山东焦家金矿煌斑岩特征及其与金矿化关系

Lamprophyre characteristics and their relation to gold mineralization of Jiaojia gold deposit,Shandong

焦家金矿煌斑岩为钙碱性云斜煌岩和拉辉煌斑岩,为成矿后脉岩。区内煌斑岩及金矿体的产状统计表明,二者产状无明显相关性。地球化学分析表明,煌斑岩中w(SiO2)为38.56%～47.52%,w(TiO2)为0.85%～2.20%,Mg#为45～70,Rb/Sr为0.02～0.08,显示幔源特征。矿石中广泛发育的含CO2包裹体、辉碲铋矿的存在及前人关于氦氩同位素的研究结果表明,幔源物质参与了本区成矿。胶东地区煌斑岩时代集中于89～130 Ma,与大规模成矿作用几乎同时发生;本次研究获得其K-Ar年龄为93.5±1.4 Ma,认为焦家金矿中的煌斑岩与金矿化为幔源C-H-O流体分异演化不同阶段的产物,形成于晚白垩世中国东部岩石圈持续伸展减薄的地球动力学背景。

The lamprophyre in Jiaojia gold deposit includes calc-alkalic kersantite and odinite,which is the post-ore vein.The statistical data of the occurrence of lamprophyre dykes and gold bodies show that they have no significant correlation.Geochemical analysis indicates that the lamprophyre samples show obvious characteristics of the mantle source with w（SiO2） =38.56％ ～47.52％,w（TiO2） =0.85％ ～ 2.20％,Mg# =45 ～70 and Rb/Sr =0.02 ～0.08.The wide development of CO2-bearing inclusions and the existence of tetradymite,together with the previous research on helium and argon isotopes in the orebodies,show that mantle-derived materials were involved in the mineralization.The ages of the lamprophyre in Jiaodong Peninsula focus on 89 ～ 130 Ma,and the K-Ar age of the lamprophyre in Jiaojia deposit was 93.5 ± 1.4 Ma,almost simultaneously with the large-scale mineralization.It is considered that the lamprophyre and the gold mineralization were resulted from the differentiation of the mantlederived C-H-O fluids of different stages,and the lamprophyre was formed in the geodynamic background of continuous extension and thinning of the lithosphere in eastern China during the Late Cretaceous.