Tectonic setting of the Gawler Craton iron oxide-copper-gold mineral systems
Anthony Reid Senior Principal Geoscientist
Geological Survey of South Australia Hydrothermal zircon with sulphide inclusions, Olympic Dam
Iron oxide-copper-gold workshop 2-3 December 2019 South Australia Drill Core Reference Library, Adelaide
Hiltaba Suite granite, Hiltaba Station • Main stratigraphic units relevant to IOCG systems in South Australia
• Interpretations of tectonic setting for IOCG systems Looking east from the central Gawler Craton Rubble is silicified Jurassic sandstone
Gawler Curnamona Craton Province Gawler Curnamona Craton Province IOCG event Gawler Curnamona Craton Province
Basement Sleafordian Orogeny Gawler Curnamona Craton Province
Basement
5cm TDM (Ga) contour
Data from many sources. GIS layer and compilation by Champion, 2014 Geoscience Australia Record 2013/044 http://www.ga.gov.au/metadata-gateway/metadata/record/77772/ Gawler Curnamona Craton Province
Basalt, andesitic basalt, andesite; 51 – 59 % SiO2
Basement
Devils Playground Volcanics, c.2555 Ma • magnesian, calc-alkali
• basalt – eNdt ~ -1 Enriched lithospheric mantle Gawler Curnamona Craton Province
Donington Suite c. 1850 Ma
Basement Gawler Curnamona Craton Province
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Basement
• c. 1790 – 1740 Ma • Sedimentary and volcanic rocks, • Key unit for the eastern Gawler Craton: Wallaroo Group • Widespread distribution • Variable metamorphic grade Gawler Curnamona Craton Province
Wallaroo Group
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Basement Gawler Curnamona Craton Province
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c. 1730 - 1690 Ma Kimban Orogeny • High strain; transpression • HT-MP metamorphism
crd-bearing leucosome Gawler Curnamona Craton Province Willyama Supergroup c. 1710 – 1640 Ma
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Basement
Hores Gneiss, meta-volcanic unit host to Broken Hill orebody. View towards Broken Hill mullock heap Empirical observation: distribution of pre-1590 Ma metamorphism
c. 2440 Ma
c. 1730 – 1690 Ma Olympic Dam Empirical observation: distribution of pre-1590 Ma metamorphism
Pre-1740 Ma low c. 2440 Ma metamorphic grade rocks
c. 1730 – 1690 Ma Olympic Dam
~1730 – 1690 Ma High-T; Transpression Kimban Orogeny Low –grade or no metamorphism
~1730 – 1690 Ma High-T; Transpression Kimban Orogeny Low –grade or no metamorphism ~1720 – 1640 Ma sedimentation; ~1730 – 1690 Ma extension High-T; Transpression Kimban Orogeny Broken Hill mineralisation: broadly coeval with deposition ~1685 Ma Gawler – Curnamona setting ca. 1710–1690 Ma
Gawler – transpression – transtension: Curnamona – extension: •Metamorphism and deformation – Kimban Orogeny •Sedimentation ~ Lower Willyama Supergroup •Subdued topography •Magmatism – e.g. Ameroo Subsuite •Local sedimentation (e.g. Labyrith Fmn)
Kalinjala Shear Zone Broken Hill Zn-Pb-Ag
‘Gawler’ crust ‘Curnamona’ – thinned crust Gawler Curnamona Craton Province
St Peter Suite
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Basement Reid et al 2019 AJES
Magnesian to ferroan composition St Peter Suite, c. 1620 Ma • Mantle-derived, enriched • Interpreted subduction-related Enriched mafic rock composition
Skirrow et al. 2019
Reid et al 2019 AJES
St Peter Suite, c. 1620 Ma • Mantle-derived, enriched • Interpreted subduction-related Gawler Curnamona Craton Province Large igneous province: • Hiltaba Suite • Bimbowrie Suite • Gawler Range Volcanics • Benagerie Volcanics Cover Cover
Basement Hiltaba Suite, c. 1595- 1575 Ma • A- and I-type • High temperature, oxidized magmas Lower GRV; basalt, flow banding, volcanicalstic units
Gawler Range Volcanics, c. 1590 Ma • Compositional variation in Lower • Large volume felsic lavas in Upper • High temperature • Benagerie Volcanic Suite – virtually identical Eucarro Ryholite, Upper GRV Gawler Curnamona Craton Province
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Basement Upright late folding, Olary 1630 – 1590 Ma Olarian Orogeny: • Early HT-LP metamorphism & subsequent compression
• Deformation and metamorphism in parts of Gawler Craton
950 °C, 6.5 kbar
Cutts et al. 2011
High T metamorphism, Coober Pedy Ridge, Gawler Craton. Olarian Orogeny: • Spatial arrangement of higher metamorphic grade exhumed at margins of Gawler Craton and Curnamona Province • Upper crust preserved in central Gawler Craton… UPPER • …where most of the mineral CRUST deposits are, including the hematite IOCG systems
Decreasing metamorphic grade • Main stratigraphic units relevant to IOCG systems in South Australia
• Interpretations of tectonic setting for IOCG systems Early model – plume-related magmatism 1993, Bulletin 54, Geological Survey of South Australia Geodynamic setting for IOCG deposits: Skirrow et al., 2019 Ore Geology Reviews 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 DISCLAIMER
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