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

Abstract

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.

Keywords

• tectonic karst
• karst development characteristics
• groundwater circulation
• new isotope
• engineering influence
• jinshajiang fault zone