Determining mine water sources and mixing ratios affected by mining in a coastal gold mine, in China

This study aimed to identify the potential water sources of the Sanshandao Gold Mine and determine the end-member mixing ratios, to prevent seawater intrusion and water inrush disasters. Based on the hydrogeological setting, an end-member model of mine water based on the hydrogeochemical and isotopic analysis was established. Then, the maximum likelihood method was used to estimate the mixing ratios of water sources at each site and analyze the evolution rules of mine water. The results indicated that this method can effectively identify the water sources and calculate the mixing ratios. The fitting results between the calculated and measured values of the stable isotopes and ion concentrations were good. The mean values of deviation for δ 18 O, δD, K + , Na + , Ca 2+ , Mg 2+ , Cl − , SO 4 2− , and Ca 2+ +Mg 2+ were 0.01, 0.02, 0.17, 0.00, − 0.23, 0.38, 0.00, 0.04, and − 0.02, respectively. The mixing ratio results demonstrate that seawater is the main component of the mixed water and the proportion varies with the mining activities; especially in 2011 and 2014, the seawater had a high proportion in the entire mine. The effect of mining on mixing was studied by dividing the study area. Both horizontal and longitudinal mixing were analyzed. The water sites located in the south of F3 (this area is less affected by mining) had a low proportion of seawater. The main range affected by fresh water was at the 465-m sublevel and above. The water flow around F3 was greatly affected by mining, and the proportion of seawater around F3 fluctuates greatly every year; so F3 should be monitored more frequently.