Geochemistry of an experimental waste rock pile, Cluff Lake, Saskatchewan

Roger Beckie, Leslie Smith, Karin WagnerRoger Beckie, Leslie Smith, Karin Wagner

Frederic GuerinFrederic Guerin

ArevaAreva Mining Mining –– CogemaCogema Resources Inc.Resources Inc.

OutlineOutline

1.1. Overview of experimentOverview of experiment

2.2. Primary mineralogy Primary mineralogy

3.3. Aqueous phaseAqueous phase

4.4. Secondary mineralogySecondary mineralogy

5.5. Loading estimatesLoading estimates

Field Site DescriptionField Site Description•• MultiMulti--ring Carswell ring Carswell meteorite impact meteorite impact structurestructure

Waste rock: Waste rock: ––PeterPeter--River aluminous River aluminous

gneissgneiss

––Earl River feldspathic Earl River feldspathic gneissgneiss

––Small amounts of Small amounts of Athabasca sandstoneAthabasca sandstone

Cluff Lake Uranium Mine

Cluff Lake Mine & Cluff Lake Mine & WasteWaste Rock Rock PilePileCluff Lake

DJ-N

DJ-X

(M.D. Haug, 2001)

1996: mined1996: mined

1998: placed in pile1998: placed in pile

ConstructedConstructed WasteWaste Rock Rock PilePile ExperimentExperiment

z = 5 m

x, y = 8 m

W E

Pad and Piping

16 heat-traced outflow pipes

Lysimeter dividers

PVC and HDPE geomembrane

Top Surface of CPE

123456789101112

13141516

Instrumentation Hut & Outflow SamplingInstrumentation Hut & Outflow Sampling

Experimental Program

Pile deconstruction.June 2004

Covered with compacted waste rock.

Aug. 2002

Natural and artificial rainfall, tracers.

Aug. 1999 – Aug. 2002

Wetting up period.Sept. 1998 – Aug. 1999

Construction of pile.1997 – Sept. 1998

Hydrology

• Average Annual Air Temp: ~0°C (-45 to +35)• Annual Rainfall: 305 mm• Annual Precipitation: 455 mm

Net infiltration(% of precipitation)

Full pile: 56%Individual lysimeters: 30% to 121%

Mean water residence time: ~2.8 years

Low-Permeability Cover

• August 2002, waste rock with cobbles removed was added to surface of CPE and compacted to create a lower-permeability cover (K ~ 10 -7 m/s)

• Basal discharge reduced by factor ~2.5

DJX Waste Rock Grain Size Distribution

0

20

40

60

80

100

0.00010.0010.010.11101001000Grain Size [mm]

Perc

ent F

iner

Tha

n

““soilsoil--likelike”” –– matrix flow dominatesmatrix flow dominates

0.25

mm

GeochemistryGeochemistry•• MineralogyMineralogy

–– Thin sectionsThin sections

–– Whole rock analysisWhole rock analysis

–– XX--rayray

–– SEMSEM

–– LecoLeco Furnace (total S)Furnace (total S)

•• Water chemistryWater chemistry–– Anions with IC (nAnions with IC (n≈≈2500)2500)

–– Cations with ICPCations with ICP--OES (n=272) and ICPOES (n=272) and ICP--MS (n=165)MS (n=165)

–– Electrical conductivityElectrical conductivity

–– Standard water for calibrations (Jayne Standard water for calibrations (Jayne SimserSimser, , National Water Research Institute)National Water Research Institute)

Primary MineralogyPrimary Mineralogy

•• quartz, kquartz, k--feldspar, albite, chlorite, muscovite, feldspar, albite, chlorite, muscovite, kaolinite, smectite and amphibolekaolinite, smectite and amphibole

•• Sulfide bearing minerals: pyrite and pyrrhotiteSulfide bearing minerals: pyrite and pyrrhotite

•• Sulfide content: 0.45 wt % Sulfide content: 0.45 wt % -- 0.33 wt %0.33 wt %

•• Paste pH ~ 3.6Paste pH ~ 3.6

•• NP/AP ratio ~0.3NP/AP ratio ~0.3

Aqueous Geochemistry

• Major anion: sulfate

• Concentration range: 600 – 35,000 mg/l

• Maximum: ~ 400,000 mg/l

• High spatial and temporal variability

• General decrease of sulfate concentration in the outflow water during the experiment

• pH 3.2 – 3.6, low variability

Outflow – Sulfate Concentrations

0

4000

8000

12000

16000

20000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Lysimeter

Sulfa

te c

once

ntra

tion

[mg/

l]

2000200120022003

Outflow Outflow –– Major CationsMajor Cations

0%

5%

10%

15%

20%

25%

30%

Mg Al Ca Na Ni U Li Mn others

Perc

ent o

f cat

ion

sum

[meq

/l]

60%

K, Co, Sr, Zn, Fe, Ce, Be, Cu, La, Se, Cr and As

200-1500050-5500

300-800

20-800 10-700

5-5501-350

5-200Conc. range [mg/l]

Results – E.C. vs. Sulfate Concentration

0

5000

10000

15000

20000

25000

30000

35000

0 10 20 30EC [mS/cm]

Sulfa

te [m

g/l]

19992000-20022003

Sulfate correlation

0.1

1

10

100

1000

10000

100000

100 1000 10000 100000 1000000Sulfate Concentration [mg/L]

Met

al C

once

ntra

tion

[mg/

l]

MgAlNiCoZnCu

h

0.001

0.01

0.1

1

10

100

1000

10000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

conc

entra

tion

[meq

/l]

Mg Al K Ca Cr Mn Fe Co Ni Cu Zn Sr U

Dilution

Hydrated magnesium & aluminum sulfates Hydrated magnesium & aluminum sulfates MgSOMgSO44--nHnH22O & KAlO & KAl33(SO(SO44))22(OH)(OH)66

Annabergite NiAnnabergite Ni33(AsO(AsO44))22--8H8H22OO

Brown coating: goethite and ferryhydrite (Brown coating: goethite and ferryhydrite (FeO(OHFeO(OH), Fe), Fe22OO33--0.5H0.5H22O)O)

Yellow coating: jarosite KFeYellow coating: jarosite KFe33(SO(SO44))22(OH)(OH)66

Scanning Electron Microscopy

50 microns

Hydrated aluminum sulfatesHydrated aluminum sulfates

Pore water chemistry

0.0

1.0

2.0

3.0

4.0

5.00 1000 2000 3000 4000 5000

cation concentration [mg/l]

dept

h [m

]

0 5000 10000 15000 20000 25000 30000 35000 40000

sulfate concentration [mg/l]

Mg Al Ca Na SO4

Flow Rates and Outflow Chemistry

Dry conditions

Flow in fine-grained matrix

Relatively slow

Outflow water relatively concentrated

Long time for water-rock interactions

Wet conditions

Flow in coarse grained material

Relatively fast

Outflow water relatively fresh

Short time for water-rock interactions

Event Effects: Freshening of Outflow

0

10

20

30

40

50

60

70

31-Jul-027-Aug-02

14-Aug-0221-Aug-02

28-Aug-02time

Flow

rate

[l/d

ay]

0

2000

4000

6000

8000

10000

12000

14000

Sulfa

te C

once

ntra

tion

[mg/

l]

Flow - chemistry

Flow Rates and Outflow Chemistry

0

5

10

15

20

25

30

Apr-01

Oct-01

Apr-02

Oct-02

Apr-03

Oct-03

flow

rate

[l/d

ay]

0

5000

10000

15000

20000

25000

30000

sulfa

te c

once

ntra

tion

[mg/

l]cover

Loading at Base of CPE(mg SO4/kg/week)

~0.1163.52002

~0.1113.82001

~0.1195.62000

Winter Low

Summer High

MeanYear Humidity Cells

Hollings et al (2001)

27Coarse 2 mm

66Fine 0.6 mm

Aerobic leach columns

35 35 –– 40 kg, 3 L rinse per week40 kg, 3 L rinse per week

Percent of initial leached

SUNi

Pore Volumes

34 %

17 %

11 %

79 %

50 %

37 %

N/A~1.25 (2 weeks)Leach Columns

N/A~10 (20 weeks)

5 %~1.25 (5.5 years)Pile Experiment

DJX Waste Rock Grain Size Distribution

0

20

40

60

80

100

0.00010.0010.010.11101001000Grain Size [mm]

Perc

ent F

iner

Tha

n

Reactive fraction?Reactive fraction?

0.25

mm

Conclusions• Principal buffer minerals: chlorite and muscovite.

• E.C. good predictor of chemistry.

• Dominant chemistry; relative proportions constant.

• Dilution highly variable in space and time.

• General inverse correlation between outflow chemistry and flow.

• Low permeability cover induced a decrease in flow rates and coincident reduction in outflow concentrations.

• During the 4 year experiment ~ 5 % or 150 kg of sulfur were released.

• U and Ni appear to be dominantly in finer, leachable fraction.

Acknowledgments

Joe Joe MarcolineMarcoline, John , John JamborJambor, Craig Nichol, , Craig Nichol, Justin Justin StockwellStockwell, Pete Hollings, Pete Hollings