Geoffrey Ba* Research Associate Professor ExxonMobil Fellow Goldilocks and the Fi5h Pillar Exhuma9on studies and their relevance to orogenic gold explora9on in the Yilgarn
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Geoffrey Ba*Research Associate ProfessorExxonMobil Fellow
Goldilocks and the Fi5h PillarExhuma9on studies and their relevance to orogenic gold explora9on in the Yilgarn
Exhuma;on represents a significant contribu;on to the development of discoverable and economically recoverable ore systems
Pilot studies using modern single-‐crystal (U-‐Th)/He techniques show promise
Control of this element of ore systems is challenging in the orogenic gold deposits of the Yilgarn
TAKE-‐HOME MESSAGES
Met
al
sou
rc
e
Sca
ven
gin
g fl
uid
flu
id F
oc
usi
ng
Rea
cti
ve
ho
st s
ite
Exh
um
ati
on
Kalgoorlie mining opera-onsCourtesy Newmont Australia Ltd
Orogenic gold deposit styles and examples from the Yilgarn Craton, a5er Goldfarb et al., (2005)
0
5km
10km
15km
20km
100°C
10°C
200°C
300°C
400°C
500°C
Bre
ccia
Lod
es
Dis
sem
inat
ed L
odes
Shea
r Z
ones
Lam
inat
ed V
eins
Vei
n Se
ts
Wiluna
Racetrack
Granny Smith
Mt Charlotte
Golden Mile
Lancefield
Sons of Gwalia
Great Eastern
Norseman
Frasers/Hopes Hill
Marvel Loch
Nevoria
Westonia
Griffins Find
Economic ExploitabilityDiscoverability
Orogenic gold deposit styles and examples from the Yilgarn Craton, a5er Goldfarb et al., (2005)
0
5km
10km
15km
20km
100°C
10°C
200°C
300°C
400°C
500°C
Bre
ccia
Lod
es
Dis
sem
inat
ed L
odes
Shea
r Z
ones
Lam
inat
ed V
eins
Vei
n Se
ts
Wiluna
Racetrack
Granny Smith
Mt Charlotte
Golden Mile
Lancefield
Sons of Gwalia
Great Eastern
Norseman
Frasers/Hopes Hill
Marvel Loch
Nevoria
Westonia
Griffins Find
The Goldilocks Zone
The Goldilocks Zone
Not too liCle, not too much
Diorite King
Auckland
Victor Well
Riviera
Harbour LightsTower Hill
What do the differences in endowment represent?
Primary contrast in metallogenic processes
Contras-ng magnitudes of post-‐mineralisa-on
exhuma-on
Lack of preserva-on Inadequate exhuma-on
Orogenic gold deposit styles and examples from the Yilgarn Craton, a5er Goldfarb et al., (2005)
Economic ExploitabilityDiscoverability
Zircon (U-Th)/He
Apatite (U-Th)/He
Apatite Fission Tracks
Muscovite Ar
Biotite Ar
Zircon Fission Tracks
0
5km
10km
15km
20km
100°C
10°C
200°C
300°C
400°C
500°C
Bre
ccia
Lod
es
Dis
sem
inat
ed L
odes
Shea
r Z
ones
Lam
inat
ed V
eins
Vei
n Se
ts
Wiluna
Racetrack
Granny Smith
Mt Charlotte
Golden Mile
Lancefield
Sons of Gwalia
Great Eastern
Norseman
Frasers/Hopes Hill
Marvel Loch
Nevoria
Westonia
Griffins Find
Previous a*empt unsuccessfulWeber, 2002
Ph.D. thesis, Melbourne University
Previous a*empt unsuccessfulWeber, 2002
Ph.D. thesis, Melbourne University
Technical developments
2002Mul9-‐grain aliquots
2010Single crystal analysis
Discard
Previous a*empt unsuccessfulWeber, 2002
Ph.D. thesis, Melbourne University
Technical developments
2002Mul9-‐grain aliquots
2010Single crystal analysis
Zircon
(U-‐Th)/He age (M
a)
3000
1500
750
0
2250
Zircon
(U-‐Th)/He age (M
a)
3000
1500
750
0
2250
Alpha par;cle fluence (1015 α/g/M.yr.)0.1 1000100101
Zircon
(U-‐Th)/He age (M
a)
3000
1500
750
0
2250
Alpha par;cle fluence (1015 α/g/M.yr.)0.1 1000100101
Conclusions
Quan-fying exhuma-on has significant poten-al relevance in the establishment of explora-on models for hypogene mineral
systems
Thermochronometric constraint is accompanied by significant technical challenges in the Australian Archaean
Modern (U-‐Th)/He da-ng shows promise as a means of resolving exhuma-on history within the Yilgarn terrane, but
technical challenges remain to be addressed
Ba# CET Science Day, December 2010
For further comment on this and other resource-‐related ques-ons, contact the author at [email protected]
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