河北平原地下水锶同位素形成机理

为了研究河北平原地下水锶同位素的来源与形成机理, 对所采水样进行了分析.研究了87Sr/86Sr比值“时间积累效应”: 随着地下水年龄和埋深的增大而增大; 与地下水中过剩4He_exc呈正相关关系, 与δ18O和δD呈负相关关系.探讨了Sr2+与87Sr/86Sr比值的关系, 将地下水分为3类: (1) 中等Sr2+含量与高87Sr/86Sr比值水(Ⅰ类水); (2) 低Sr2+含量与高87Sr/86Sr比值水(Ⅱ类水); (3) 高Sr2+含量与低87Sr/86Sr比值水(Ⅲ类水), 即热水.通过综合分析认为: (1) 河北平原第四系地下水中的放射成因Sr是由富含Na和Rb的硅酸盐矿物风化作用提供的, 主要矿物为斜长石; (2) 黄骅港热水中的放射成因Sr是由碳酸盐溶解形成的, 87Sr/86Sr比值低, Sr/Na比值大; (3) 补给区地下水是由流经火成岩和变质岩区地下水的侧向补给的, 87Sr/86Sr比值中等.第三系地下水放射成因Sr的来源及形成机理尚须进一步研究. 

Formation Mechanism of Sr Isotopes in Groundwater of Hebei Plain

To analyze the genesis of Sr isotopes ingroundwater of Hebei plain, time-accumulative effect of 87Sr/86Sr ratios was studied. It is shown that 87Sr/86Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to 4He_exc and a negative correlation to δ18O and δD. The groundwater is divided into three groups to discuss the relation between 87Sr/86Sr ratio and Sr2+ content: (1) moderate Sr2+ content and higher 87Sr/86Sr (water I); (2) lower Sr2+content and higher 87Sr/86Sr (water Ⅱ); and (3) higher Sr2+ content and lower 87Sr/86Sr (water Ⅲ), that is hot water. On the basis of integrated analysis, it was considered that (1) the radiogenic Sr in the Quaternary groundwater (Q4-Q1) originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; (2) the radiogenic Sr of hot water in Huanghua port is attributed to carbonate dissolution, with lower 87Sr/86Sr and higher Sr/Na; (3) the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate 87Sr/86Sr ratio. However, the genesis of Sr isotopes in Tertiary groundwater needs further studies.