Résumé
The upper mantle is critical for our understanding of terrestrial magmatism, crust formation 5 element cycling between Earth's solid interior, hydrosphere, atmosphere, and biosphere. Mantle composition and evolution has been primarily inferred via surface sampling and indirect methods. We recovered a long (1268 m) section of serpentinized abyssal mantle peridotite, interleaved with thin gabbroic intrusions. We find depleted compositions, with significant variations in mantle mineralogy controlled by melt flow. Dunite zones have predominantly 10 intermediate dips, in contrast to the originally steep mantle fabrics, indicative of oblique melt transport. Extensive hydrothermal fluid-rock interaction is recorded across the full depth of the core and is overprinted by oxidation in the upper 200 m. Alteration patterns are consistent with vent fluid composition in the nearby Lost City hydrothermal field.