胶莱盆地东北缘前垂柳金矿床S、Pb同位素组成:对成矿物质来源的指示

S and Pb isotopic compositions of the Qianchuiliu Gold Deposit on the northeastern margin of the Jiaolai Basin:Implication on the source of ore-forming material

前垂柳金矿为胶东胶莱盆地东北缘新发现的蚀变岩型金矿床,金矿体主要赋存于牧牛山岩体(二长花岗岩)、荆山群地层和鹊山岩体(糜棱岩化二长花岗岩)之间厚大的构造蚀变带内,截止目前推测资源量达到中型规模,但矿床的成矿物质来源尚不明确。基于前人研究及野外调查,选择典型矿体中含金黄铁矿作为研究对象,开展了S、Pb同位素分析,探讨了矿床的成矿物质来源。测试结果显示:矿石硫化物δ^(34)S值总体为10.13‰~12.39‰,极差为2.26‰,平均值10.98‰,均一程度高,具高δ^(34)S值特征,反映了深部成矿流体上侵过程中混染了更多的地层中的硫,显示了荆山群地层对成矿有一定贡献;矿石铅同位素^(206)Pb/^(204)Pb比值为17.149~18.886,^(207)Pb/^(204)Pb比值为15.482~15.677,^(208)Pb/^(204)Pb比值为37.860~40.073,显示前垂柳金矿铅为壳幔混合来源,且具有下地壳铅的特征。该矿床S、Pb同位素特征显示成矿物质来源为壳幔混源,与周边辽上、蓬家夼等典型矿床成矿物质来源一致,反映了该区燕山期大规模成矿事件,预示了胶莱盆地东北缘具有较大的找矿潜力。

The Qianchuiliu Gold Deposit on the northeastern margin of the Jiaolai Basin is a newly discoverd altered rock type gold deposit,and is a medium-sized gold deposit hosted in the structural alteration zone between Muniushan,Jingshan Group and Queshan monzonitic granites.However,the source of ore-forming materials and the ore genesis are not clear.Based on previous field and analytical studies,the authors conducted sulfur and lead isotopic analyses on gold-bearing pyrite from typical ores as the research target.Theδ^(34)S values are high and homogeneous ranging from 10.13‰-12.39‰,with an average of 10.98‰and polar odds of 2.26‰.These sulfur isotopic results reveal a mixing process of sulfur in the Jingshan Group during the upwelling of deep ore-forming fluid.The ratios of^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb,and^(208)Pb/^(204)Pb vary from 17.149-18.886,15.482-15.677,and 37.860-40.073,respectively,suggesting a crust-mantle mixed source.In conclusion,sulfur and lead isotope analysis results of the Qianchuiliu Gold Deposit show a crust-mantle mixed source and are similar to those of typical gold deposits in this region.The gold deposits on the northeastern margin of the Jiaolai Basin formed at the large-scale Yanshanian metallogenic event,indicating great prospecting potential in this area.