Geochemistry of the metamorphic Al-rich sedimentary series and its constraint on provenance in the Paleoproterozoic Liao-Ji active belt

Liao-Ji active belt contains various types of rocks and is characterized by widely distributed sedimentary rocks which can record material source information and provide significant evidence of Paleoproterozoic tectonic evolution of the Liao-Ji active belt. In this study, representative low compositional maturity sedimentary rock samples were collected from the active belt and a detailed research on geochemistry was carried out. It is shown by discriminant diagram that the sandstone types of he metamorphic Al-rich clastic rocks are greywacke and shale. Low CIA index, low to mid-degree weathering condition and the consistent rare earth and trace element distribution indicate that all the samples were from the same source which underwent rapid accumulation in an active background with no obvious sedimentary cycle. The geochemical features of the Al-rich clastic rock reveal that the material source was felsic rock formed in a continental island arc or an active continental margin tectonic setting. In combination with previous zircon age obtained in the study area, it is concluded that material source of the Al-rich sedimentary series was formed in Paleoproterozoic, implying that the Paleoproterozoic terrane which served as the material source of the Al-rich clastic rock had tectonic setting features of continental island arc or active continental margin, and that the closing process of the Liao-Ji active belt was probably associated with arc continental collision in an active continental margin tectonic setting.