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

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1 Komatiite-hosted Ni-Cu-(PGE) deposits: understanding deposit and camp footprints Steve Beresford newgenco

2 Acknowledgements Co-authors Marco Fiorentini Jon Hronsky Nic Rosengren Dave Bertuch Paul Duuring Ahmad Saleem Bill Stone Mark Barley Ray Cas Ben Grguric Former colleagues at WMC and BHPBilliton Various company support over last 10 years, WMC, Falconbridge, INCO, Lionore, MPI Collaborators and Sponsors of AMIRA P710 Host of past students and postdocs

3 TALK Outline Introduction Focus on new ideas on geological, geochemical and geophysical footprints 1. Continuum of deposit styles and controls 2. Deposit diversity Footprint of these diverse styles How our exploration methodologies change 3. Camps Need to improve predictive methodologies

4 Take home messages Komatiite hosted Ni-Cu Cu-(PGE) deposits exhibit considerable diversity (in terms of massive sulfide types) Kambalda is only an end member Significant variation in exploration strategy between the deposit end members Despite 40 years of exploration they are still truth machine intensive we must maximise in hole data? Do isolated komatiite-hosted Ni-Cu Cu-(PGE) deposits represent underexplored camps? We outline current knowledge in delineation of camps but further work is required at a scale rarely attempted.

5 Our common view of komatiite-hosted Nickel sulfides is Kambalda centric Frost years of outstanding discovery and production of the same style

6 Cowden 1986

7 Primary sulfide textures Katinniq Blebby ore Foster Yakabindie

8 Secondary sulfides textures

9 The search for footprints to Ni-Cu-(PGE) deposits PROXIMAL DISTAL Kelley 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

10 1. Continuum of deposits Controls on diversity Parent magma Emplacement (intrusive vs extrusive) Host rock Parent magma variation (part of continuum for all NiS) - Genetic and exploration significance - Recognition and implications of komatiitic basalt Raglan style deposits in the Yilgarn eg Collurabbie, Windarra

11 1. Parent magma Continuum 15 Raglan* Shebandawan Collurabbie 20 Windarra Fortaleza Thompson* 1300OC - 2 PaS MgO OC PaS Perseverance Kambalda Mt Keith 35 Komatiite Transitional Komatiitic basalt * Proterozoic

12 Archaean 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 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)

13 2. Deposit diversity and footprint Numerous classification schemes Main textural association of sulfides Type 1 Type 2 Type 3 Remobilisation Wiluna Mt Clifford 3 Boston Creek Genetic Intrusive vs extrusive Compositional Dunite vs Peridotite 1 2 Kambalda Perseverance Goliath Mt Goode- Cosmos Six Mile Mt Keith Biggest control is host rock- facies association Komatiite basalt Komatiite felsic Komatiite-sediment

14 A. Kambalda style deposits Seminal work of Woodall, Ross, Gresham et al has stood the test of time Well understood derivative exploration model Recent ideas: Channel and trough are not the same Increasing use of structure and 3D tenor variation as exploration tool Ni dispersion into footwall Diversity of sediment association and thickness variations Stratigraphic correlation of sedimentary units with felsic volcanics (below) Camp Spacing is predictable within camps Distal felsic fall deposit intercalated with Silver Lake Peridotite, Kambalda

15 Exploration Basal flow thickness (>30m) Sediment-ore antithetism High MgO thick cumulates, High Ni, Ni:Cr Amygdaloidal domains are common Sediment free ore prism Ore environment is structurally complex with prominent metasomatic zones and chlorite tectonites (originally termed chlorite sediments) Seat 2002

16 Trough-Channel Cross-Cutting Cutting Relationships at Kambalda Stone et al 2006 Lunnon channel trough Fisher N N channel trough kilometres Ken-McMahon McMahon McMahon McMahon channel (no trough) thrust E Ken Lower Trough FWB KLT kilometres Ken volcanic channel kilometres

17 Ni leakage and dispersion Lunnon shoot Stone et al 2006 Anomalous Ni in basalts (>600 ppm) beneath the ore shoot