The Copper Canyon deposits, occur in proximity to the regionally
distinctive formational boundary between the Staveley Formation and
Marimo Shale. The mineralisation here is associated with breccias, veins,
and alteration zones near the base of the Marimo Shale unit and in the
underlying evaporitic dolomite-dololutite dominant Staveley Formation. The Marimo Shale unit, in its basal 60 metres, is highly carbonaceous
and hosts ubiquitous but minor diagenetic (?) copper-pyrite, and on
occasion, extensive albite-microcline alteration centres, pyritic
(cobaltiferous)-quartz veins, and microcline-quartz_+plagioclase veins or
veinlet arrays. The most significant mineralisation, such as at the
Greenrnount prospect, consists of a shallowly dipping package of
alteration zones overprinted by multiple generations of pink-orange
microcline-quartz-chalcopyrite-pyrite-(arsenopyrite) and albite-calcite- phlogopite veins. Accessory mineralogies in most of these mineralisation
styles consist of tourmaline, monazite, rutile, and apatite. Chalcopyrite
(and secondary chalcocite) and gold are associated with each generation
of alteration but are best developed in the later stages of veining. In the underlying Staveley Formation, which is a conformable
transition between the Corella Formation limestones and the Marimo
Shale, chalcopyrite (cobaltiferous)-pyrite mineralisation occurs as
disseminations in pre- and syntectonic breccias, and with disaggregated
silica pseudomorphs (after thinly bedded evaporitic sulphate beds) and
associated dolomitised limestone-calcilutite. Although this mineralisation
may be partly diagenetic in origin the 200 in thick evaporitic packages are
also host to a locally widespread (2 to 4 km long and 200 to >500 metres
wide) and pervasive 'redrock' styled microcline-dolomitehematite
alteration. Within this gross alteration package there also seems to be a
consistent association with narrow (10 to 100 metres wide), linear
(stratabound) semi-massive magnetite-hematite-microcline and
quartz-chalcedony replacement zones. Like much of the nearby Corella Formation the Staveley Formation,
under the Marimo Shale, has undergone dissolution, paleo-solution
karsting (breccias) and tectonic brecciation such that the precursor
lithological details have been progressively obliterated. The
post-diagenetic to post-tectonic fluid pathway development and
metasomatic alteration history of this important lithostructural package of
rocks has been traced from preliminary studies only. The ability to do so
is largely due to the absence of significant regional and contact
metamorphic overprinting, and the local preservation of precursor
sediment profiles. It is proposed that both the base of the Marimo Shale
and parts of the underlying evaporitic-limestone-dololutite have acted as
conformable fluid pathways for hydrothermal and (perhaps)
diagenetically derived, Cu-Au-(Co As) K-Na-Ti-REE bearing, fluids
and brines.