The Influence of the East Pacific Rise Hydrothermal Field on the Distributions of Dissolved Fe, Mn, Zn, Cu and Cd in the South Pacific

Abstract:

East Pacific Rise (EPR) hosts the largest hydrothermal field in the world. The concentrations of dissolved key trace metals (Fe, Zn, Cu and Cd) were determined in the seawater samples collected from EPR to Tahiti in the South Pacific along 10-15 ºS during U. S. GEOTRACES 2013 by means of Mg(OH)₂ co-precipitation isotope dilution method using ICP-MS. Dissolved Mn was determined in these samples using a new method combining Mg(OH)₂ co-precipitation with calibration with external standards of ⁵⁷Fe, ⁵²Cr and ⁵⁹Co. The results show substantial mid-depth maxima of Fe and Mn extended from EPR. These hydrothermally-enriched Fe and Mn show long-distance westward transportation to the central South Pacific. The mid-depth enrichment of Zn was also observed at stations close to EPR. In contrast, Cu and Cd show depletions around the hydrothermal vent near EPR. Overall the results suggest that hydrothermal activity is a source for Fe, Mn and Zn and a sink for Cu and Cd.