Fe Isotopic Composition Heterogeneity of Seawater Profiles and Its Influence Factors
Wang Jianqiang
Li Xiaohu
Bi Dongwei
Wu Xichang
Chu Fengyou
Abstract：The isotopic compositions of Fe in the seawater profiles are remarkably heterogeneous.Dissolved Fe concentrations and Fe isotopic compositions in the seawater from the mid-ocean ridge and coastal zone of the Atlantic Ocean,the East Pacific and the West Pacific back-arc spreading centers were analyzed.In this paper,the dissolved Fe concentrations and Fe isotopic compositions in the seawater from surface layer,middle layer and deep sea are investigated,and the controlling factors on the ocean Fe cycle and the contribution of seafloor hydrothermal activity to seawater Fe isotopic composition are unveiled.Primary conclusions are as follows:(1) both the dissolved Fe concentrations and Fe isotopic compositions in the seawater profiles vary from region to region.The Fe isotopic compositions keep in line with dissolved oxygen concentration,but exhibit mirror image relationship with dissolved Fe concentrations;(2) the main controlling factors of dissolved Fe concentrations and Fe isotopic compositions in different seawater depths are different.Surface water is influenced by atmospheric dust and biological effects,which leads to heavier Fe isotopic composition,but it tends to become lighter when affected by the river.The deep-sea water is mainly influenced by sediment and seafloor hydrothermal activity.The non-reducing dissolved Fe from the sediment leads to heavier Fe isotopic composition,while mid-ocean-ridge hydrothermal fluid contributes to lighter Fe isotopic composition;(3) the estimated global hydrothermal fluid contribution to seawater Fe budget reaches to about 5.5％ based on the relationship between dissolved Fe isotope and its flux,when put the minimum value of hydrothermal dissolved Fe (0.5 Gmol/a) as mid ocean ridge hydrothermal inputs to the global ocean.Owing to the fact that the dissolved Fe isotope flux from hydrothermal fluid is more than 0.5 Gmol/a,the contribution of the dissolved Fe to seawater may greatly exceed the previous estimation (6.0％).
Keywords：dissolved FeFe isotopeFe fluxheterogeneityhydrothermal fluidmarine geology
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：12( 1519-1530 )