Formation Mechanism of Sr Isotopes in Groundwater of Hebei Plain
-
摘要: 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4Heexc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.Abstract: 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 4Heexc 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.
-
Key words:
- strontium /
- 87Sr/86Sr /
- groundwater /
- Hebei plain.
-
图 1 河北平原第四纪地层轻矿物含量变化对比图(据陈望和和倪明云, 1987)
Fig. 1. Comparison by content between quartz and feldspar in Quaternary stratum of Hebei plain
表 1 沧州地区地层中元素平均含量与克拉克值的对比(据杨子赓, 1979)
Table 1. Comparison between mean element content and carat gram value from Quaternary stratum of Cangzhou
表 2 研究区深层地下水化学分析结果及取样深度(单位: mg/L)
Table 2. Groundwater chemical data and depth of study area
-
[1] Chen, W. H., Ni, M. Y., 1987. Geology of Hebei Provinceduring Quaternary. Geology Publishing House, Beijing (in Chinese). [2] Franklyn, M. T., McNutt, R. H., Kamineni, D. C., et al., 1991. Groundwater87Sr/86Sr values in the Eye-Dashwa Lakes pluton, Canada: Evidence for plagioclase-waterreaction. Chemical Geology (Isotope Geoscience Section), 86: 111-122. doi: 10.1016/0168-9622(91)90057-4 [3] Fritz, B., Richard, L., McNutt, R. H., 1992. Geochemical modeling of Sr isotopic signatures in the interaction betweengranitic rocks and nature solutions. In: Kharaka, Y. K., Maest, A. S., eds., Proc. 7th Int. Symp. Water-Rock Interaction, 927-930. [4] Huang, W. H., Yang, M., Yu, B. S., et al., 2006. Strontiumisotope composition and its characteristics analysis of Cambrian-Ordovician carbonate in Tazhong district, Tarimbasin. Earth Science—Journal of China University of Geosciences, 31 (6): 839-844 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DQKX200606012.htm [5] McNutt, R. H., 1987. 87Sr/86Sr ratios as indicators for water-rock interactions: Applications to brines found in Precambrian age rocks from Canada. In: Fritz, P., Frape, S. K., eds., Saline waters and gases in crystalline rocks. Geol. Assoc. Can. Spec. Pap., 33: 81-88. [6] McNutt, R. H., Frape, S. K., Fritz, P., 1984. Strontiumiso-topic composition of some brines from the Precambrian Shield of Canada. Isot. Geosci., 2: 205-215. [7] Pingitore Jr, E. N., East man, P. M., 1986. The coprecipitation of Sr2+with calcite at 25℃ and 1 atm. Geochim. Cosmochim. Acta, 50: 2195-2203. doi: 10.1016/0016-7037(86)90074-8 [8] Sun, M. L., 1995. The mass spectrometric measurement of heliumisotopein water. Journal of Chinese Mass Spectrometry Society, 16 (1): 34-37 (in Chinese with English abstract). [9] Wan, J. W., Liu, C. F., Chao, N. Y., et al, 2003. Theory and practice of isotopes hydrology. China University of Geosciences Press, Wuhan (in Chinese). [10] Whitford, D. J., Andrew, A. S., Carr, G. R., et al., 1998. Application of isotope studies of Australiangroundwaters to mineral exploration: The abra prospect, western Australia. In: Arehart, G. B., Hulston, J. R., eds., Water-rockinteraction. Balkema, Rotterdam, 9: 583-586. [11] Yang, Z. G., 1979. Several basic problems about Quaternarysediments in Hebei plain. Acta Geologica Sinica, 53 (4): 263-279 (in Chinese with English abstract). [12] Zhou, A. G., Gan, Y. Q., Liu, C. F., et al., 2005. Srisotope characteristics of groundwater in Hebei plain. Acta Geoscientica Sinica, 26 (Suppl.): 279-282 (in Chinesewith English abstract). [13] 陈望和, 倪明云, 1987. 河北第四纪地质. 北京: 地质出版社. [14] 黄文辉, 杨敏, 于炳松, 等, 2006. 塔中地区寒武系-奥陶系碳酸盐岩Sr元素和Sr同位素特征. 地球科学——中国地质大学学报, 31 (6): 839-844. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200606012.htm [15] 孙明良, 1995. 水中氦同位素的质谱分析. 质谱学报, 16 (1): 34-37. https://www.cnki.com.cn/Article/CJFDTOTAL-ZPXB501.005.htm [16] 万军伟, 刘存富, 晁念英, 等, 2003. 同位素水文学理论与实践. 武汉: 中国地质大学出版社. [17] 杨子赓, 1979. 试论河北平原东部第四纪地质几个基本问题. 地质学报, 53 (4): 263-279. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE197904000.htm [18] 周爱国, 甘义群, 刘存富, 等, 2005. 河北平原地下水锶同位素特征. 地球学报, 26 (增刊): 279-282. https://www.cnki.com.cn/Article/CJFDTOTAL-DQXB200806017.htm