A comprehensive dynamic measurement system for geophysical and hydrochemical characteristics of clayey sand

JianXin Liu; JiaJia Zeng; Jing Xie; RuJun Chen; RongWen Guo; Hang Chen

doi:10.6038/cjg2025S0687

Ion-absorption type rare earth deposits play a crucial role in China's global competitiveness and resource security concerning critical rare earth minerals. To explore the spectral induced polarization (SIP) and streaming potential (SP) response characteristics of ion-absorption minerals, we designed and developed a flow system capable of simultaneously measuring the geophysical and hydrochemical properties of clayey sand. This system is based on the metallogenic theory of ion-absorption type rare earth deposits and the principles of the electrical double layer, integrating both electrical and hydrochemical measurement functions. The system is capable of measuring streaming potential difference, complex conductivity, and pore water pressure of clayeys and samples saturated with different salinity solutions under varying hydraulic gradients. Additionally, it facilitates the collection of pore fluids for subsequent chemical analysis. A series of measurements were conducted, including the complex conductivity of tap water and solutions with different salinities, as well as the complex conductivity of different clayey sand samples saturated with solutions of varying salinity. The formation factor of the sand samples was also estimated. Moreover, pore water pressure and streaming potential difference were measured simultaneously under different hydraulic gradients to evaluate the hydraulic and electrical parameters of the sand samples. The experimental results indicate that the complex conductivity of tap water is consistent with previous studies. The measured complex conductivity for solutions with varying salinities exhibits a strong linear correlation with values obtained from a conductivity meter. Furthermore, the formation factor of the sand samples, estimated from the complex conductivity of saturated quartz sand, falls within the theoretical range, and the complex conductivity of clayey sand samples with different salinities and clay contents aligns closely with conclusions from earlier studies. Additionally, under saturated conditions, both the average streaming potential difference and average flow rate show a linear relationship with the average pressure difference. The saturated hydraulic conductivity and the streaming potential coupling coefficient, as derived from the measurements, also fall within the theoretical range. Overall, these findings validate the efficacy and stability of the proposed experimental system, laying a solid foundation for investigating the relationship between the chemical characteristics of ore formation and electrical responses (SIP and SP) in line with the metallogenic enrichment mechanism, and for developing potential exploration techniques for ion-absorption type rare earth deposits

A comprehensive dynamic measurement system for geophysical and hydrochemical characteristics of clayey sand

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