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Geochemical &

Spectral Alteration Zonation

at the Mt Rawdon Gold Deposit Mines & Wines Conference, 4th September 2015

Ned Howard, Senior Exploration Geologist

Outline

Regional Geology

Local Geology

Lithogeochemistry

Alteration & Mineralisation

Spectral geology

Pathfinder geochemistry

Alteration geochemistry

Note on genesis

Location 75km SW of Bundaberg

20km South of Mt Perry

Early mining 1950

Mt Rawdon Production

Discovered 1946

Alluvials & artisanal worked 1950s

Exploration: 1969-1998

Mining: 2001-present

Production: 45.6 Mt @ 1.0 g/t Au for

1.35 Moz

Resource: 50.7 Mt at 0.7 g/t Au for

1.16 Moz

Endowment: 2.51 Moz

Mt Rawdon 2001

Lookout

Sept 2013

Regional Geology

Triassic Aranbanga Volcanics

Esk Basin assigned

Wandilla Province

Coastal Subprovince

Mt Morgan (VHMS/IR)

Mt Rawdon (IRGD)

Gympie (Or)

Cracow (LSE)

Regional Geology Aranbanga Volcanics

Late Triassic

Hogsback Granite

Perry & Swindon Faults

Local Geology Dipping rhyodacitic volcanoclastic pile

Dacitic stocks & dykes

Late- to post-mineral

basalt-andesite

& rhyolite dykes

500m

Mount Rawdon Section looking NE

Local Geology Complicated cross-cutting relationships

500m

Diagram showing

schematic

relationships?

DAC2

DAC1

RHYO2

RHYO1

DAC1

VC

DAC1

VC

VC

Standing, 2014

Lithogeochemistry

Medium(-high) K calc-alkaline

Arc signatures on all

discrimination diagrams

Alteration and Mineralisation

Harris, A 2010, Albite-

actinolite-chlorite-pyrite

Early propyllitic

(chl-carb ep ser py)

Early phyllic

(ser-qtz py)

Mineralisation related:

Sericitic (ser-qtz-py)

Silica-pyrite ( feldspar?)

Chloritic (chl-carb-ep-act-sd)

Actinolite-albite (act-fs-ep-sd)

Late illite-smectite kaolinite

Harris, 2010

Harris, 2010

Harris, 2010

Alteration and Mineralisation

MRNX1114, 50.4m

(2m @ 9.12g/t)

Associated with chloritic, albite-actinolite & sericitic

alteration

Pyrite-base metal sulphides

sulphosalts-bismuth-hessite-

matildite-gold

Harris, 2010

Geochemistry & Spectral Survey ~15,000 ASD analyses

~2,000 multi-element analyses

4 acid digest

ICP-MS/AES

48 element suite

~800 existing ME samples

Mineral Identification

SWIR

Clays, micas

Chlorite, biotite, epidote, etc

Carbonates

NOT Quartz, feldspar, sulphides, etc

Spectroscopy Background

100%

Refl

ec

tio

n

Absorption

features

Wavelength (nm)

Spectrum line

0%

100%

Refl

ec

tio

n

Absorption

features

Wavelength (nm)

Spectrum line

0%

Spectroscopy Background

Spectral indices

Sericite crystallinity temperature of formation

Spectral Zonation Sericite Crystallinity

300m

Ser XT

Spectral Zonation Sericite Crystallinity

Spectroscopy Background

Sericite: wAlOH = Al substitution Chlorite: wFeOH = Fe-Mg substitution

Spectral indices

Sericite composition & Chlorite composition

Spectral Zonation Sericite Composition

300m

Spectroscopy Background

Sericite: wAlOH = Al substitution Chlorite: wFeOH = Fe-Mg substitution

Spectral indices

Sericite composition & Chlorite composition

Spectral Zonation

Chlorite composition

Intermediate in deeper,

proximal zones

Outer Fe-chlorites

Some lithological

influence doesnt hide

patterns

Chlorite wFeOH

Pathfinder Zonation

Deep Shallow Marginal

Mn

As

Pb

Zn

Cu

Ag

Au

Bi

Te

S

Pathfinder element zonation

Metal Associations Defined visually, correlation coefficients & PCA on Z-scores

Log Z-scores

Averaged for

each association

Assocn with max

value shown

Pathfinder Zonation Sectional zonation patterns

Shallow Section Deep Section

Pathfinder Zonation Summary metal zonation

Position relative to and within gold zone

~200m

~2

00

m

Alteration Geochemistry Major element mass changes

Reflects alteration mineral addition/removal

Relative to unaltered rock type

Low sulphidation epithermal example

Alteration Geochemistry

Albite

K-Feldspar/Biotite

Phengite

Muscovite

Chlorite/

Kaolinite

Mt Rawdon major element mass changes

Alteration Geochemistry

Mt Rawdon overall model of

alteration geochemistry

30

Summary of alteration mass changes

Subtle/variable in most areas

Mineralised zone-parallel, gold-bearing structures control

alteration

~200m

~200m

Genesis

Genetic implications of geochemical

characteristics & classification

Near-neutral, low salinity

~300+oC fluid

Near-neutral, weakly acidic,

cooler fluid ( 1.5g/t

Au >0.67g/t

1o fluid flow controlling

structure

2o fluid flow controlling

structure

Structure associated with

Western Dacite contact

High grade trend on Eastern

Dacite contact

Eastern Dacite

Western

Dacite

Current land surface SW NE

~200m

~200m

Likely epizonal intrusion-related gold deposit (IRGD)

Fluid inclusions Low-mod salinity, 250-350oC, indications of boiling

Temperature, mixing & boiling all plausible deposition mechanisms

Related to intrusion at depth below the Western Dacite?

Summary Epizonal IRGD

Metals, alteration geochemistry and spectral

zonation mimic gold distribution

Exploration Tools:

Clear metal zonation patterns

TeBiCu-AgAs-ZnMn-Pb-Zn

Spectral indices

Sericite crystallinity, sericite wAlOH

Summary

*ASD and Mass Spectrometer sold separately

Pathfinder Zonation

Deep Shallow Marginal

Mn

As

Pb

Zn

Cu

Ag

Au

Bi

Te

S

Tellurium >0.5ppm Bismuth >10ppm

Pathfinder Zonation

Deep Shallow Marginal

Mn

As

Pb

Zn

Cu

Ag

Au

Bi

Te

S

Silver (dashed >2ppm, solid >4ppm)

35

Manganese >1900nm

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