Early Cretaceous uplift of the Jiaobei Terrane: Evidence from the detrital zircon and sediment compositions of sandstones in the Jiaodong Peninsula, China

In this study, we conducted sandstone petrography analyses and determined detrital zircon U-Pb ages and Hf isotopes for sandstones collected at different stratigraphic levels of the lowest strata of the Laiyang Group. All results nearly point to an evolutionary trend for the source regions of the strata. The detrital zircon U-Pb results reveal multiple age groups at 140-123 Ma, 810-700 Ma, and 2,500-1,750 Ma, but variable age proportions for two sandstones (19LY-01Z and -05Z) collected at lowermost and middle levels of strata, respectively, but only one unimodal age mode at ca. 1,850 Ma for the uppermost sandstone 19LY-09Z. Provenance analysis illustrates that the lower strata likely include two source regions, including the Jiaobei Terrane and the Sulu orogen, whereas the upper strata appeared to have one dominant source region (i.e., Jiaobei Terrane). Framework modes of sandstones display that lower samples contain more metamorphic lithic fragments, which corresponds to the recycled orogenic field in the Q-F-L diagram, while middle-upper samples are enriched in feldspars but deficient in lithics and plot in the basement uplift field of the Q-F-L diagram. This compositional variation reflects an evolution of the source regions from the Sulu Orogen to the Jiaobei Terrane, completely consistent with the observation of an increase in the amount of detrital zircons sourced from the Jiaobei Terrane, but decreasing detrital zircons from the Sulu Orogen in an upward order. This shift in the provenance of sediments reflects two tectonic events including exhumation of the Sulu Orogen to the surface before sedimentation of the Laiyang Group, and a rapid uplift of the Jiaobei Terrane after ca. 125 Ma following removal of lithospheric mantle.