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To ensure the effective long-term storage of CO₂ in candidate geological storage sites, evaluation of potential leakage pathways to the surface should be undertaken. Here we use a series of natural CO₂ seeps along a fault in South Africa to assess the controls on CO₂ leakage to the surface. Geological mapping and detailed photogrammetry reveals extensive fracturing along the mapped fault trace. Measurements of gas flux and CO₂ concentration across the fracture corridor give maximum soil gas measurements of 27% CO₂ concentration and a flux of 191 g m⁻² d⁻¹. These measurements along with observations of gas bubbles in streams and travertine cones attest to CO₂ migration to the surface. Permeability measurements on the host rock units show that the tillite should act as an impermeable seal to upward CO₂ migration. The combined permeability and fracture mapping data indicate that fracture …