Using surface regolith geochemistry to map the major crustal blocks of the Australian continent

Multi-element near-surface geochemistry from the National Geochemical Survey of Australia has been evaluated in the context of mapping the exposed to deeply buried major crustal blocks of the Australian continent. The major crustal blocks, derived from geophysical and geological data, reflect distinct tectonic domains comprised of igneous, metamorphic and sedimentary rock assemblages representing a time scale ranging from early Archean to recent Cenozoic. The geochemical data have been treated as compositional data to uniquely describe and characterize the geochemistry of the major crustal blocks across Australia according to the following workflow: imputation of missing/censored data, log-ratio transformation, multivariate statistical analysis, classification/allocation, and multivariate geospatial (minimum/maximum autocorrelation factor) analysis. Using cross validation techniques the uniqueness of each major crustal block has been quantified. The abilities to predict (1) the membership, or lack thereof, of a surface regolith sample to one, or none, of the major crustal blocks, and (2) the major crustal block at sites that have not been sampled are demonstrated. In conclusion, the surface regolith of the Australian continent contains a geochemical record of the original crustal block composition, despite secondary modifications due to physical transport and chemical weathering effects. Citation: E.C. Grunsky, P. de Caritat, U.A. Mueller, Using surface regolith geochemistry to map the major crustal blocks of the Australian continent, Gondwana Research, Volume 46, 2017, Pages 227-239, ISSN 1342-937X, https://doi.org/10.1016/j.gr.2017.02.011