Big system–big footprint: integrating Laverton’s geology ... · Wallaby Granny Smith Simplified solid geology CH FE B Explore the Laverton camp Key tasks: • Identify the upper

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


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


200 m200 m

EW

200 m

N

Link deposit scale structures to fluid types, identify domains with chemical gradient = prospective targets


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


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


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


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


NE – Cross Trends at the

District Scale

Barnicoat Fault

Far East Fault

Sunrise Dam



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


Pathways of deep – reduced

juice


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


Wallaby deposit

2km


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



Notes

• Oxidized pathways highlight


• Predict using geophysical images


Wallaby

Layer 2 conductance

5 km


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


Wallaby deposit

2km


CH

FE B


Sunrise Dam


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


VELVET

SIMS (hangingwall)

TROY

Carl Young

Hangingwall faults

Diorite dykes

Footwall faults (sandstone unit contacts)

Fitzroy Fault

S2

Oxidized pathways

Reduced pathways



N S

WallabyDeposit


Miller (2005)


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


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

Documents

Big system–big footprint: integrating Laverton’s geology ... · Wallaby Granny Smith Simplified solid geology CH FE B Explore the Laverton camp Key tasks: • Identify the upper