Kanmantoo Trough - Mineralisation
A.C. Burtt (contributions by W.V. Preiss, C.G. Gatehouse, J.C. Gum and P.J. Abbot)
Base-metal mineralisation is widespread within the Kanmantoo Group although production has mostly been minor. Most occurrences appear to be stratabound or strongly controlled by stratigraphy. The Carrickalinga Head, Talisker Calc-siltstone, Tapanappa and Tunkalilla Formations are favoured hosts for mineralisation.
The largest ore producer within the Kanmantoo Trough has been the Kanmantoo Mine (copper, minor gold) where discordant, structurally controlled lenses of chalcopyrite mineralisation occurred within schist of the Tapanappa Formation. Other significant deposits in the Tapanappa Formation between Kanmantoo and Strathalbyn include the Angas Prospect (Pb-Zn-Ag-Au), Bremer (Cu), Aclare (Ag-Pb-Zn) and Wheal Ellen (Pb-Ag-Zn-Cu-Au)(Fig. 3). At Angas Prospect lead and zinc sulphide occurs over a 2km zone and is up to 100 metres thick within garnet, gahnite and staurolite-bearing quartz-biotite-muscovite schist. An exhalative origin is interpreted as a source for this mineralisation (Toteff, 1999).
Pyritic and calcitic phyllite layers within the Talisker Calc-siltstone host mineralisation at Mt Torrens Prospect (Pb-Zn-Ag), Talisker (Ag-Pb-As) and Brukunga (pyrite - 5 Mt sulphide ore produced from 1955 to 1972)(Fig. 3). The Karinya Shale (ie. Talisker Calc-siltstone equivalent) in the Karinya Syncline has elevated Pb-Zn-As-Mn and Cu values occurring within carbonate-rich horizons above a sequence boundary contact with the Backstairs Passage Formation.
The Carrickalinga Head Formation hosts minor Cu-Pb-Zn-Ag and Au occurrences in fault zones cross-cutting the Milendella Limestone Member within the Karinya Syncline (Fig. 3).
On Kangaroo Island recent drilling programs have discovered anomalous Pb-Zn and Au mineralisation in Kanmantoo Trough and shelf sediments adjacent to the Kangaroo Island Shear Zone. Historically there have been several small workings along this shear zone including the Kohinoor Mine (Pb-Zn ± Au)(Fig. 3).
As a result of subsequent metamorphism, secondary enrichment of mineralising fluids migrating along permeable stratigraphic horizons or structural corridors appears to have further concentrated mineralisation into favourable stratigraphic and structural traps, particularly in the Karinya Syncline. This possibility and the complex basin structure and deformational history of the Kanmantoo Trough greatly enhances the prospect of discovering hidden economic mineralisation.
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- Page Last Modified: November 8, 2011