Manuel Knorsch: An introduction to clay-hosted REE deposits in Australia

Rare earth elements (REEs) are on the critical mineral list in multiple countries due to their application in renewable technologies, electromobility, and defence. Exploration in Australia focusses on clay-hosted REE deposits, which may have a higher proportion of heavy REEs (e.g. terbium and dysprosium) relative to light REEs. Several studies were published on (ionic) clay-hosted REE deposits in South China and Madagascar, and little is known about the mineralogy and viability of clay-hosted REE projects in Australia. A review of exploration activity identified 88 clay-hosted REE projects in Australia, most of which are in the Yilgarn Craton, Albany-Fraser Orogen, and the Gawler Craton. Thirteen Mineral Resource Estimates have been completed that have a median grade of 840 ppm TREO (total rare earth oxide) and 98 million tonnes (Mt) across all resources. Our microcharacterisation study has identified monazite, bastnaesite, allanite, zircon, and apatite as the main REE sources in granitic-to-mafic protoliths which are (partially) broken down during weathering. Secondary REE minerals such as aluminium phosphate sulphate (APS) group minerals, rhabdophane, bastnaesite, and cerianite form in the regolith profile. This talk documents the intense exploration activity in Australia over the last two years, presents microcharacterisation data to identify the deportment of REEs, and outlines some mineral system criteria.