Study On Geochemical Characteristics And Fluid Inclusions Of The Dayana W-Mo Deposit In Dongwu County,Inner Mongolia

Dayana W-Mo deposit is located in Dongwu County,Inner Mongolia.It is located at the southwestern end of the Dongwuqi-Nenjiang metallogenic belt,and the middle of the Dongwuqi-e' lunchun fold belt.It is a small and medium-sized ore deposit mainly composed of quartz vein wolframite and associated molybdenite.The predecessors conducted a preliminary study of the geological characteristics of the deposit and the age of diagenesis and mineralization,on the basis of detailed field investigations,this paper has studied the characteristics of ore-forming fluids in the area,and explored the genesis of the deposits through the work of rock and mineral appraisal,microscopic testing of fluid inclusions,and geochemical analysis of rocks.The metallogenic model has achieved the following main results and understanding:(1)Based on field output characteristics observation combined with indoor microscopic identification,the mineralization of the Dayana W-Mo deposit was divided into three stages:Quartz-mica stage,quartz-molybdenite(black tungsten)stage and quartz-wolframite stage.The wolframite is mainly formed after molybdenite,but both have experienced a period of symbiosis.(2)Through the geochemical characteristics of the Jianshan biotite granite,The ore-forming rock mass is rich in silicon(more than 70%),rich in alkali(more than 8%of K2O+Na2O),K-rich,Al-rich,and low-Ti features,it is the quasi-aluminum to peraluminous granite;Trace element features are characterized by significant enrichment of high field strength elements Th,U,and Nd,significant loss of Ba,Sr,and Nb,typical characteristics of low Ba,Sr,and high Rb,the Nb/Ta ratio is lower than the 17±1 ratio of mantle-derived magma;The characteristics of rare earth elements have obvious negative Eu anomalies,and the fractionation of light and heavy rare earths is obvious.The ratio of fractional distillation index(La/Yb)N is lower than that of mantle-derived magma 17.The above characteristics indicate that the ore-forming rock masses have undergone high-intensity magmatic evolution differentiation,have typical crust-derived magmatic characteristics,and are formed in a tension-type structural environment.(3)Fluid inclusion studies show that the fluid in the area has five hydrothermal activities,the first three of which are hydrothermal activities in the mineralization period,and the latter two are post-mineralization hydrothermal activities.The hydrothermal activity in the ore-forming period is characterized by medium-high temperature(220?300?),medium-low salinity(10%?10%NaCleq),weak acidity(pH=5.99?6.05),partial oxidation(Eh=0.0571V?0.0099V)characteristic,may be dominated by magmatic fluids in the early stage,and the proportion of groundwater and atmospheric precipitation in the late stage increases.The mixing of high salinity fluids from magma and low salinity fluids from groundwater and atmospheric precipitation results in the precipitation of ore-forming materials in the area.(4)Dayana W-Mo mineralization is mainly produced in quartz veins.The characteristics of filling and metasomatism are obvious.It is a multi-stage pulsation hydrothermal fluid-filling genesis deposit associated with the Cretaceous Jianshan biotite granite.