The Oceanic Signature in Diamond: From Hydrothermal Alteration to Defect Architecture

Diamonds provide exceptionally durable records of geological processes occurring within Earth’s mantle, preserving information through mineral and fluid inclusions, isotopic compositions, growth structures, impurities, and lattice defects. Increasing evidence demonstrates that altered oceanic crust and serpentinized oceanic mantle can be transported into the deep Earth through subduction and subsequently contribute to diamond-forming systems. However, whether the influence of recycled oceanic material can be recognized through an integrated combination of diamond-scale chemical and spectroscopic characteristics remains unresolved. Here, we propose the Oceanic Signature Hypothesis (OSH), which predicts that diamonds formed in systems involving recycled oceanic lithosphere or oceanic-derived fluids should exhibit statistically distinguishable combinations of isotopic, inclusion, chemical, growth-related, and spectroscopic characteristics relative to diamonds formed predominantly from non-oceanic mantle reservoirs. We develop a conceptual framework linking seawater alteration of oceanic lithosphere, subduction, dehydration and melting, fluid–rock interaction, and diamond crystallization. We further evaluate the geological information potentially preserved through mineral and fluid inclusions, stable isotopes, nitrogen systematics, cathodoluminescence, Fourier-transform infrared spectroscopy, photoluminescence, and trace-element chemistry. Rather than predicting a unique “marine” crystallographic defect, the OSH proposes that oceanic influence may emerge as a multidimensional architecture produced by the interaction between recycled materials and diamond-forming environments. We outline a falsifiable research strategy based on independently constrained geological provenance, spatially resolved characterization of individual diamonds, appropriate non-oceanic controls, and multivariate statistical analysis. The proposed framework provides a testable approach for determining whether the geological consequences of oceanic recycling can be reconstructed from the internal architecture of natural diamonds.