作　　者： ; ; ; ; ; ;

机构地区： 中国科学院广州地球化学研究所

出　　处： 《地球化学》 2010年第4期326-336,共11页

摘　　要： 水-岩反应次生矿物的沉淀作用不仅控制着地下水成分的演化,而且对核素的迁移和阻滞作用有重要影响。但在常温系统中,矿物的成核生长需要过饱和驱动力的存在,而且不同次生矿物成核生长所需的过饱和度有差异。本文在对日本和加拿大花岗岩地区水-岩系统的地质和地球化学特征进行分析研究的基础上,使用地球化学模拟软件PHREEQC 2.15和数据库llnl.dat计算了次生矿物在地下水中的饱和指数,从而对各种矿物的沉淀饱和指数进行了估算。结果表明,方解石的化学活动性较强,容易溶解和沉淀,其沉淀饱和指数大约为0.5;针铁矿是地下水中铁的主要沉淀形式,其饱和指数的计算结果与pe值关系密切,沉淀饱和指数高达4.0±0.5;结合高岭石、伊利石、钙蒙脱石和钠蒙脱石之间的相平衡关系,估算其沉淀饱和指数分别为4.0±0.5、4.5±0.5、4.3±0.5和4.3±0.5。 The precipitation of secondary minerals not only controls the evolution of components in groundwater, but also has a significant influence on the migration and retardation of radionuclide in water-rock systems. Under ambient conditions, however, a driving force of oversaturation is required to break the nucleation barrier for the precipitation and growth of secondary minerals, and different degrees of over-saturation are required for the precipitation of different secondary minerals. In this study, saturation indices （SI） for the precipitation of various minerals that would form as secondary phases under ambient conditions, are estimated by using the geochemical simulation software of PHREEQC 2. 15 and the database of llnl. dat based on the geological and hydro-geochemical data from Japanese and Canadian granite regions. The results indicates that calcite is subjected to dissolution and precipitation due to its strong chemical activity, and is expected to precipitate at SILO. 5. Goethite is considered to be a Fe sink in groundwater, the calculated SI value is closely associated with the pe value, and precipitates at SI = 4.0 ± 0. 5. Combined with thermodynamic constrains on secondary clay minerals, the SI values for the precipitation of kaolinite, illite, Ca-montmorillonite and Na-montmorillonite are estimated to be 4. 0 ± 0. 5, 4.5±0. 5, 4.3± 0. 5 and 4.3 ± 0.5, respectively.

关 键 词： 花岗岩 地下水 次生矿物 饱和指数 水 岩反应

领　　域： [天文地球] [天文地球] [天文地球] [天文地球]