Study On Uranium Geological Characteristics And Metallogenic Rules In The Middle Of Guyuan-Hongshanzi Uranium Metallogenic Belt

Guyuan-Hongshanzi uranium mineralization belt,located in the northern margin of the northern China craton and the southern edge of the magmatic tectonic belt of the Greater Khingan Mountains,an important part of the littoral Pacific metallogenic domain covering an area of approx.40,000km²,is one of the important volcanic type uranium metallogenic belts in northern China.In recent years,its uranium exploration?in the study area?has drawn much attention.Based on the latest uranium exploration results,via comparative analysis on the typical domestic and oversea volcanic rock type uranium deposits,this paper has summarized the geological characteristics of various types of uranium deposits or occurrences.Furthermore,by means of Electronic Probe,LA-ICP-MS et al,this paper has also done some research on the diagenesis-mineralization and metallogenic regularities,given objective evaluation of the study area's prospect,improved the cognition of uranium mineralization in the study area and has laid a solid foundation to the volcanic rock type uranium deposit's exploration and research work in northern China.Based on the geological mapping,drilling-core recording,laboratory analysis and uranium exploration summary,this paper has discussed the geological,geophysical,orebody and ore characteristics and alteration features of various type of uranium deposit,and occurrence?Hetaoba,Danjinghutong,Luotuo Mountain,Xigangou And Sandaogou?in the middle of Guyuan-Hongshanzi uranium mineralization belt in details,comprehensively summarized their uranium mineralizing information and geological features,which has laid a foundation for uranium exploration and research work in the study area.Study on the origin of ore bearing volcanic rock in representative deposits or occurrences shows that acidic volcanic rocks in the study area is rich in SiO₂ and K₂O,poor in Al₂O₃,less Sr,Ba,Eu,Ti,P and high Rb/Sr ratio?21.74²4.53?,and REE distribution curve is swan like with Eu loss,typically geochemical features of A type granite.Therefore,it is speculated to be formed by partial melting of the crust source rocks.The LA-ICP-MA zircon U-Pb age of the Yixian formation in the Sandaogou area are 132.2±0.6 Ma and 132.8±0.8 Ma,indicating that the formation age is the later early Cretaceous.At the same time,the formation age of the Yixian formation was defined firstly,which is between 132.8 Ma and 122.0 Ma and play an important role in solving the stratigraphic attribution problem in Sandaogou area.The hosted volcanic rocks in Danjing hutong uranium deposit are formed in 143.8±0.5Ma and 141.5±0.5Ma,and its diagenetic age is speculated as in the early of early Cretaceous.The mineralography study shows that the mineralized minerals of the Hetaoba uranium deposit and Yishengdian uranium-silver deposit are mainly uranite,and its mineralization can be divided into four stages:early albite metasomatic stage,early hydrothermal mineralization stage,late hydrothermal mineralization stage and post-mineralization stage.They have similar mineralizing features,ore-forming fluid and metallogenesis that indicats the regional ore-forming fluid may be same phased,rich in uranium and bearing silicic acid?complex compound?.To summarize,the uranium deposits type of the study area is alkali-metasomatic hydrothermal one,whose metallogenesis is closely related to the alkali metasomatism,subvolcanic rock.According to the comprehensive study of pitchblende U-Pb isotope age,electron probe chemical age and isochronal age,Hetaoba uranium deposits was formed around99.1Ma,which is the metallogenic product in the late Cretaceous.In addition,metallochronology shows that primary uranium metallogenic age in the middle section of Guyuan-Hongshanzi uranium metallogenic belt should be around 100 Ma,namely the late Cretaceous.Together with No.460 deposit and No.470 deposit,they finally formed a space-time pattern that is old in the southwest,young in northeast in the metallogenic belt.The study of metallogenic rule shows that the middle section?study area?of Guyuan-Hongshanzi uranium metallogenic belt have favorable geological structure,magmatic rock,uranium source,hydrothermal alteration condition,obvious ore-controlling factors,remarkable potential of uranium resource,broad prospect for ore exploration,so great breakthrough may be achieved in next exploration and research work.The Heataoba uranium deposit is expected to be the large or super-large uranium-polymetallic one,and other uranium occurrences are expected to be new deposits.The Yixian formation in Sandaogou area has favorable uranium metallogenic conditions,which are favorable to the yield of uranium metallogenesis and probably has produced similar uranium deposits.Thus,the lower Cretaceous Yixian formation is a new ore-prospecting layer in the Guyuan-Hongshanzi uranium metallogenic belt,and the northeastern trending silicified tectonic belt is the potential prospecting target.