The size and scope of copper in Australia

By Jeames McKibben, Matthew Stephens and Stefan Mujdrica of Xstract Mining Consultants*

With the boost in development of copper projects in recent years and some significant discoveries over the last three decades, the exploration dollar now needs to be squeezed even harder and further. Advances in technology will also assist explorers to identify new copper-rich deposits in years to come.

Australia currently ranks fifth in the world, accounting for 6 per cent of global copper production after Chile (37 per cent), Peru and the USA (both tied at 8 per cent) and China (6 per cent).
Australia holds the world’s second largest resource base (12 per cent) after Chile (30 per cent) but ahead of the USA and Indonesia (both 7 per cent) and Peru, Poland and Mexico (all 6 per cent). Australia’s estimated copper resource base rose by 13 million tonnes in 2008 to 120 million tonnes.
Between 1999 and 2006, the copper price surged, rising from US $0.60 to US$ 3.75 per pound of copper, a five-fold increase. This rapid rise fuelled the desires of many small to mid-tier exploration and mining companies to advance rapidly towards production by acquiring prospective ground and delineating resources.
At the same time, improvements in drilling techniques, acid soluble copper assaying, advanced extractive metallurgy for copper, the introduction of heap leach, SX-EW (solvent extraction electro winning) operations and more effective grade control techniques in both open pit and underground mining, resulted in previously classified, lower grade, sub-economic resources becoming suddenly viable.
The new Millennium heralded the major discoveries of Prominent Hill and Carrapateena in South Australia, along with Rocklands/Las Minerales near Cloncurry in Queensland. Resurrections of old copper mines along with nearby discoveries and additions saw a marked increase in copper mining, development and exploration.
More than two dozen old copper mining areas in Australia were regenerated in the last ten years, the majority of which were in Queensland, South Australia and New South Wales.
Australia now has approximately 15 “great copper provinces” i.e. geologically and structurally defined areas in which copper deposits of variable size and style exist. These areas also contain historic workings as well as new discoveries and rejuvenated old mines.
These provinces have been arbitrarily labelled by their geologic/geographic region and are, in no particular order, Isa Block and eastern Tasman Fold Belt in Queensland; Stuart Shelf, Gawler Craton and Adelaide Geosyncline in South Australia; Eastern and Western Lachlan Fold Belt in New South Wales; the Paterson, Yilgarn, Bangemall and Pilbara in Western Australia; the Arunta, Tennant Creek and Pine Gap in the Northern Territory; and Dundas in Tasmania.
The two main variants of copper occurrences within every province are size and style. Size can be broken down into three simplified categories based on historical and current copper production. The first category is defined by those provinces in which more than 10 million tonnes of copper has been produced and currently this includes the Isa Block and Stuart. The next category lies between 1 and 10 million tonnes produced and there are five such Provinces, namely Eastern Lachlan, Gawler, Paterson, Yilgarn and Dundas. The third group are those that produced between 100 thousand and 1 million tonnes such as Eastern Queensland, Western Lachlan, Adelaide, Arunta, Tennant Creek, Pine Gap, Bangemall and the Pilbara.
Deposit styles also vary within each province, with no clear correlation universally apparent between size and deposit type. For example, there are some very large IOCG (Iron Oxide Copper Gold) deposits such as Olympic Dam, Ernest Henry and Prominent Hill but equally there are some smaller producers which can be found in the Tennant Creek Province for example. Porphyry copper deposits also can be quite significant in size (e.g. Cadia/Ridgeway) but more often are smaller and lower in copper grade (i.e. uneconomic/sub-economic), such as those occurring along the eastern coast of Queensland.
Volcanogenic (Hosted) Massive Sulphide, Replacement/Epigenetic, Sediment/Breccia Hosted and Hydrothermal Replacement make up the rest of the majority of deposit styles for major Australian copper mines.
Another point worth noting is that there are also occurrences within some provinces where there are major size variations within the one deposit style. The Mount Isa Block is an example of this scenario wherein there are literally dozens of similar style deposits ranging in size from a few thousand tonnes to hundreds of millions of tonnes of copper that has been produced.
As mentioned previously, there has been an exponential increase in metals exploration within Australia over the last 30 years and significant discoveries have been achieved. However, due to the application of more advanced, thorough and diligent exploration techniques, a lay person could be forgiven for assuming with certainty that the days of finding a major outcropping or sub-cropping copper deposit are very limited to non-existent. Essentially this means that now the ever important exploration dollar must be squeezed even harder and further. This won’t be an easy task given that copper explorers must now drill deeper in their attempts to locate additional resources.
Clearly, there is a case for progressing from purely the search below and outwards from the known copper deposits and brownfield areas towards more greenfield type areas which lie beyond explorers traditional ‘comfort zones’.
The old saying of “looking for elephants in elephant country” still rings true for copper explorers within Australia as the majority of exploration dollars and efforts are being applied to our two greatest copper producing provinces i.e. around Mount Isa – Cloncurry and Olympic Dam – Prominent Hill. Areas such as these offer the greatest possibilities for return not only for the obvious reason of hosting large deposits but also because they have most of the prospective host rocks buried below varying depths of surficial cover . This cover alone would have excluded most of the earlier explorers from either their initial investigation and/or not finding anything near surface. Advances in exploration techniques which provide explorers with the ability to visualise deeper into the crust will assist with identifying new copper-rich deposits. Olympic Dam is an example where geophysical techniques such as aeromagnetic and gravity data facilitated in the discovery of a world-class mineralised system.
Given that there is approximately 1014 tonnes of copper in the top one kilometre of the earth’s crust (albeit mostly uneconomic), it is likely that we will be exploring for and mining copper in Australia at successively lower grades and at deeper depths for many years to come.

* Stefan Mujdrica, general manager of geology and technologies at Xstract Mining Consultants, will be presenting a paper at the upcoming Australian Copper Conference in Brisbane.
Xstract’s team of consultants and specialists have extensive operational and consulting experience in the fields of geology, resource/reserve estimation, mine engineering and planning, mineral processing, mineral asset valuation and business analysis.
For more details on the information contact tel: +61 (0)7 3221 2366; email: jmckibben@xstractgroup.com; or visit: www.XstractGroup.com