胶西北金成矿区He、Ar同位素组成及成矿流体来源研究

胶东半岛西北地区是我国重要的金成矿区,主要受三山岛断裂、焦家断裂、招平断裂带控制。为探讨3条主要成矿带成矿流体的来源与区别,对成矿带内典型矿床载金黄铁矿中流体包裹体进行了He、Ar同位素测试。结合前人数据表明三山岛成矿带3He/4He均值为1.95 Ra,焦家成矿带^3He/^4He均值为1.74 Ra,招平成矿带^3He/^4He均值为1.54 Ra,从西往东逐渐降低,说明地幔流体参与成矿自西往东逐渐降低。黄铁矿流体包裹体中放射性成因Ar所占比例范围三山岛成矿带1.17%~87.12%,平均33.04%,焦家成矿带15.57%~90.00%,平均55.75%,招平成矿带7.94%~92.69%,平均44.23%,说明在成矿过程中,地壳成矿流体参与成矿作用焦家成矿带最高,招平成矿带次之,三山岛成矿带最低。结合H、O稳定同位素研究,认为成矿流体主要来源于地壳,并有地幔流体加入,具地壳流体和地幔流体混合特征,上升过程中可能还有少量大气降水的参与。

A study of the He-Ar isotopic composition and the source of metallogenic fluid in the gold concentration area of Northwestern Jiaodong

The Jiaodong gold province contains more than 4 000 tons of gold reserves and is hence the most important gold-producing area in China. The gold deposits are mainly controlled by the NE-striking Sanshandao, Jiaojia, and Zhaoping faults from west to east, and form three gold metallogenic belts. In order to explore the source of ore-forming fluids in these metallogenic belts, the authors investigated He and Ar isotopes of fluid inclusions in the gold-bearing pyrite form several typical deposits, and the results show that the mean ratio of ³He/⁴He is 1.95 Ra in the Sanshandao belt, 1.74 Ra in the Jiaojia belt, and 1.54 Ra in the Zhaoping belt, with a decreasing trend from west to east. The values of radioactive Ar are 1.17%~87.12% (averagely 33.04%) in Sanshandao, 15.57%~90.00% (averagely 55.75%) in Jiaojia, and 7.94%~92.69% (averagely 44.23%) in Zhaoping, suggesting that the highest contribution of crustal fluids was from Jiaojia, the medium contribution was from Zhaoping, and the lowest contribution was from Sanshandao. Combined with H-O isotopic data, the authors hold that the ore-forming fluids in the Jiaodong gold province were mainly mixed crust-derived and mantle-derived fluids, with possible contribution of meteoric water during the fluid ascending.