NEWGEN21-Proceedings-Full

~5 m oz total Au production OFFICIAL












Navarre Minerals Maiden Resource
Arete Capital Partners announcement 12 March

2021: (Miningnews.net) DDH: 1,203m @ 6 g/t Au (Resolution, Adventure prospects
304,300 oz @ 2.43g/t Au.
(no ETW) during underground resource testing
(30 March 2021)…this is how

modern Magdala (~3Moz-) started!





































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Talk outline






• Geological setting for Victorian orogenic gold




• Competing tectonic models for the Early Palaeozoic – confusing for gold explorers




• Structural / stratigraphic mapping + potential field geophysics: powerful

tools…

• …but Deep Seismic Reflection data drives systems-scale understanding



• Application to mineral systems models at crustal scale…



• Constrained retrodeformation scenarios – critical to take geological systems

analysis from crustal scale to lithospheric scale



• Towards a Unifying Theory for Eastern Australian Early Palaeozoic geology and
mineral systems




• Wrapping up









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Gray & Foster, 1999, 2000:



A breakthrough tectonic

model that honoured
structural vergence,

deformation timing,

and the accretionary
character of some

Ordovician stratigraphy



Benambran deformation –
Late Ordovician
VandenBerg et al. 2000 36 NewGenGold Conference 2021 36
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Convergent margin key elements and systematics
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Distal back-arc: Magmatic arc: Accretionary wedge: cold, inherent
transition to hot, igneous-dominated strong syn-
intraplate sedimentary shortening
Back-arc basin: deformation, amagmatic

hot, syn-sediment (thickening crust)
magmatism, extension Intraplate: cold,

weak/strong deformation undeformed,
amagmatic































(Stern, 2002)






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Gray & Foster, 2000
Subduction / accretion

models for Late Ordovician Victoria –



….they don’t work perfectly.






Wagga Omeo zone
looks like a Ordovician back arc,
not an arc
Stawell does look like an accretionary wedge,
but its Cambrian, not part of the Lachlan story

Miller et al., 2003



Accretion does not fit well
Accretion fits well













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The model doesn’t account for the influence of
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huge subsequent strike-slip faults










Gray & Foster, 2000




Blue (accretionary wedge) against

Green (back arc):
a relationship not observed in simple

convergent margins





























Mylonite in granite,

Kiewa Shear Zone
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Field geology –


Sedimentology,

Palaeogeography


can also provide


critical constraints…


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Fergusson et al., 1989








































Field geology –


Sedimentology,

Palaeogeography


can also provide


critical constraints…


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Models that honour

paleogeographic
constraints, and account

for strike-slip faults…..



eg. the Baragwanath

Transform concept…



(VandenBerg et al. 2000,

Willman et al., 2002)





Tectonic models of the
very little Au
1990’s-early 2000’s all

have major shortcomings…

and don’t specifically

help predict Orogenic gold


75 Moz+ Au ~5 Moz+ Au location or endowment!







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Talk outline
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• Geological setting for Victorian orogenic gold




• Competing tectonic models for the Early Palaeozoic – confusing for gold explorers




• Structural / stratigraphic mapping + potential field geophysics: powerful

tools…

• …but Deep Seismic Reflection data drives systems-scale understanding



• Application to mineral systems models at crustal scale…



• Constrained retrodeformation scenarios – critical to take geological systems

analysis from crustal scale to lithospheric scale



• Towards a Unifying Theory for Eastern Australian Early Palaeozoic geology and
mineral systems




• Wrapping up









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Images: Geoscience Australia



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OFFICIAL Google Earth TM

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Images: Geoscience Australia



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Western Tasmania and its northern

extension…


the Selwyn Block.

(Cayley et al., 2002)




The Vandieland microcontinent –

Proterozoic crust beneath central Victoria


(Cayley, 2011)





Cambrian Jamieson Volcanics (Vic)





coeval with (and along strike from)


Mount Read Volcanics


Dundas ‘Trough’ (Tas)









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Early Lancefieldian –


~490Ma+
































Bear Gully Gritstone


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Delamerian Lachlan Fold Belt
Fold Belt
















































A Cambrian unconformity underlies Central Victoria!
Time-space plot : Victoria


Cayley & Musgrave, in prep



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Gray & Foster, 2000





















The Selwyn Block model –
SELWYN
alternative explanation for

some observed changes in
BLOCK Lachlan Fold Belt sedimentation

and deformation timing

MICROCONTINENT (particularly overlying
Melbourne Zone)









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Talk outline
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• Geological setting for Victorian orogenic gold




• Competing tectonic models for the Early Palaeozoic – confusing for gold explorers




• Structural / stratigraphic mapping + potential field geophysics: powerful

tools…

• …but Deep Seismic Reflection data drives systems-scale understanding



• Application to mineral systems models at crustal scale…



• Constrained retrodeformation scenarios – critical to take geological systems

analysis from crustal scale to lithospheric scale



• Towards a Unifying Theory for Eastern Australian Early Palaeozoic geology and
mineral systems




• Wrapping up









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Deep Seismic Reflection





























































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Sample slide title, 30pt Black






Sample Body Text, 24pt Arial, Black 25% lighter

















































OFFICIAL GA, pmd*crc
2006 regional deep seismic transects: NewGenGold Conference 2021 52

Laterally diverse crust in the Lachlan Fold Belt OFFICIAL



0 km








45km










Selwyn Block?

















MOHO



Cayley et al., 2011











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Possible source of gold:



Cambrian metavolcanics like those exposed

in the Moornambool Metamorphic Complex,

in the Avoca Fault, in the Heathcote Fault Zone and,
farther east, in the Governor Fault Zone



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Detail of the Heathcote Fault Zone






















































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This research shows that OFFICIAL


tens of thousands of


cubic kilometres of

Cambrian metavolcanic


rocks underlie

the Bendigo goldfields






– a source for gold?


Goldfields geology


is thick-skinned!
























Cayley et al., 2011

Forward modelling NewGenGold Conference 2021 56
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MagnetoTelluric data

provides independent
evidence:

Heinson et al., 2021





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Heinson et al., 2021: MT data
shows the region

imaged as dominated by Early

Cambrian mafic igneous rocks in
Seismic Reflection data is also less

electrically resistive.

The overlying interlayered and
metasediment-dominated

successions are highly resistive.








































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Victoria – State-wide 3D geological model






















































Rawling et al., 2011





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Talk outline
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• Geological setting for Victorian orogenic gold




• Competing tectonic models for the Early Palaeozoic – confusing for gold explorers




• Structural / stratigraphic mapping + potential field geophysics: powerful

tools…

• …but Deep Seismic Reflection data drives systems-scale understanding



• Application to mineral systems models at crustal scale…



• Constrained retrodeformation scenarios – critical to take geological systems

analysis from crustal scale to lithospheric scale



• Towards a Unifying Theory for Eastern Australian Early Palaeozoic geology and
mineral systems




• Wrapping up








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Eg: Gaboury, 2019 Applied Earth Science /

Cox, 2016 Econ Geol

Eg: Willman 2007 Min Dep
Minerals Systems Models:



























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This process need not be efficient – the data indicates

tens of thousands of cubic km of potential mafic igneous source rocks






















Willman et al., 2010













Line 06GA-V2 - interpretation














Cayley et al., 2011 NewGenGold Conference 2021



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Delamerian Selwyn Block








































Cayley et al., 2011 NewGenGold Conference 2021 63
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One hypothesis:




‘Corridors’ of gold
Possible source of gold:
prospectivity, aligned
above the buried margins
Cambrian metavolcanics like those exposed
of the Selwyn Block
in the Moornambool Metamorphic Complex, and, further west,
in the Avoca Fault, in the Heathcote Fault Zone and, pre-Ordovician Gondwana

farther east, in the Governor Fault Zone










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Stawell, Ararat OFFICIAL Bendigo, Fosterville





















Delamerian
Selwyn Block








Willman et al., 2010












1: Late Ordovician orogenic gold event












Rawling et al., 2011

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Stawell, Ararat OFFICIAL Bendigo, Fosterville Costerfield, etc





















Delamerian
Selwyn Block








Willman et al., 2010











2: Early Devonian orogenic gold event…etc

…potentially reactivating earlier plumbing

Systems to introduce extra generations of
mineralisation, with additional new ones…..





Rawling et al., 2011

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Rawling et al., 2007 GSV 3D Vic






















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Full crustal section, Stawell and Bendigo zones –

a tool for testing at-depth controls on orogenic gold locations































Delamerian
Selwyn Block








West East







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East
West





Inflection-point mapping, using

the Victorian crustal-scale 3-D model






















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Inglewood









Bendigo Fosterville

Tarnagulla















Castlemaine




Taradale

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1500 metre buffer…..around mapped surface fault trace positions (yellow around red):
Captures 41% known Au deposits, 27% intermediate-large size Au deposits



1500 metre buffer…around interpreted 3D model fault dip inflections projected to surface

(green around purple): Captures 67% known Au deposits, 60% intermediate-large size Au
deposits + 30% smaller buffer area

Fault dip inflection projections win as a predictor of significant goldfields locations!




Is THIS why its been so
Inglewood calibrating hypotheses against
hard to understand the
known goldfield distribution
controls localising Victorian

Orogenic Gold at goldfield Rawling et al., 2011

scale?
Bendigo Fosterville

A key control is 15km down! Tarnagulla
Once calibrated, large
mappable fault positions

CAN be used to predict

the offset locations of
orogenic gold deposits!



Castlemaine Including undercover!




Taradale

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Talk outline
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• Geological setting for Victorian orogenic gold




• Competing tectonic models for the Early Palaeozoic – confusing for gold explorers




• Structural / stratigraphic mapping + potential field geophysics: powerful

tools…

• …but Deep Seismic Reflection data drives systems-scale understanding



• Application to mineral systems models at crustal scale…



• Constrained retrodeformation scenarios – critical to take geological systems

analysis from crustal scale to lithospheric scale



• Towards a Unifying Theory for Eastern Australian Early Palaeozoic geology and
mineral systems




• Wrapping up








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eg VandenBerg, 2017




(Gray et al., 2006: restoration of
Victoria’s uppermost crust)
















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Gray et al, 2006













Cayley et al., 2011
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Cayley, 2011


































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Pre-440 Ma ocean








Cayley, 2011


































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Gale simulations of basin closure (continental collision)
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Constrained crustal-scale retrodeformations
can give geometrical start-points for

lithospheric-scale modelling of…




..tectonic scenarios that potentially formed
orogenic-gold –laden continental crust from

collisional thickening of an oceanic crust

precursor (ie: no local crust subduction)
















Gale simulations carried out by Guilla OFFICIALume Duclaux – CSIRO NewGenGold Conference 2021 77
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Gale simulations of basin closure









• Initial formation of basin-


dipping bounding faults









• Moyston F., Heathcote F.








• Subsequent development


of back thrusts









• High strain zones within

the basin







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Recreates large bounding faults….

and a network of internal faults reminiscent of what is observed

in map-view in the Stawell and Bendigo zones

















































See: Rawling et al., 2011 79

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…and reminiscent of what is observed

in cross-section in the Stawell and Bendigo zones…..












































See: Rawling et al., 2011






As these models are refined, improved predictive capacity for orogenic gold is sure to follow…..



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Possible source of gold:



Cambrian metavolcanics like those exposed

in the Moornambool Metamorphic Complex,
in the Avoca Fault, in the Heathcote Fault Zone and,

farther east, in the Governor Fault Zone





Numerical modelling of crustal-scale deformation.



Eg. Leader & Wilson, 2010, Cayley et al., 2011 OFFICIAL NewGenGold Conference 2021 81
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15%

shortening


Schaubs et al., 2012 NewGenGold Conference 2021 82




NewGenGold Conference 2021
OFFICIAL

Talk outline
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• Geological setting for Victorian orogenic gold




• Competing tectonic models for the Early Palaeozoic – confusing for gold explorers




• Structural / stratigraphic mapping + potential field geophysics: powerful

tools…

• …but Deep Seismic Reflection data drives systems-scale understanding



• Application to mineral systems models at crustal scale…



• Constrained retrodeformation scenarios – critical to take geological systems

analysis from crustal scale to lithospheric scale



• Towards a Unifying Theory for Eastern Australian Early Palaeozoic geology
and mineral systems




• Wrapping up






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