Finding greenfield areas in the brownfield geochemical database, Queensland

Geochemical exploration has been utilized in Queensland for 70 years, targeting mainly the outcropping geology that covers approximately 30% of the State. The Geological Survey of Queensland has compiled and released 5.6 million geochemical and drill-hole data that have been extracted from exploration reports and academic publications. Although these data were intended to expedite exploration in Queensland, they have also led to a common misconception that all near-surface economic deposits within the well-exposed and explored areas have been discovered, effectively and indirectly sterilising these grounds from further exploratory work. A thorough appraisal of the current exploration data demonstrates that most of the well-sampled areas in Queensland are under-explored. Past exploration techniques applied mineralisation models of the time, targeting narrow search corridors in which samples were analysed for a limited number of targeted elements. Identifying data gaps and the removal of poor-quality data expose extensive greenfield areas within the broader brownfield areas. The latter therefore remain essentially under-explored for such commodities. This fact necessitates exploration focus on these under-explored regions, considering the current demands for rare-earth, battery and technology metals. An effective discriminant for data quality is to use the baseline elemental concentrations of geologic units as the normalising factor to establish whether the geochemical results are sensitive enough for geochemical exploration. Low-precision data have detection limits few magnitudes above their rock background concentrations and are inappropriate for exploration. Re-sampling and/or re-assaying is/are necessary if existing samples have not been analysed for the desired commodity, if target areas have not been sampled, or if the current data are of low quality. As all data in the Queensland geochemical database are referenced to a company or report, it is possible to track archival samples to previous explorers. If these samples are not available, a new field campaign will be required to acquire new samples of high data quality.