Geological and Exploration Characteristics of Iron Oxide-Copper-Gold Deposits: The Australian Experience

Mining Rocks! CIM Toronto 2005
Abstract Australia has several of the best documented and
economically most significant iron
oxide-copper-gold ("IOCG")deposits world-wide.
The deposits formed in late Paleoproterozoic to
early Mesoproterozoic rock systems that have
possible analogs in western North America. All
of these systems involved major thermal events
manifested by batholith-scale magmatism and/or
regional metamorphism. There is also a strong
association with regionally-extensive sodium
metasomatism though this is apparently absent
from the Tennant Creek district which is also
unique in a number of other respects. The
deposits are diachronous and formed in diverse
geological settings characterized by varying host
rock composition/metamorphic grade and physical
conditions of mineralization. Examples formed at
greater crustal depths (e.g. Ernest Henry) have
brittle-ductile structural associations,
magnetite as the the most abundant iron oxide and
occur in varied and zoned alteration systems
involving albitization, potassic alteration and
skarn. Shallow systems ( e.g. Olympic Dam) have
abundant hematite and low temperature silicate
alteration. Cu-Au distribution is commonly
neither well-, nor predictably-correlated with
potential field data meaning that large iron
oxide systems may need extensive drilling before
they are effectively tested.
Keywords: Copper, Gold, Australia, IOCG, Geology, Exploration
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