Geological,Geochemical Characteristics And Its Genesis Of The Huaniushan Pb-Zn Deposit,Beishan,Gansu Province

Huaniushan Pb-Zn deposit is located in the south margin of Beishan orogenic belt and the north side of Liuyuan-Daqishan fault.It is a medium-sized Pb-Zn deposit with typical genetic significance in the middle Tianshan-Beishan area.On the basis of summarizing the previous research results,this paper further studied the Huanniushan Pb-Zn deposit,determined the genesis of the deposit and preliminarily discussed the metallogenic mechanism by studying the geological characteristics of the deposit,the geochemical characteristics of trace elements and the geochemical characteristics of isotopes of sphalerite.Mining area is composed of three ore sections,country rocks of the the first and second ore sections are mainly second and third lithologic section of the Nanhuaian-Sinian Xichangjing group,the ore bodies are located in the contact area between the marlized limestone and the shallow metamorphic clastic rocks of the second and third lithologic section and the adjacent interbedded fracture zone.Country rocks of the the third ore sections are mainly second and third lithologic section of the Huainushan group,the ore bodies are located in the contact surface between marlized limestone and basalt and the adjacent interbedded fracture zone.Ore minerals are mainly sphalerite,galena,pyrite and pyrrhotite,wall rock alteration are mainly silicification and pyritization,ore-forming process is divided into three stages,?: quartz-stage of arsenopyrite and pyrite,?: quartz-polymetallic sulfide phase,?: calcite phase.The sphalerite in the Huanniushan Pb-Zn deposit is characterized by riching in Fe,Mn,Cd,In,Cu,poor Ga,Ge,Co,Ni and other elements.Mn,Fe,In,Cd,Cu is in the lattice of sphalerite in the form of isomorphism,Fe based on simple cation exchange(Fe2 + ? Zn2 +)into the crystal lattice of the sphalerite,Cd may into the crystal lattice of the sphalerite in the form of alternative Fe(Cd2 + ? Fe2 +),Ag and Pb in the form of microscopic inclusions occur in sphalerite.According to the geological thermometer of sphalerite,the metallogenic temperature was 250~265?,and the metallogenic temperature was considered to be medium temperature combined with the trace elements character of sphalerite.Sulfur isotope show that source of sulfur may be mixed with Triassic syenogranite and strata source,the lead isotope is mainly the mixed source of mantle and upper crust,and the in-situ s-pb isotope of ore indicates that the ore-forming material mainly comes from the Triassic syenogranite,H-O isotopes and fluid inclusions shows that the ore-forming fluid was dominated by magmatic water in the early stage and was added with meteoric precipitation later,combined with the field geological characteristics and trace elements in sphalerite indicating that Huanniushan Pb-Zn deposit is the medium-high temperature magmatic hydrothermal type deposit.