摘要
为了探讨高放废物地质处置甘肃北山预选区旧井和新场预选地段的古地下流体来源、成因、化学演化历史以及水-岩相互作用,文章系统研究了该地段花岗岩填隙方解石的产出特征及其碳、氧、锶同位素的组成特征。测试结果表明,旧井和新场方解石的δ13 C组成均较稳定且为负值(分别为-11.6‰^-5.7‰和-9.9‰^-5.1‰);δ18 O分别为-0.7‰~19.7‰和10.9‰~21.9‰,旧井方解石具有更宽的δ18 O取值范围。87 Sr/86 Sr也略有差异,旧井为0.708584~0.718749,新场为0.708838~0.732967,二者随深度增加而呈明显的降低趋势。研究表明,北山预选区地下流体来源及成因较复杂,浅部地下水受大气降水的影响较大,深部流体则主要源于地下咸水,为低温流体蚀变成因。花岗岩裂隙中的水-岩反应强度总体较弱,地下水环境相对稳定。相比较而言,新场岩体深部的地球化学环境更稳定,更有利于高放废物的长期处置。
In order to understand the origin, genesis, chemical evolution history and water/rock interac- tion of the paleo-groundwater in Beishan area, the pre-selected site for geological repository of high-level radioactive waste in China, the carbon, oxygen and strontium isotope composition of the filling calcite in Jiujing and Xinchang granite have been systematically analyzed. The results show that the δ13C values of calcite in Jiujing （-11.6‰4-5.7‰） and Xinchang （-9.9‰^-5.1‰） are both negative and rela- tively stable. Theδ18O values of calcites in Jiujing （-0. 7‰-19.7‰） are wider in range than those in Xinchang （10.9‰-21.9‰） . The 87Sr/86 Sr ratios are slightly different between Jiujing （0. 708584- 0. 718749） and Xinchang （0. 708838 -0. 732967）, but both obviously decreased with depth increas- ing. Those results suggest that the origin and genesis of the paleo-groundwater in Beishan site are fairly complex, with strong influence of meteoric water in the shallow part, while affected by underground brine in the deep part. Most of calcites were formed due to low temperature fluid reaction. The groundwa- ter environment of Beishan site was relatively stable with a less extent of the water/rock interac- tion. Compared with Jiujing sub-area, the geochemical environment of Xinchang sub-area is more stable for long-term disposal of hiarh level radioactive waste.
出处
《铀矿地质》
CAS
CSCD
2014年第1期23-29,共7页
Uranium Geology
