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GEOCHEMICAL GEOCHEMICAL CHARACTERIZATION OF WASTE CHARACTERIZATION OF WASTE
ROCK ROCK
ANTAMINA MINEANTAMINA MINE
PERUPERUDavid Brown, Golder Associates Rens Verburg, Golder Associates
Henri Letient, AntaminaCeledonio Aranda, Antamina
BC/MEND WorkshopNovember 30, 2005
Presentation Overview• Site Background• Waste Rock and Ore
– Issues– Investigation– Results
• Ongoing Work and Conclusions
• Peruvian Andes (4,200m)• Upper Amazon drainage basin• Copper-zinc-molybdenum mine• Full production in 3rd quarter 2001• Daily tonnage:
• Ore – ~100,000, • Waste - ~300,000
• Mine life of 23 years
Site Overview
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)
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
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
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
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
Geochemical Characterization Program
• Static tests– Metals, ABA, leach tests (DI, H2O2): 100s of
samples• Mineralogy• Kinetic testing (8 cells)• Field cells (27 cells)• Waste rock and LG/MG ore stockpile
runoff monitoring
Summary of Field Cells• 27 Field Cells Constructed
(2002 - 2005) – 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
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
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
Rock Field Cell Results Zn (Hornfels & Marble Cells)
Hornfel, Marble and Limestone Field Cells
0.001
0.01
0.1
1
10
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
Date
Zinc
(mg/
L)
0.00
0.02
0.04
0.06
0.08
0.10
Dec
-02
Dec
-03
Dec
-04
Date
Cop
per (
mg/
L)
Cell01:HornfelClassC Cell02:HornfelClassA
Cell08:HornfelClassA Cell14:MarbleClassB
Cell15:MarbleClassA Cell17:HornfelClassB
Cell19:MarbleClassC Cell 21: Marble Class
Cell 22: Marble Class B Cell 23: Hornfel Class
Cell 24: Marble Class B Cell 25: Hornfel Class
Rock Field Cell Results Zn (LG/MG Ore Cells)
0.001
0.01
0.1
1
10
100D
ec-0
2
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
Date
Zinc
(mg/
L)
Cell 06: Marginal Grade Ore (M1-ML)
Cell 09: Low Grade Ore (M2-BL)
Cell 10: Marginal Grade Ore (M4-ML)
Cell 12: Low Grade Ore (M4A-BL)
Cell 13: Marginal Grade Ore (M2-ML)
Cell 18: Low Grade Ore (M1-BL)
CO-22
s
Rock Field Cell Results Zn (Intrusives and Skarn Cells)
6
7
8
9
10
D a te
Cell 03: Intrusive Class A (High Range)
Cell 04: Intrusive Class A (Average Range)
Cell 05: Intrusive Class A (High Range)
Cell 07: Endoskarn Class A (Average Range)
Cell 11: Exoskarn Class A (High Range)
Cell 16: Exoskarn Class A (Average Range)
Cell 20: Endoskarn Class A (High Range)
Intrusive, Endoskarn and Exoskarn Field Cells
0.001
0.01
0.1
1
10
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
Date
Zinc
(mg/
L)
Zn Field and Lab Cell ResultsF ie ld C e l l 4 - In t r u s iv e s
0 .0 0 0
0 .0 0 5
0 .0 1 0
0 .0 1 5
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
F ie ld C e l l 6 - M a r g in a l G r a d e O r e M 1 - M L
0 .0 0 0
0 .0 0 5
0 .0 1 0
0 .0 1 5
0 .0 2 0
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
F ie ld C e l l 7 - En d o s k a r n
0 .0 0 0
0 .0 0 5
0 .0 1 0
0 .0 1 5
0 .0 2 0
0 .0 2 5
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
F ie ld C e l l 1 4 - M a r b le C la s s B
0 .0 0 0
0 .0 0 2
0 .0 0 4
0 .0 0 6
0 .0 0 8
0 .0 1 0
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
L a b C e ll F ie ld C e ll
Rock Field Cell Results Mo (LG/MG Ore Cells)
6
7
8
9
10
D a te
Cell 06: Marginal Grade Ore (M1-ML)
Cell 09: Low Grade Ore (M2-BL)
Cell 10: Marginal Grade Ore (M4-ML)
Cell 12: Low Grade Ore (M4A-BL)
Cell 13: Marginal Grade Ore (M2-ML)
Cell 18: Low Grade Ore (M1-BL)
LG/MG Ore Field Cells
0.01
0.1
1
10
100
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
Date
Mol
ybde
num
(mg/
L)
Rock Field Cell Results Mo (Intrusives & Skarn Cells)
6
7
8
9
10
D a te
Cell 03: Intrusive Class A (High Range)
Cell 04: Intrusive Class A (Average Range)
Cell 05: Intrusive Class A (High Range)
Cell 07: Endoskarn Class A (Average Range)
Cell 11: Exoskarn Class A (High Range)
Cell 16: Exoskarn Class A (Average Range)
Cell 20: Endoskarn Class A (High Range)
Intrusive, Endoskarn and Exoskarn Field Cells
0.01
0.1
1
10
100
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
Date
Mol
ybde
num
(mg/
L)
Mo Field and Lab Cell Results
Field Cell 7 - Endoskarn
0
1
2
3
4
5
0.01 0.1 1 10 100
Cumulative Water:Rock Ratio (L:kg)
Load
ing
(mg/
kg)
Lab Cell Field Cell
SO4Mo Field and Lab Cell Results
L a b C e ll F ie ld C e ll
F ie ld C e l l 6 - M a r g in a l G r a d e O r e M 1 - M L
0
2 0
4 0
6 0
8 0
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
F ie ld C e l l 7 - E n d o s k a r n
0
5 0
1 0 0
1 5 0
2 0 0
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
F i e ld C e l l 1 4 - M a r b le C la s s B
0
2
4
6
8
0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
F ie ld C e l l 1 5 - M a r b le C la s s A
0
5
1 0
1 5
2 0
0 .0 0 1 0 .0 1 0 .1 1 1 0 1 0 0
C u m u la t iv e W a t e r :R o c k R a t io ( L :k g )
Load
ing
(mg/
kg)
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 short-term leach testing)
Water Quality Simulations
• Predictive water quality modellingcompleted 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
Water Quality SimulationsKey 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
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)
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
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
THANK YOUTHANK YOU
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