USING INDUCED POLARIZATION TO DETECT ACID-PRODUCING ROCK: SEDIMENTARY, METAMORPHIC, AND HYDROTHERMAL PYRITE

Acid rock drainage (ARD) is the highly acidic water produced by the oxidation of pyrite. When large amounts of pyritic rock are disturbed and exposed to water and air by construction or mining, sufficient acid is produced to create serious engineering and environmental problems. The potential value of IP in detecting pyritic zones has been known for some time, but the method is not widely used, in part, perhaps, because IP surveys are not always successful. The few case studies that have been published describe the successful use of IP to detect pyrite in metamorphic rocks. Our results, presented here, suggest that IP can be used to detect and characterize hydrothermal pyritic zone, but that sedimentary pyrite does not have a strong IP response. If further work confirms this pattern, then it may be possible to avoid fruitless surveys in rocks with fine-grained disseminated sedimentary pyrite, thus increasing the success rate of the method.