THE INCREASED REACTIVITY OF PYRRHOTITE AND MAGNETITE PHASES IN SULFIDE MINE TAILINGS

The magnetic fraction of sulphide mine tailings immediately above and below the watertable were examined. Samples originated from an experim ental test cell at the Mattabi Mine refinery site, Sturgeon Lake, Onta rio, Canada. XRD powder patterns of saturated zone samples show anomal ous peaks for pyrrhotite and magnetite. The anomalous peaks are sugges ted to result from modifications to mineral structures due to the pres sures and stresses associated with the milling of ore. Magnetite is ob served to have developed (100) cleavages, and for pyrrhotite, a shift of the 20 (2) over bar peak to lower 2 theta values occurs. The attenu ation of anomalous magnetite and pyrrhotite peaks in unsaturated zone samples indicate milling increases the rate and susceptibility of thes e iron bearing phases to oxidation processes. Surface analysis of pyrr hotite grains using XPS shows Fe(OH)(3) as the dominant species on uns aturated zone surfaces and FeOOH as the predominant species on saturat ed zone surfaces. Fe(III) sulphate salts form in the capillary fringe immediately above the water table.