<p>Large-scale mineral exploitation inevitably generates massive quantities of tailings enriched with heavy metals, posing long-term risks to groundwater systems when leakage occurs from tailings storage facilities. Although engineered anti-seepage measures are widely implemented, liner degradation, construction defects, or aging infrastructure can result in sustained infiltration of metal-laden tailings wastewater into underlying aquifers. However, the influence of pollution source geometry on groundwater contaminant transport remains poorly understood. In this study, a coupled groundwater flow and solute transport modeling framework was developed to investigate the spatiotemporal evolution of copper (Cu) contamination under different tailings leakage source configurations. Three representative pollution sources, an area source, a flow-perpendicular line source, and a flow-parallel line source, were conceptualized with an identical leakage footprint and loading condition to isolate geometric effects. Using a representative copper mine in southern Tibet as a case study, temporal variations in maximum Cu concentration, spatial plume evolution at different concentration peaks, and contaminant migration pathways were systematically analyzed. The results demonstrate that pollution source geometry exerts a first-order control on groundwater Cu contamination dynamics. The area source produces the highest initial concentration peak (approximately 2.4 mg L⁻¹) but attenuates rapidly, whereas the flow-parallel line source generates prolonged exceedance durations, repeated secondary peaks, and a pronounced long-tail effect, remaining above the Class III groundwater quality standard for more than 60% of the simulation period. Spatial analysis reveals a clear decoupling between plume expansion and high-concentration risk, with the maximum plume footprint occurring later than the highest concentration exceedance. Migration pathway analysis further indicates that early-stage plume organization is strongly governed by source geometry, while long-term transport progressively converges along the regional groundwater flow field. These findings highlight the critical role of pollution source geometry in controlling groundwater contamination persistence and provide valuable insights for groundwater risk assessment and management in mining-impacted regions.</p>