Localized nitrogen and hydrogen defect heterogeneities at mineral inclusion interfaces in eclogitic diamonds

The incorporation of nitrogen (N) and hydrogen (H) into the diamond lattice is a fundamental aspect of diamond growth and defect chemistry. While these impurities are typically linked to parental fluids composition, the influence of encapsulated mineral phases on defect distribution remains largely unexplored. This study utilizes synchrotron radiation micro-Fourier transform infrared mapping to resolve the spatial interplay between N and H impurities and mineral inclusions (sulfide, garnet, and graphite) in four eclogitic diamonds from the Yakutian field, Siberian craton.Mapping of the characteristic infrared absorption bands reveals significant point-defect heterogeneities localized at the inclusion-diamond interfaces. A coupled increase in N- and H-related absorbance is uniquely associated with sulfide inclusions, suggesting that sulfides may act as a local source (or sink) for these species during (and following) the entrapment. In contrast, proximity to garnet and graphite only correlates with localized enrichment of H-related defects (specifically the 3107 cm−1, 1405 cm−1, and 3236 cm−1 bands). Previous studies on N and H incorporation in minerals at high pressures and temperatures support our interpretations. In particular, H- enriched zones extend tens of micrometers into the host lattice, indicating that the effective diffusivity of H is either slowed by deep trapping mechanisms (e.g., formation of stable CN and NH complexes) or that the H enrichment halos record a transient re-equilibration with the diamond growth medium. In contrast, a sluggish kinetic would explain the occurrence of nitrogen halos observed adjacent to sulfide inclusions; a continuous, high-concentration chemical source is required to sustain a localized, measurable gradient against billions of years of potential relaxation. These findings provide new insights into the factors governing the spatial distribution and abundance of impurities in diamonds, with broader implications for understanding defect incorporation in both natural and synthetic systems.