兰坪白秧坪铜银多金属矿床成矿物质来源的铅和硫同位素示踪

白秧坪铜银多金属矿床主要产于白垩系下统景星组石英砂岩、粉砂岩中,矿石铅同位素组成特征与景星组砂岩的铅同位素组成比较接近,表明壳源物质参与了成矿作用。作ZartMan图解和Δγ-Δβ图解表明,矿石铅属于壳幔混合来源。矿石铅μ值介于9.43~9.65之间,Th/U比值介于3.72~3.87之间,表明矿石铅为壳幔混合铅。该矿床硫同位素组成表明,硫来源于深部地幔硫遭受地壳硫的混入。该矿床的成矿作用发生于开放体系之中,成矿物质来源为深部幔源物质混合了壳源物质。

Lead and sulfur isotopic tracing of the ore-forming material from the Baiyangping copper-silver polymetallic deposit in Lanping, Yunnan

The Baiyangping copper-silver polymetallic deposit in Lanping, Yunnan occurs dominantly in the quartz sandstones and siltstones from the Lower Cretaceous Jingxing Formation. The lead isotopic compositions of the ores from the deposit are similar to those of the sandstones from the Formation, implying that the crust-derived matter seems to have been involved in mineralization. The Zartman diagram and △γ-△β plot show that the ore lead has a mixed crust-mantle origin, with the μ values ranging between 9.43 and 9.65 and the Th/U ratios between 3.72 and 3.87. The sulfur in the ore deposit is derived from the deep-seated mantle sulfur mixed by the crustal sulfur. The mineralization of the copper-silver deposit took place in an open system, and the ore-forming material consists of the deep-seated mantle-derived material mixed by the crust-derived material.