硫、铅同位素对江西紫云山岩体及其周边W-Cu-Mo-U多金属矿床成矿作用制约

S and Pb isotopic constraints on the multi-metal(W-Cu-Mo-U) mineralization of Ziyunshan Intrusive Rocks, Jiangxi Province

为探讨研究区大规模成矿流体演化特征,对紫云山岩体及其周边的W-Cu、Mo-Cu、Mo、U多金属矿床的硫、铅同位素特征进行了系统研究。研究区的多金属矿硫化物的δ34SCDT为1.2‰~21.1‰,分属1.0‰~3.0‰和21.1‰两个区间附近,分别对应W-Cu-Mo矿化和U矿化,推测研究区的W-Cu-Mo成矿流体中硫以幔源为主,而铀成矿流体则可能是有围岩硫的加入。研究区的W-Cu-Mo多金属矿床的硫化物矿石铅同位素组成:^(208)Pb/^(204)Pb=38.541~38.742,平均38.705;^(207)Pb/^(204)Pb=15.617~15.710,平均15.654;^(206)Pb/^(204)Pb=18.240~18.433,平均18.299。黑钨矿的铅同位素组成:^(208)Pb/^(204)Pb=38.649~39.595,平均39.122;^(207)Pb/^(204)Pb=15.542~15.828,平均15.685;^(206)Pb/^(204)Pb=20.842~21.319,平均21.081。石英的铅同位素组成:^(208)Pb/^(204)Pb=37.683;^(207)Pb/^(204)Pb=15.602;^(206)Pb/^(204)Pb=20.442。紫云山花岗岩铅同位素组成:^(208)Pb/^(204)Pb=38.583~39.182,平均38.943;^(207)Pb/^(204)Pb=15.635~15.683,平均15.657;^(206)Pb/^(204)Pb=18.714~19.276,平均18.937。综合全方位对比法、三参数法和模式图解法,认为研究区成矿物质具有岩浆和地层混合铅的特征,也有部分幔源铅的加入。研究矿区发生的过大规模的双源成矿流体作用以及流体的多阶段演化,导致W-Cu-Mo-U成矿元素共生分异的现象。

Systematic analyses of Pb and S isotopes are conduct on the W-Cu-Mo-U ore deposits in the Ziyunshan Intrusive Rocks （ZIR）, in order for better understanding of the evolution of large-scale ore-forming fluids. Sulfides from the ores are characterized by δ34ScDT = 1.2‰--21.1‰, with 1.0‰-3.0‰ for W-Cu-Mo metallogenesis and 21.1‰ for U metallogenesis, and have 208pb/204pb =38.541-38.742 （averaging at 38.705）, 207pb/204pb= 15.617- 15.710 （averaging at 15.654）, and 206pb/204pb = 18.240-18.433 （averaging at 18.299）. Wolframites have 208pb/204pb = 38.649-339.595 （averaging at 39.122）, 207pb/204pb = 15.542--15.828, （averaging at 15.685） and 206pb/204pb = 20.842-21.319 （averaging 21.081）, and quartzes have 208pb/204pb = 37.683, 207pb/204pb = 15.602 and 206pb/204pb = 20.442. The ZIR have 208pb/204pb = 38.583--39.182 （averaging at 38.943）, 207pb/204pb = 15.635 -15.683 （averaging at 15.657 ） and 206pb/204pb = 18.714-19.276 （averaging at 18.937）. These isotopic data suggest that the source materials of the ore deposits could not be solely derived from the ZIR. In combination withthe literature Pb isotopic data for the volcanic rocks of the study area, we concluded that the metallogenic hydro- thermal fluids from ZIR and Yuhuashan volcanic rocks play important roles in the genesis of the W-Cu-Mo-U ore deposits.