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Assessment of Waste Rock Weathering Characteristics at the Antamina Mine Based on Field Cells Experiment

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Assessment of Waste Rock Weathering Characteristics at the Antamina Mine Based on Field Cells Experiment ASSESSMENT OF WASTE ROCK WEATHERING CHARACTERISTICS AT THE ANTAMINA MINE BASED ON FIELD CELLS EXPERIMENT by CELEDONIO ARANDA CLEMENTE B.A.Sc. Universidad Nacional Santiago Antúnez de Mayolo, 2000 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Mining Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) March 2010 © Celedonio Aranda Clemente, 2010 ABSTRACT The weathering behaviour of waste rock is being evaluated using field cell experiments at the Antamina Mine. The results presented here are a component of a larger study that is being conducted in Antamina, whose objective is to understand the geochemical and hydrological behaviour exhibited by different waste rock types, and their potential operational and post-closure impacts on the environment, in order to identify and implement prevention/mitigation measures. The waste rock is currently classified into three classes based on metal (zinc, arsenic) and sulfide contents: reactive (A), slightly reactive (B), and non-reactive (C). This thesis presents the analysis only of Class B marble and hornfels material. Particle size was measured through the standard sieving method and Elutriation techniques, and surface area through geometrical estimation and the BET methods. The data gathered was correlated with chemical assay results and complemented with the mineralogical and mineral availability for leaching data obtained using a Mineral Liberation Analyzer. Minerals containing copper, lead, and zinc, and all sulfide minerals were examined. Seven field kinetic cells were installed with samples having particles of less than 10 cm in diameter. Metal leaching, elemental production rates and release rate trends from two years of data are presented. The relationship between mineral availability and field cells drainage data was investigated. A refined waste rock classification system for Class B was recommended including the incorporation of lithology, mineralogy, mineral availability for leaching, and sulfur-sulfide content. The diopside marble samples were found to be coarser than the black marble and gray hornfels samples. Large surface were reported in the black marble, this was because a relatively higher proportion of clay minerals were found in this sample. Acid-base accounting testing reported that all samples were non-acid generating. However, Cu, Pb, Zn, and Sb were reported in higher concentrations in the leachate from the field cells. Solid phase concentrations of these elements were found to increase as the size fractions decreased, but in two diopside samples, Cu, Pb and Zn minerals were available for leaching in high proportion from the coarse particles. The main sources of these elements were chalcopyrite, galena, and sphalerite. ii TABLE OF CONTENTS ABSTRACT ................................................................................................................................................... ii TABLE OF CONTENTS ............................................................................................................................... iii LIST OF TABLES ......................................................................................................................................... vi LIST OF FIGURES....................................................................................................................................... ix ACKNOWLEDGEMENTS ........................................................................................................................... xv DEDICATION ............................................................................................................................................. xvi 1 INTRODUCTION...................................................................................................................................1 1.1 Description of Research Project....................................................................................................1 1.2 Research Objectives .....................................................................................................................3 1.2.1 General ................................................................................................................................3 1.2.2 Specifics...............................................................................................................................3 1.3 Study Site Description ...................................................................................................................3 1.4 Background ...................................................................................................................................4 1.4.1 Geology of the Deposit ........................................................................................................4 1.4.2 Waste Rock Classification ...................................................................................................7 1.5 Waste Rock Sampling ...................................................................................................................8 1.6 Thesis Components ....................................................................................................................12 2 LITERATURE REVIEW.......................................................................................................................13 2.1 Acid Rock Drainage and Metal Leaching (ARD/ML)...................................................................13 2.2 Neutral Rock Drainage and Metal Leaching (NRD/ML) ..............................................................14 2.3 Prediction of Acid Rock Drainage / Metal Leaching....................................................................15 2.3.1 Sampling............................................................................................................................16 2.3.2 Analytical Test Methods.....................................................................................................17 2.3.3 Application of Different Tests for Acid/Neutral Rock Drainage Prediction.........................21 2.4 Waste Rock Characterization......................................................................................................23 2.5 Weathering of Neutralizing Minerals ...........................................................................................26 2.5.1 Mineral Solubility................................................................................................................26 2.5.2 Comparison of Dissolution Rates ......................................................................................28 2.5.3 Rates of Rock Weathering.................................................................................................28 2.6 Mineralogical Characterization....................................................................................................29 2.6.1 Mineral Liberation Analyzer (MLA) ....................................................................................31 3 WASTE ROCK CHARACTERIZATION ..............................................................................................33 3.1 Introduction..................................................................................................................................33 3.2 Preparation of Sample.................................................................................................................33 3.3 Particle Size Analysis ..................................................................................................................34 3.3.1 Sieving Method ..................................................................................................................35 3.3.2 Elutriation Technique .........................................................................................................35 3.4 Density Determination .................................................................................................................39 iii 3.5 Surface Area Determination ........................................................................................................42 3.5.1 The Geometrical Estimation (GE) Method.........................................................................42 3.5.2 The Brunauer, Emmett, and Teller (BET) Method.............................................................45 3.6 Mineral Assay..............................................................................................................................52 3.7 Acid-base Accounting (ABA) Testing ..........................................................................................54 3.8 Moisture Content .........................................................................................................................56 3.9 Mineralogical Evaluation by the Mineral Liberation Analyzer (MLA)...........................................56 3.9.1 Determining Mineral Phases..............................................................................................57 3.9.2 Determining Mineral Availability for Leaching....................................................................60 4 FIELD CELLS EXPERIMENT .............................................................................................................68 4.1 Introduction..................................................................................................................................68 4.2 Field Cell Installation
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