Evidence is presented to show that a strong mineralogical/chemical zoning exists in seven deposits of the Cobar-Nymagee area. Characteristically, the within-deposit zoning, perpendicular to bedding, consists of a siliceous chalcopyrite-pyrrhotite eastern side with diffuse contacts against adjacent siltstone-shale host rocks, and a relatively massive sulphide, banded, pyrite-sphalerite-galena western side with sharp contacts against host rocks. Features such as these are typical of those in exhalative deposits in volcanic terrain and are taken here to indicate a similar origin in this essentially non-volcanic environment. The deposits are contained in distal turbidite facies of the Devonian Cobar Supergroup, deposited in a meridional trough bounded on its eastern flank by a possible penecontemporaneous growth fault separating the trough from an adjacent shelf area on which were deposited shallow-water marine sediments and terrestrial and marine volcanics. This volcanism and the Cobar sedimentary-exhalative deposits may be related through rifting in the area which produced the proposed growth faults and the subsequent Cobar Trough. The deposits, now in 20° discordancy to bedding, are considered to have been transposed into the prominent regional cleavage during post-ore deformation. Using the syn-sedimentary exhalative concept, two mineralised horizons and a possible tight syncline may be recognised in the CSA mine.