The World-class Huoshaoyun Nonsulfide Zinc-lead Deposit,Xinjiang,NW China:Formation By Supergene Oxidization Of A Mississippi Valley-type Deposit

Huoshaoyun is a newly discovered world-class nonsulfide zinc-lead deposit in Xinjiang,NW China,so its genesis attracts many geologists'attentions.Conformable orebodies in the deposit contain massive and minor stratiform and breccia-hosted ores that are dominated by smithsonite and cerussite.Ores are hosted by Middle Jurassic sedimentary gypsum-bearing platform facies carbonate.Clearly,the carbonate is typical host for Mississippi Valley-type?MVT?deposit rather than for sedimentary exhalative?SEDEX?deposit.Galena is common in the ores and was replaced by cerussite,implying that precursor mineralization in the deposit was zinc and lead sulfides.?³⁴S_V-CDT-CDT values?-33.2‰^-18.7‰?of the galena indicating that derivation of reduced sulfur was related to bacterial sulfate reduction?BSR?process,which is common in MVT deposits but is scarce in magmatic-related Zn-Pb deposits.Together with the absence of magmatic-related hydrothermal alteration and mineralization,it suggests that primary mineralization at Huoshaoyun is of MVT origin.Oxygen isotopic compositions of water that reached isotopic equilibrium with smithsonite and cerussite are low in temperature and light in?¹⁸O values.The equilibrium temperature of the II ore body in the upper ore layer is 0.58?,the?¹⁸O_V-SMOW-SMOW value of water is-14.5‰;the equilibrium temperature of the III ore body of the lower ore layer is8.93?,and the?¹⁸O_V-SMOW-SMOW of water-12.1‰,implyimg that meteoric water was involved in the two mineral formations.Combined with the observation that galena was replaced by cerussite and lead characteristics of galena and cerussiteor are similare.The average values of galena ²⁰⁷Pb/²⁰⁴Pb are 15.685?n=8??15.692?n=5?;²⁰⁶Pb/²⁰⁴Pb are 18.541?n=8??18.536?n=5?.The average values of cerussiteor²⁰⁷Pb/²⁰⁴Pb 15.687?n=9??15.680?n=5?;²⁰⁶Pb/²⁰⁴Pb are 18.541?n=9??18.536?n=5?.We suggest that the smithsonite and cerussite were the result of intensive supergene oxidization of primary znic and lead sulfides of MVT origin.