Abstract:The Huoshaoyun deposit in Hotan County, Xinjiang, is one of the important superlarge(giant) deposits which have been found in the western part of the Qinghai—Xizang(Tibet) Plateau in recent years. It is the largest zinc—lead deposit in China and the rare giant smithsonite deposit in the world. The proved lead and zinc resource reserves of the Huoshaoyun deposit are more than 18 million tons, it is thus especially notable for the deposit origin due to its great economic value. Based on the detailed observation of the outcrop of orebody and a number of drilling cores, the host Longshan Formation consists of micrite, calcarenite, oolitic limestone and bioclastic limestone, with well developed bird’s eye structure, fenestral cavities and geopetal stromatactis structure, indicated that the Longshan Formation was formed in a beach environment (shell, oolitic) of the Middle Jurassic carbonate platform. There are over twenty orebodies within two ore- bearing layers have been found in the ore district, and the main orebody reserves account for more than 95 percent of the total. The zinc orebodies appear to be stratiform and lenticular with a very small angle to the host carbonate bedding. The smithsonite is the main ore mineral, a few galena and cerussite; calcite is the main gangue mineral, a few gypsum. The smithsonite ores are massive, vuggy, banded, with the idiomorphic—semi- idiomorphic microcrystalline, metasomatic and zebra texture. The formation of the large, high- grade Huoshaoyun Zn deposit occurred during three successive metallogenic stages with smithsonite(Sm1), smithsonite(Sm2)—(galena) and smithsonite(Sm3)—galena (anglesite), main stage of smithsonite ore (Sm 1) is composed of smithsonite 80% of the total. The carbon and oxygen isotopes of the simthsonite and the host limestone are similar, confirming the simthsonite dependence on the host limestone. The carbon—oxygen isotopic characteristics together with the metasomatic texture of the smithsonite ore, support the hypogene hydrothermal metasomatic origin of Huoshaoyun Zn deposit. Based on the detailed petrographic and carbon—oxygen isotopic study, a new type of hypogene smithsonite mineralization for the Huoshaoyu deposit is proposed in this paper. Through the coupling process with calcite (limestone) dissolve—smithsonite precipited, the hydrothermal fluid with Zn- rich,Pb- low and S2- - poor metasomatic replace the host limestone of the Longshan Formation in the Huoshaoyun ore district. Thus, the Huoshaoyun deposit is not formed by supergene oxidation of a MVT zinc sulfide deposit, nor a SEDEX zinc carbonate deposit, it is a hypogene zinc carbonate deposit.