Geochemistry of the Middle Oligocene-Pliocene sandstones from the Nanpu Sag, the Bohai Bay Basin (Eastern China): Implications for provenance, weathering, and tectonic setting

摘要

Major, trace and rare earth elements of 37 sandstones of the Middle Oligocene-Pliocene from the Nanpu Sag, Bohai Bay Basin were analyzed to evaluate their provenance, weathering, tectonic setting.Low-intermediate values of the Chemical Index of Alteration (CIA) reveal that these sandstones experienced relatively weak chemical weathering. Trace element ratios and REE characteristics show that the source rocks mainly consisted of felsic magmatic rocks that formed in the Yanshan Fold Belt during Mesozoic Yanshanian period. Tectonic setting discrimination diagrams show that the sandstones were deposited in a reactivated innercontinental setting, supporting the origin of the Bohai Bay Basin as being related to subduction of the Pacific plate towards the Eurasian plate.