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Northern Gawler Province Model

Large potential field anomalies have been observed in the Marla Region of Northern South Australia and have been used to define the northern limit of the Gawler Craton. This project’s aim was to model the source of those anomalies in order to understand the sources of those anomalies. 

In this area, basement is buried beneath Neoproterozoic-Recent cover, of the Eastern Officer, Arckaringa and Eromanga Basins, so the first step in the analysis was to constrain the geometry of the basins. The outcropping geology, drillhole data and seismic reflection profiles were used to map out the depth to crystalline basement, and depth to the Base of the Arckaringa Basin. The depth to basement horizon, shows the complex geometry of the Munyarai Trough which forms a foreland to the uplifted Musgrave Block; the Marla Overthrust Zone and Ammaroodinna Ridge which were uplifted after the deposition of Cambrian to Silurian sedimentary rocks; the Middle Bore Fault Zone which was last active during deposition of the Arckaringa Basin and the Wintinna Trough. Note that the geometries of faults are interpreted based on seismic data where the faults are often poorly imaged, especially the Middle Bore Fault. 

Also shown in the model are isosurfaces of physical properties (density and magnetic susceptibility) for constrained UBC-GIF inversions. To the south of the Middle Bore fault zone anomalies are small, and are often shallowly sourced and the magnetic and gravity anomalies are broadly coincident. To the north of the Middle Bore Fault, a large density body is observed, whereas below the Ammaroodinna Ridge and extending a little to the Southeast below the Manya Trough is an offset magnetic anomaly. The largest magnetic susceptibility body appears to dip to the North west and is consistent with the general dip of structures imaged by the GOMA seismic line (Korsch et al., 2010). 

To conclude the major potential field anomalies in the region have a basement source, and represent a crust with significantly different properties to the southern Nawa Domain, south of the Middle Bore Fault and the Musgrave Block further to the North. This region may indicate a major geological boundary, although significance and age of the boundary are unclear. However, rocks across the entire region all show evidence of Kimban aged granulite to amphibolite grade metamorphism or magmatism (Fanning et al., 2007; Payne et al., 2008)

References

Fanning CM, Reid A and Teale G 2007. A geochronological framework for the Gawler Craton, South Australia. Bulletin 55.

Korsch RJ et al 2010. Geological Interpretation of the deep seismic reflection and magnetotelluric line 08GA-OM1: Gawler Craton-Officer Basin-Musgrave Province-Amadeus Basin (GOMA), South Australia and Northern Territory. In: RJ Korsch and N Kositcin (Editors), GOMA (Gawler Craton-Officer Basin-Musgrave Province-Amadeus Basin) Seismic and MT Workshop, pp. 63–86.

Payne JL, Hand M, Barovich KM and Wade BP 2008. Temporal constraints on the timing of high-grade metamorphism in the northern Gawler Craton implications for assembly of the Australian Proterozoic. Australian Journal of Earth Sciences, 55: 623–640.

Using the model

In order to increase its accessibility, the Northern Gawler Province model has been converted to .pdf format, allowing for maximum portability and eliminating the need for the end user to purchase any specialised software.
 
The user can fully interact with the model using Adobe Acrobat’s 3D Toolbar (Note: the toolbar varies with the version of Acrobat Reader):

  1. Rotate
  2. Spin
  3. Pan
  4. Zoom
  5. Default view
  6. Select view
  7. Toggle model tree
  8. Pause animation
  9. Use orthographic projection
  10. Model render mode
  11. Enable extra lighting
  12. Background colour (disabled if a gradient background is being used)

Adobe Acrobat 3D toolbar

The user can also:

  • Selectively activate and/or deactivate any geological unit, cross section or isopach 
  • Enable geological surfaces to be displayed as transparent, solid or as a solid-wireframe

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Software Information
The models can be viewed with Acrobat Reader 9 as it incorporates 3D visualisation capabilities. Acrobat Reader 9 can be downloaded free from the Adobe website.

Download the Northern Gawler Province 3D Geology Model

Northern Gawler Province 3D model 

 

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Note: these models are presented as a 'proof of concept' only and their accuracy (spatial or otherwise) should not be relied upon for exploration or other decision making processes.