Global on-axis hydrothermal element fluxes at submarine plate boundaries

Estimates of on‑axis hydrothermal element fluxes commonly assume that basalt‑hosted, black smoker‑type vent fluids dominate global hydrothermal cooling of the oceanic lithosphere. However, hydrothermal vent fluids exhibit substantial compositional diversity related to different substrate types (basaltic, ultramafic, sedimented, intermediate‑felsic) and geological settings (mid-ocean ridges, back‑arc spreading centers, volcanic arcs), which has not yet been adequately incorporated into global flux estimates.

Here, we account for this diversity by analyzing the current plate boundary configuration and a global database of hydrothermal vent fluid compositions (MARHYS Database, Version 4.0). We calculate weighting factors for the relative contributions of different hydrothermal fluid types to lithospheric cooling by integrating ridge and arc strike lengths, spreading rates, and substrate distributions across plate boundary types. Using these weighting factors, we estimate the partitioning of vent fluid types and quantify global submarine on-axis hydrothermal element fluxes.

We show that element-to-energy flux ratios vary significantly among geological settings and differ markedly from characteristics of purely basalt-hosted, fast-spreading ridges. As a result, substantially different fluxes are obtained for several key elements (e.g., H₂, CH₄, Fe) associated with hydrothermal cooling across diverse plate boundaries and substrate types. Our results demonstrate that oceanic element fluxes are regionally variable and that the partitioning of plate boundary types (e.g., ultraslow versus fast‑spreading ridges; volcanic arcs and back‑arc spreading centers versus mid‑ocean ridges) plays a major role in regulating element transfer between the oceanic crust and the ocean over geological timescales.