy rare earth elements patterns with weak negative Eu anomalies, which implies that the main provenance is lower Carboniferous intermediate–acid volcanic rocks. In addition, multiple major- and trace-element‐based discrimination diagrams show that the parent rock of clastic sediments formed mainly in a continental island arc and active continental margin environment, consistent with previous studies on the tectonic background of the East Junggar region during the late early Carboniferous. Immature sediments are present in the Permian Lucaogou oil shales and have a weak weathering intensity. The provenance of the clastic sediments of the Permian Lucaogou oil shales was predominantly early Carboniferous intermediate–acid volcanic rocks. The clastic sediments of the Permian Lucaogou oil shales were developed in a continental island arc and active continental margin environments. The Permian Lucaogou oil shales provide crucial information for tectonic setting and evolution of the northern Xinjiang during the Carboniferous–Permian. [ABSTRACT FROM AUTHOR]