金沙江断裂带中段岩溶发育和地下水循环特征

金沙江断裂带中段碳酸盐岩分布区水文地质结构复杂、岩溶水量丰富, 是工程地质安全的重要威胁之一。文章在岩溶地貌和水文地质调查的基础上, 采用水化学和新型同位素测年与示踪的方法, 研究了金沙江断裂带中段岩溶发育特征, 分析了岩溶水补给、径流和排泄过程。结果表明: 岩溶空间分布和地下水补给、径流、排泄均受构造控制; 在垂向上主要存在3个高程级别的岩溶发育分区, 其中二级和三级顶部岩溶的发育时间分别为晚中新世至晚更新世和上新世至晚更新世; 岩溶水补给区海拔4400~4600 m, 主要补给源为大气降水和冰湖水, 水中228Ra/226Ra数据显示非定曲断裂控制范围内水源难以形成跨断裂影响范围的补给; 岩溶水循环速度快, 岩溶大泉的85Kr年龄＜15 a, 且基本没有年龄较大的地下水混合; 径流过程中碳酸盐岩溶蚀和阳离子交换作用不充分。在工程中应充分考虑活动断裂影响下岩溶水径流通道空间分布、高水压影响和特殊天气条件带来的地质灾害威胁。 

Characterization of karst development and groundwater circulation in the middle part of the Jinshajiang fault zone

The complex hydrogeological structure and abundant karst water in the carbonate rock distribution area in the Jinshajiang fault zone's middle section are essential threats to engineering safety. Based on karst landform and hydrogeological investigations, the article presents the karst development characteristics in the Jinshajiang fault zone's middle section, and analyzes the recharge source, runoff process, and discharge characteristics of karst water using the methods of hydrochemical and new isotopic dating and tracing. The results show that structures control the spatial distribution of karst and the groundwater circulation in the study area. There are mainly three elevation-level karst development zones in the vertical direction. The development time of the second elevation-level karst is from the late Miocene to the late Pleistocene, and the top of the third elevation-level karst is from the Pliocene to the late Pleistocene. The karst water recharge area is at an elevation of 4400~4600 m. The primary recharge sources are atmospheric precipitation and glacial lake water. The 228Ra/226Ra data in the water shows that it is difficult for water sources under the control of a non-fixed-curvature fault to form recharge across the affected area of the fault. The karst water circulates fast, the 85Kr age of the karst spring is < 15 a, and there is basically no older groundwater mixing. Carbonate rock dissolution and cation exchange are not sufficient during groundwater runoff. In the engineering project, the spatial distribution of karst water runoff channels under the control of active faults, the influence of high-water-pressure and the threat of geological disasters caused by special weather conditions should be fully considered.