Formation of Fe-oxyhydroxides from the East Pacific Rise near latitude 13°N:Evidence from mineralogical and geochemical data

查看全文 作　　者：ZENG [1]ZhiGang;WANG [1,2]XiaoYuan;ZHANG [1,2]GuoLiang;YIN [1]XueBo;CHEN [1,2]DaiGeng;WANG [1,2]XiaoMei

机构地区：[1]The Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;[2]Graduate School of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Science China Earth Sciences》索引2008年第51卷第2期,共10页

基　　金：Supported in part by the Pilot Project of Knowledge Innovation Project, Chinese Academy of Sciences (Grant No. KZCX3-SW-223);the Special Foundation for the Tenth Five Plan of COMRA (Grant No. DY105-01-03-1) 摘　　要：The mineralogical and geochemical characteristics of Fe-oxyhydroxide samples from one dredge station (long. 103°54.48'W, lat. 12°42.30'N, water depth 2655 m) on the East Pacific Rise near lat 13°N were analyzed by XRD, ICP-AES, and ICP-MS. Most Fe-oxyhydroxides are amorphous, with a few sphalerite microlites. In comparison with Fe-oxyhydroxides from other fields, the variable ranges in the chemical composition of Fe-oxyhydroxide samples are very narrow; their Fe, Si, and Mn contents were 39.90%, 8.92%, and 1.59%, respectively; they have high Cu (0.88%―1.85%) and Co (65×10?6―704×10?6) contents, and contain Co+Cu+Zn+Ni> 1.01%. The trace-element (As, Co, Ni, Cu, Zn, Ba, Sr) and major-element (Fe, Ca, Al, Mg) contents of these samples are in the range of hydrothermal sulfide from the East Pacific Rise near 13°N, reflecting that this type of Fe-oxyhydroxide constitutes a secondary oxidation product of hydrothermal sulfide. The Fe-oxyhydroxide samples from one dredge station on the East Pacific Rise near 13°N are lower in ΣREE (5.44×10?6―17.01×10?6), with a distinct negative Ce anomaly (0.12 ― 0.28). The Fe-oxyhydroxide samples have similar chondrite-normalized rare-earth-element (REE) patterns to that of seawater, and they are very different from the REE composition characteristics of hydrothermal plume particles and hydrothermal fluids, showing that the REEs of Fe-oxyhydroxide are a major constituent of seawater and that the Fe-oxyhydroxides can become a sink of REE from seawater. The quick settling of hydrothermal plume particles resulted in the lower REE content and higher Mn content of these Fe-oxyhydroxides, which are captured in part of the V and P from seawater by adsorption. The Fe-oxyhydroxides from one dredge station on the East Pacific Rise near 13°N were formed by secondary oxidation in a low temperature, oxygenated environment. In comparison with the elemental (Zn, Cd, Pb, Fe, Co, Cu) average content of hydrothermal sulfide samples from the East Pacific Rise near 13°N, the Zn, Cd, and Pb contents of the Fe-oxyhydroxides are lower, and their Fe, Co, and Cu contents are higher. 关键词：mineral GEOCHEMISTRY formation Fe-oxyhydroxide East PACIFIC RISE 13oN

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Formation of Fe-oxyhydroxides from the East Pacific Rise near latitude 13°N:Evidence from mineralogical and geochemical data

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