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Gawler Craton

The Gawler Craton is an extensive region of Archaean to Mesoproterozoic crystalline basement underlying approximately 440 000 square kilometres of central South Australia.

You can view the interpretated subsurface geology of the Gawler Craton as a JPG.

The Gawler Craton has been defined as that region of crystalline basement which has not been substantially deformed or remobilised, except for minor epirogenic movements, since 1450 Ma. Much of the area is covered by thin platformal sediments and regoliths of Neoproterozoic to Cainozoic age. The boundaries of the craton are defined to the northeast, northwest and west by faulted margins and thick Neoproterozoic and Phanerozoic sedimentary basins. To the east and southeast the Torrens Hinge Zone defines the margin, adjacent to the western limit of the Adelaide Fold Belt. The southern boundary is coincident with the edge of the continental shelf. The craton boundary is clearly visible on the high resolution aeromagnetic image.

Crust forming and tectonothermal events occurred during the late Archaean to earliest Proterozoic (Sleafordian Orogeny, 2440 Ma), Paleoproterozoic (Kimban Orogeny, 1850–1700 Ma) and Mesoproterozoic (Kararan Orogeny 1670–1540 Ma).

View the suggested nomenclature and correlation between Precambrian rocks of the Gawler Craton as a PDF (~93k) or view the suggested nomenclature and correlation between Precambrian rocks of the Gawler Craton as a Gif.  

Gawler Craton in summary

  • This is a stable crystalline basement province comprising late Archaean to Mesoproterozoic rocks mantled in part by thin platformal sediments and regoliths of Neoproterozoic to Cainozoic age.
  • Archaean basement (Sleaford and Mulgathing Complexes) comprises chemical and clastic metasediments, mafic lavas, felsic volcanics and granitic rocks.
  • Palaeoproterozoic rocks include metamorphosed marine shelf sediments of the Hutchison and Wallaroo Groups, granitoids of the Donington and Moody Suites, mafic dykes and younger metamorphosed sediments and felsic volcanics.
  • Thick sheets of Mesoproterozoic, felsic Gawler Range Volcanics (1590 Ma) occur over much of the Gawler Craton. These are associated with extensive comagmatic granite intrusions  (Hiltaba Suite), one of which hosts the Olympic Dam deposit.

Mesoproterozoic granites, felsic volcanics and gneisses in the Gawler Craton and Curnamona Province contain anomalously elevated uranium and thorium concentrations relative to global Proterozoic averages (Neumann et al, 2000) and generate high heat flows.  For example, the Mesoproterozoic Hiltaba Suite hosts the Olympic Dam copper-gold-uranium deposit.

The Gawler Range Volcanics (1590 Ma) form a huge felsic volcanic province, in the central Gawler Craton, with over 25 000 km2 of preserved outcrop. They are divided into two broad groups, an upper and lower unit. The lower unit is more varied, gently to steeply tilted and contains dacite-rhyodacite-rhyolite, ignimbrites and flows with thick, interlayered sequences of basaltic lavas whereas the upper unit contains thick, subhorizontal, porphyritic dacite sheets predominantely ignimbritic in origin.
The extensive Hiltaba Suite (1600–1585 Ma) is comagmatic with the Gawler Range Volcanics and is dominated by felsic granite plutons. Outcrop is most abundant in the central Gawler Craton particularly on the western and south-western margins of the Gawler Range Volcanics. This unit is characteristically pink due to hematite dusting of the feldspar crystals.  The Hiltaba Suite and Gawler Range Volcanics were derived from partial digestion of the crust by mantle plumes and are the source for widespread Au-Cu-U mineralisation within the Gawler Craton.

Contact between Hiltaba Suite Granite (bottom) and porphyritic Gawler Range Volcanics (top)

The Corunna Conglomerate unconformably overlies the Moonabie Formation and McGregor Volcanics and is intruded by dykes of the Gawler Range Volcanics. The basal conglomerate contains abundant basement clasts fining upwards to thick carbonaceous siltstone and sandstone. In the Kingoonya area the Mentor Formation, consisting of chloritic and sericitic mudstone, altered and tuffaceous granite breccia and tuffaceous rhyolite, overlies the Labyrinth Formation. This unit is considered contemporaneous with extrusion of the Gawler Range Volcanics and prospective for Au-Cu-U mineralisation.

 Purple sandy bed in polymict Corunna Conglomerate

The last known magmatic event in the Gawler Craton is the intrusion of the Spilsby Suite granites (1510 Ma). Outcrop is restricted to islands of the Sir Joseph Banks Group in the Spencer Gulf between Eyre and Yorke Peninsulas.

More information on the Gawler Craton

Neumann, N, Sandiford, M and Foden, J 2000. Regional geochemistry and continental heat flow, implications for the origin of the South Australian heat flow anomaly. Earth and Planetary Science Letters, 183, 107–120.