Characterization study of As and Se in pyrites from two historic mines in British Columbia

Arsenic (As) and selenium (Se) can be toxic if they occur as soluble species at elevated concentrations. One process that can mobilize these elements into the environment is the oxidation of As- and Se-containing pyrites. This study presents the initial mineralogical (XRD, SEM-EDS, LA-ICP-MS, and synchrotron micro-XRF and micro-XANES) characterization of As- and Se-pyrites from two historic mines in British Columbia, the Sullivan Mine and the Sunro Mine. Results show that As occurs in some of the pyrites from the Sullivan Mine; comparison of the micro-XANES measurements to published data suggests As substitutes for sulphur. Selenium is detected in pyrites from the Sunro Mine but this Se is slightly more oxidized than measured in previous studies on Se-pyrite and further investigation of these samples is required. Results from this characterization study will be incorporated into the next phase of research measuring element mobilization after oxidation reactions to identify the effects of As or Se substitution on these reactions