GEOCHEMICAL CHARACTERIZATION OF WASTE ROCK ANTAMINA MINE PERU

Transcription

1 GEOCHEMICAL CHARACTERIZATION OF WASTE ROCK ANTAMINA MINE PERU David Brown, Golder Associates Rens Verburg, Golder Associates Henri Letient, Antamina Celedonio Aranda, Antamina BC/MEND Workshop November 30, 2005

2 Presentation Overview Site Background Waste Rock and Ore Issues Investigation Results Ongoing Work and Conclusions

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4 Peruvian Andes (4,200m) Upper Amazon drainage basin Copper-zinc-molybdenum mine Full production in 3 rd quarter 2001 Daily tonnage: Ore ~100,000, Waste - ~300,000 Mine life of 23 years

5 Site Overview

6 Geochemical Issues Potential impacts to water quality from Sulfide oxidation Acid generation Metal leaching Dissolution of stored oxidation products Mineral dissolution Metal leaching (under neutral conditions e.g. Cu, Zn, Mo)

7 Waste Rock Issues Over 1.3 billion tonnes of waste rock, to be distributed in three major dumps LG/MG Ore processed year 23 (LOM) Operational/post-closure site drainage management

8 Objectives Establish long-term monitoring plan of waste dumps and stockpiles Refinement of waste rock classification Define operational criteria for waste rock routing Optimization of closure requirements and operational/post-closure site drainage management

9 Gap Analysis Significant static geochemical waste rock characterization completed prior to mining Samples not always representative of current rock Additional information available through pit development Develop characterization program to take advantage of exposed rock

10 Waste Rock Classification Three classes: A, B, C A: skarn, intrusive A, B, C: hornfels, marble, limestone Sulfide, zinc, arsenic content Current system protective of environment, but refinement feasible

11 Geochemical Characterization Program Static tests Metals, ABA, leach tests (DI, H 2 O 2 ): 100s of samples Mineralogy Kinetic testing (8 cells) Field cells (27 cells) Waste rock and LG/MG ore stockpile runoff monitoring

12 Summary of Field Cells 27 Field Cells Constructed ( ) Hornfels & Marble Class A 4 Cells Class B 7 Cells Class C 3 Cells Class A Skarn & Intrusives Intrusives 3 Cells Endoskarn 2 Cells Exoskarn 2 Cells LG Ore 3 Cells MG Ore 3 Cells

13 Waste Rock Program Field Cell Construction Field cell construction Clean 55-gallon plastic drum Drum placement on terraced and secure area Bottom drainage layer ( 15 cm silica sand) overlain by filter fabric

14 Field Cell Monitoring Leachate sample collection Variable sampling frequency monthly during wet season, more frequent at beginning of wet season, and not in dry season Field parameters & laboratory analysis

15 Rock Field Cell Results Zn (Hornfels & Marble Cells) Hornfel, Marble and Limestone Field Cells Cell01:HornfelClassC 0.10 Cell02:HornfelClassA 0.08 Zinc (mg/l) Copper (mg/l) Cell08:HornfelClassA Cell15:MarbleClassA 0.00 Dec-02 Dec-03 Cell19:MarbleClassC Date Dec-04 Cell14:MarbleClassB Cell17:HornfelClassB Cell 21: Marble Class Cell 22: Marble Class B Cell 23: Hornfel Class Dec-02 Feb-03 Apr-03 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Cell 24: Marble Class B Cell 25: Hornfel Class Date

16 Rock Field Cell Results Zn (LG/MG Ore Cells) Zinc (mg/l) 0.1 s Cell 06: Marginal Grade Ore (M1-ML) Cell 09: Low Grade Ore (M2-BL) 0.01 Cell 10: Marginal Grade Ore (M4-ML) Cell 12: Low Grade Ore (M4A-BL) Cell 13: Marginal Grade Ore (M2-ML) Dec-02 Feb-03 Apr-03 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Cell 18: Low Grade Ore (M1-BL) CO-22 Date

17 Rock Field Cell Results Zn (Intrusives and Skarn Cells) 10 Intrusive, Endoskarn and Exoskarn Field Cells Cell 03: Intrusive Class A (High Range) Cell 04: Intrusive Class A (Average Range) Zinc (mg/l) Cell 05: Intrusive Class A (High Range) 10 Cell 07: Endoskarn 9 Class A (Average Range) Cell 11: Exoskarn Class A (High Range) Cell 16: Exoskarn Class A (Average Range) 6 Dec-02 Feb-03 Apr-03 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Cell 20: Endoskarn Class A (High Range) Da te Date

18 Zn Field and Lab Cell Results Fie ld C e ll 4 - In tr u s ive s Fie ld C e ll 6 - M a r g in al G r ad e O r e M 1-M L Loading (mg/kg) Loading (mg/kg) C u m u lative W ate r:rock Ratio (L :k g) C um u lative W ate r:rock Ratio (L:k g ) Field Cell 7 - Endoskarn Fie ld C e ll 14 - M ar b le C las s B Loading (mg/kg) Loading (mg/kg) C u m u lative W ate r:rock Ratio (L :k g) C um u lative W ate r:rock Ratio (L:k g ) Lab Cell Field Cell

19 Rock Field Cell Results Mo (LG/MG Ore Cells) 100 LG/MG Ore Field Cells Cell 06: Marginal Grade Ore (M1-ML) Molybdenum (mg/l) Cell 09: Low Grade Ore (M2-BL) 10 Cell 10: Marginal Grade Ore (M4-ML) 9 Cell 12: Low Grade Ore (M4A-BL) 8 7 Cell 13: Marginal Grade Ore (M2-ML) Dec-02 Feb-03 Apr-03 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Da te Cell 18: Low Grade Ore (M1-BL) Date

20 Rock Field Cell Results Mo (Intrusives & Skarn Cells) Intrusive, Endoskarn and Exoskarn Field Cells Cell 03: Intrusive Class A (High Range) 100 Cell 04: Intrusive Class A (Average Range) Molybdenum (mg/l) Cell 05: Intrusive Class A (High Range) 10 Cell 07: Endoskarn 9 Class A (Average Range) 8 Cell 11: Exoskarn Class A (High Range) Cell 16: Exoskarn Class A (Average Range) 6 Dec-02 Feb-03 Apr-03 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Cell 20: Endoskarn Class A (High Range) Da te Date

21 Mo Field and Lab Cell Results Field Cell 7 - Endoskarn 5 Loading (mg/kg) Cumulative Water:Rock Ratio (L:kg) Lab Cell Field Cell

22 SO 4 Mo Field and Lab Cell Results Fie ld C e ll 6 - M a r g in al G r a d e O r e M 1-M L Fie ld C e ll 7 - En d o s k arn Loading (mg/kg) Loading (mg/kg) Cum ulative W ate r:rock Ratio (L:k g) C um ulative W ate r:rock Ratio (L :k g) Fie ld C e ll 14 - M a r b le C la s s B Field Cell 15 - M arble Class A 8 20 Loading (mg/kg) Loading (mg/kg) C u m u lative W ate r:ro ck Ratio (L :k g ) C um ulative W ate r:rock Ratio (L :k g) Lab Cell Field Cell

23 Water Quality Simulations LG/MG ore and waste rock metal release simulated using existing field cell loading rates (supplemented by evaluation of data from laboratory kinetic testing and shortterm leach testing)

24 Water Quality Simulations Predictive water quality modelling completed to evaluate potential impacts to the receiving environment from: existing waste rock classes (Life of Mine) potential modifications to waste rock classification system and placement strategies Varying Class A skarn and intrusives content Varying Class A hornfels/marble Varying Class B hornfels/marble content

25 Water Quality Simulations Key Findings Continued treatment of East Dump and LG/MG ore stockpile drainage Simulated concentrations similar or higher than current levels Tucush Dump drainage quality very sensitive to the amount of Class A skarn and intrusive material placed in the dump increase in proportions of Class A skarn and intrusives has adverse impact on water quality in the Tucush drainage Varying the Class B material content in the Tucush Dump minimal impact on water quality

26 Ongoing Work Waste Rock Classification Development of quality control and characterization procedures for waste rock placement Continued refinement of the waste rock classification system On-going monitoring of field cells Instrumentation of test piles ~6,000 tonnes, ~38m x 38m x 10m high (UBC)

27 Characterization of Other Materials Tailings Static testing (metals, ABA, short-term leach) Mineralogy Laboratory and field cell Tailings porewater quality collected from piezometers installed in beach Tailings impoundment pond and seepage water quality monitoring data Lake Sediments Static and laboratory kinetic cells

28 Conclusions Importance of initiating this type of program early on in the mine life Field cells more reliable than lab tests (if time permits) Need for ongoing testing and monitoring Water quality prediction based on field cells data used for waste rock management and long term planning

29 THANK YOU