Relationship between rock slope failures, natural acid rock drainage and ferricretes in the Axial Pyrenees (Spain)

• RSFs in pyrite-rich slates influence ferricrete and acidic spring distribution. • Acidic Fe-rich waters form via pyrite oxidation enhanced by RSF fracturing. • Four ferricrete types reflect depositional, flow, and cementation differences. • Slope deformation increases permeability, reinforcing weathering–instability feedback. • Ferricretes indicate and promote long-term RSF evolution in post-glacial settings.