Geochemistry And Uranium Metallogenic Condition Of Granite Rocks Of The Haizishan-gnei Area In Western Sichuan

The Haizishan-Gnei region is located in the Yidun Island arc tectonic belt in the western Sichuan and is characterized by high uranium geochemical anomalies.The study of granite uranium metallogenic conditions in the study area is very significant not only for the investigation and research of uranium resources in the western Sichuan,but also for the exploration of granite-type uranium deposits in western China.On the basis of collecting previous data,this paper studied geological and chronological geochemical characteristics of granites from Tenozic,Hala,Luocuoren,and Gnei of the Haizishan-Gnei region through field geological surveys and later data compilation and comprehensive studies,and Compared it with the characteristic parameters of uranium-producing granites in South China,analysing and discussing of granite uranium metallogenic conditions in the area.The results are as follows:(1)For the first time,the age of Gnei granite measured by the zorcom U-Pb method was 9.52±0.081 Ma.It was formed in the Himalayan period and the main lithology was medium-grained monzonitic granite.The Gnei body is formed by an extension stopped by the uplift of the Tibet plateau after orogeny of the Yidun Island arc collisional orogenic belt,a rapid vertical pull-up,large-scale thrust overburden,and Himalayan granite slurry activity along the translational faults near the north-south direction.(2)The granites in the study area are all A-type granites.Tenozic,Hala,and Luocuoren granites were formed in an extensional tectonic setting after the collision or after the orogenic period.In the process of tectonic evolution,they developed both in the late stage of island arc and in collisional orogenic cycles.In the sequence of magmatic activity,it was formed in the late stage of the evolution of arc granite--syn-collisional granite--late collisional orogenic granite.It is a typical A-type granite.(3)Through simple comparison with uranium-producing granites in South China,the granites in the study area have certain similarities with uranium-producing granites in South China,and have the general characteristics of uranium-producing granites in South China.At the same time,due to the different genetic types of rocks,U content in zircons of A-type granites has been found that there is a certain negative correlation between the U content in the zircon and the uranium potential in the rock.(4)A preliminary analysis of the granite uranium metallogenic conditions in the study area was conducted.The evaluation believes that there are unfavorable conditions for U-activated enrichment and mineralization in granites in the study area.However,under the superimposition of intense fissure tectonics and hydrothermal alterations in the later period,such as the Haizishan area,and discover several high-level uranium anomaly,which indicating that the granite in the study area still has certain uranium metallogenic potential.(5)Uranium may undergo active migration during weathering of rock masses;Grassland soils and sandy soils with organic matter on the plateau are more likely to enrich uranium;Or having ample fluid,especially under hydrothermal action,the uranium in the rock mass can be activated with the fluid migration,and enriched in suitable sites,such as structural fracture zone,which are easy to contain ore.