Mineral Systems &

Gold Exploration

Outline of talk Exploration Success- 3 examples Relevance to exploration targeting at

different scales Phoenix Gold probability analysis test case Current state of play for exploration industry?

Janet Tunjic

Exploration Success using Mineral Systems Concepts

Critical Concepts• Structural architecture (particularly influence

of early growth faults) (J Miller & R Blewett)• Role of an intrusion to the south of the

deposit as a possible source/heat/fluids? (S Halley)

• Chemistry of different basalts and preference for hosting gold deposits

• Fluid migration and redox depositional environments (J Walshe & S Halley)

>1Moz deposit discovered

Deposit scale target identified in a mature well explored camp by incorporating mineral system concepts

HAMLETDEPOSIT

from Neumayr et al., 2008

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

Success in Applying Mineral Systems Concepts -Prediction through to Discovery

Critical Concepts• What are the “fundamental building blocks”

of the craton (J Hronsky & G Begg)?• 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

Rand Gold Boron soil anomaliesSource Rand Gold annual report

Fekola Deposit

Fekola Deposit Regional Geology, Gold DepositsSource latest Papillion Resources website

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

>3Moz deposit discovered (and growing)

Success in Applying Mineral Systems Concepts -Prediction Through to Discovery

Critical Concepts• 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 SystemPredicted and Subsequently

Discovered

Camp scale target identified in the Yilgarn (potential acquisitions)

Mineral System Models

Fluid centric gold mineralisation models ofJon Hronsky & Steven Cox

Source Jon Hronskyhttp://www.wesminllc.com/cms assets/documents/34704-560500.gsa-talksep2010-compatibility-mode.pdf

http://www.ga.gov.au/webtemp/image_cache/GA16579.pdf

Geodynamics: Application to Exploration

From an explorers perspective

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

• Youngest domains host most of the gold

• Understanding of stratigraphy/structure, granites also important

1900195020002050210021502200225023000

2

4

6

8

10

12

14

Gold Mineralisation Orogenic

Tarkwa reef mineralisation

Ashanti Belt Tarkwain Seds

Birimian Sed/volcanics

Kumasi granitoids

Sefwi Belt Rhyolite

Granite suite

Bui Belt Granitoid

Cape Coast Granite

Hydrothermal Gold(2070- 2034Ma)

Hydrothermal Gold(2122- 2099Ma)

NNW-SSE Comp.Sinistral Slip

Au (~2060Ma)

D3NW-SE Comp.

Eburnean Orog.

(2090 – 2075 Ma)Au (~2100Ma)

D2

Paleoplacer Gold

Literature Compilation of Age Dating for Ghana - 2009

Cape Coast Granites(2120- 2050Ma)

2090 – 2075 Ma NW-SE CompressionEburnean Orogeny

Kumasi Intrusive Activity

Sefw

i Belt

Ashan

ti Belt

Kumasi B

asin

Kibi B

elt

New Discoveries in the Kumasi Basin

Dating of samples 2090-2075Ma

2070 – 2034 Ma NNW-SSE CompressionSinistral Strike SlipD3 Au Mineralization

Ashanti belt- explored- 116Moz discovered

Kibi-Winneba belt- Underexplored- 0.5Moz discovered recently

Dating of samples 2070-2034Ma

Metamorphic Facies with Au Showings- Abitibi

GSC Map 1475A

Detail from “Metamorphic Map of the Canadian Shield”

Gold preferentially found at greenschist-sub-greenschist boundary and greenschist-low amphibolite boundary

Source Flood Consulting

Phoenix Gold - Test Case

Mineral systems and prospectivity mapping for Broads Dam Tenements

Process:• Define data sets that are

best proxies for mineral system components

• Evaluate correlations statistically

• Integrate layers with best correlations

Location Map

Broads Dam Tenements

Metamorphism, source of reduced fluids, structural weakness…

• 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

Broads Dam Tenements

Depositional Environment: Redox Gradients

Oxidised fluids• Mo & Bi geochemistry• Mag anomalies

Reduced Fluids• As and Sb• Edge of Kurrawang

basin

Fluids/Alteration/Intrusions

• Gradients are important• Strong correlation to gold

deposits• Mapping potassic alteration• Lithology• Fluid movement• Intrusions

Broads Dam Tenements

Final Probability Map for Broads Dam Area

Probability Map

Final map, 15 layers incorporated…not just structure!

• Data layers were proxies for mineral system components

• Predicted the spatial position of known deposits

• Identify 3 targets , currently being drilled

Mineral Exploration Expenditure Australia 2013

http://www.abs.gov.au/ausstats/abs@.nsf/mf/8412.0

Better indication is the amount of exploration geologists recently retrenched

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

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!

Are we Doing Anything Different to Paddy’s

Exploration Methods?

Drowning in Data?Modern day explorers are required to effectively analyse multiple datasets and identify map patterns critical for predicting mineralisation:• 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.

• And derivatives of these datasets

Applying Conceptual Mineral System Thinking to Exploration Finds Deposits

Knowledge and Systems Thinking• Provides the explorer with a means

of understanding the enormous data as proxies for processes that formed deposits

Creativity• Explorer have a framework to work

within but still be creativeOpen Mind• Opens the search space to new

possibilities beyond existing dogma

Take Home Messages

• 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 TunjicPrincipal Geologist OptiroJTunjic@Optiro.com