Effective field-based testing tools for rapid ARD prediction

Accurate prediction of acid rock drainage (ARD) during early life-of-mine stages is critical for the development of effective waste management strategies. However, tests and methodologies used by industry focus on the extensive use of geochemical tests i.e., those associated with acid base accounting. Due to the high costs and turn-around time of such tests, only a limited number of samples are selected for predictive testwork. Consequently, detailed ARD characteristics of a deposit cannot be understood, resulting in the development of inadequate waste management plans and rehabilitation strategies. Instead, industry requires effective tools and protocols which allow for a greater number of samples to be evaluated, and are simple enough to perform in a fieldlaboratory, thus keeping costs to a minimum and turn-around time short. To satisfy such requirements, simple field-based pH tests should be utilised. In addition, methods to improve mineralogical characterisation in drill core materials should be employed including an ARD focused logging code, chemical staining and the use of portable instruments (i.e., portable XRF, Equotip). Finally, methods for evaluating geometallurgical data for ARD prediction should be used, and have real potential to add-value to existing datasets.

These new tools and protocols were developed and tested using drill core and waste rock materials obtained from several Australian mines with differing geology, mineralogy and mineralisation style. Our research shows that by adopting these improved tests and methods, the industry will be able to: i) perform effective predictive ARD testwork; ii) achieve detailed deposit-wide characterisation, iii) develop the best possible waste management plan; and iv) evaluate only the most suitable rehabilitation options.