South Australian Three-dimensional Geological Models

Two, three-dimensional models were constructed, the first of which (upper crustal-level) occupies a spatial window on the Australian Map Grid orthogonal to (50⁰⁰⁰mE, 7000⁰⁰⁰mN) and (1000⁰⁰⁰mE, 6200⁰⁰⁰mN), the second model covering an area from (-100⁰⁰⁰mE, 7100⁰⁰⁰mN) to (1100⁰⁰⁰mE, 6400⁰⁰⁰mN).

South Australian Upper crustal-level Surface Model
All surfaces were created to honour the geological data, the ascribed delineation of gravimetric features and cross-sectional interpretations of the kind shown in figures 5 to 8. Lithological variations in the shallow-level geology were simplified into an assemblage of 18 units. These include;
• the lower boundaries of the Gawler Range Volcanics and comagmatic Hiltaba Suite Granitoids;
• the lower boundaries of the Cariewerloo Basin, Stuart Shelf and Adelaidean Fold Belt;
• the lower boundaries of the Willyama and Mount Painter Inliers;
• the lower boundaries of accretionary complexes of the Peake & Denison Inlier, the Mount Woods Inlier, the Mabel Creek Ridge, the Ifould Complex and the Lincoln Complex;
• the lower boundaries of the Hutchison Group, the St Peters Suite Granitoids and Moondrah Gneiss;
• the lower boundaries of the Musgrave Block and Undifferentiated Precambrian rocks.

Several additional features were created to define important lithospheric elements. These include:
• the boundaries of the Gawler craton;
• the lower boundaries of the sub-crustal lithospheric mantle (SCLM);
• the lower boundaries of the lower crust;
• the Kimban Suture Zone;
• a regional-scale mafic underplate;

The macroscopic nature of interpreted subsurface geological features of the Gawler Craton and surrounding environs are shown in figures 10 & 11.

Figure 10. gOcad three-dimensional surface representation of upper crustal-level structures of the South Australian model. View is towards N335 at 25 degrees elevation. (Click here to view 3D gOcad™ model; VRML plugin available at http://www.parallelgraphics.com/)

These figures enable conceptual visualisation of the complex geometry of the Gawler Craton in which the following significant features are observable:
• the relatively large volume of rock occupied by the Gawler Range Volcanics;
• the widespread spatial distribution of the Hiltaba Suite Granitoids;
• the geometry of accretionary terranes and their relative orientations on the cratonic margins
• the geometry of the eastern cratonic margin.

Figure 11. gOcad three-dimensional surface representation of upper crustal-level structures of the South Australian model. View is towards N025 at 25 degrees elevation.

South Australian Deeper crustal-level Surface Model
Lithospheric variations in the deeper-level geology were simplified into an assemblage of 13 blocks (Figures 12 & 13). These include;
• the boundaries of the Gawler Craton in the north and west and the Kimban Suture Zone defining the eastern margin;
• the boundaries of the eastern, western and lower cratonic elements;
• the lower boundaries of the Fowler Orogenic Belt as delineated by blocks defined by the Coorabie Fault, the Karari Fault Zone and units of undifferentiated Pre-Cambrian Rocks;
• the lower boundaries of the Musgrave Block and the Officer Basin;
• the lower boundaries of the ‘reworked’ Torrens Hinge Zone along the eastern margin of the Gawler Craton;
• the upper boundaries of a possible high-density displaced crustal block beneath the Adelaidean Fold Belt.

Figure 12. gOcad three-dimensional surface representation of the deeper crustal-level structures of the South Australian model. View is towards N335 at 25 degrees elevation.

Figure 13. gOcad three-dimensional surface representation of the deeper crustal-level structures of the South Australian model. View is towards N025 at 25 degrees elevation.