geochemical characterization of waste rock antamina...

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 12: Low Grade Ore (M4A-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 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


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


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


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 12: Low Grade Ore (M4A-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 04: Intrusive Class A (Average 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


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


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


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


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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