Acid Rock Drainage (ARD) Prediction: Protecting the environment of mining

Transcription

1 Acid Rock Drainage (ARD) Prediction: Protecting the environment of mining Dr. Anita Parbhakar-Fox CRC Optimising Resource Extraction University of Tasmania

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12 25 20 Rapid population growth increasing global demand for commodities Billions Year Source: World Bank

13 Ore Grades (Cu, Pb, Zn, Au, Ni, U, Diamonds) Declining ore grades Copper (%Cu) Gold (g/t) Lead (%Pb) Zinc (%Zn) Uranium (kg/t U3O8) Nickel (%Ni) Diamonds (carats/t) Silver (g/t) Year 2,600 2,275 1,950 1,625 1, Year Mudd (2008) 0 Ore Grade (Ag)

14 Waste Rock (Cu, Diamonds, U, Brown Coal) (t) Copper (Mt) Uranium (Mt) Diamonds (Mt) Brown Coal (Mm3) Gold (Mt) Black Coal (Mm3) Year Waste rock increased production 1,600 1,400 1,200 1, Waste Rock (Gold, Black Coal) (m 3) Mudd (2008)

15 Waste Rock (Cu, Diamonds, U, Brown Coal) (t) Copper (Mt) Uranium (Mt) Diamonds (Mt) Brown Coal (Mm3) Gold (Mt) Black Coal (Mm3) Year Waste rock increased production 1,600 1,400 1,200 1, Waste Rock (Gold, Black Coal) (m 3) Mudd (2008)

16 Low ph High metals & As

17 Human health Landscape degradation Global financial liability= $100 billion Hudson-Edwards et al. (2011)

18 Human health Why is ARD still Landscape degradation such a major issue? Global financial liability= $100 billion Hudson-Edwards et al. (2011)

19 1) Misuse of ARD predictive tests 2) Outdated ARD protocols

20 Traditional ARD Prediction Approach Total geochemistry Field kinetic tests Acid base accounting The Wheel Morin and Hutt (1998) Lab kinetic tests Net acid generation testing Mineralogy You can t reinvent the wheel

21 Traditional ARD Prediction Approach Field kinetic tests Total geochemistry The Wheel Morin and Hutt (1998) Acid base accounting ARD likely ARD potential ARD unlikely Coal (no data) OZMIN database (1997) Lab kinetic tests Mineralogy Net acid generation testing We MUST reinvent the wheel

22 The GMT Approach Geochemistry Mineralogy Parbhakar-Fox et al. (2011) Texture Innovative and Cost Effective

23 The GMT Approach SAMPLES GROUPING Decrease in number of samples analysed STAGE ONE STAGE TWO Increase in analytical sophistication STAGE THREE

24 The GMT Approach SAMPLES GROUPING STAGE ONE STAGE TWO Use a robust 1 in every 2m/5m sampling regime STAGE THREE Accurately map geological and ARD variability Best Practice sampling achieved

25 The GMT Approach SAMPLES GROUPING STAGE ONE Short wave Infrared techniques (SW-IR) STAGE TWO Examination of mineralogy and texture STAGE THREE Field portable X-Ray Fluorescence (FP-XRF) Define mesotextural groups

26 The GMT Approach SAMPLES GROUPING Paste ph testing STAGE ONE X-Ray Diffractometry STAGE TWO Sulphur analysis STAGE THREE New pre-screening stage ARD Index

27 The GMT Approach SAMPLES GROUPING Acid forming / neutralising STAGE ONE STAGE TWO Non-acid forming STAGE THREE No further testing for inert samples

28 The GMT Approach SAMPLES GROUPING STAGE ONE STAGE TWO Net Acid Generation tests STAGE THREE Net Acid Producing Potential tests Screening tests performed

29 The GMT Approach SAMPLES GROUPING STAGE ONE Highly acid forming/ neutralising STAGE TWO STAGE THREE Potentiallyacid forming Only extreme samples progressed

30 The GMT Approach SAMPLES Advanced Geochemical tests GROUPING STAGE ONE STAGE TWO Mineral Liberation Analysis Cd Pb Electron Microprobe Analysis STAGE THREE ARD controls characterised Laser Ablation ICPMS

31 The GMT Approach ARD Block Model Highly acid forming Non acid forming Neutralising Potentially acid forming Result: Improved ARD risk assessment

32 The GMT Approach Croydon, QLD: Abandoned Mines Parbhakar-Fox et al. (2013a); Parbhakar-Fox et al. (2013b) Ernest Henry, QLD: Operational Mine Parbhakar-Fox et al. (2013c) Positive outcomes new study sites

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34 Support Acknowledgement Transforming resource extraction and its evaluation Dr Steve Walters (CRC ORE, Australia) Professor Bernd Lottermoser (University of Exeter, UK) Professor Dee Bradshaw (University of Queensland, Australia) Dr Karsten Goemann (University of Tasmania, Australia) Dr Nathan Fox (University of Tasmania, Australia) Tim Howard (CRC ORE, Australia)