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  

MineralisaMon:  Broadly  coeval  with  deposiMon  ~1685  Ma  

~1720  –  1640  Ma  sedimentaMon;  

extension  

Low  –grade  or  no  metamorphism  

Gawler – Curnamona setting ca. 1710–1690 Ma Gawler  –  transpression  –  transtension:  • Metamorphism  and  deformaMon  –  Kimban  Orogeny  • Subdued  topography  • Local  sedimentaMon  (e.g.  Labyrith  Fmn)  

Curnamona  –  extension:  • SedimentaMon  ~  Lower  Willyama  Supergroup  • MagmaMsm  –  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

granulite  

Decreasing  metamorphic  grade  

UPPER  CRUST  

ca. 1590 Ma

Hiltaba Event:

magmatism,

hydrothermal fluid

flow, synchronous

with late Olarian

structures

BVS  Hiltaba  

Hiltaba  

Hillside  

PorMa;  Kalkaroo  

Moonta  -­‐  Wallaroo  

Carrapateena  

Olympic  Dam  

Prominent  Hill  

ca. 1590 Ma

Mineralisation

IOCG  mineralisaHon:  High  fluid  volume;  relaHvely  oxidised  

Gold-­‐dominated  mineralisaHon:  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