Monitoring experiment of in-situ leaching in ion-type rare earth mines based on temporal variations in resistivity

Ion-adsorbed rare earth ore is a relatively rare earth ore resource, and in-situ leaching is the main way of mining ion-type rare earth ore. Monitoring the diffusion of leaching liquid in deep depth can provide important support for efficient mining of rare earth ore and environmental control. The leaching liquid presents relatively low resistance in the regolith, and it is theoretically feasible to monitor the diffusion of leaching liquid by using the time-lapse change of resistivity. This study focuses on a rare earth ore exploration area in Fujian Province. First, a high-density resistivity exploration line is arranged in the target liquid injection area, and a shallow resistivity structure model of 50 meters along the measurement line is obtained. An area with low resistance regolith and high resistance granite is selected for liquid injection. Then, the time-shifted high density resistivity method was used to collect data on the line. The collection time lasted for 22 days, and a total of 11 groups of original observation data were obtained. Through fine processing, information extraction and inversion calculation of time-shifted high density resistivity method data, the time-shifted variation characteristics of apparent resistivity and inversion resistivity during liquid injection were systematically studied, the diffusion range of liquid injection solution was effectively identified, and the influence of underground structure on the seepage direction of liquid injection solution was discussed. The comprehensive research results of the time-shifted high-density resistivity method show that the deep resistivity of the injection area decreases gradually with the extension of the injection time. The characteristics of resistivity change can effectively identify the diffusion of liquid injection solution. Under the blocking effect of deep intact granite, the leaching liquid diffused evenly in both sides of the weathering layer. The fluctuation shape of the top surface of granite has obvious influence on the diffusion range of the leaching liquid, and the diffusion rate of the leaching liquid is greater on the side with the larger buried depth of the top surface. In addition, the detection also revealed the resistivity structure of the deep surface recovery roadway, showing the longitudinal diffusion of leaching liquid along the deep fracture. The experimental results demonstrate that it is feasible to monitor the deep diffusion range of leaching liquid through the resistivity variation law, and the research results have important reference value for the accurate layout of liquid injection holes and recovery roadways in ion-type rare earth mines.