A quantitative evaluation of pyrite weathering

Abstract

Namurian sediments at Mam Tor, Derbyshire are cut by a major landslide and a geological fault. Both channel oxygenated waters into fragmented pyritic shales. Pyrite is rapidly oxidized to sulphuric acid, 1.5 g being destroyed by each litre of water passing through the fault‐crush. More than 99 per cent of the acid, however, is immediately consumed in clay‐mineral transformation and carbonate dissolution reactions. The typical acid‐sulphate ‘ochre’ springs thus retain less than 1 per cent of the acid generated in the crush zone. These very rapid and large scale chemical transformations probably contribute to the slide's continuing activity.