UW_Diavik_Presentation_Nason (1)

Diavik Waste Rock ProjectDiavik Waste Rock Project
MEND
Diavik Test Piles Group
Meeting
Project Update:
Tonalite
Dr. Peter Nason (Postdoctoral Fellow)
panason@uwaterloo.ca
UW: Saturday 7th November 2015

Diavik Waste Rock Project
DIAVIK WASTE ROCK PROJECT
Content Of Presentation
 Project Update
 Experimental Tests Conducted/Planned
 New Static Test Data
 Carbonate Study Focus
 Metal Release Focus
 Suitability of Tonalite as an Alternative Cover Material
 Planned Publications
2

3
Project Update: Tonalite Used as Cover Material
Sourced from production of
the A21 Kimberlite Pipe
(2018+)
A21 Lake sediments:
Sealing Layer (0.5-1.0 m)
A21 Waste Rock (Tonalite):
Protective Cover (3m)
Utilisation: 2021-2023
Project Directions:
1. Limiting ARD Formation with an Alkaline-Generating Cover
2. Understand metal release, mobility, transport and attenuation processes
3. Interaction of Tonalite-derived constituents with underlying Type III waste rock
constituents over time in an Arctic-clime

Experimental Tests Conducted/Planned
Aim 1: Targeting and Evaluating Carbonate Weathering Potential
» XRF, XRD, SEM
» Carbon-Sulphur
» Transmitted and Reflected Light Microscopy
» 80-week Humidity Cell Experimental Leachate Data
» PHREEQC Modelling: Calcium S.I.
Aim 2: Sulphide Weathering and Metal Mobility
» XRF, SEM
» μ-XRF
» Modified 7-step Sequential Extraction Procedure
» Carbon-Sulphur
» Transmitted and Reflected Light Microscopy
» 80-week Humidity Cell Experimental Leachate Data
» MPN and DNA-isolation
4

New Static Tests
Core used in New Experiments
HCE: Used Composites of three cores:
New Experiments: 1 Core
• NP:AP: 17.5 (NAG > 3)
• Paste pH: 10.10
• Fizz Test: None
• SulfideTotal: <0.01%
• SulfurTotal: 0.006%
5

Carbon, Calcium and Carbonate Mineralogy
Static Tests indicated < 0.8 % CaCO3
Optical Transmitted Mineralogical Analysis indicated trace
dolomite in hydrothermally-emplaced veins (< 0.1%)
XRD Mineral Analysis: Ankerite (Dolomite) Ca(Fe,Mg,Mn)(CO3)2
Fresh Tonalite Carbon Content (n = 3): 0.34 ± 0.013 %
• Crystalline Quartz (60%), Albite (Na) and Anorthite (Ca) (30%)
• Muscovite in the form of sericitization (5%)
• K-Feldspar: orthoclase/microcline (5%)
• Conforms to a typical Tonalite Igneous Rock Geochemistry
We assume C-data = Carbonates – Graphite? Steel-contamination?
We assume Ca-data = Carbonates – Gypsum? Anorthite?
6

Carbon Data
7
0 1 2 3 4 5 6 7 8
L1
L2
L3
Room Temperature Cell 1 Room Temperature Cell 2
Difference to Fresh Tonalite (%)
0 1 2 3 4 5 6 7 8
L1
L2
L3
Cold Temperature Cell 1 Cold Temperature Cell 2
Difference to Fresh Tonalite (%)

Indication of Carbonate Weathering
 Next: PHREEQC Modelling – Dolomite Weathering and Gypsum8
6
7
8
9
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: pH
Week
pH
0
20
40
60
80
100
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Calcium
Week
Concentration(mmol/L)
0
20
40
60
80
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Magnesium
Week
R² = 0.6089
0
10
20
30
40
50
0 20 40 60 80
Ca:Mg Ratio
Calcium (mmol/L)
Magnesium(mmol/L)

Dolomite Weathering
1. CaMg(CO3)2(s) = MgCO3(s) + Ca2+ + CO3
2-
2. MgCO3(s) = Mg2+ + CO3
2−
3. CaMg(CO3)2(s) + Mg2+ = Ca2+ + 2MgCO3(s)
 Dissolution is much slower than calcite – release over time
 Dissolution is not indicated by Alkalinity
 Dissolution is much slower is Mg and Ca dissolved in solution
9

Alkalinity in the Leachate
10
0
5
10
15
20
25
30
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Alkalinity
Week
Concentration(mg/LCaCO3per100ml)
 Indicates Alkalinity is generated – possible Calcite Dissolution
 Dissolved Calcium and Alkalinity have some correlation
indicating Calcium may be released by both Dolomite
dissolution and some other process (Calcite Dissolution)
R² = 0.4044
R² = 0.5843
0
10
20
30
40
50
0 1 2 3 4
Calcium (mg/L)
Ca:Alkalinity Ratio (TR1 and TC1)
Alkalinity(mg/LCaCO3per100ml)

Calcium and Magnesium Retention
Mass Balance Calculations:
 Ca and Mg are relatively enriched compared to Mass Change
 This reflects immobility and retention
 Next: PHREEQC Modelling – Dolomite Weathering and Gypsum 11
0.00 100.00 200.00 300.00
Ca
Mg
TR1-L1
TR1-L3
TR1-L2
Element Mass Change (%)
0.00 100.00 200.00 300.00
Ca
Mg
TC1-L1
TC1-L3
TC1-L2

Indication of Dolomite
• XRD Mineral Analysis: Ankerite (Dolomite)
Ca(Fe,Mg,Mn)(CO3)2
• Leachate Data Ca:Mg Ratio = Correlated Release
• Mg – Ca leachate data – plotted to have depleted after 160
weeks in both Cold and Room Temperature Experiments (3
years):
• Only other source of Mg – Chlorite and biotite weathering
• Biotite was present in low (<2%) concentrations in mineralogy
12

Tonalite Mineralogy
• XRD and Optical Mineralogy confirm Rock Type: Tonalite
• Albite (NaAlSi3O8) – 30%
• Anorthite (CaAl2Si2O8) – 5%
• Quartz – 55%
• Microcline (KAlSi3O8) – 5%
• Orthoclase (KAlSi3O8) - <1%
• Muscovite/ Biotite – 5%
• Trace Dolomite (<1%)
• Sulphides (<0.1%)
13

Metal Release Focus (Leachate)
14
 No indication of Sulfide Weathering
 Flush Effect from fine fraction
0
100
200
300
400
500
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Iron
Week
Concentration(µmol/L)
0
10
20
30
40
50
60
70
80
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Sulphate
Week
R² = 0.1628
0.0
10.0
20.0
30.0
40.0
50.0
0 200 400 600
Fe:SO4 Ratio
Fe (µmol/L)
Sulphate(mmol/L)

Metal Release Focus (Leachate)
15
0
50
100
150
200
250
300
350
400
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Copper
Week
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Chromium
Week
0
10
20
30
40
50
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Nickel
Week
0
100
200
300
400
500
600
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
TR1 vs TC1: Zinc
Week

Metal Release Focus (Mass Balance Graphs)
16
 Only As, Cr, and Zn released in this pH environment
 Cr as Chromate (CrO4
2-), Arsenic (V), Zn2+
-100 0 100 200 300
Ni
Pb
Cu
Cr
Zn
As
TR1-L1
TR1-L3
TR1-L2
-100 0 100 200 300
Ni
Pb
Cu
Cr
Zn
As
TC1-L1
TC1-L3
TC1-L2
-100 -50 0 50 100
Fe
S
TR1-L1
TR1-L3
TR1-L2
-100 -50 0 50 100
Fe
S
TC1-L1
TC1-L3
TC1-L2

Metal Release Focus (Optical Mineralogy)
17
 Sulphides (Pyrite/Chalcopyrite/Sphalerite) are locked
inside mineral grains – not available to surface weathering
 Both Room and Cold: Sulphides Remain Un-altered in
SEM and optical mineralogical analysis
Fresh: In-situ Pyrite Room: In-situ Pyrite Cold: In-situ Pyrite

Metal Release Focus (µ-XRF)
18
 Sulphides contain source of metals
 Weathered waste rock – Loss of Cu and Zn and Sulphur
 Spread of dissolved metals limited – pH controlled
 Retention of Zn elsewhere – mass balance – but also
largest concentrations (mmol) released in leachate
Fe Sulphur Cu Cr Pb Zn
Fresh
Room Tº

Microbiology: MPN Enumerations
19
0.001 0.01 0.1 1 10 100 1000 10000
SOBa IOB SOBn
TR1-L2
TR1-L3
MPN/g
TR1-L1
0.001 0.01 0.1 1 10 100 1000 10000
SOBa IOB SOBnMPN/
Fresh Tonalite
0.001 0.01 0.1 1 10 100 1000 10000
SOBa IOB SOBn
TC1-L2
TC1-L3
MPN/g
TC1-L1
Fresh: Minimal Communities (<50 MPN/g)
Weathered: Both Temperatures:
• Low SOBa – supressed in Room Tº
• High (>2000 MPN/g) SOBn
• Moderate IOB ~ 240 MPN/g
• Reflects circum-neutral pH
• Low amounts of Iron and Sulphur

Steel Fragment Contamination
20
 Optical and SEM indicate metal contamination from steel
fragments likely from drill core and/or crushing
 Samples were crushed and magnetically separated
 99% of metals grains were steel fragments
 Steel contains Fe, Mn, Cr, and Carbon, and other metals.
 No Sulphur is contained in these fragments
1 2 3 4 5 6 7 8 9 10
keV
0
1
2
3
4
5
6
7
8
cps/eV
FeFe Mn
Mn
Ni
Ni
ZnZn CdCd Si

Sequential Extractions
 Modified 7-step Selective/Sequential Extraction procedure developed in-
house at University of Waterloo
 Currently: Ongoing – certifying the efficiency of Aqua Regia Step
 Can not compare other steps until Aqua Regia – Focus for rest of year
 Modification of Arrenhius Equation to calculate Dolomite Weathering
Step Fraction Target phase(s) Target description
1 Water soluble Soluble species Dissolution by simulated precipitation input (humidity cell
replication) and saturation—easily soluble ions
2 Exchangeable Weakly or non-specifically adsorbed
ions
Changes in the ionic composition or lowering of pH could
cause remobilisation of metals
3 Carbonates, less-
readily exchangeable
Specifically sorbed species Bound by covalent forces that require H+ or soft cation to
displace
4 Reducible Fe-amorphous to –crystalline minerals Primarily Fe(II)
5 Reducible Fe-crystalline minerals Unweathered and weathered Fe minerals, Fe(II) and
Fe(III)
6 Oxidizable Sulfides Available sulfides—pyrrhotite, chalcopyrite, pyrite,
sphalerite—with weathered coatings
7 Residual Residual non-silicate mineral Non-silicate and less resistant aluminosilicates

Suitability of Tonalite as an Alternative Cover
 Minimal Release of Dissolved Metals
 Constituent Release Interaction with Frozen Core Over Time
 Mass Loading Calculations based on volume of Material
 Comparison with Type 1 material
Smith (2006)

Planned Publications
1. Carbonate weathering potential of an inert
engineered cover material to alleviate acid
rock drainage formation in an unsaturated
waste rock pile in an Arctic clime
2. Developing novel laboratory-scale solutions to
evaluate sulphide-weathering evolution of a low-
sulphide containing waste rock
3. Environmental Engineered Tonalite Cover
interactions over a PAG – containing mine
waste rock pile in an Arctic Clime
23

Diavik Waste Rock ProjectDiavik Waste Rock Project
MEND
Diavik Test Piles Group
Meeting
Thank you for Listening
Dr. Peter Nason (Postdoctoral Fellow)
panason@uwaterloo.ca
UW: Saturday 7th November 2015

UW_Diavik_Presentation_Nason (1)

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