tectonic setting of the gawler craton iron oxide-copper ......gawler –curnamona setting ca....
TRANSCRIPT
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Tectonic setting of the Gawler Craton iron oxide-copper-gold mineral systems
Anthony Reid
Senior Principal Geoscientist
Geological Survey of South Australia
Iron oxide-copper-gold workshop
2-3 December 2019
South Australia Drill Core Reference Library, Adelaide
Hydrothermal zircon with sulphide inclusions, Olympic Dam
Hiltaba Suite granite, Hiltaba Station
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• Main stratigraphic units relevant to IOCG systems in South Australia
• Interpretations of tectonic setting for IOCG systems
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Looking east from the central Gawler CratonRubble is silicified Jurassic sandstone
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GawlerCraton
Curnamona Province
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GawlerCraton
Curnamona Province
IOCG event
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GawlerCraton
Curnamona Province
BasementSleafordianOrogeny
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5cm
GawlerCraton
Curnamona Province
Basement
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TDM (Ga) contour
Data from many sources. GIS layer and compilation by Champion, 2014Geoscience Australia Record 2013/044 http://www.ga.gov.au/metadata-gateway/metadata/record/77772/
http://www.ga.gov.au/metadata-gateway/metadata/record/77772/
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GawlerCraton
Curnamona Province
Basement
Devils Playground Volcanics, c.2555 Ma • magnesian, calc-alkali• basalt – eNdt ~ -1
Enriched lithospheric mantle
Basalt, andesitic basalt, andesite; 51 – 59 % SiO2
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GawlerCraton
Curnamona Province
Basement
Donington Suitec. 1850 Ma
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GawlerCraton
Curnamona Province
Basement
Cover
• c. 1790 – 1740 Ma• Sedimentary and volcanic rocks, • Key unit for the eastern Gawler Craton: Wallaroo Group• Widespread distribution• Variable metamorphic grade
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GawlerCraton
Curnamona Province
Basement
Cover
Wallaroo Group
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GawlerCraton
Curnamona Province
Basement
Cover
c. 1730 - 1690 MaKimban Orogeny
• High strain; transpression• HT-MP metamorphism
crd-bearing leucosome
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GawlerCraton
Curnamona Province
Basement
Cover Cover
Hores Gneiss, meta-volcanic unit host to Broken Hill orebody.View towards Broken Hill mullock heap
Willyama Supergroupc. 1710 – 1640 Ma
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c. 2440 Ma
c. 1730 –1690 Ma
Empirical observation: distribution of pre-1590 Ma metamorphism
Olympic Dam
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Pre-1740 Ma lowmetamorphic grade rocks
c. 1730 –1690 Ma
c. 2440 Ma
Olympic Dam
Empirical observation: distribution of pre-1590 Ma metamorphism
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~1730 – 1690 MaHigh-T;
TranspressionKimban Orogeny
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Low –grade or no metamorphism
~1730 – 1690 MaHigh-T;
TranspressionKimban Orogeny
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Broken Hillmineralisation:broadly coevalwith deposition~1685 Ma
~1720 – 1640 Ma sedimentation;
extension~1730 – 1690 Ma
High-T;TranspressionKimban Orogeny
Low –grade or no metamorphism
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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
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GawlerCraton
Curnamona Province
Basement
Cover Cover
St Peter Suite
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St Peter Suite, c. 1620 Ma• Mantle-derived, enriched• Interpreted subduction-related
Reid et al 2019 AJES
Magnesian to ferroan composition
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St Peter Suite, c. 1620 Ma• Mantle-derived, enriched• Interpreted subduction-related
Enriched mafic rock composition
Reid et al 2019 AJES
Skirrow et al. 2019
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GawlerCraton
Curnamona Province
Basement
Cover
Large igneous province:• Hiltaba Suite• Bimbowrie Suite• Gawler Range Volcanics• Benagerie Volcanics
Cover
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Hiltaba Suite, c. 1595- 1575 Ma• A- and I-type• High temperature, oxidized
magmas
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Gawler Range Volcanics, c. 1590 Ma• Compositional variation in Lower• Large volume felsic lavas in Upper• High temperature• Benagerie Volcanic Suite – virtually identical
Lower GRV; basalt, flow banding, volcanicalstic units
Eucarro Ryholite, Upper GRV
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GawlerCraton
Curnamona Province
Basement
Cover Cover
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1630 – 1590 Ma
Olarian Orogeny:
• Early HT-LP metamorphism & subsequent
compression
• Deformation and metamorphism in parts of
Gawler Craton
Upright late folding, Olary
High T metamorphism, Coober Pedy Ridge, Gawler Craton.
950 °C, 6.5 kbar
Cutts et al. 2011
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UPPER CRUST
Decreasing metamorphic grade
Olarian Orogeny:
• Spatial arrangement of higher metamorphic grade exhumed at margins of Gawler Craton and Curnamona Province
• Upper crust preserved in central Gawler Craton…
• …where most of the mineral deposits are, including the hematite IOCG systems
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• Main stratigraphic units relevant to IOCG systems in South Australia
• Interpretations of tectonic setting for IOCG systems
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Early model – plume-related magmatism1993, Bulletin 54, Geological Survey of South Australia
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Geodynamic setting for IOCG deposits: Skirrow et al., 2019 Ore Geology Reviews
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Key points
• IOCG systems associated with c. 1590 Ma large igneous province and major
tectonometamorphic event: active tectonic setting
• Pre- c. 1590 Ma crust included low metamorphic grade sequences in the
eastern Gawler Craton and Curnamona Province – regions with most IOCG
deposits
• Gawler Craton mantle shows multiple stages of enrichment/metasomatism
including in Archean
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DISCLAIMER
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Department for Energy and Mining (DEM) and originates from a variety
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