Geology,Geochemistry,and Tectonic Background Of The Early Creteceous Granite In Alihe Area,Great Xing'an Range

The Alihe area of the Great Xing'an Range is located in the mineralization belt of the Great Xing'an Range,which is the intersection area of The Erguna block and the Xing'an block,the area has been subjected to intense magmatism since Mesozoic,resulting in the development of large-scale intrusive rocks in this area.The formation period of granite in Alihe area of the Great Xing'an Range in 1:200,000 regional geological survey report of Alihe was classified as monzonitic granite of the Devonian Alihe unit and syenite granite of middle Jurassic.758 upland unit,in fact,the granite in this area was formed in the early Cretaceous,and was composed of monzonitic granite and monzohranite.In this paper,through the zircons U-Pb dating analysis of the intrusive rocks in the Alihe area of the Great Xing'an Range,the zircon U-Pb isotopic ages of LA-ICP-MS were obtained in monzonitic granite rock mass,respectively,133 Ma,137Ma and 140 Ma.Based on the field investigation,it is found that monzogranite invades monzonitic granite,and the early Cretaceous syenogranite is determined.The early Cretaceous granite in the Alihe area of the Great Xing'an Range shows the characteristics of I type granite with high potassium calcalkaline,source rocks are newly accretive basic lower crust-derived materials,it may be a tensile-post-orogenic extensional tectonic environment accompanied by extrusion and uplift.In the late Jurassic-early Cretaceous,the Mongol-okhotsk orogenic belt entered the stage of post-orogenic extension.The Mongol-okhotsk take on a scissor-like gradually closed from west to east,and finally closed collisional orogeny in the east to early Cretaceous,the early Cretaceous granite in the Alihe area is closely related to the evolution of the Mongol-okhotsk ocean,and formed in the lithospheric extension tectonic environment after the Mongol-okhotsk ocean closed.