SIMULATIONS OF THE NEUTRALIZING CAPACITY OF SILICATE ROCKS IN ACID MINE DRAINAGE ENVIRONMENTS 1

Pyritic rocks with little or no carbonate mineral content generally produce acid mine drainage when exposed to the atmosphere and moisture. In the absence of carbonate minerals, it is often suggested that silicate minerals can provide some level of acid buffering. At the current time, databases of reaction kinetics are sufficiently detailed to allow calculations of the rates of silicate mineral dissolution reactions relative to the rate of pyrite oxidation. These types of calculations have been conducted for conditions of abiotic oxidation of pyrite by O2 to estimate the acid neutralizing capacity of silicate rock types in terms of specific mineral contents. Using the criteria of maintaining a pH > 5.0 for 10-years, these calculations yield the following results for some generalized igneous rock types.