I study the circulation of rare earth elements (REE) and other economically strategic metals in the critical zone, specifically the enrichment of these elements to form world class regolith-hosted ore deposits. My research aims to delineate the factors controlling the mobility of these elements in Earth's surface environment, establish the mechanisms of the supergene processes that liberate, transport, and fix these elements in the critical zone, and develop generalized models to illustrate the associated ore formation. I apply mineralogical and geochemical techniques for micro- to nano-scale investigation on the mineral-fluid interaction and research from an integrated approach of interconnected field, experimental, and theoretical perspectives. Currently, I am also investigating the weathering process on granites and carbonatites, and the geomorphological evolution of granitic landscape. My study areas cover Finland, South China, Vietnam, Malaysia, and the US.