structural controls cu deposits, northern chile_skarmeta

11

STRUCTURAL CONTROLS ON PORPHYRYCu DEPOSITS, NORTHERN CHILE

J. Skarmeta 1, K. McClay 2, & A. Bertens 1,

Gerencia Corporativa de Exploraciones, Codelco, Chile Royal Holloway University of London

LOCATION MAPOF

CENTRAL ANDES(USGS DEM)

20

25

30

75 70 65

PACIFICOCEAN

ALTIPLANO

SIERRASPAMPEANAS

Antofagasta

STUDYAREA

22

TERTIARY PORPHYRYCu-Mo DEPOSITS,NORTHERN CHILE

(from Cuadra & Camus, 1998)

Ujina (34-32 Ma)

Collahuasi (34-32 Ma)

Quebrada Blanca (37-36 Ma)

El Abra (37-36 Ma)Radomiro Tomic (33-31 Ma)

Chuquicamata (34-31 Ma)Mansa Mina

Telegrafo (40 Ma)

Salar deAtacama

Chimborazo (40 Ma)

La Escondida, Zaldivar (35-31 Ma)

Exploradora (33-32 Ma)

El Salvador (44-41 Ma)

Potrerillos (36 Ma)

Iquique

Tocopilla

Taltal

Mt Fine Cu

13

1

34

90

14

36

36

26

70 69

22

24

100km

CORDILLERADOMEYKO

ATACAMAFAULT

SYSTEM

Antofagasta

UD

U D

UD

AIMSDetermine 4D Structural Evolution of theCordillera Domeyko, Northern Chile

Determine Structural Controls on Cu-MoMineralization

Determine Structural Styles and StrainPartitioning using Analogue Models

Develop 4D Evolutionary Models

Develop New Models for Porphyry Cu-Mo Mineralization in Oblique SubductionRegimes

33

TECTONIC EVOLUTION OFTHE CORDILLERA DOMEYKO

Permo-Carboniferous Basement

NW-SE Triassic Rift Basins

N-S Jurassic - Lower Cretaceous Back Arc Rift Basins

Late Cretaceous - Oligocene Contraction

Paleocene - Oligocene Porphyry Intrusion

Late Oligocene - Present Day Contraction

Chronostratigraphy from Domeyko Range

v v v v vv v v v v

v v v vv v v v v

v v v v v

v

+ + + ++ +

++ ++

+

++

+

?

LogitudinalValley

DomeykoRange

PreandeanDepression

WesternCordilleraQuaternary

Pliocene

Neogene

Tertiary

Paleocene

Paleogene

Cretaceous

Jurassic

Triassic

Tectonicstages

Fore-arcbasin

TertiaryInversion

Hiatus

JurassicBack-arc

Basin

TriassicContinental

Rift

M.a.1,65,2

25,2

36

54

66

96

131

152

180

210

CretaceousRift

PorphyryCopper

Intrusives

PorphyryIntrusives

Structuralfeatures

Normal Faulting

Thin-Skinned Thrusting

(nverted Fault,Thin and Thick-Skinned

Structures

Steep Nomal Faults& LIstric Faults

Thermal Subsidence,Little Faulting

Steep BasementNormal Faults

en-echelon NW -SEHalf-graben Basins

Eocene

Oligocene

Miocene

Later

Early

Later

Early

Middle

Later

Early

CONTRACTION

EXTENSION

EXTENSION

THERMALSUBSIDENCE

44

CHUQUICAMATAMINE

Cretaceous-TertiaryIntrusives

Thrust Fault

Anticline

Syncline

Quebrada

Loa River

StructuralCross-Section

Permo-CarboniferousCollahuasi Fm.Intrusives

Permo-CarboniferousCollahuasi Fm.Volcanics

Permo-CarboniferousMetamorphic ComplexC

C

B

B

AA

Chuquicamata

Calama

El Abra

Qda.Chug Chug

Rio San Salvador

Rio Loa

Rio Loa

Qda.Sama

Pampa Puno

Qda. Arcas

Qda.Quehuita

Qda. Guatacondo

10 km

Q.Blanca

Chuquicamata

Calama

El Abra

Q. Blanca

Qda.Chug Chug

Rio San Salvador

Rio Loa

Rio Loa

Qda.Sama

Pampa Puno

Qda. Arcas

Qda.Quehuita

Qda. Guatacondo

C

C

B

B

A

10 km

A

55

0 2 4 Km

?

Quebrada Guatacondo - Quebrada Blanca

?

W34-37 Ma38 Ma

Quebrada Blanca

34-35 Ma

> 1000 m

5150

00

5050

00

4950

00

-3

5200

00

5

4

3

2

1

0

4900

00

5000

00

5100

00

-1

-2

Quebrada Blanca-Quebrada Quebrada Blanca-Quebrada Guatacondo Section Guatacondo Section A-A`A-A`

ICANCHE FORMATION, SIERRA YOCAS

Sierra Sierra Yocas Cross Section Yocas Cross Section B-B`B-B`

5 Km

B B

66

CC

5 km

Capillas Capillas Cross SectionCross Section

77

FOLDED SICHAL FORMATION

88

ESCONDIDA

99

QUEBRADA VAQUILLAS QUEBRADA PROFETA

1010

TRIASSIC BASEMENT THRUST OVER JURASSIC FOLDED JURASSIC-CRETACEOUS SHALES & LIMESTONES

1111

LANDSAT:Exploradora - El Salvador

Salar dePedernales

Sierra Castillo

Sierra Exploradora

El Salvador

20 km

N

N

Riolithic Porphyrs and Sills

Cretaceous (Fm Santa Ana, Fm Llanta)

Jurassic (Fm Montandn)

Triassic-Jurassic ( Fm Quebrada del Salitre - Upper Member)

Triassic ( Fm Quebrada del Salitre - Lower Member)

Pre-T riassic Rift Basement ( Permian intrusive complex & Fm La Tabla)

Jm

Kll

JKqv

Terpr

TJqv(1)

Tqv(2)

LEGEND

PZgr

Jurassic - Cretaceous (Fm Q.V icuas, Fm Sierra Fragua)

Ja Jurassic (Fm Asientos)

0 km

1

2

3

4

W E

Section-2(B-B): Q. Sur Ins ChicaW-E: 1 17

Jm Jm

PZgr

Tqv(2)

TJqv(1)

Jkqv

Ja

Jm

Jm Terpr JmKsa

Tqv

Q

PZgr

Tqv(2)

PZgr

0 4 km

N = 255

Dip Data STEREOPLOT

Photo-2BPhoto-2A

Quebrada Doa Ins Chica

1212

N

Ja

Jm Tjqs Ja

PZgr

PZgr

PZgr

Pin point

0km

1

2

3

4

0 4km

W E

Section-1(A-A): Cuesta MontandnW-E: 115

Kll JKsfPZgr

SCFQBF

Jm

Tertiary Porphyry Intrusives and Sills

Cretaceous (Fm Agua Helada, Fm Sierra Fragua,Fm Llanta)

Jurassic-Cretaceous (Fm Q.V icuitas)


Triassic-Jurassic ( Fm Quebrada del Salitre)

Pre-T riassic Rift Basement ( Permian intrusivecomplex & Fm La Tabla)

Kp / Kll

JKqv

TJqs

Jurassic (Fm Asientos)

PZgr

Jm

Ja

LEGEND

Terpr

Te r p r

Photo-1A

Photo-1B

Cuesta Montandon

1313

Section-1 Cuesta Montandn-Restoration

JKsf

KllKp

JKqv

Ja

JmTJqs

PZgr

Pin point

0km

-3

-2

-1

-4

PZgr

UpperJurassicCretaceous Basin

W E

Paleocene (Fm Estratos de Cerro V aliente)

Cretaceous (Fm Agua Helada, Fm Sierra Fragua,Fm Llanta)

Jurassic-Cretaceous (Fm Q.V icuitas)


Triassic-Jurassic ( Fm Quebrada del Salitre)

Pre-T riassic Rift Basement ( Permian intrusive complex& Fm La Tabla)

Kp / Kll

JKqv

TJqs

TerCv

Jurassic (Fm Asientos)

PZgr

Jm

Ja

LEGEND

?

Cuesta de Montandon Resortation

1414

2 x 3 m Deformation Rig

Homogeneous Dry Quartz Sandpack

90 to 15 Oblique Subduction Angles

Digital Photography & Animation

Vertical & Horizontal Sectioning

1 cm in Models ~ 1 km in Crustal Strata

SCALED ANALOGUE MODELLINGOF OBLIQUE SUBDUCTION

ForelandForedeep

Foreland Fold-Thrust Belt

OphioliteCrystalline Nappe

Shear Zone

Metamorphic Core

Multiply Deformed Pluton

Shear Zone

MetamorphicComplex with

M a f i c - U l t r a m a f i c sSlate Belt

Foredeep

Late Post-Tectonic PlutonOphiolite Suture

Foreland

Moho

++ +

+

+

+

Foreland Fold-Thrust Belt

Foredeep

Miogeoclinal Fold-Thrust BeltGneiss and / orSchist

Slate Belt

C o n c o r d a n t U l t r a m a f i cBodiesHigh-Angle ShearZones

Pre- and Syn-OrogenicPlutons

Post-Orogenic Pluton

Ophiolite Complex

Continental Basement

Mantle+++ +

(after Hatcher & Williams, 1986)

DOUBLY-VERGENT OROGEN

1515

Detachment Sheet

Layered Sand Pack

Subduction SlotMotor 2.5 cm

Motor

StaticSandpack

MovingSandpack

90

Detachment Sheet BaseVariable Angle Subduction Slot

60 45 30 15

1 - 3 m

1 mSubductionVector

DEFORMATION RIG

Plan View

Cross-Section View

2D DOUBLY-VERGENT WEDGE MODELCROSS-SECTION

T2

T1

T3

T4 TRT5

T6

Forward-Breaking Thrust Sequence

Subduction Slot

1616

SubductionVector

Subduction Subduction SlotSlot

MovingMovingSandpackSandpack

StaticStaticSandpackSandpack

10 cm10 cm

90 ORTHOGONALMODEL

LONGITUD L (km)

LONGITUD L (km)

MA

XIM

O D

ES

PLA

ZA

MIE

NT

O d

(km

) ??10

0

??10

- 3

L= 1

0km

Fallasde

modelos

106

105

104

10

103

103

102

102

101

101

100

100

10-1

10- 1

10- 2

10-2

10- 3

10- 3

10- 4

123456789

12

21

90 ORTHOGONAL MODEL - CROSS-SECTIONS

32


1717




SubductionVector

10 cm10 cm

45 OBLIQUE MODEL

15

25

45 OBLIQUE MODEL - CROSS-SECTIONS

30


1818

SubductionSubductionSlotSlot



SubductionVector

10 cm10 cm

30 OBLIQUE MODEL10

22

30 OBLIQUE MODEL - CROSS-SECTIONS

35


1919

SubductionSubductionSlotSlot



SubductionVector

10 cm10 cm

15 OBLIQUE MODEL

i

345-500 m

>1000 m

2020

SUMMARY OF ANALOGUE MODELS

90 Convergence - Doubly-VergentWedge - Dip-Slip Thrusting

75 - 45 Convergence - Doubly-VergentWedge - Oblique-Slip Thrusting

2121

10

0

10

20

30

40

50

60

90 80 70 60 50

Nazca (Farallon)

Hotspot

Phoenix33 - 8 Ma

10

0

10

20

30

40

50

60

90 80 70 60 50

Nazca (Farallon)

Hotspot

Phoenix48-33 Ma (after Cole, 1990)

Cretaceous Syn-Extension

Porphyry

Tip-Line Folds

Erosion ofInversion Anticline

Syn-Inversion

MAGMA

Jurassic Syn-Extension

ForelimbThinning

BasementPalaeozoic T riassic

PORPHYRY EMPLACEMENT DURING INVERSION

2222

Emplacement ofIntrusion along

Steep ReverseFault

MAGMA EMPLACEMENT DURING CONTRACTION

2323

Torres del Paine Intrusion in Steeply-Dipping Thrust Fault Torres del Paine Intrusion Southern Chile

2424

APPLICATIONSTO THE

CHUQUICAMATADISCTRICT

(Castelli, 2002, Pardo y Rivera, 1998)

Surface Geology Structural compilation

Chuqicamata Disctrict

2525

Geology below gravels

CMTRTP

Geology level - 500 m

RTP -5002a DV RTP -500

2626

Section 7550000

Section 7536000

Section 7526000

Section 7517000

2727

Esquema de evolucin estructural

M xima dilatacin

STRUCTURAL EVOLUTION

Zone of maximum dilation

Neutralsurface

STRA

IN R

ATE

COMPRESSION

EXTENSION

SLIP ZONE(VERY WEAK)

NUMERICAL VISCOUS MODELING:TWO LAYER BASIN INVERSION

STRONG

WEAK

HOMOGENEOUS

STRONG

WEAK

2828

Tectonic Map of the southern segment of the Cordillera de Domeyko

AncestralAtacama

FaultSystem?

70 ObliqueSubduction

Obliquely InvertedJurassic-Cretaceous

Retro-Arc Basin

ForelandFold-Thrust

Belt

Retro-ArcForeland

Basin

AccommodationZone

PorphyryIntrusions

OffshoreAccretionary

Complex

RelictJurassic-

Cretaceous Arc

Eocene-OligoceneArc

ContinentalMargin

N

LATE EOCENE - OLIGOCENE SUBDUCTION

2929

CONCLUSIONS - I

Northern Cordillera Domeyko Exhibts N-SContractional Tectonics with Little Evidenceof Strike-Slip Deformation

Eocene - Oligocene Porphyries Emplaced as Sills and Tabular Dykes along Thrusts

Porphyries are Emplaced in a Regional Contractional Stress Field

Basement Blocks Show Significant Uplift

There is a Close Spatial Association of Basement Uplifts, Reactivated Faults andPorphyry Intrusions

3030

CONCLUSIONS - II

Eocene-Oligocene Plate Motions Indicate Consistent N70E Oblique Convergence

Modern Subduction Margins Show StrongPartitioning with Consistent Margin Normal Shortening & Very Limited Strike-Slip

Scaled Analogue Models of Oblique Subduction Only Show Strike-Slip Faulting at Convergence Angles , 45

An Inversion Model is Proposed for theEmplacement of Porphyry Cu-Mo Depositsin Northern Chile

structural controls cu deposits, northern chile_skarmeta

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