New Mexico Geological Society Annual Spring Meeting — Abstracts

Mineral dissolution rates of pure minerals such as forsterite and pyrrhotite abound in the literature. In contrast, the use of mine tailings containing these minerals to assess mineral dissolution rates has received little attention. In this study, we investigate forsterite and pyrrhotite dissolution rates using actual mine tailings from a nickel mine in Norway. Kinetic testing using these tailings was conducted for seventy weeks. Weekly leachate chemistry was used as input parameters for inverse modelling using PHREEQC. Results from inverse modelling suggest that Mg and Fe are mostly associated with forsterite and pyrrhotite dissolution respectively. Pyrrhotite dissolves faster than forsterite by an order of magnitude, slower than commonly found in the literature. This result could be due to the fact that when present with other minerals, grain interactions and the degree of surface area in contact with water and oxygen can enhance or limit the dissolution of these minerals. This approach of using dissolution rates from kinetic testing can be used to provide more accurate field values than the commonly used laboratory dissolution rates.