Download - Exhumation of Hypogene Mineral Deposits
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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
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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
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Met
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gin
g fl
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id F
oc
usi
ng
Rea
cti
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ho
st s
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Exh
um
ati
on
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Kalgoorlie mining opera-onsCourtesy Newmont Australia Ltd
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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
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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
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The Goldilocks Zone
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The Goldilocks Zone
Not too liCle, not too much
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Diorite King
Auckland
Victor Well
Riviera
Harbour LightsTower Hill
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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
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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
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Previous a*empt unsuccessfulWeber, 2002
Ph.D. thesis, Melbourne University
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Previous a*empt unsuccessfulWeber, 2002
Ph.D. thesis, Melbourne University
Technical developments
2002Mul9-‐grain aliquots
2010Single crystal analysis
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Discard
Previous a*empt unsuccessfulWeber, 2002
Ph.D. thesis, Melbourne University
Technical developments
2002Mul9-‐grain aliquots
2010Single crystal analysis
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Zircon
(U-‐Th)/He age (M
a)
3000
1500
750
0
2250
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Zircon
(U-‐Th)/He age (M
a)
3000
1500
750
0
2250
Alpha par;cle fluence (1015 α/g/M.yr.)0.1 1000100101
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Zircon
(U-‐Th)/He age (M
a)
3000
1500
750
0
2250
Alpha par;cle fluence (1015 α/g/M.yr.)0.1 1000100101
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Conclusions
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Quan-fying exhuma-on has significant poten-al relevance in the establishment of explora-on models for hypogene mineral
systems
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Thermochronometric constraint is accompanied by significant technical challenges in the Australian Archaean
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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
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Ba# CET Science Day, December 2010
For further comment on this and other resource-‐related ques-ons, contact the author at [email protected]