【摘要】 研究了碧口群硅铁质岩的地质地球化学特征，认为碧口群硅铁质岩是碧口古洋盆发育过程中海底热液喷流产物，产于类洋脊环境。碧口硅铁岩的REE配分模式，特别是Eu异常及Ce异常变化提供了不同流体相互作用的信息。Eu正异常说明有高温流体参入，其异常程度与古流体和海水的混合程度有关；Ce负异常与Eu正异常出现在同一样品中说明在热液沉积物沉积前热液流体与海水发生了对流混合，异常大小可能反映海水与热液流体对流混合时参与比例不同。更多还原

【Abstract】 Bikou terrane,located on the south side of M ian (xian ) -Lue (yang ) suture zone which divides south Qinling paleo-plate into two parts during the later Paleozoic and early Mesozoicera,is a part of Qinling orogenic belt. The terrane is composed of Bikou-group volcanic rocks and other Proterozoic stratum. Bikou group is the main host stratum of copper deposits and hydrothermal ferruginous silica rocks. The origin of the ferruginous silica rocks has been identified according to their geologic and geochemical characteristics. It is thought that the ferruginous silica rocks are the paleo-seafloor hydrothermal exhalative products during development of Bikou paleo-ocean. The geological setting of the ancient seafloor hydrothermal system is similar to modern oceanic ridge.The REE patterns of the rocks possess Eu and Ce anomalles,which reflect an interaction between hydrothermal water and seawater. The positive Eu anomaly and its various magnitude show a mixing of hightemperature fluid with ambient seawater. Those samples with both negative Ce and positive Eu anomalles indicate that during their formation,a circulating and convecting mining process prior to the precipitation of the ferruginous silica matter was involved. Meanwhile,the variable magnitudes of the Ce anomalies most likely re flect the participation of seawater with different proportions.,更多还原