金顶超大型铅锌矿床的成矿金属来源——来自铅同位素组成的制约  

Metal source of Jinding superlarge lead-zinc deposit:Constraint from lead isotopic composition

作　　者：郝宏达[1,2] 宋玉财[1] 庄天明 马建雄[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学地球科学与资源学院,北京100083 [3]烟台黄金职业学院,山东招远265401

出　　处：《矿床地质》2017年第2期379-390,共12页Mineral Deposits

基　　金：国家重点研发计划项目(编号:2016YFC0600306);国家自然科学基金(编号:41273050;41403043;41320104004);国土资源大调查项目(编号:DD20160024-02)联合资助

摘　　要：金顶矿床是世界著名的超大型铅锌矿床,其巨量的金属堆积引起许多学者对成矿金属来源的关注。前人通过铅同位素示踪研究,提出了成矿金属来自地幔、上地壳、下地壳及不同端员混合等不同认识。理论分析表明,这些观点认识的差异可能源于不同作者分析铅同位素数据存在测试误差。基于此,笔者在金顶矿床选择了7个代表性硫化物样品,再次进行了铅同位素分析。结果显示,矿床铅同位素组成为^(206)Pb/^(204)Pb=18.3945~18.4429、^(207)Pb/^(204)Pb=15.6412~15.6583、^(208)Pb/^(204)Pb=38.6266~38.6772,在铅同位素演化模式图解(Zartman et al.,1979)中数据点分布集中,处于"造山带"和"上地壳"演化曲线之间,未显示出明显的线性分布特点,表明金顶矿床成矿金属来源主要为壳源;区域对比表明,金顶矿床明显比白秧坪矿带铅锌矿床贫放射性成因铅,而与区域VMS型矿床铅同位素组成更为接近,这表明金顶矿床与白秧坪矿带矿床有着不同的金属物源区,其金属可能来自盆地底部晚三叠世火山岩或其内早期的VMS矿化。The Jinding deposit is a famous superlarge lead-zinc deposit, whose huge amounts of metal accumulation has caused many scholars to focus on the ore-forming material sources. Based on isotope tracing, the opinions in the past were controversial, and the opinions concerning metal sources of the Jinding deposit divided into coming from the mantle, from the upper crust, from the lower crust and from the mixing of different end-members. However, through theoretical analysis, the authors found that the differences between these viewpoints may come from the testing errors of lead isotopic analysis. On such a basis, the authors chose 7 representative sulfide samples for lead isotope analysis again. The results demonstrate the lead isotope compositions of the deposit are 206Pb/204Pb=18.3945-18.4429, 207Pb/204Pb=15.6412-15.6583, 208Pb/204Pb=38.6266-38.6772. The data distribution is concentrated on the lead isotope evolution curves （Zartman et al., 1979）, between the ＂orogene＂ evolution curve and the ＂upper crust＂ evolution curve and does not illustrate a liner characteristic. All the evidence suggests that the ore-forming metal sources of the Jinding deposit were mainly derived from the crust. What is more, the regional comparison shows that the Jinding deposit contains less radiogenic lead than the Baiyangping lead-zinc ore concentration area, which is close to the lead composition of the regional VMS type deposits. These data indicate that the Jinding deposit and the Baiyangping ore concentration area have different metal sources, and that the metal source of the Jinding deposit probably came from the late Triassic volcanic rocks on the bottom of the basin or the early VMS mineralization in the basin.

关 键 词：地球化学 铅同位素 金属来源 测试误差 金顶 

分 类 号：P618.42[天文地球—矿床学] P618.43[天文地球—地质学]