Onset of zircon decomposition during saprolitic weathering

Abstract

Abstract Zircon is conventionally considered as refractory in supergene environments, enabling the preservation of geochemical records for tracing various Earth’s processes and the use of the zircon structure as a nuclear waste form. However, how refractory zircon is during weathering, especially when crystalline and in an early stage of weathering, is unknown. In this study, we demonstrate that crystalline zircon would start to weather during an early-stage saprolitic weathering. Nano-scale examination reveals that weathering of zircon proceeds through dissolution of primary, crystalline zircon and precipitation of secondary, amorphous zircon. Non-formula elements, like U, Th and heavy rare earth elements, are uptake and structurally incorporated in this process. Thereby, metamictisation of the zircon would accelerate and eventually promote the dissolution of zircon. In supergene environments, zircon would steadily weather, calling for further evaluation on the geological and environmental applications of zircon.