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Adelaide Fold Belt Geology

The Adelaide Fold Belt occurs to the east of the Gawler Craton, the eastern edge of which is marked by the Torrens Hinge Zone. This also forms the divide between undeformed Late Proterozoic (approximately 1000 to 540 million years) sediments on the Stuart Shelf and their thicker, deformed equivalents in the Adelaide Fold Belt.

During the early tectonic evolution of the Adelaide Fold Belt, it is interpreted that large scale rifting and broad subsidence were responsible for the accumulation of the thick sedimentary sequences. At the base of the sequence, the Callana Group contains basalts and mixed evaporitic clastics and carbonates. These are overlain by the Burra Group sandstones, dolomites and limestones. The base of the overlying Umberatana Group is marked by a glacial conglomerate (Sturtian) and comprises thick basinal clastic sequences of shale, siltstone and sandstone, with minor carbonate. A second glaciation (Marinoan) was followed by a marine transgression during which sediments of the Wilpena Group were deposited.

Deposition ceased with the onset of the Delamerian Orogeny at about 500 million years. This event is marked by granite intrusions, folding and low-grade metamorphism. The cores of anticlines commonly contain structurally complex and tectonically disrupted zones of Callana Group sediments, interspersed with basic igneous bodies and extensive areas of carbonate breccia. These breccias have been interpreted to be diapiric in origin.

Following uplift caused by the Delamerian Orogeny, erosion of the exposed older formations has taken place and younger Palaeozoic and Cainozoic sediments unconformably overly the Adelaidean sediments.

 

Stratigraphic Location of Copper Occurrences within the Adelaide Fold Belt Sediments

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