Copper-gold deposits associated with iron
oxide rich rocks (ironstones) form a distinctive
and significant ore association which occurs
widely, but not exclusively, in the Proterozoic.
The ironstone association is geochemically
distinct from the BIF-hosted gold association
(Phillips and Groves, 1983). Not only is the
former association higher in its copper and
commonly uranium, FEE, ±bismuth, molybdenum
contents, but also the ironstones in many cases
do not originate as chemical sediments. Although
both associations form in metamorphic environs,
they reflect differing tectonostratigraphic
settings and with consequent differences in
ore-forming fluids and ore-forming mechanisms.
This paper discusses the nature and origin of the
ironstone-related copper-gold association, with
particular reference to the Tennant Creek
district in northern Australia, and emphasises
the two stage origin of mineralisation. The
genetic model developed has significant
implications for other ore-bearing environments.