LANDSCAPE EVOLUTION AS THE CONTEXTUAL KEY FEATURES FOR GREENFIELDS GEOCHEMICAL EXPLORATION IN REGOLITH-DOMINATED TERRAINS: THE ALBANY-FRASER OROGEN-YILGARN CRATON MARGIN, WESTERN AUSTRALIA

Most world-class ores have been discovered close to the surface. Many of these large-tonnage deposits are either mined out or are largely decreasing in production. This situation, coupled with a substantial increase in demand for mineral resources, is driving development of exploration protocols to discover deep ores, by identifying the geochemical footprints of mineral systems at regional scale.

Climatic shifts combined with tectonic stability on large portions of the continental crust have generated thick and extensive weathered cover, across wide areas of Australia, Western Africa, Central-South America and India (Regolith-Dominated Terrains, RDTs).

Mineral exploration in RDTs is challenging due to the lack of fresh bedrock outcrop, and complexity in geochemical identification of geology at depth, since weathering obscures expression of the basement geochemistry, blurring or obliterating the geochemical footprints of mineral systems.

The Yilgarn Craton (YC) and Albany-Fraser Orogen (AFO) of Australia are RDTs. Greenfields mineral exploration protocols have yielded outstanding successful discovery results in the YC over the last 40 years, whereas their effectiveness has been inconsistent uneven for the AFO. Both terrains shared the same tectonic stability, palaeoclimatic evolution, and similar geochemical processes driving element dispersion. However, the sedimentary dynamics and landscape evolution in the YC has been dominated by fluvial systems, whereas in the AFO these were characterized by palaeogeographic changes of an adjoining coastline with a complex network of islands and estuarine zones driven by multiple transgression–regression cycles.

This variation in the context of regolith framework becomes an essential element to better understand surface geochemical features at a large scale, and therefore to identify mineral systems undercover. The understanding of landscape evolution at cratonic scale is a critical element in greenfields mineral exploration in RDTs.