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

0.01

0.1

1

10

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)

0.0001

0.001

0.01

0.1

1

10

100

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)

0.1

1

10

100

1000

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)

0

2

4

6

8

10

12

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)

-50

-30

-10

10

30

50

70

90

110

130

150

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

-50

0

50

100

150

200

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.

0.1

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.