As a result of the work outlined in this report it is concluded that the possibility of economic tonnages of copper ore within the area of Special Mining Lease no. 165 are restricted to three localities, Breaden Hill, Boorloo and East Rook. All...
As a result of the work outlined in this report it is concluded that the possibility of economic tonnages of copper ore within the area of Special Mining Lease no. 165 are restricted to three localities, Breaden Hill, Boorloo and East Rook. All three prospects are characterised at the surface by mineralised quartz veins to which the grade and extent of mineralisation appear to be related. The copper appears to have been introduced into the veins from an epigenetic source. The density of quartz veining appears to be related to tectonic stresses, so that warps and folds form suitable loci for mineralisation. The tendency for certain relatively favourable sedimentary horizons to respond to stress in this way is reflected in the repeated pattern of mineralised vein swarms along certain stratigraphic horizons, like the dolomites and grits in the Dunn's - East Rook Line, or the arkosic grits of the Serle Conglomerate. This could be due to differential response in adjacent beds of different competency, as exemplified in the dolomitic breccia in some of the pits at Breaden Hill. The grade of the surface copper mineralisation appears to be distinctly higher at Breaden Hill than at the Boorloo and East Rook prospects. This may be due to its location at a focal point of regional fault and fold stress, and perhaps justifies the hope of an economic grade in the untried sulphide zone. This is the basis for recommending a drilling programme to test the Breaden Hill mine below the depth of historic workings. At Boorloo detailed mapping has established the relationship between copper mineralisation and vein systems at the surface, with evidence of dispersal of copper into the surrounding surface rocks. A distinct zone of leaching is present, which seems from its position to be related to a part of the Serle - Yudnamutana Sub-group unconformity, and not strictly to the disposition of copper mineralised quartz veins. Neither of the two previously completed diamond drillholes was collared in such a position as to test the downward projection of the strongest zones of quartz vein and copper concentration at the surface.
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