Geochemical Characristics And Genesis Of Wuliji'aobao Fluorite Deposit In The Southern Segment Of Great Xing'an Range,NE China

The Wuliji'aobao fluorite deposit locates in the eastern part of the Xingmeng orogenic belt,sandwiched between the Siberian plate and the North China plate.In order to study the fluorite metallogenic mechanism and the genesis of the deposit in the study area,this study analyzed the regional geological background and the geological characteristics of the ore deposit in the study area on the basis of long-term detailed field geological survey and mining exploration.Through the systematic sampling and testing and analysis work,the origin and ore-forming fluid characteristics and evolution of the study area are discussed from the aspects of deposit geochemistry and fluid inclusions,and the achievements are as follows.The Baiyin'gaolao group of the Early Cretaceous is the ore-host strata in the Wuliji'aobao fluorite deposit.That is composed of dacitic-andesitic-containing breccia Crystallino-elastic and rock fragment tuff.The N-NE tectonic faults and their secondary faults are the main ore-controlling structures.The Veins are nearly parallel to the distribution,tend to west,along the N-NE to fill the fracture.Ore texture mainly is self-shaped granular structure and semi-self-shaped structure.Ore structure are dominated by massive structure,banded structure and brecciated structure.The wall rock alteration is dominated by silicification and sericite.The surrounding rock has been proved to have the characteristics of high-SiO2,high-K,and weakly peraluminous,belonging to calc-alkaline rhyolite volcanic rock series,through the study of petrology and geochemistry.The distribution pattern of trace elements in fluorite samples is basically the same,which reflects the similarity of the source region in the formation process.The trace element patterns of fluorite and the surrounding rock are similar,which indicates that the ore-forming material are related to the surrounding rock.The study of REE characterization shows that the REE pattern of fluorite has the same overall trend,which indicates that the mineralization has homology.The Sm/Nd ratio of fluorite and ore-bearing rocks is not much different,which indicates that there is a correlation between ore-forming material and ore-bearing surrounding rock.The Eu and Ce anomalies of the fluorite and surrounding rocks indicate the low-temperature,weakly oxidized environment during the fluorite mineralization.The content of Y in fluorite is lower,and there is a significant negative correlation in Y/Ho-La/Ho chart,which indicates that the mineralization of fluorite in the deposit is homologous and there are many times of mineralization.That fluorite in the Tb/Ca-Tb/La relationship map mainly falls in the hydrothermal origin reflect the hydrothermal cause of the fluorite.The study of fluid inclusions in fluorite in the mining area has shown that the ore-forming fluid temperature is 94~349?,the salinity is 0.18%~6.88%.The ore-forming fluid temperature is mainly concentrated in the range of 110~150? and 230~350?.The salinity is mainly concentrated in the range of 0.3%~1.0% and 2.0%~4.5%.The densities are concentrated at 0.92~0.96g/cm3 and a higher 0.75~0.8g/cm3.That indicates that the fluorite may have experienced two mineralization periods,and on the whole,the ore-forming fluids in this area have characteristics of low temperature,low salinity and low density.The mineralization depth is 0.88~1.81 km,with an average of 1.35 km,which indicates that the deposit is a shallow deposit.The results of the major,minor,and rare earth elements have shown that the ore-forming material of the Wuliji'aobao fluorite deposit is closely related to the ore-bearing surrounding rock,and the Ca mainly comes from the ore-hosting rock.The source of ore-forming fluids is mainly atmospheric precipitation.The fluid-inclusions homogeneous temperature-salinity relationship reflects the existence of two periods of fluid evolution in fluorite deposits,and fluorite is mainly concentrated in the low temperature mineralization.The water-rock reaction is the main mineralization mechanism.Based on the comprehensive analysis of metallogenic conditions,ore geochemistry and ore-forming fluid characteristics,it is believed that the fluorite deposit belongs to a shallow and medium-low temperature hydrothermal filling type deposit.