胶东山后金矿成矿流体及成矿物质来源:来自H-O、Sr-Nd-Pb、He-Ar同位素证据

Ore-forming Fluid and Sources of Shanhou Gold Deposit in Jiaodong Area Evidence from H-O,Sr-Nd-Pb,and He-Ar Isotopes

胶东山后金矿地处招远-平度断裂带南段,规模为大型金矿床。本文在详细的矿相学观察及黄铁矿显微结构研究基础上,对山后金矿主成矿阶段(第Ⅱ、Ⅲ阶段)的石英H-O同位素、载金黄铁矿Sr-Nd-Pb、He-Ar同位素组成进行了系统的分析。测试结果表明,山后金矿载金黄铁矿中流体包裹体的^(3)He/^(4)He为0.45~1.15 Ra,并含有一定量的地壳放射性成因的^(40)Ar,成矿流体显示壳幔混合流体的特征;石英H-O同位素组成也表明,成矿流体可能来自富集地幔流体。^(40)Ar/^(36)Ar值为679.32~804.23,与我国东北部来源于富集地幔样品的^(40)Ar/^(36)Ar特征值相近;H-O和He-Ar的同位素组成均表明,成矿流体很可能来自富集地幔流体。Sr-Nd和Pb同位素组成的分析结果表明,成矿物质可能主要来源于玲珑期花岗岩和郭家岭期花岗岩。

Shanhou gold deposit is a large-scale gold deposit,locating in the southern part of Zhaoyuan-Pingdu gold mineralization belt.On the basis of detailed mineralogical observation and microstructure study of pyrite,isotopic composition of quartz H-O,gold bearing pyrite Sr-Nd-Pb,He-Ar in main mineralization stage(the second and third stages) of Shanhou gold deposit have been analyzed systematically.As showed by the test results,the fluid inclusions in the gold bearing pyrite in Shanhou gold deposit are 0.45~1.15Ra(Ra is the value of air),and contain a certain amount of crust radioactive η^(40)Ar.The ore-forming fluid shows the characteristics of crust mantle mixed fluid.The H-O isotope composition also indicates that the ore-forming fluid may have come from enriched mantle fluids.The Ar value of ^(40)Ar/^(36)Ar ranges from 679.32 to 804.23,which is 2~3 times the characteristic value of atmospheric saturated water,and is similar to the characteristic value of ^(40)Ar/^(36)Ar derived from enriched mantle samples in northeastern China.The H-O and He-Ar isotopic compositions also indicate that the ore-forming fluid may come from enriched mantle fluid.The analysis results of Sr-Nd and Pb isotopic compositions indicate that the ore-forming materials may mainly come from Linglong granite and Guojialing granite.Accompanying with Cretaceous extensional activity and large scale magmatic activity in Jiaodong area,the multi-stage granite body formed intruded and replaced the Jiaodong rock group.In summary,the ore-forming fluid of Shanhou gold deposit is crust mantle mixed fluid,which mixed with atmospheric precipitation in the late stage of mineralization.The ore-forming materials are mainly from Linglong granite,Guojialing granite and Precambrian metamorphic basement.