Growing demand for rare earth elements (REEs), driven by low-carbon energy technologies and advanced electronics, has heightened the need for secure and sustainable extraction from subsurface systems. Environments such as groundwater and hydrothermal systems control REE mobilization, transport, and concentration through coupled hydromechanical and geochemical processes that are inherently stochastic and operate across multiple scales. Hydromechanical factors regulate fluid flow, permeability, and fracture networks, influencing REE movement and localization. Meanwhile, geochemical processes—such as complexation with ligands, adsorption–desorption, redox transformations, and mineral reactions—govern REE speciation, solubility, and fractionation. Subsurface heterogeneity and temporal variability introduce significant uncertainty, complicating prediction and resource assessment. This session invites interdisciplinary contributions integrating field observations, experiments, and modeling to better understand these coupled systems. Emphasis is placed on advancing predictive frameworks, improving extraction strategies, and supporting environmentally responsible and sustainable recovery of REEs.

• EP - Earth and Planetary Surface Processes
• H - Hydrology
• NS - Near Surface Geophysics
• P - Planetary Sciences