Predictive waste classification using field-based and environmental geometallurgy indicators, Mount Lyell, Tasmania

Abstract

Best practice for acid rock drainage (ARD) risk assessment predominately relies on the geochemical properties of sulfidic rocks. Consequently, a plethora of geochemical tests are routinely utilised by the mining industry to predict ARD formation. Due to limitations associated with these tests and their relatively high costs, analysis of recommended best practice sample numbers is rarely achieved, thus reducing the accuracy of waste management plans. This research aimed to address this through identifying potential geometallurgy indicators using drill core samples (n = 70) obtained from the Comstock Chert, a new prospect proximal to Mount Lyell, western Tasmania, Australia. Samples were subjected to a range of mineralogical analyses, routine ARD geochemical tests (i.e., paste pH; acid-base accounting, ABA; net acid generation, NAG), field-based techniques (e.g., portable X-ray fluorescence, pXRF; short-wave infrared spectrometry, SWIR), and geometallurgical analyses (i.e., HyLogger, Equotip). This study demonstrated: (1) HyLogger data allows identification of acid-neutralizing carbonate minerals; (2) Equotip hardness data provide a conservative indication of lag-time to acid formation; (3) CARD risk grading accurately identifies high and low risk ARD domains; and (4) pXRF data provides a sound indication of the abundance of environmentally significant elements. Consequently, the application of geometallurgical techniques to drill core allows the prediction of ARD characteristics that inform waste characterization and management plans.