Exploration concepts for Olympia Dam-type deposits in Precambrian rocks of the midcontinental United States

The Middle Proterozoic Olympic Dam (OD) deposit contains over 2 billion tons of Cu-U-Au-Ag ore. Fluid inclusion and stable isotope data show that OD minerals were deposited by fluids from two sources; a younger, Cu-bearing fluid overprinted a cu deposit on a Kiruna-type Fe deposit. Reeve et al. interpret the Cu deposition to have accompanied emplacement of maar-related diatremes and mafic dikes associated with Gawler Range volcanism. Knutson et al., suggest that the Gawler Range Volcanics are possible source rocks for Cu at OD and in younger Adelaidean sediment-hosted Cu deposits. OD has a local gravity anomaly that is superimposed on a regional gravity anomaly suggesting that OD hematitic breccias overlie a mafic pluton OD-type targets should have a similar gravity signature. A magnetic anomaly could represent any type of magnetite-rich rock and should not be over emphasized when listing exploration criteria. Efforts should focus on Cu provinces that have igneous terranes similar to the Stuart shelf; preferably near sediment-hosted Cu deposits. Basalt-rich terranes (i.e. the Midcontinent Rift) may offer better targets than basalt-poor terranes (i.e. the St. Francois terrane)