西藏龙玛拉矽卡岩型铅锌多金属矿床金属矿物特征及地质意义OA北大核心CSTPCD

The Longmala lead-zinc polymetallic deposit is a typical Pb-Zn deposit in the Nyainqentanglha skarn type polymetallic metallogenic belt on the northern margin of the eastern Gangdise metallogenic belt.The deposit is dominated by lead-zinc-silver mineralization,accompanied by iron-copper mineralization,and characterized by rich mineralized elements and high grade.Obvious mineralization zonation is developed vertically in the deposit.Lead-zinc-silver mineralization,zinc-copper mineralization,iron-copper mineralization and iron mineralization are successively developed from the top to foot of the orebody,indicating the element combination and mineral association were developed from low temperature to high temperature from the top to foot of the orebody.The re-sults of microscopic identification and electron probe analysis show that the main metal minerals of the deposit are galena,sphalerite,chalcopyrite,pyrite,pyrrhotite and magnetite,as well as minor bismuth minerals such as cosalite,natural bismuth and secondary minerals such as marcasite,covellite and malachite.The ore minerals have a complex intersperses metasomatism relationship,which is studied from detailed field observation and mi-croscopic identification,and the mineral paragenesis was clarified.The Co/Ni ratio of multi-stage pyrite is con-centrated in the range of 1～5,showing the characteristics of magmatic hydrothermal origin,and the Fe/(S+As)ra-tio and colloidal pyrite suggest that the deposit was formed in a mesogene to hypabyssal environment.Sphalerite in the Longmala deposit is rich in Fe and Mn,mostly marmatite,indicating that it was formed in a medium to high temperature environment.The Fe element thermometer estimates that the metallogenic temperature of spha-lerite is 259～305℃.The pyrrhotite is mainly monoclinic pyrrhotite and it occurs in abundance in both ore bodies and sand slate,indicating that ore forming fluids cooled rapidly after moving to the surface.Sulfide precipitation occurred under strong reduction condition.The Longmala deposit is a distal magmatic hydrothermal skarn depo-sit.The bismuth minerals in the deposit have a close relationship with silver,which indicates that bismuth may play an important role in silver enrichment,and has certain indicative significance for the study of silver minera-lization in this belt.