Geochemical Signatures of Hydrothermal Fluids in Marine Sediments from the Mid-Atlantic Ridge: Implications for Mantle Composition and Seafloor Mineralization

Abstract:

This study investigates the geochemical signatures of hydrothermal fluids in surface sediments (0–20 cm) from 48 sampling sites along the Mid-Atlantic Ridge (MAR), covering the North Atlantic (20°N–45°N), Equatorial Atlantic (0°–10°S), and South Atlantic (20°S–40°S) segments. Samples were collected between 2021–2023 using remotely operated vehicles (ROVs). Hydrothermal anomalies are identified by elevated concentrations of chalcophile elements (Cu, Zn, Pb, Au), lithophile elements (Li, B, As), and rare earth elements (REEs), with ΣREE ranging from 32.6 to 189.4 mg/kg (average=87.3 mg/kg). Stable sulfur isotopes (δ³⁴S) of sulfide minerals range from -4.2‰ to 6.8‰ (VCDT), reflecting mixed mantle-derived (magmatic) and seawater sulfur sources. Trace element ratios (Li/Y, B/Nb, Zr/Hf) indicate that hydrothermal fluids are derived from partial melting of a depleted mantle with minor enriched mantle components. Seafloor mineralization associated with hydrothermal activity is characterized by sulfide-rich zones (Cu-Zn-Pb sulfides) and oxide-rich zones (Fe-Mn oxides), with Au concentrations reaching up to 2.8 ppm in mineralized sediments. This study provides new insights into mantle composition and hydrothermal processes along the MAR, supporting exploration for seafloor mineral resources and understanding of oceanic crust formation.