Trends In Australia's Economic Demonstrated Resources Of Major Mineral Commodities

• Black Coal
• Bauxite
• Iron Ore
• Figure 1: Trends in Economic Demonstrated Resources (EDR) for major commodities since 1975
• Gold
• Nickel
• Copper
• Mineral Sands
• Uranium

The trends in EDR for Australia's major mineral commodities have undergone significant and sometimes dramatic changes over the period 1975-2007 (Fig. 1). These changes for each commodity can be attributed to one, or a combination of the following factors:

• increases in resources resulting from discoveries of new deposits and delineation of extensions of known deposits,
• depletion of resources due to mine production,
• fluctuations in commodity prices and currency exchange rates which can move previously subeconomic resources into EDR,
• advances in mining and metallurgical technologies, eg. carbon-based processing technologies for gold have enabled economic extraction of gold from low-grade deposits which previously were uneconomic,
• adoption of the resource classification scheme (JORC Code) 1 by the Australian minerals industry and the subsequent impacts on re-estimation of ore reserves and mineral resources to comply with the requirements of the Code. Many companies re-estimated their mineral resources to comply with the Code and some re-assessment was made of resource data for other deposits identified by Geoscience Australia's predecessor, the Bureau of Mineral Resources. The impacts of the Code on EDR occurred at differing times for each of the major commodities.

Past trends and changes in EDR for a number of Australia's major mineral commodities are discussed below.

A major re-assessment of New South Wales coal resources during 1986 by the NSW Department of Mineral Resources and the Joint Coal Board resulted in a large increase in black coal EDR as reported in 1987 (refer 'a' on Fig. 1).

EDR for black coal has declined since 1998 due to the combined impacts of mining companies re-estimating ore reserves and mineral resources more conservatively so as to comply with requirements of the JORC Code, and increased rates of mine production.

Increases in bauxite EDR in 1989 resulted from delineation of additional resources in deposits on Cape York Peninsula ('b' on Fig. 1). Decreases in bauxite EDR in 1992 were due to re-classification of some resources within deposits on Cape York Peninsula so as to comply with requirements for the JORC Code ('c').

EDR for iron ore declined from 1996 to 2001 due to the combined impacts of mining companies re-estimating ore reserves and mineral resources more conservatively so as to comply with requirements of the JORC Code, and increased rates of mine production. However since 2003 EDR has increased due to reclassification of magnetite resources to economic, newly reported resources and increases in resources at some major mines.

Gold EDR has increased steadily since 1975 with a clear increase in the rate of growth since 1983. Much of the increase can be attributed to the successful introduction of the carbon-based processing technology which allowed the profitable processing of relatively low grade ore deposits. In addition, the higher than previous prevailing gold prices (denominated in US$) supported high levels of exploration for gold to the extent where gold accounted for over half of the total mineral exploration expenditure in Australia for many years. Increased exploration contributed to the increases in EDR.

The EDR for nickel increased during the period 1995 to 2001 by 18.2 Mt. This was mainly due to progressive increases in resources of lateritic deposits at Bulong, Cawse, Murrin Murrin, Mt Margaret, Ravensthorpe (all in WA), Marlborough (Qld), Syerston and Young (NSW). Australia's EDR of nickel doubled in 2000 (compared to the level at the end of 1999) - this dramatic increase was due to further large increases in resources at the Mt Margaret and Ravensthorpe deposits, and other lateritic deposits in the Kalgoorlie region (WA). In addition, during the period 1995 to 2001 there were increases in resources of sulphide deposits at Yakabindie, and discoveries of the Silver Swan and Cosmos high-grade sulphide deposits (all in WA).

From 2001 onwards, the sharp rises in market prices for nickel led to increased expenditures on exploration and on evaluation drilling at many known deposits. This contributed to further increases in total EDR for sulphide deposits at Perseverance, Sally Malay, Maggie Hays, Anomaly 1, Honeymoon Well, deposits in the Forrestania area as well as new deposits at Prospero and Tapinos (all in WA), Avebury (Tas), and remnant resources at several sulphide deposits in the Kambalda region including Otter-Juan and Lanfranchi groups of deposits.

From 2001 onwards EDR there has been only minor increases in nickel EDR because increases in resources for some deposits have been offset by companies reclassifying their lateritic nickel resources to lower resource categories pending more detailed drilling and resource assessments.

Following the adoption of the JORC Code by the Australian mineral industry, many companies first used this code for reporting their copper resources in 1989. These companies re-estimated mineral resources in order to comply with the Code. This resulted in a sharp fall in Australia's copper EDR in 1989 ('d').

The sharp increase in copper EDR in 1993 was due mainly to an increase in company announced resources for Olympic Dam deposit (SA). Additional resources were also reported for Ernest Henry (Qld), North Parkes (NSW) and other smaller deposits ('e').

Re-assessments of copper resources by Geoscience Australia in 2002 and 2003 resulted in further transfers (reclassification) of Olympic Dam resources into EDR ('f'). In 2007, copper resources increased by 40% mainly due to a large increase in resources for Olympic Dam. Drilling over recent years has outlined large resources in the south eastern part of the deposit.

The adoption of the JORC Code in 1988 by the Australian mineral industry led to a re-estimation of mineral resources by many companies to align with the Code, and some re-assessments of resource data for other deposits by the former Bureau of Mineral Resources. This resulted in a sharp fall in Australia's lead and zinc EDR in 1989 ('g').

Increases in EDR for lead and zinc in 1993 were due to re-classification of paramarginal demonstrated resources into EDR for McArthur River (NT) and Hilton deposits (Qld). Additional resources were also reported for Century and Cannington deposits (Qld) ('h').

Increases in EDR of ilmenite from 1996 to 2003 resulted from discovery and subsequent evaluation drilling of heavy mineral sands deposits in the Murray Basin - these deposits are in Victoria (Wemen and Woornack), New South Wales (Gingko and Snapper) and South Australia (Mindarie project). In addition, from 1998 onwards there were progressive increases in resources at mineral sands deposits in the North Swan Coastal Plain area north of Perth, and the Blackwood Plateau region (includes the Beenup deposit) in Western Australia.

The majority of Australia's uranium deposits were discovered between 1969 and 1975 - approximately 50 deposits (15 with significant resource estimates) were discovered during this short period. Since 1975, only another six deposits have been discovered - of these, only two deposits (Kintyre in the Paterson Province, WA and Junnagunna, north west Qld) have Reasonably Assured Resources recoverable at less than US$80/kg U (equates with EDR). Hence, the progressive increases in Australia's EDR for uranium from 1975 to the present (as shown in Fig. 1) were largely due to on-going delineation of resources at known deposits.

From 1983 onwards, the Olympic Dam deposit has been the major contributor to increases in Australia's EDR. The large increases shown on Fig. 1 were due to the following:

• in 1983, initial resource estimates for Olympic Dam and Ranger No. 3 Orebody (NT) made by the former Australian Atomic Energy Commission ('i').
• in 1993, further increases in EDR for Olympic Dam (based on estimates reported by WMC Resources Ltd), and first assessment of resources for the Kintyre deposit by the former Bureau of Mineral Resources ('j').
• in 2000, increases were due to continuing additions to the Olympic Dam resources.
• in 2007, major increase in EDR for Olympic Dam. Drilling in recent years has outlined major extensions to the south eastern part of the deposit.