12 tunjic minsys gold exploration

Mineral Systems
&
Gold Exploration
Outline of talk

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Exploration Success- 3 examples

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Phoenix Gold probability analysis test case

Relevance to exploration targeting at different
scales
Current state of play for exploration industry?

Janet Tunjic


Exploration Success using Mineral Systems Concepts
Deposit scale target identified in a mature well explored camp by incorporating mineral system
concepts
Critical Concepts

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Structural architecture (particularly influence of early growth faults) (J Miller &
R Blewett)

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Role of an intrusion to the south of the deposit as a possible
source/heat/fluids? (S Halley)

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Chemistry of different basalts and preference for hosting gold deposits
Fluid migration and redox depositional environments (J Walshe & S Halley)

HAMLET
DEPOSIT

from Neumayr et al., 2008

>1Moz deposit discovered


Success in Applying Mineral Systems Concepts -Prediction through to Discovery

Camp scale target identified in a poorly explored region of the West African craton with extremely sparse data (identified for possible
acquisition)

Critical Concepts

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What are the “fundamental building blocks” of the craton (J Hronsky & G

Begg)?

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Where are the mantle tapping structures?
How does this all fit together (Jon Claoue-Long)?
Needed to construct a layer of greenstone belts?
Investigated alteration patterns through ASTER?
Integrated into a prospectivity analysis

Identified Mineralised Position Before Discovery


Success in Applying Mineral Systems Concepts From -Prediction Through to Discovery

Fekola Deposit

Fekola Deposit Regional Geology, Gold Deposits
Rand Gold Boron soil anomalies

Source latest Papillion Resources website

Source Rand Gold annual report

>3Moz deposit discovered (and growing)

Success in Applying Mineral Systems Concepts -Prediction Through to Discovery

Camp scale target identified in the Yilgarn
(potential acquisitions)
Critical Concepts

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Architecture and where were the mantle tapping structures?
Folds and granite cored domes
Defined anomalism in magnetic and gravity data?
Fluids/alteration through ASTER?
Influence of intrusions?
Integrated into a prospectivity analysis

Mineralised System
Predicted and Subsequently Discovered


Mineral System Models

Source Jon Hronsky
assets/documents/34704-560500.gsa-talksep2010-compatibilitymode.pdf

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Fluid centric gold mineralisation models of
Jon Hronsky & Steven Cox


Geodynamics: Application to Exploration

From an explorers perspective

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Thinking about an area as a collection
of individual components and how they
interact

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Youngest domains host most of the gold
Understanding of
stratigraphy/structure, granites also
important


Literature Compilation of Age Dating for Ghana - 2009
D2

D3

NW-SE Comp.

NNW-SSE Comp.

Eburnean Orog.

Sinistral Slip

(2090 – 2075 Ma)

Au (~2060Ma)

14

Au (~2100Ma)

12

10

Gold Mineralisation Orogenic
Tarkwa reef mineralisation

Hydrothermal Gold

Hydrothermal Gold

(2122- 2099Ma)

(2070- 2034Ma)

8

Paleoplacer Gold

Ashanti Belt Tarkwain Seds
Birimian Sed/volcanics

6

Kumasi granitoids
Sefwi Belt Rhyolite

4

Granite suite
Bui Belt Granitoid

2

Cape Coast Granites
(2120- 2050Ma)

2300

2250

2200

2150

2100

2050

2000

1950

0
1900

Cape Coast Granite


2090 – 2075 Ma NW-SE Compression

Kib
i

Be
lt

Be
lt
an
ti
As
h

Ku

m
as
iB
as
in

Se
fw
i

Be
lt

Eburnean Orogeny
Kumasi Intrusive Activity

Dating of samples 2090-2075Ma

New Discoveries in the Kumasi Basin


2070 – 2034 Ma NNW-SSE Compression
Sinistral Strike Slip
D3 Au Mineralization

Dating of samples 2070-2034Ma

Ashanti belt
- explored
- 116Moz discovered

Kibi-Winneba belt

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Underexplored
0.5Moz discovered recently


Metamorphic Facies with Au Showings- Abitibi

Source Flood Consulting
Gold preferentially found at greenschist-sub-greenschist boundary and greenschist-low amphibolite
boundary

Detail from “Metamorphic Map of the Canadian Shield”

GSC Map 1475A


Phoenix Gold - Test Case

Mineral systems and prospectivity mapping for
Broads Dam Tenements

Process:

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Define data sets that are best proxies for

mineral system components

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Broads Dam
Tenements

Location Map

Evaluate correlations statistically
Integrate layers with best correlations


Metamorphism, source of reduced fluids, structural weakness…

Broads Dam
Tenements

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Outline of interpreted extent of M3a thermal anomaly (pre main gold event)
Strong correlation to gold deposits
Edge of Kurrawang basin- source of reduced fluids
Increased permeability and fluid flow

Weakened crustal region
Abundance of N/S trending structures which are incredibly important for localising
gold are located preferentially within this domain

Source Ben Goscombe


Depositional Environment: Redox Gradients

Oxidised fluids

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Mo & Bi geochemistry
Mag anomalies

Reduced Fluids

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As and Sb
Edge of Kurrawang basin


Fluids/Alteration/Intrusions

Broads Dam
Tenements

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Gradients are important
Strong correlation to gold deposits
Mapping potassic alteration
Lithology
Fluid movement
Intrusions


Final Probability Map for Broads Dam Area

Final map, 15 layers incorporated
…not just structure!

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Data layers were proxies for mineral system
components

Probability Map

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Predicted the spatial position of known deposits

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Identify 3 targets , currently being drilled


Mineral Exploration Expenditure Australia 2013

Better indication is the amount of exploration geologists recently retrenched

Explorers have been remarkably unsuccessful at discovering new deposits in Australia
Why would investors want to give their money to explorers?

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Are we Doing Anything Different to
Paddy’s Exploration Methods?
Tried and tested methods of testing gold soil
anomalies, stream sediment sampling and
stumbling across outcrop deposits are great
exploration tools but not the only tools
available.

There is a overwhelming need to change and be smarter, more cost efficient, more reliable…mineral
systems!


Drowning in Data?
Modern day explorers are required to effectively analyse

multiple datasets and identify map patterns critical for
predicting mineralisation:

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e.g. gravity, magnetics, IP, AEM, worms, geology,
structure, folding, domes, spectra, metamorphic maps,
redox gradients, DEM, alteration haloes, regolith maps,
porphyry composition, mineralogy, ASTER, HYMAP,
geomorphology, basaltic compositions, tomographic
data, seismic, MT, alteration geochemistry, whole rock
geochemistry, till geochemistry.

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And derivatives of these datasets


Applying Conceptual Mineral System Thinking to Exploration Finds
Deposits
Knowledge and Systems Thinking

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Provides the explorer with a means of understanding the
enormous data as proxies for processes that formed
deposits

Creativity

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Explorer have a framework to work within but still be
creative

Open Mind

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Opens the search space to new possibilities beyond existing
dogma


Take Home Messages

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Applying mineral systems concepts to exploration finds deposits
Challenging existing biases by engaging with academics and consultants is a good thing
Use data/concepts creatively
We don’t have a very good discovery success rate, support research and be more innovative!
Important for researchers to disseminate new findings to the wider community


Thank you

Janet Tunjic
Principal Geologist Optiro