Temporal evolution of the Pobeda hydrothermal site (MAR): Utility of proximal sediment cores

Abstract

Temporal evolution of hydrothermal processes used to be reconstructed based on chemistry and chronology of the sediments around vent fields. However particle-by-particle deposition of metalliferous sediments proximal to sulfide mounds is usually superimposed by mass-wasted events. Quantitative assessment of the relative amount of slumped sulfide debris and plume fallout matter in metalliferous sediments has been done for ∼83 kyr on Pobeda hydrothermal site at the 17°08′ N, Mid Atlantic Ridge.Three sediment cores have been investigated for uranium series isotopes and rare earth elements (REE). Their distribution patterns with an enrichment in heavy REE, a weak positive Eu, and negative Ce anomalies give evidence to the contribution of slumped sulfides from nearby edifices. The 230ThU radiochronology dataset for distal and proximal metalliferous sediments and sulfide deposits from different Atlantic and Pacific hydrothermal sites allowed for the distinction between sediments containing oxidized sulfide debris and those derived predominantly from plume fallout oxyhydroxide particles in terms of 230Th/Fe vs. U/Fe ratios. The calculated amount of plume particulates and the sedimentation rate for each core allowed accurate temporal reconstruction of the hydrothermal activity within the Pobeda site through a novel approach.