DISCUSSION ON THE ORE TYPES AND GENESIS OF LAOCHANG POLYMETALLIC DEPOSIT IN LANCANG AREA, YUNNAN PROVINCE

The Laochang deposit in Lancang, Yunnan Province, is one of the most important Pb-Zn-Cu-Mo polymetallic deposits in the southern Sanjiang metallogenic belt. According to different ore-bearing characteristics, lithology, ore structures and metallogenic elements, the ore types of the study area are systematically divided into Pb-Zn sulfide ore, Pb-Zn oxidized ore, granular Cu-bearing pyrite ore, massive Cu-bearing pyrite ore, skarn-type ore and porphyry molybdenum ore. The orebody occurrence, trace element geochemistry and chronology all show that the Pb-Zn sulfide ore, granular Cu-bearing pyrite ore and massive Cu-bearing pyrite ore are of volcanic exhalation sedimentary origin (VMS type), while the Pb-Zn oxide ore, skarn-type ore and porphyry molybdenum ore are of porphyry hydrothermal origin. The main ore-controlling factor of VMS type is strata, that of Pb-Zn oxide ore is structure, that of skarn-type ore is lithology and that of porphyry molybdenum ore is rock mass.