The Geological Features And Mineralization Of Dadonggou Pb-Zn Ore Deposit, Altay Xinjiang

Dadonggou Pb-Zn ore deposit is a new discovered middle mineral deposit,located in the Kelan basin along the southern margin of Altay Mountains.The known deposits and ore spots in the basin are of volcanic sedimentary-exhalative type characterized by stratabound formation,regular mode of occurrence, stable thickness and useful compositions.Based on detailed field study of geological background,deposit feature,mineralization stages of Dadonggou Pb-Zn deposit,using some feasible methods such as EMPA,fluid inlusion homoternperature and freezing temperatures measuring,Chromatographic analysis,laser raman spectroscopy analysis,stable isotope measuring and lead isotope measuring,this dissertation recognizes its characteristics and source of ore-forming fluid,source of ore-forming materials,and then gives a reasonable explaination about its genesis.The main achievements are summaried as follow:1) The orebody of Dagonggou Pb-Zn deposit occurs in layers with the same trending as the strata. Ore bearing country rock is mainly volcanic sedimentary rock of the Lower Devonian Kangbutiebao Formation and ore occurs in beded,disseminated and veinlet.Ore minerals consist simply of galena, sphalerite and pyrite.2) The analysis on fluid inclusions indicated that the ore-forming temperature is 220～480℃,The gas components of fluid inclusions are mainly CO₂ and H₂O,with minor amounts of CH₄,N₂ and H₂ etc.The liquid components of fluid inclusions are mainly Na⁺,Ca²⁺,F,CI-,minor K and SO42-,and a little Mg²⁺, Br^- and NO₃^-.The calculated fluid density is 0.89～1.08 g/cm³,and pressure is 10～45 MPa.The ore-forming materials is mainly transported by the complex of F,Cl^-,and the changes of physicochemical conditions and the fluid boiling had main effect in the ore material precipitation.3) Theδ¹³C_V-PDB values of calcite range from -4.2‰to 0.4‰,theδD_V-SMOW of the inclusions in quartz range from -89‰to -127‰,and theδ¹⁸O_H2O values of quartz and calcite range from -11.4‰to 7.6‰.It is suggested that the ore-forming fluid was mainly derived from the mixture fluid of meteoric water and magma water.4) Theδ³⁴S_V-CDT values of sulfides range from -22.3‰to 11.7‰,which show that the S of the Dadonggou deposit had both the magmatic and sedimentary origin.5) Lead isotope analyses provide evidence that the lead in galena of Danggoungou Pb-Zn deposit drived from a single normal source,with mainly mantle component,which is similar with the lead in galena and colcanic rocks of the other Pb-Zn deposits in Kelan basin.