The Petrological And Geochemical Characteristics Of Amphibolite Metamorphic Rock Series In Xunyangba Area, South Qinling Tectonic Belt, And Their Geological Significance

The South Qinling Tectonic Belt belongs to the passive continental margin in the north of the Yangtze Plate before the Early Silurian,of which,the basement information represents the ancient basement tectonic evolution of the Yangtze Plate.The basement of the Yangtze Plate is a double basement,consisting of the ancient hornblende-geneiss facies crystalline basement and the greenschist facies folded base.In this paper,we did the petrological,chronological,and geochemical study of the amphibolite facies metamorphic rock series newly discovered in Xunyangba,Southern Qinling and it is of great significance to explore the tectonic evolution history of the Yangtze plate and the Qinling Orogenic Belt,especially the South Qinling Tectonic Belt.The research shows that the primary rocks of amphibolite is basic island arc calcium-alkaline basalt.The amphibolite was formed in the Early Proterozoic(2362±100Ma)under the action of island arc magma may be reconstruction product of Middle-Late Archean crustal rock.Later,the metamorphism occurred at 1500?1800Ma.Then,terrestrial clastic materials and carbonate rocks deposited on the metamorphic basic volcanic rock of the South Qinling Structural Belt.And experienced the transformation of the Jinning period(?840Ma)together.In Caledonian(?440Ma),another metamorphism occurred as the Yangtze Plate subducted towards the North China Plate.In late Indosinian period,the Mianlue ocean basin was closed and the Qinling Orogenic Belt collided,uplifted into a mountain,and metamorphism(?200Ma)occurred again.Then,with the tectonic extrusion and strike-slip of the orogenic belt,the deep basement rock in the Xunyangba area exposed the surface.