全球海水剖面Fe同位素组成的不均一性及其影响因素  

Fe Isotopic Composition Heterogeneity of Seawater Profiles and Its Influence Factors

作　　者：王建强[1,2] 李小虎[1,2] 毕冬伟 伍锡昌 初凤友[1,2] Wang Jianqiang Li Xiaohu Bi Dongwei Wu Xichang Chu Fengyou(Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China)

机构地区：[1]国家海洋局海底科学重点实验室,浙江杭州310012 [2]国家海洋局第二海洋研究所,浙江杭州310012

出　　处：《地球科学（中国地质大学学报）》2017年第9期1519-1530,共12页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(Nos.41276055;41406066);国家重点基础研究发展计划项目(No.2013CB429705);浙江省自然科学基金项目(No.LY14D060005)

摘　　要：全球海水剖面Fe同位素组成存在显著不均一性.对大西洋洋中脊、大西洋近海岸带、东太平洋和西太平洋弧后扩张中心多个站位的海水剖面溶解Fe浓度和Fe同位素组成进行了综合分析,得出以下主要认识:(1)不同区域的海水剖面溶解Fe浓度和Fe同位素组成呈现不同的变化特征,海水Fe同位素的变化趋势与海水溶解氧浓度变化一致,而与海水溶解Fe浓度呈镜像变化关系;(2)不同深度的海水溶解Fe浓度和Fe同位素组成特征的主要控制因素不同.表层海水受到大气降尘、生物作用影响呈现富重Fe同位素特征,受河流的影响Fe同位素组成偏轻;深层海水主要受到深海沉积和海底热液活动的影响,其中沉积物中的非还原溶解Fe导致海水富集重Fe同位素,而受洋中脊热液流体影响的深部海水显著富集轻Fe同位素;(3)将目前已知海底热液溶解Fe通量最小值(0.5Gmol/a)作为全球大洋的热液溶解Fe通量,利用不同来源的溶解Fe同位素与其通量间的关系估算海底热液对海洋的Fe循环的贡献为~5.5%.由于海底热液流体的Fe通量可能远大于0.5Gmol/a,因此,海底热液活动对海洋溶解Fe的贡献可能远超过前人的估算结果(6.0%).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（0.5Gmol/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 0.5Gmol/a,the contribution of the dissolved Fe to seawater may greatly exceed the previous estimation（6.0%）.

关 键 词：溶解Fe FE同位素 Fe通量 不均一性 热液流体 海洋地质 

分 类 号：P736.4[天文地球—海洋地质]