Brownfields Exploration is defined as exploration of areas of favourable geology extending from adjacent to mines and mineral deposits to distances limited only by the economic transport of ore to an existing mill. Such data-rich areas have exciting potential for new insights based on informed compilations (especially in 3D).

The two-fold aim of this theme is:

• to increase the cost-effectiveness of Brownfields Exploration though improved targeting of new deposits, and;
• to avoid value destruction in mature areas.

Research will initially be directed to exploration for orogenic and intrusion-related gold, sulphide nickel and high grade, low P, BIF-hosted iron ore.

Issues and Challenges

Brownfields Exploration is inherently lower risk than Greenfields Exploration because of its proximity to existing mines. Nevertheless, value can be destroyed if exploration is continued after all substantial economic deposits in the district have been discovered.

Brownfields Exploration now accounts for more than 70% of mineral exploration expenditure in WA. Its effectiveness will determine the medium term outlook for maintaining current levels of production of the higher value mineral commodities (Au, Ni, Co, Cu, Pb, Zn). These commodities represented about 33% of total mineral production in WA in 2001-02 and more than 80% of exploration expenditure. Success in Brownfields Exploration is also the key to maintaining current levels of production of the most valuable component of the State’s iron ore exports i.e. high grade, low P, BIF-hosted ore.

Gold accounts for over 60% of mineral exploration expenditure in WA and, since 1997, this expenditure has been increasingly focussed on Brownfields Exploration. However, the fact that gold production has declined by 22% over the last five years illustrates the need for higher value outcomes.

Outputs, Outcomes and Strategies

• Improved empirical models based on extensive data sets that identify critical parameters such as geology, geometry, geochemistry, geochronology, rheology, size distribution, cluster characteristics, and grade quality and variability.
• Compilations of geophysical and geochemical signatures of these deposits, including their primary and surface expressions.
• Practical exploration tools based on integration of the above with outputs from the progressive risk and value analysis theme. These tools will consist of key elements distilled from the above data sets, linked to the business principles of exploration, in a readily accessible form.
• Graduates with strong training in basic geology, data integration and the application of targeting research to mineral exploration.

These outputs will be of direct value to industry. Improved empirical models and signature recognition will lead to better target selection and the practical exploration tools should lead to more cost effective exploration. To achieve them, the following strategies will be employed:

• Work from the inside out (from the known to the unknown) employing a wide range of scales; for example, from detailed mine scale to around 25km from the headframe/open pit. Integrate observations across this range of scales.
• Ensure that empirical data sets and models have a strong geological foundation based on critical observations in the field.
• Work closely with pmd*CRC and the Minerals and Energy Research Institute of Western Australia (MERIWA) projects, to avoid overlap and deliver mutual benefits wherever practical.
• Establish strong links to the principal sources of new and existing data (including company data where available) relating to the study of orogenic and intrusion-related gold, sulphide nickel and high grade iron ore deposits. Examples are CSIRO, the Geological Survey of Western Australia (GSWA), Geoscience Australia (GA) and other research groups in Australia and overseas. Optimise access to their past and current outputs.
• Encourage and engage in collaborative research that will enhance CET’s capacity to deliver outputs. For example: the regolith expression of primary geochemical signatures (with CRC LEME); the enhancement of geophysical signatures with CSIRO and GA); and the presentation and accessibility of 3D outputs (Fractal and pmd*CRC).

Actions and Resources

During the first two years, the emphasis will be on extracting maximum information relating to orogenic and intrusion-related gold, sulphide nickel and high-grade iron ore deposits from the extensive data in the literature and theses, and from industry, where accessible. The identification, selection and compilation of data will be based on a developing appreciation of what is most relevant to robust empirical models and exploration targeting.

Analysis of this data will focus on identifying vectors to ore within larger mineralised systems, and critical factors that appear to influence ore quality. The resulting parameters will be addressed in new industry-linked, field-based projects that can include both new deposits and revisiting previously studied deposits.

The data will also be used to provide more robust information on geometry, physical properties and mineralogy that will assist in predicting, interpreting and optimising the geophysical signatures of deposits and mineralised environments. Comparable information for the mineralogy and geochemistry of the primary zone will be transferred to collaborative research projects with CRC LEME to improve geochemical signature recognition in the regolith.

It is anticipated that around 30% of the Centre’s resources will be devoted to this theme; the pro tem theme leader will be Associate Professor Steffen Hagemann.

Possible Projects

• Produce robust empirical models for orogenic gold deposits in the Yilgarn Block through data compilations and field documentation.
• Compile atlases of primary and secondary geochemical signatures of gold and sulphide nickel deposits, with the emphasis on WA.
• Extend the critical parameters of gold and sulphide nickel deposits into the 3D definition of targets* and consolidate this knowledge into the development of 3D prospectivity mapping software in collaboration with Fractal..
• Identify the critical parameters of high-grade orogenic gold ore shoots in 3D*.
• Identify vectors to ore* (eg, gold, sulphide nickel, high-grade iron ore) and develop innovative visualisation tools · Develop criteria for early recognition of major new mineralised systems within the Brownfields environment..
• Develop bolt-on software to proprietary products for practical functions. For example, converting original rock type and metamorphic grade to rheological index in a GIS environment.

* This would require appropriate modelling input from ESMG.