Major Advances in Exploration Geochemistry, 1998-2007

Exploration geochemistry continues to be a major contributor to mineral exploration programs at all scales. The decade has spanned a complete economic cycle in the minerals industry, during which there has been a change in exploration emphasis from the dominance of Au and diamonds to the addition of a range of base metals and the recent revival of U exploration. Increasing metal prices and the development of new geochemical techniques have allowed exploration activity to expand in previously underexplored terrains, including those characterised by thick, transported regolith cover. There has been significant evolution and refinement of geochemical dispersion models for transported regolith, especially processes associated with oxidizing sulphide mineralisation. These models have prompted further developments in sampling methods, analytical techniques and approaches to anomaly detection. The routine measurement of fundamental soil and groundwater properties, such as pH, has been demonstrated to assist in detecting geochemical and mineralogical effects of buried mineralisation on regolith. New lithogeochemical techniques have been developed for terrane selection and early discrimination of potentially mineralised units. The production of regolith-landform maps, including 3-D models, and more detailed techniques for differentiating the origin and nature of regolith materials now underpins the design of exploration programs in a number of terrains. Various exploration techniques, such as biogeochemistry and soil gas, have been revitalised by the application of new technologies. Ongoing improvements to detection limits and the reliability of multielement analytical methods have permitted development and routine application of a wide range of selective geochemical extraction methods aimed at detecting subtle geochemical haloes developed in transported regolith cover. The results from a plethora of selective extraction orientation studies have, however, indicated the reliability of such methods to be uncertain, especially in arid terrains. Low-density geochemical mapping of large regions has been undertaken by government agencies for a variety of resource, environmental and health purposes, including attracting mineral exploration. Such maps typically demonstrate the dominance of underlying geology on regional geochemical patterns in regolith, even in industrialised regions. Philosophical and numerical approaches to defining and detecting geochemical anomalies continue to be reviewed. There is a need to supplement classical parametric outlier-detection approaches, routinely applied to geochemical data, with statistical techniques that reflect a recognition that subtle, multivariate patterns related to the geochemical effects of mineralisation may emanate from within the main data cloud and not outlying or distinct clusters. Future directions will likely include further convergence of exploration and environmental geochemistry and more substantial consideration of the effects of biological systems in understanding the processes involved in element mobility in the surficial environment. There will be an increased role for isotope analysis in terrane selection and mineralisation detection. An increasing risk to the technical capacity of the minerals exploration sector to discover new deposits is the progressive decline in the number of universities offering suitable geoscience programs.