Komatiite-hosted Ni-Cu-(PGE) deposits: understanding deposit and camp footprints

Steve BeresfordSteve Beresfordnewgenconewgenco

AcknowledgementsAcknowledgements�� CoCo--authorsauthors

•• Marco Marco FiorentiniFiorentini•• Jon Jon HronskyHronsky•• Nic Nic RosengrenRosengren•• Dave Dave BertuchBertuch•• Paul Paul DuuringDuuring•• Ahmad Ahmad SaleemSaleem•• Bill StoneBill Stone•• Mark Mark BarleyBarley•• Mark Mark BarleyBarley•• Ray CasRay Cas•• Ben Ben GrguricGrguric

�� Former colleagues Former colleagues at WMC and at WMC and BHPBillitonBHPBilliton�� Various company support over last 10 years, Various company support over last 10 years,

WMC, Falconbridge, INCO, WMC, Falconbridge, INCO, LionoreLionore, MPI, MPI�� Collaborators and Sponsors of AMIRA P710Collaborators and Sponsors of AMIRA P710�� Host of past students and Host of past students and postdocspostdocs

TALK OutlineTALK Outline�� IntroductionIntroduction

�� Focus on new ideas on geological, Focus on new ideas on geological, geochemical and geophysical geochemical and geophysical footprintsfootprints

1. Continuum of deposit styles and 1. Continuum of deposit styles and controlscontrols

2. Deposit diversity 2. Deposit diversity Footprint of these diverse stylesFootprint of these diverse styles

How our exploration methodologies changeHow our exploration methodologies change

3. Camps3. CampsNeed to improve predictive methodologiesNeed to improve predictive methodologies

Take home messagesTake home messages�� KomatiiteKomatiite hosted Nihosted Ni--CuCu--(PGE) deposits exhibit (PGE) deposits exhibit considerable diversity (in terms of massive considerable diversity (in terms of massive sulfidesulfidetypes)types)

�� Kambalda is only an end memberKambalda is only an end member

�� Significant variation in Significant variation in exploration strategy exploration strategy between between the deposit end membersthe deposit end membersthe deposit end membersthe deposit end members

�� Despite 40 years of exploration they are still truth Despite 40 years of exploration they are still truth machine intensive machine intensive –– we must maximise in hole data?we must maximise in hole data?

�� Do isolated Do isolated komatiitekomatiite--hosted Nihosted Ni--CuCu--(PGE) deposits (PGE) deposits represent underexplored camps? represent underexplored camps?

�� We outline current knowledge in delineation of camps We outline current knowledge in delineation of camps but further work is required at a scale rarely attempted.but further work is required at a scale rarely attempted.

Our Our common view of common view of komatiitekomatiite--hosted Nickel hosted Nickel sulfidessulfides

is is Kambalda Kambalda centriccentric

Frost 1992

30+ years of outstanding discovery and production of the same style

Cowden 1986

Primary sulfide texturesPrimary sulfide textures

Katinniq

Blebby ore

Yakabindie

Foster

Secondary Secondary sulfidessulfides texturestextures

The search for footprints to Ni-Cu-(PGE) deposits

Kelley2 2007

The best and possibly the only reliable geochemical tracer of komatiite associated

nickel sulfide deposits is the presence of Ni sulfides” Barnes et al 2004

PROXIMAL

DISTAL

1. Continuum of deposits1. Continuum of deposits

�� Controls on diversityControls on diversity

•• Parent magmaParent magma

•• Emplacement (intrusive vs extrusive)Emplacement (intrusive vs extrusive)

•• Host rockHost rock

�� Parent magma variation (part of Parent magma variation (part of continuum for all NiS)continuum for all NiS)

-- Genetic and exploration significanceGenetic and exploration significance

-- Recognition and implications of Recognition and implications of komatiitic basalt Raglan style deposits in komatiitic basalt Raglan style deposits in the Yilgarn eg Collurabbie, Windarrathe Yilgarn eg Collurabbie, Windarra

1. Parent magma Continuum1. Parent magma Continuum15

25

20

Windarra

Fortaleza

Shebandawan

Raglan*

Thompson*

Collurabbie

1300 C - 2 PaSO

MgO

30

35

Komatiite Transitional Komatiitic basalt

Perseverance

Mt Keith

Kambalda

1600 C - 0.01 PaSO

MgO

* Proterozoic

Archaean komatiitic basalt depositsArchaean komatiitic basalt deposits

Geochemistry

• Cr saturation (Ni:Cr vectors are

not applicable)

• High PGE, Pd:Ir

• MgO contents (lower Fo)

Geology• Oikocrystic peridotites and pyroxenites

• Poddy ore bodies• Poddy ore bodies

• Thick internal sulfides

• Thick matrix sulfides possible (50-60m)

• Diversity of new sulfide textures including Leopard

texture sulfides

Geophysics

• Discontinuous conductors (line spacing, moving loop)

• Constrain geometry (magnetic inversion)

2. Deposit diversity and footprint2. Deposit diversity and footprint

�� Numerous classification schemesNumerous classification schemes�� Main textural association of sulfidesMain textural association of sulfides

•• Type 1Type 1•• Type 2Type 2•• Type 3Type 3•• RemobilisationRemobilisation

�� GeneticGenetic

3Boston Creek

Wiluna

Mt Clifford

�� GeneticGenetic•• Intrusive vs extrusiveIntrusive vs extrusive

�� CompositionalCompositional•• Dunite vs PeridotiteDunite vs Peridotite

�� Biggest control is host rockBiggest control is host rock-- facies associationfacies association•• Komatiite basaltKomatiite basalt•• Komatiite felsicKomatiite felsic•• KomatiiteKomatiite--sedimentsediment

1 2Kambalda

Perseverance Mt Goode-Cosmos

Goliath

Six Mile

Mt Keith

A. A. KambaldaKambalda style depositsstyle deposits�� Seminal work of Woodall, Ross, Seminal work of Woodall, Ross,

Gresham et al has stood the test of timeGresham et al has stood the test of time�� Well understood derivative exploration Well understood derivative exploration

modelmodel

Recent ideas:Recent ideas:�� Channel and trough are not the sameChannel and trough are not the same�� Increasing use of structure and 3D Increasing use of structure and 3D

tenor variation as exploration tooltenor variation as exploration tooltenor variation as exploration tooltenor variation as exploration tool�� Ni dispersion into footwallNi dispersion into footwall�� Diversity of sediment association and Diversity of sediment association and

thickness variationsthickness variations�� StratigraphicStratigraphic correlation of sedimentary correlation of sedimentary

units with units with felsicfelsic volcanicsvolcanics (below) (below) �� Camp Spacing is predictable within Camp Spacing is predictable within

campscamps

Distal felsic fall deposit intercalated with Silver Lake Peridotite, Kambalda

Exploration Exploration

�� Basal flow thickness Basal flow thickness (>30m)(>30m)

�� SedimentSediment--ore ore antithetismantithetism�� High High MgOMgO thick cumulates, thick cumulates,

High Ni, High Ni, Ni:CrNi:Cr�� Amygdaloidal domains are Amygdaloidal domains are

commoncommoncommoncommon�� Sediment free ore prismSediment free ore prism�� Ore environment is Ore environment is

structurally complex with structurally complex with prominent prominent metasomaticmetasomaticzones and chlorite zones and chlorite tectonitestectonites (originally (originally termed chlorite sediments)termed chlorite sediments)

Seat 2002

TroughTrough--Channel CrossChannel Cross--Cutting Cutting Relationships at KambaldaRelationships at Kambalda

N

trough

channel

Lunnon Fisher

N

Stone et al 2006

trough

channel kilometres

0 0.5

Ken

Ken

volcanic

Lower

channel

Trough

kilometres

0 0.5

McMahon

Ken-McMahon

McMahon channel (no trough)

McMahon

thrust

FWB

KLT

k ilomet res

E

Ni leakage and dispersionNi leakage and dispersion

Lunnon shoot

Anomalous Ni in basalts (>600 Anomalous Ni in basalts (>600 ppmppm) beneath the ) beneath the ore shootore shoot

Stone et al 2006