Chemically geodynamic significances of Sm-Nd isotopic system and U-Pb dating and Hf isotopic compositions of zircons in clastic sedimentary rocks/sediments: Theory, methods and practices

This paper has summarized the theory, methods and practices of clastic sedimentary rocks and sediments for chemically geodynamics. Clastic sedimentary rocks/sediments can record their provenances effectively. Nd isotopic compositions and U-Pb dating as well as Hf isotopic compositions of zircons in clastic sedimentary rocks/sediments are critical approaches to decipher provenances of clastic materials, interactions between the crust and the mantle, different blocks of their derived regions, and formation and evolution history of provenance's regional crust. Nd model age of a bulk sample indicates an average extraction time of its derived regional crust from the depleted mantle as a whole. Hf model age of a zircon grain shows its source characteristics during its formation. The chemistry of fine-grained clastic sedimentary rocks/sediments represent average compositions of their derived regional upper crust for most insoluble elements during weathering, transportation, and deposition in water, such as Nb, Ta, Th, Sc, Zr, Hf, Sc, Ti and REE. The authors' practice shows that the formation and evolution histories of the North China Plate, the Yangtze Plate, and the Central Asian Orogen represented by the Da Hinggan Mountains are significantly different from each other. Crustal growth occurred predominantly in Neoproterozoic-Paleozoic periods in the Da Hinggan Mountains. During chemically geodynamic analysis of clastic sedimentary rocks/sediments, such factors as complexity of geological processes and combination between micro-and macro-scales as well as between locality and integrity should be considered systematically.