Discovery and Geology of the

Pampa Escondida Porphyry,

Escondida, Chile

May 2010

Location

Pampa

Escondida

Escondida Norte

Escondida

Chimborazo

5 km

Véliz, 2004

Schematic Geological Map

Escondida

Escondida Norte

Pampa

Escondida

Paleozoic Complexes

Thin cover of Mesozoic rocks

Mesozoic Sequences (Jr - Tt)

Mesozoic Plutonic Complexes

Domeyko fault System

Incl. West Fissure Fault

38 - 34 Ma Porphyries

in both sides of the fault system

Minera Escondida Limitada (MEL)

Escondida Norte

Belongs to BHP Billiton 57.5%; 30.0% to Rio Tinto Plc; 10.0% to JECOCorp. and 2.5% to IFC. BHPBilliton is the Operator.

In 2009 produced 1,102,976 metric tons of fine copper (70% inconcentrates and 30% in cathodes), representing the ~ 8% of worldproduction.

Produces sulphide concentrate by flotation (Laguna Seca and LosColorados plants) and cathodes through leaching of oxides ore andbioleaching of low grades sulphides ore (SX-EW plant).

The mines (Escondida and Escondida Norte) move together annually,more than 360 million metric tons of rock.

Copper concentrate is carried by two pipelines from the mine to PuertoColoso (near Antofagasta).

A seawater desalination plant is located in Coloso, to provide part ofthe requirements of the operations.

www.escondida.cl

Discovery

Historical Drillholes

• 136 leachable ore condemnation holes

• length ~250 m

• average gravel cover depth 60 m

389 m with

last 97 m with Cu grades

host rocks

389 m long, having the last 97 m

with “porphyry-type” alteration assemblages and Cu mineralization style.

host rocks

First New Drillholes

Hole # 2: 1.200 m

disseminated Cpy + Bo

host rocks + Granodioritic Porphyry Hole # 1: 722 m

disseminated ore: Cpy + Bo

host rocks

Hole # 3: 800 m

disseminated ore Cpy + Bo

host rocks

389 m with

97 m with “porphyry-type” alteration assemblages and Cu mineralization style

host rocks

Early Mineralization Model 2007

Cpy top?

?

Hole #3:

disseminated Cpy + Bo

host rocks

Hole #2:

disseminated Cpy + Bo

host rocks + Granodioritic Porphyry

SW NE

+

+

+

+

+

+

+

+

97 m @ primary ore: porphyry-style

alteration and mineralization (Cpy + Bo)

Hole #1:

disseminated Cpy + Bo

host rocks

2.000 m

3.000 m

Geology

Pampa Escondida: deep drillholes collars

Escondida Norte

Escondida

Lithology: Porphyries – Host rocks

3.000 m

2.000 m

1.000 m

W E35,2 Ma

35,0 Ma

36,1 Ma

36,1 Ma

37,6 Ma

287,6 Ma

293,0 Ma

288,8 Ma

Lithology: Breccias

1

10

10 0

10 0 0

La C e Pr N d Sm Eu Gd Tb D y Ho Er Tm Y b Lu

Ro

ck R

EE

/ C

ho

nd

rite

RE

E

287,6 ± 3,3 Ma

293,0 ± 4,3 Ma

35,0 ± 0,8 Ma

36,1 ± 0,7 Ma

REE Patterns: Paleozoic - Tertiary

Pampa Escondida Porphyry• Strong potassic FK >> Bt

• Qz veinlets > 10% volume

• Cpy – Bo – (Cv - Dg)

Intramineralization• Chl-Ser overprinted in K alteration

•Qz veinlets ~ 3 - 4% volume

•Cpy – Py – (Bo)

Late Intramineralization• Chl-Ser overprinted in K alteration

• Qz veinlets < 1% volume

• Py > Cpy

Dacitic Post-Mineralization• Qz-Ser-Chl alteration

• D veinlets

• Py >> Cpy

37 Ma

34 Ma

1 0.5 0Cu%

Pampa Escondida Porphyries

Contacts relationships porphyries - veinlets

Post Dacitic 34,3 Ma

Hydrothermal breccia

Late Intramineral 35,0 Ma Refractary Qz veinlets in

Late Intramineral 35,0 Ma

“A” veinlet

Chilled margin

“A” veinlet

Cpy-Bo

“A” veinlet

Cpy > Py (Bo)

Intramineral 36,1 Ma

Radiometric dating Pampa Escondida Porphyries

37,6

36,1 36,1

35,0

34,3

36,1

32

33

34

35

36

37

38

39

Early Diorite

Pampa

Escondida Intramineral

Late

Intramineral Post Dacitic

Hydrothermal

Biotite

Ma

U-Pb Zircon ages K-Ar Bt age

Modal Evolution of Pampa Escondida Porphyries

Post Dacitic (34,3 ± 0,6 Ma)

Late intramineral (35,0 ± 0,8 Ma)

Pampa Escondida (36,1 ± 0,7 Ma)

Early Diorite (37,6 ± 0,5 Ma)

Pampa Escondida

Porphyry Complex

Evolution in time

37 Ma

36 Ma

34 Ma

E - W Section - Lithology + Primary Ore

W E

Cpy - Py0,3 - 0,5 % CuT

Cpy - Bo> 0,5 % CuT

Py - Cpy< 0,2 % CuT

Py< 0,3 % CuT

Bo + Cpy

Cpy + Py

W E

Cpy

Py

349 m1,1%

0,4%

Bn

Cpy

Cc-Dg

800 m

2,6%2,3%

0,1%0,3%

Ore Zonation

Cpy + Bo

Cpy + PyPy

Py > Cpy

Plan View 2.000 m - Porphyries/Minzone projection

Bo – Cpy

Minzone

Envelope

Cpy – Py

Minzone

Envelope

Pampa

Escondida

Porphyries

1.000 m

Hydrothermal Alteration

Bt

W E

Cu Au

Cu - Au Correlation

Au

Bo

Cu - Mo Correlation. Plan view 2.000 m

Cu Mo

37,7 ± 0,8

34,2 ± 0,7

37,5 ± 0,5

38,7 ± 1,3

Escondida N

Escondida

Zaldivar

36,1 ± 0,6

Pampa Escondida System projection

Pinta Verde

##

#

#

# #

#

#

# # #

# #

#

#

#

#

#

#

#

##

# ##

# # # #

# # # #

#

# # #

#

N S

0,5 - 1,0 % Cu

0,5 - 1,0 % Cu

0,5 - 1,0 % Cu

Escondida Norte Escondida

Pampa Escondida

Primary mineralization event: 36 - 38 Ma (Primary ore: Sulphides)

Secondary mineralización event: ~15 Ma (Secondary ore: Sulphides-Oxides)

> 2 % Cu> 2 % Cu

~2 km

Schematic N-S Section

The End