Abstract: LA-ICP-MS technology is widely used in the field of geoscience to finely characterise the composition of min erals.As one of the most widely distributed sulphides in nature,pyrite is rich in trace elements and can be indicative of deposit genesis.In this paper,LA-ICP-MS was applied to test in situ trace elements and in situ sulphur isotopes of pyrite in the lead zinc ore body of the Yangla Cu polymetallic deposit,and the results show that the pyrite in the early stage of mineralisation (Py Ⅰ) was produced in the form of authomorphic-heteromorphic grains,and the pyrite in the late stage of mineralisation (PyⅡ) was produced in the form of irregular fine veins.Both stages of pyrite are enriched in Ge,As,Ag,and Sb,and poor in Mn,Zn, and Sn.Pb in pyrite exists in the form of galena microinclusions,and Ag,Sb,and Cu are present in the galena lattice in the form of plasma isomorphisms.The in situ sulphur isotope variations range from 0.60‰ to 4.22‰,with an average of 2.08‰, indicating that sulphur mainly originates from the mantle or magma.The two phases of pyrite are rich in low-temperature ele ments such as As and Sb,poor in high-temperature elements such as Se and Te,and the Co content is basically located in the low-temperature pyrite interval,indicating that the two phases of pyrite are mainly formed in the low and medium temperature conditions.The w(Co)-w(Ni)-w(As) ternary diagram,w(Co)-w(Ni) binary diagram and w(Sb)/w(Bi)-w(As)/w(Ag) binary diagram all indicate that the pyrite is of hydrothermal-sedimentary genesis.Combining the results of previous research and the geological characteristics of the orebody,this paper concludes that pyrite is of hydrothermal-sedimentary origin.

Key words: pyrite,trace element,S isotope in situ,lead-zinc ore body,Yangla Cu-polymetallic Deposit