扬子陆块西北缘新元古代早―中期地层与岩浆活动:进展、争议与认识OA

The Early-Middle Neoproterozoic is a critical period for the assembly and breakup of the Rodinia Supercontinent.The northwestern margin of the Yangtze Block,preserving abundant information on stratigraphic records and magmatic activities during the Early to Mid-Neoproterozoic,serves as an important window to probe the Precambrian tectonic evolution of the Yangtze Block and its links to the supercontinent's assembly and breakup.This study systematically summarizes the Early-Middle Neoproterozoic stratigraphic sequences and magmatic characteristics to clarify the stratigraphic ages,basin properties,and tectonic settings of magmatic rocks in different subregions of the northwest Yangtze.Results prove that the Bikou Group,Liujiaping Formation,Tiechuanshan Formation,and Xixiang Group in the northwest Yangtze Block are coeval with the maximum depo-sitional age of(825±5)Ma.They are characterized by continental volcanic rocks,pyroclastic rocks,and alluvial-pluvial purplish red polymictic conglomeratic sandstone,and formed in a continental rift basin.The Sanhuashi Group and Baimianxia Formation of the underlying Tongmuliang Group,Huodiya Group and Sanwan Formation exhibit significant lateral variations in rock associations and sedimentary sequences,which may reflect the dis-tinct evolutionary characteristics of different masses.Magmatic activities can be divided into four stages:985-905 Ma,898-887 Ma,884-830 Ma,and 825-750 Ma.These stages correspond to the tectonic settings of initial subduction of intra-oceanic arc,passive continental margin,evolution of arc-basin systems,and amalgamation of blocks,and intracontinental rifting and extension,respectively,responding to the entire assembly-breakup cycle of the Rodinia Supercontinent.