Regional tectonic context of the

Curnamona Province

Anthony Reid and Wolfgang Preiss Geological Survey of South Australia

Pb-Ag-Zn deposit

Cu deposit / occurrence

Pb-Ag-Zn deposit

Cu deposit / occurrence

Olympic Cu-Au Province

Age (Ma)

Central/Western Gawler Craton

Curnamona Province

Eastern Gawler Craton

Central/Western Gawler Craton

Curnamona Province

Eastern Gawler Craton

Basement

Cover

Large igneous province & metallogenic event

Cover

Age (Ma)

Central/Western Gawler Craton

Curnamona Province

Eastern Gawler Craton

Basement

Cover Cover

Age (Ma)

Large igneous province & metallogenic event

Gawler Craton

Curnamona Province

Adelaide

Broken Hill

Marla

~1730 – 1690 Ma High-T;

Transpression Kimban Orogeny Broken Hill

Mineralisation: Broadly coeval with deposition ~1685 Ma

~1720 – 1640 Ma sedimentation;

extension

Low –grade or no metamorphism

Gawler – Curnamona setting ca. 1710–1690 Ma

Gawler – transpression – transtension: •Metamorphism and deformation – Kimban Orogeny •Subdued topography •Local sedimentation (e.g. Labyrith Fmn)

Curnamona – extension: •Sedimentation ~ Lower Willyama Supergroup •Magmatism – e.g. Ameroo Subsuite

‘Gawler’ crust ‘Curnamona’ – thinned crust

Kalinjala Shear Zone Broken Hill Zn-Pb-Ag

ca. 1600 Ma Previously unmetamorphosed

Metamorhpic belt

1630 – 1590 Ma

Olarian Orogeny:

Early HT-LP

metamorphism &

subsequent

compression

1630 – 1590 Ma

Olarian Orogeny:

Early HT-LP

metamorphism &

subsequent

compression

Similar aged

deformation and

metamorphism in

northern Gawler Craton

Decreasing metamorphic grade

UPPER CRUST

ca. 1590 Ma

Hiltaba Event:

magmatism,

hydrothermal fluid

flow, synchronous

with late Olarian

structures

Hiltaba

Hillside

Portia; Kalkaroo

Moonta - Wallaroo

Carrapateena

Olympic Dam

Prominent Hill

ca. 1590 Ma

Mineralisation

IOCG mineralisation: High fluid volume; relatively oxidised

Gold-dominated mineralisation: more reduced

The Curnamona Province is a small

remnant of an originally continuous

system of Late Palaeoproterozoic

(1.75-1.64 Ga) sedimentary basins

and

an ~1.6 Ga orogenic belt

extending at least from

north Queensland to

Fleurieu Peninsula

Evidence from seismic surveys:

• Curnamona E-W line

• Curnamona N-S line

• Gawler Craton E-W line

East-dipping thrusts cutting Corunna

Conglomerate, pre-1590 Ma Gawler

Range Volcanics

Northern margin of deformed Willyama

Supergroup thrust against 1.59-1.58 Ga

Radium Creek Gp of Mt Painter Inlier:

clastic sediments deposited in syn-

Olarian foreland basin

CURNAMONA

PROVINCE

Olary Domain

Broken Hill

Domain

Southeast-dipping thrusts across

Curnamona Province

Domains and Inliers of the

Curnamona Province

Olary Domain crops out in Kalabity, Plumbago,

Outalpa and Weekeroo Inliers

Broken Hill Domain crops out in Broken Hill,

Euriowie and Poolamacca Inliers

Redan Domain crops out in Broken Hill Inlier

Moolawatana Domain crops out partly in Mount

Painter and Mount Babbage Inliers

Mulyungarie, Mudguard, Moorowie and

Quinyambie Domains are entirely subsurface

Part of the original

‘Seamless Geology’

map (solid geology)

of Curnamona Province

in SA and NSW

showing stratigraphic

subdivision as envis-

aged in the 1990s

Paragon Group

Sundown Group

Broken Hill Group

Thackaringa Group

Redan Gneiss

Total magnetic intensity of part of Olary Domain showing high and low TMI of

Neoproterozoic rift corridors & complex magnetic pattern of Willyama Supergroup

Olarian thrusts 1640-1620 Ma pelitic blanket 1580 Ma bimodal volcanics, sediments

1590 Ma

foreland basin

Northern Olarian thrust front

CURNAMONA N-S SEISMIC

SUNDOWN GROUP

BROKEN HILL GROUP

Larry Macs Subgroup: Plumbago, Bimba Ettlewood Calc-silicate Member

THACKARINGA GROUP

RANTYGA GROUP

15 m.y. hiatus

Purnamoota Subgp: Hores Gneiss

PARAGON GROUP

?15 m.y. hiatus

Allendale Metasediments

OLARY DOMAIN BROKEN HILL DOMAIN Ma

Walparuta Formation

Raven Hill Subgroup

STRATHEARN GROUP

Mount Howden Subgroup ~1655-1640

~1705

~1710

~1715-1720

~1720

~1695-1700

CURNAMONA GROUP

Ethiudna Subgroup

Peryhumuck Formation v v v v v v v

Cathedral Rock Formation

Tommie Wattie Formation v v v v v v

Wiperaminga Subgroup v v v v v v v

~1685

+ + +

+

+

+

- - -

- -

+

-

+ Upright nappe limbs - Inverted nappe limbs

Solid geology of

part of Bimbowrie

Conservation Park

• Major rock units and

structures

• Syndepositional faults

in Ethiudna Subgroup

• A-type Ameroo

Subsuite intruded

during hiatus between

Ethiudna and Larry

Macs Subgroups

• Refolded overturned

nappe limb

• Sturtian glacial valley

fill

• Delamerian shear zone

younging

younging

• Early high-temperature metamorphism and migmatisation, perhaps under

a thick insulating pelitic blanket

• Early continuous and progressive ductile deformation in mid-crust by

isoclinal, recumbent folding and thrusting, resulting in gradual crustal

thickening

• Early folds with sheath morphology to explain diverse fold axis

orientations and apparent vergences; overall tectonic transport to NW

• Later folds tend to be more upright and thick-skinned, but formed within

the same overall stress regime

• Granites result from mid-crustal melting of sediments, perhaps induced by

a regional deep crustal or mantle event (‘Hiltaba Event’) at 1590 Ma • Granites may be incidental to Olarian Orogeny

TECTONIC EVOLUTION OF OLARIAN OROGENY ~?1620–1590 MA OLARIAN OROGENY ?1.63 – 1.59 Ga

Major events in the Curnamona Province

• 1.72-1.715 Ga: Rifting of a continental basement; deposition of Curnamona

Group evaporitic siliciclastic sediments (known only in Olary and

Mulyungarie Domains); A-type felsic volcanism

• 1.71-1.70 Ga: Extensional faulting; intrusion of Ameroo Subsuite A-type

granite and hiatus in deposition in Olary Domain; deposition of siliciclastic

sediments of Rantyga and Thackaringa Groups in Broken Hill Domain

• 1.70-1.695 Ga: Larry Macs Subgroup transgressive onto eroded surface of

Curnamona Group; base-metal anomalous Bimba Formation (Olary

Domain) and Ettlewood Calc-silicate Member (Broken Hill Domain); thin

volcaniclastic Plumbago Formation deposited on maximum flooding

surface; ?conformable transition from Thackaringa to Broken Hill Group

• 1.695-1.685 Ga: Broken Hill Group (Broken Hill Domain) and Raven Hill

Subgroup (Olary Domain) mainly fine-grained siliciclastic deposition

Major events in the Curnamona Province

• 1.685 Ga: Mafic intrusives; submarine volcaniclastic Hores Gneiss and formation of inhalative Broken Hill Pb-Zn-Ag orebody (Broken Hill Domain)

• 1.685-1.67 Ga: Dominantly fine siliciclastic deposition of Sundown Group in Broken Hill Domain; possible equivalents in Olary Domain

• 1.67-1.655 Ga: Possible hiatus in deposition in both domains

• 1.665-1.64 Ga: Dominantly fine siliciclastic deposition of Paragon Group (Broken Hill Domain), Strathearn Group (Olary & Mulyungarie Domains)

• 1.64-1.63 Ga: Speculative deposition of thick insulating pelitic blanket

• 1.63-1.62 Ga: Earliest onset of Olarian metamorphism and migmatisation; uncertain onset of Olarian deformation

• 1.62-1.60 Ga: Olarian Orogeny possibly diachronous and propagating from southeast to northwest; northwest-verging nappes, thrusts and sheath folds; low-angle foliations; possibly peak metamorphism from granulite in the southeast to greenschist in the north

Major events in the Curnamona Province • 1.60-1.59 Ga: Continued northwest-directed tectonic transport refolds nappes

into upright folds defining the arcuate ‘grain’ of Curnamona Province; steep axial plane foliations; ; northern thrust front intersected on N-S seismic transect near Moolawatana; deposition of upward-coarsening Radium Creek Group in a syn-Olarian foreland basin

• 1.59 Ga: Intrusion of late tectonic Ninnerie Supersuite granites, including S-type Bimbowrie and Mundi Mundi Suites; I-type intrusions in western Olary Domain indicate mantle involvement; part of the regional ‘Hiltaba Event’

• 1.59-1.58 Ga: Extrusion of Benagerie Volcanics in central Curnamona

• 1.59-1.57 Ga: Network of steep anastomosing greenschist-facies shear zones cuts the whole Curnamona Province with E-W, ENE-WSW and WNW-ESE orientations; bending of upright fold trends and fold interference on E-W axes to produce dome and basin structures; differential uplift, exhuming the deepest nappes in the southeast (granulite facies) and shallowest in central Curnamona where Benagerie Volcanics are still preserved

• 1.57-0.83 Ga: Peneplanation with no recorded events; speculative Musgravian overprint at 1.2 Ga?

Major events in the Curnamona Province

• 0.83-0.8 Ga: Willouran-age NE-SW rifting and intrusion of mafic dykes (Gairdner Dolerite and equivalents

• 0.8-0.7 Ga: Initiation of half grabens along SW margin of Curnamona Province; deposition of Burra Group siliciclastics and carbonates

• 0.7-0.65 Ga: Sturtian-age rifts encircle the Curnamona Province and define its margins; thick glacio-marine sedimentation

• 0.65-0.51 Ga: Remainder of thick Neoproterozoic and early Cambrian sedimentation; thin platform cover over central Curnamona

• 0.51-0.49 Ga: Delamerian Orogeny; interfering NNW-SSE and ENE-WSW fold trends; partial inversion of rift half grabens to form corridors between inliers; mostly greenschist facies metamorphism of basement and cover

• 0.49-0.12 Ga: Peneplanation and deep weathering

• 0.12-0 Ga: Onlap of marine (Cretaceous) and non-marine (Cenozoic) sediments; uplift of Flinders, Olary and Barrier Ranges as ancient reverse faults are reactivated under E-W compression