Neoproterozoic Magmatism Of Douling Block In South Qinling And Its Geological Significance

Douling block is located in marginal sea basins of the South Qinling of Qinling-Dabie Neoproterozoic-Mesozoic orogenic belt in the north margin of the Yangtze plate.Their tectonic history is very complex.Its magmatism in Neoproterozoic has important significance for the aggregation and dispersion events of Rodinia supercontinent in the area.There is no comprehensive and systematic understanding of the Neoproterozoic tectonic evolution in this region.Zircon U-Pb chronology and petrogeochemical test of the Shuxilou pluton show that the time of rock intrusion is 871 ± 11 Ma,was formed in the island arc environment,and was the product of subduction and reduction of the many islands and oceans in the ancient Qinling Mountains.The volcanic rocks of Yaolinghe show that Yaolinghe group was formed in 858 ±20Ma,it is the product of volcanic action in continental plate,and it is the continental margin rift environment under the arc extension environment.Because of its adjacent subduction zone,there are a few basalt with island arc characteristics in some parts.The study of Zhaochuan pluton shows that the emplacement time of Zhaochuan pluton is 790 ± 11 Ma,formed in the rift environment under the extension system,is the fracture of the lithosphere caused by the upwelling and bottom splitting of the mantle in the soft flow circle,and the magma intrudes in place along the weak surface of the structure.The study of Banbanshan rock mass shows that the intrusion time of Banbanshan rock mass is about 743 Ma,which is Neoproterozoic,which is formed in the collision environment.The geochemical characteristics of the volcanic arc environment are related to the fluid metasomatism of the residual subduction oceanic crust dehydration.According to the regional data analysis and research,Rodinia supercontinent formed the island arc tectonic magmatic rock represented by the comb building rock mass and the continental margin rift magmatic rocks(Yaolinghe volcanic rock,Zhaochuan pluton,etc.)in the process of oceanic crust subduction plate convergence in 1000-860Ma;The S-type granite represented by Doufujian pluton and Banbanshan pluton was formed in 860-743Ma;After 743 Ma,it entered the post-collision stage,forming granite(Xiaomoling pluton,Tuwushan pluton,etc.)under the extensional constitution.The analysis of the Neoproterozoic magmatic evolution and structural evolution of Douling block can provide a basis for the discussion of the polymerization and cracking process of Rodinia supercontinent in the Neoproterozoic period in this area,and continuously improve the level of regional basic geological research,and provide reference for the subsequent geological work.