In recent years, a great deal of progress has been made in the development of geoenvironmental models to predict the potential for environmental contamination associated with the current and legacy mineral resource development. Such models provide public land managers and environmental quality agencies an important tool for developing management and remediation strategies. An essential aspect of developing geo-environmental models is access to high quality water, sediment, and soil chemistry data sets from well-characterized mineral deposits. These data sets can be used to predict the identity and levels of potentially toxic trace elements based on similarities in ore deposit mineralogy, host rock lithology, and other geo-environmental variables. It is also essential that the key physicochemical processes controlling trace element speciation (e.g. oxidation state, aqueous-solid phase partitioning, and mode of association with major/minor element phases) are understood in order to extend the geoenvironmental model concept to include prediction of downstream trace element mobility and potential bioavailability, as well as to provide insights into the efficacy of potential treatment and remediation scenarios.

The focus of this project is to provide a detailed analysis of the chemical composition of waters and sediments associated with select mineral deposits in the Tintina Gold Province (TGP). This region encompasses a large portion of interior Alaska and Yukon, including the Kantishna district of Denali National Park and Preserve. The specific aim of our work is to elucidate the factors that control the speciation of antimony (Sb), and co-associated arsenic (As), in deposits containing abundant stibnite (Sb₂S₃) and arsenopyrite (FeAsS). A number of geoenvironmental studies within the TGP have shown that acid mine drainage derived from oxidation of sulfide minerals is generally limited in extent as a result of either low sulfide content of ore materials or high natural acid buffering capacity of waters. In general, these studies have observed that surface waters draining natural mineral occurrences and legacy mining operations (e.g. abandoned tailings, adits, and other workings) contain concentrations of priority contaminant metals, such as copper, lead, zinc, and mercury, below EPA drinking water standards and typically at, or just above, background values. A notable exception is the common observation of elevated dissolved concentrations of Sb and As derived from the weathering of stibnite and arsenopyrite, respectively.