Showing papers by "Roussos Dimitrakopoulos published in 2001"

Quantitative Analysis of Mineral Resources for Strategic Planning: Implications for Australian Geological Surveys

Abstract: A quantitative valuation study has been made of Australian state surveys with the specific goals of (1) establishing the 'worth' of current programs upgrading state government geoscientific information infrastructure, and (2) considering the results of the valuation in terms of strategic planning. The study has been done from the perspective of the community as a whole and has been undertaken in two phases reflecting the different objectives of Australian state surveys in terms of the exploration industry and government policy-making. This paper reports on the second part of this valuation process, measuring the impact of upgraded survey data on government mineral policy decision processes. The valuation methodology developed is a comparative approach used to determine net benefit foregone by not upgrading information infrastructure. The underlying premise for the geological survey study is that existing and upgraded data sets will have a different probability that a deposit will be detected. The approach used in the valuation of geoscientific data introduces a significant technical component with the requirement to model both favorability of mineral occurrence and probability of deposit occurrence for two different generations of government data. The estimation of mineral potential uses modern quantitative methods, including the U.S. Geological Survey three-part resource-assessment process and computer-based prospectivity modeling. To test the methodology mineral potential was assessed for porphyry copper type deposits in part of the Yarrol Province, central Queensland. Results of the Yarrol case study supports the strategy of the state surveys to facilitate effective exploration by improving accuracy and acquiring new data, as part of resource management. It was determined in the Yarrol Province case study that in going from existing to upgraded data sets the area that would be considered permissible for the occurrence of porphyry type deposits almost doubled. The implication of this result is that large tracts of potentially mineralized land would not be identified using existing data. Results of the prospectivity modeling showed a marked increase in the number of exploration targets and in target rankings using the upgraded data set. A significant reduction in discovery risk also is associated with the upgraded data set, a conclusion supported by the fact that known mines with surface exposure are not identified in prospectivity modeling using the existing data sets. These results highlight the absence in the existing data sets of information critical for the identification of prospective ground. Quantitative resource assessment and computer-based prospectivity modeling are seen as complementary processes that provide the support for the increasingly sophisticated needs of Australian survey clients. Significant additional gains to the current value of geoscientific data can be achieved through the in-house analysis and characterization of individual data sets, the integration and interpretation of data sets, and the incorporation of information on geological uncertainty.

Integration of assay and cross-hole tomographic data in orebody modelling: joint geostatistical simulation and application at Mount Isa mine, Queensland

Abstract: An extended conditional indicator simulation method is described that can be used to integrate cross-hole tomographic data with traditional diamond drill-hole assay data. The non-parametric, stochastic simulation algorithm allows modelling based on the 'hard' assay data while 'soft' tomographic data are used where appropriate, having regard to their quality or accuracy and compatibility with the assay data. The technique is demonstrated through an application at Mount Isa copper mine, Queensland, Australia, where it was used to integrate cross-hole conductivity data obtained by the radio imaging method into orebody modelling on the basis of Cu assay data. Modelling based on the direct integration of diverse data is a promising and powerful tool for advanced orebody modelling.