Visualizing the Distribution of Water in Nominally Anhydrous Minerals at the Atomic Scale: Insights From Atom Probe Tomography on Fayalite

Abstract

AbstractNominally anhydrous minerals (NAM) such as olivine are important reservoirs for water in the Earth’s upper mantle, although the association of water with crystallographic defects is poorly understood. Here, hydrated regions at the atomic scale in fayalite (Fe2SiO4) are directly resolved using atom probe tomography. Site‐specific analyses reveal regions that are either compositionally homogenous or contain nanometer‐long channels that are consistent with hydrated defects. Na as a minor element is also enriched within the interlayers, indicating the formation environment is associated with Na geochemically. The ability to directly visualize and characterize hydrated regions at the nanometer scale can provide critical insight into the material properties of NAM and their impact on planetary‐scale processes, such as the influence of water‐bearing minerals on mantle rheology and geodynamics.