a few notes on the geological reasoning , page-3

G'Day Wozza,

The significance of the change from a silicate oxide assemblage to one of sulphide carbonate relates back to the distal/proximal relationship which i was referring to earlier.

Having magnetite present in such systems is actually quite useful when it comes to exploration. Probably straying away from your question a bit but ill give a bit of historical background to the discovery of Cannington.

When geologists realized that the Gawler craton, Broken Hill block and Mt Isa block had a shared geological history from a multitude of events and the discovery of Ernest Henry which is an IOCG just like Olympic Dam the idea came about for the presence of Broken Hill type mineralisation in the eastern succession of the Mt. Isa block.

Initial investigations found that the Broken Hill types in the Mt Isa block had magnetite which Broken Hill did not have. So BHP went and flew 1.5 million dollars worth of aeromag and discovered on Cannington station.....Cannington.

The relevance of the carbonate is that it is a proximal alteration mineral where in the case of Maranoan and Cannington it is present as Calcite and in Broken Hill as Rhodonite and Hedenbergite.

The change from oxide facies (Magnetite Fe3O4)to Sulphide (FeS, PbS, ZnS2) relates back to the change in oxygen and sulphide fugacity which i mentioned earlier.

Hope that helps.