predictive mineral discovery Cooperative Research Centre
Big system–big footprint: integrating Laverton’sgeology, geochemistry and geophysics for predictive mineral discovery
P. Neumayr, J. Walshe, M. Pirlo, S. Halley, G. Hall, C. Young, K. Petersen, A. Roache and the Y4 team
predictive mineral discovery Cooperative Research Centre
3 Classes of Fluid in System
Mixing Box Mixing Box
Au??
Seal
Au?? 30 k
m
Fluid 1:
Ambient Fluid
H2O-CO2-NaCl
Fluid 2: Magmatic Fluids
CO2-SO2
Fluid 3: Mantle Fluid: H, Na, N, C, Cl
Interaction between these fluids and fluids and wallrock cause large-scale alteration cells
predictive mineral discovery Cooperative Research CentreDepth
Surface
Fault
Fluid Flow Path
5 km
Acidic conditions - no gold deposition
Neutral to alkaline
conditions -environment ofgold deposition
Granite
1 1
2
3
3
High grade gold
H2OH2O
CO2-SO2
CH4-N2
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200 m200 m
EW
200 m
N
Link deposit scale structures to fluid types, identify domains with chemical gradient = prospective targets
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PIMA mica AlOH wavelength
) 2,216 to 2,223) 2,212 to 2,216) 2,208 to 2,212) 2,204 to 2,208) 2,200 to 2,204) 2,195 to 2,200) 2,188 to 2,195) all others
5 km
PIMA mica AlOH wavelength
Kanowna Belle
Camp scale: where are the prospective domains?
Phengite – oxidized, alk.
Musc., Parag. – reduced, ACID
Acid domains indicate interaction of reduced fluid with ambient fluidGold potential reduced, but presence of fertile fluid indicated
predictive mineral discovery Cooperative Research Centre
Sunrise Dam
Wallaby Granny Smith
Prospective TerraneNon-prospective
Terrane
Barnicoat Fault
Far East Fault
Late Basins< 2670 Ma
Volcani-clasticsInter. Provenance2730 - 2710 Ma
Mafic - ultramafics> 2750 Ma
Proximity toLate BasinsKey tasks:• Identify the upper
crustal architecture• Link upper crustal
architecture with lower crustal and mantle architecture
• Identify alteration cells and domains of chemical gradients
• Combine structural and chemical architecture
• Drill targets which are highlighted in both the chemical and structural architecture
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Camp-scale fluid pathways: seismic view
CHFE
B
Chopping (2006)Henson et al. (2006)
Model 1: deep reduced fluid flow along LTZ: Laverton region is favourable west of the Far Eastern Fault (green surface) is best.
LTZ
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NW SE
Prospective Terrane Non-prospective Terrane
Present Surface
W
SD
Barnicoat
FaultCeliaFault
Childe Harold
Fault
Mount MargaretAnticline
u
u
u
Mafic - ultramafics> 2750 Ma
Late Basins< 2670 Ma
VolcaniclasticsInter. Provenance2730 - 2710 MaAfter Standing, Henson, Hall
predictive mineral discovery Cooperative Research CentreImage from Gocad looking north
Deep NE Trending
Crackbeneath Laverton District
??
Model 2: Deep reduced fluid flow along steep NE structures
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NE – Cross Trends at the
District Scale
Barnicoat Fault
Far East Fault
Sunrise Dam
Wallaby Granny Smith
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Model 2: Deep reduced fluid flow along steep NE structures
CH
FE B
W
SRD
GAcid, reduced fluid domains
Oxidized magmas and fluid path ways at intersections
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Pathways of deep – reduced
juice
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Pathways of Deep - Juice
2
2
3 3
Acidic Alteration
AlkaliAlteration
1
predictive mineral discovery Cooperative Research CentreFault Unconformity
2kmWallaby deposit
Phengite –oxidized, alk.
Musc., Parag. –reduced, ACID
Acid domains indicate interaction of reduced fluid with ambient fluidGold potential reduced, but presence of fertile fluid indicated
predictive mineral discovery Cooperative Research CentreFault Unconformity
Wallaby deposit
2km
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Conclusions
• Integration of structural and chemical architecture
• Integration of upper crustal and lower crustal/mantle architecture
• Create and use camp-scale data sets at large spacing
• Find the gradients• Find the seals
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Notes
• Oxidized pathways highlight
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• Predict using geophysical images
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Wallaby
Layer 2 conductance
5 km
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Laverton Model
BIF (granoblasticME QZ Grum?)
U. Amph mm
Kirgella DomeSyenite Complex
Kirgella DomeSyenite Complex
MikadoSub-
Domain
2665Ma2665Maage ?age ?
Magma Chamber ?Magma Chamber ?
IdaHill
Complex
SunriseStrat.
2730Ma2730Ma
2710Ma2710Ma
2673-2658Ma2673-2658Ma
2770Ma2770Ma
DUCK FAULT
BARNICOAT FAULT
CHILDE HAROLD SZ
ELECTRICAL FAULT
CHATTERBOX FAULT
CL
MT MARGARET
Anticlin
e
Syncli
ne
predictive mineral discovery Cooperative Research CentreFault Unconformity
Wallaby deposit
2km
predictive mineral discovery Cooperative Research Centre
CH
FE B
predictive mineral discovery Cooperative Research Centre
Sunrise Dam
Wallaby Granny Smith
Simplified solid geology
CH
FE
B
Explore the Laverton campKey tasks:• Identify the upper
crustal architecture• Link upper crustal
architecture with lower crustal and mantle architecture
• Identify alteration cells and domains of chemical gradients
• Combine structural and chemical architecture
• Drill targets which are highlighted in both the chemical and structural architecture
predictive mineral discovery Cooperative Research Centre
VELVET
SIMS (hangingwall)
TROY
Carl Young
Hangingwall faults
Diorite dykes
Footwall faults (sandstone unit contacts)
Fitzroy Fault
S2
Oxidized pathways
Reduced pathways
Link deposit scale structures to fluid types, identify domains with chemical gradient = prospective targets
predictive mineral discovery Cooperative Research Centre
N S
WallabyDeposit
Link deposit scale structures to fluid types, identify domains with chemical gradient = prospective targets
Miller (2005)
predictive mineral discovery Cooperative Research Centre
Chlorite abundance
Chlorite abundance) 0.3 to 1) 0.25 to 0.3) 0.2 to 0.25) 0.15 to 0.2) 0 to 0.15) all others
Fault Unconformity
2kmWallaby deposit
predictive mineral discovery Cooperative Research Centre
Keys to size and grade??
• Chemical gradients drive Au precipitation (redox, H2S)
• Fluid mixing most effective process to sustain gradients
• Architecture promotes fluid mixing
Fluid 1reduced
Fluid 2oxidized
Mixing Box
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