Prediction of Acid Rock Drainage from Automated Mineralogy
Automated mineralogy tools are now commonly used during mineral processing for particle characterization to help mine operators evaluate the efficiency of the selected mineral processing techniques. However, such tools have not been efficiently used to as
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Abstract Automated mineralogy tools are now commonly used during mineral processing for particle characterization to help mine operators evaluate the efficiency of the selected mineral processing techniques. However, such tools have not been efficiently used to assist in acid rock drainage (ARD) prediction. To address this, the computed acid rock drainage (CARD) risk grade protocol was developed. The CARD risk grade tool involves: (1) appropriate selection of samples (i.e., following a geometallurgical sampling campaign); (2) careful preparation of a particle mount sample; (3) analysis on a mineral liberation analyser (MLA) using the X-ray modal analysis (XMOD) function; (4) processing of the XMOD data to produce a whole particle mount backscattered electron (BSE) image and a corresponding image of classified XMOD points; (5) fusion of both images to obtain particle area data; (6) calculation of the CARD risk ratio based on carbonate and sulfide particle areas, relative reactivities (pHCaCl2 pHmineral þ CaCl2 ) and acid forming/neutralizing values (calculated based on mineral chemistry and stoichiometric factors, kg H2SO4/t); and (7) classification of CARD risk ratios ranging from extreme risk to very-low risk. Testing of the CARD risk grade tool was performed on materials selected from several mine sites representative of both run-of-mine ore A. Parbhakar-Fox (&) R.F. Berry T.L. Noble School of Physical Sciences, University of Tasmania, Private Bag 79, Hobart, TAS 7001, Australia e-mail: [email protected] R.F. Berry e-mail: [email protected] T.L. Noble e-mail: [email protected] B. Lottermoser Institute of Mineral Resources Engineering, RWTH Aachen University, Wüllner-Strasse 2, 52062 Aachen, Germany e-mail: [email protected] R. Hartner E. 7076, Ehome 2 Apartment Duong D3 Phuoc Long B Ward, Ho Chi Minh City, Vietnam e-mail: [email protected] © Springer International Publishing Switzerland 2017 B. Lottermoser (ed.), Environmental Indicators in Metal Mining, DOI 10.1007/978-3-319-42731-7_8
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and waste. This testing proved that CARD can be effectively used to map ARD risks on a deposit scale and forecast geoenvironmental risk domains at the earliest life-of-mine phases.
Introduction Various attempts to directly predict acid formation using mineralogical techniques have been made over the past two decades. Examples of acid rock drainage (ARD) focused optical mineralogy studies are given in Blowes and Jambor (1990), Gunsinger et al. (2006) and Moncur et al. (2009, 2015) in which the sulfide alteration index (SAI), primarily developed for tailings classification, is used. However, the SAI is limited by the lack of consideration given to the dissolution of adjacent metal sulfides (and release of metals) under acid conditions (i.e., sulfide mineral-associations are not considered). Other techniques used to predict acid formation include calculation of neutralizing potential (NP) directly from estimates based on whole-rock geochemical analysis and modal mine
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