Pebble Project Geochemical Characterization Stephen Day Claire Linklater SRK Consulting November 27,...
Transcript of Pebble Project Geochemical Characterization Stephen Day Claire Linklater SRK Consulting November 27,...
Pebble ProjectPebble ProjectGeochemical Geochemical
CharacterizationCharacterizationStephen DayStephen Day
Claire LinklaterClaire LinklaterSRK ConsultingSRK Consulting
November 27, 2007November 27, 2007AnchorageAnchorage
Day1_1415_SRK_Day.mp3
Geology MapGeology MapEach dot is a drill hole
Geological Cross-SectionGeological Cross-Section
Geology (Cretaceous)Geology (Cretaceous)
2007 Program Objectives2007 Program Objectives
• Continue characterization of West Zone.
• Characterization of East Zone.
• Evaluate leaching under non-acidic conditions from Tertiary rocks
• Characterization of tailings produced in 2007 from East Zone.
West Zone in 2007West Zone in 2007
• In-fill drilling for exploration.• Ongoing rock humidity cells (up to 2.5
years).– Two Cretaceous– Seven Tertiary
• Four ongoing rock subaqueous columns (2 years).
• Two ongoing low-sulfide tailings columns and two humidity cells (2.5 years).
East ZoneEast ZoneSample selection – Static TestworkSample selection – Static Testwork
• Criteria designed to ensure samples covered range in:– Rock type– Spatial variability– Geochemical characteristics (sulfur, metal content).– Calcium used as a surrogate for neutralization potential.
• Cretaceous (200 samples)– 180 samples below copper equivalent of 0.6%.– 20 samples above copper equivalent of 0.6%.
• Tertiary (200 samples) – bimodal sulfur distribution– 180 representing typical sulfur content.– 20 representing higher sulfur content (>1%).
0.001
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0% 20% 40% 60% 80% 100%
Cumulative Percentage
Sul
fur
(%)
n = 3766
Sulfur in East Zone Tertiary RocksSulfur in East Zone Tertiary Rocks
East ZoneEast ZoneSample selection – Kinetic TestworkSample selection – Kinetic Testwork
• Humidity Cells– Subset of samples studied in static testwork
program• 12 Cretaceous • 11 Tertiary
– Samples selected by:• Ranking dataset according to sulfide-S content• For each lithology, selected samples with (i) low,
(ii) average, (iii) high, and (iv) highest sulfide-S content
Confirmation of Analytical Surrogates Confirmation of Analytical Surrogates Used to Select Samples (Cretaceous)Used to Select Samples (Cretaceous)
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0.001 0.01 0.1 1 10 100
NP/AP Indicated by Exploration Database Analysis for Calcium and Sulfur by ICP Analysis
Mea
sure
d N
P/A
P b
y A
cid
-Bas
e A
ccou
ntin
g
Dashed lines indicate NP/AP=2
Confirmation of Analytical Surrogates Confirmation of Analytical Surrogates Used to Select Samples (Tertiary)Used to Select Samples (Tertiary)
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0.001 0.01 0.1 1 10
Exploration Database Sulphur Content (%)
Mea
sure
d N
P/A
P b
y A
cid-
Bas
e A
ccou
ntin
g Dashed line indicates NP/AP=2
Acid-Base Accounting Results: Acid-Base Accounting Results: East Zone Cretaceous (I)East Zone Cretaceous (I)
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0.0001 0.001 0.01 0.1 1 10 100
NP/AP
Pa
ste
pH
Diorite
Granodiorite
Porphyritic monzodiorite to granodiorite
Wacke, sandstone
Mudstone, siltstone
Fault affected material
Cretaceous Samples
Acid-Base Accounting Results: Acid-Base Accounting Results: East Zone Cretaceous (II)East Zone Cretaceous (II)
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0 100 200 300 400 500 600 700 800 900
AP, kg CaCO3/t
Mo
dif
ied
NP
, kg
CaC
O3/t
NP/AP=1
NP/AP=2
Diorite
Granodiorite
Porphyritic monzodiorite to granodiorite
Wacke, sandstone
Mudstone, siltstone
Fault affected material
Acid consuming
Uncertain potential
Potentially acid generating
Cretaceous Samples
Acid-Base Accounting Results: Acid-Base Accounting Results: East Zone TertiaryEast Zone Tertiary
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0 20 40 60 80 100 120
AP, kg CaCO3/t
Mo
dif
ied
NP
, kg
CaC
O3/t
NP/AP=1NP/AP=2Andesite, basaltConglomeratesDaciteMudstone, siltstone
Acid consuming
Uncertain potential
Potentially acid generating
Tertiary Samples
Comparison of AP results for East Comparison of AP results for East & West Zones& West Zones
• East Zone samples yielded lower AP values than West Zone 0.0
0.5
1.0
1.5
2.0
Diorite Granodiorite Porphyr.monzo-
granodiorite
Wacke,sandstone
Mudstone,siltstone
Fault affectedmaterial
Sample Type
Rat
io o
f A
P v
alu
esP
ebb
le E
ast:
Peb
ble
Wes
t
Median Cretaceous Samples
Ratio = Unity
0.0
0.5
1.0
1.5
2.0
Sedimentary Volcanic
Sample Type
Ra
tio
of
AP
va
lue
sP
eb
ble
Ea
st:
Pe
bb
le W
es
t MedianTertiary Samples
Ratio = Unity
Comparison of NP Results for East Comparison of NP Results for East & West Zones& West Zones
• East Zone samples either equivalent or lower than West Zone
• Some exceptions in Cretaceous samples:– Higher median
values wacke/sandstone
0.0
1.0
2.0
3.0
4.0
5.0
Diorite Granodiorite Porphyr.monzo-
granodiorite
Wacke,sandstone
Mudstone,siltstone
Fault affectedmaterial
Sample Type
Rat
io o
f N
P v
alu
esP
ebb
le E
ast:
Peb
ble
Wes
t
MedianCretaceous Samples
Ratio = Unity
0.0
1.0
2.0
3.0
4.0
5.0
Sedimentary Volcanic
Sample Type
Rati
o o
f N
P v
alu
es
Peb
ble
East:
Peb
ble
West Median Tertiary Samples
Ratio = Unity
Comparison of NP/AP Results ForComparison of NP/AP Results For Pebble East & West Zone Pebble East & West Zone
• Overall conclusions same for East and West:– Cretaceous mineralized
rocks are mainly PAG.– Tertiary rocks are
mainly non-PAG.
• Median NP/AP for East Zone often greater than West Zone.
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1
10
100
Diorite Granodiorite Porphyr.monzo-
granodiorite
Wacke,sandstone
Mudstone,siltstone
Fault affectedmaterial
Sample Type
Rat
io o
f N
P/A
P v
alu
esP
ebb
le E
ast:
Peb
ble
Wes
t
MedianCretaceous Samples
Ratio = Unity
0.1
1
10
100
Sedimentary Volcanic
Sample Type
Ra
tio
of
NP
/AP
va
lue
sP
eb
ble
Ea
st:
Pe
bb
le W
es
t Median Tertiary Samples
Ratio = Unity
Field Weathering TestsField Weathering Tests
Field Weathering TestsField Weathering TestsBarrel # Age Zone Rock Types
1 Tertiary East Andesite/Basalt
2 & 3 – Duplicates Tertiary West Andesite/Basalt
4 Tertiary East Dacite
5 & 6 - Duplicates Tertiary West Conglomerates
7 Tertiary East+West Wacke/sandstone
8 Tertiary East+West Mudstone
9 & 10 - Duplicates Cretaceous West Intrusive rocks
11 & 12 - Duplicates Cretaceous West Sedimentary rocks
13 --- --- Blank, left empty
Conclusions from 2007 ProgramConclusions from 2007 Program
• East Zone showing similar results to West Zone– Cretaceous mineralized rock is mainly PAG.– Tertiary rock is mainly non-PAG.