【作者】 王吉中；

【导师】 李胜荣；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2005， 博士

【摘要】 富钴结壳是一种水生成因、生长在海山上的“壳状”沉积物。它富含Mn、Fe、Co、Ni、Cu、Mo、Pt及稀土等有用元素,自上世纪80年代以来,受到世界各国的重视。富钴结壳已成为继大洋铁锰结核之后,又一重要的海洋固体矿产。 中太平洋海区是富钴结壳的主要分布区。前人研究发现,该区富钴结壳普遍遭受过磷酸盐化作用,但有关磷酸盐化对富钴结壳物质组分的影响,仅有零星的研究报道。深入系统地研究磷酸盐化对富钴结壳物质组分的影响,对于我国正在开展的海上富钴结壳调查工作,寻找优质的富钴结壳资源,具有十分重要的理论和现实意义。 本文以我国“大洋一号”船DY105-12、14航次在中太平洋威克海岭（Wake）、马尔库斯（Marcus）海脊和中太平洋海山上采集到的富钴结壳为研究对象,通过对富钴结壳分层处理,综合运用矿物学、岩石学和地球化学等研究手段和各种先进的分析测试方法,系统地研究了磷酸盐化对富钴结壳物质组分的影响,取得了以下研究成果: 1.磷酸盐化作用使富钴结壳的矿物组成发生变化。非磷酸盐化壳层中主要矿物为水羟锰矿。磷酸盐化壳层中主要矿物为水羟锰矿、碳氟磷灰石和少量钙锰矿。 2.磷酸盐化导致富钴结壳成矿元素含量发生改变。对比发现,磷酸盐化对富钴结壳中有用元素Ni、Cu、Pt和稀土元素具有富集作用,但对Co、Mn和Fe具有贫化作用。Ni、Cu和稀土元素的富集与碳氟磷灰石有关;Co、Mn和Fe的贫化与钙锰矿有关。 3.对铂族元素比值、元素相关分析以及Re-Os同位素研究表明,富钴结壳中铂族元素主要来源于内源和陆源富含铂族元素的岩石风化产物,地外宇宙尘并非富钴结壳中铂族元素的主要来源。铂的富集机理是海水中2价态铂的络合物(PtCl₄^2-)在最低含氧层附近或最低含氧层内,被Mn²⁺还原为零价态铂而进入结壳富集的。 4.依据磷酸盐化对富钴结壳物质组分的影响,分析了富钴结壳的成矿机制,在此基础上,建立了磷酸盐化富钴结壳的成矿模式。更多还原

【Abstract】 Co-rich crusts are hydrogenous crustiform precipitates which grow on seamounts and enrich Mn,Fe,Co,Ni,Cu,Pt and REEs. Since 1980, they have been focused on by governments all over the world. Following ferromanganese nodules the Co-rich crusts have become a new important sort of oceanic mineral resources now.Central Pacific seamounts are mainly distribution areas of Co-rich crusts. The former researchers discovered that most Co-rich crusts in this area generally have been phosphatized. But the research reports are fewer related to effects of phosphatization on the geochemical and mineralolgical composition of Co-rich crusts. So it is of theoretical and practical significance to throughly and systemically research the effects of phospharization on composition of Co-rich crusts for our country surveying and finding high grade Co-crusts deposits in ocean.The Co-rich crusts studied in this paper were collected from Wake range, Marcus ridge and Central Pacific seamounts during "No.1 Dayang" DY105-12,14 cruise in 2003, China. By dividing the Co-crusts into different crust layers, synthetically using mineralogy, petrology, geochemistry method and various advanced test technology, the author has systemically studied the effects of phosphatization on composition of the Co-rich crust. The main achievements are as follow:1 Phosphatization has in certain degree changed the mineral composition of the Co-rich crusts. Non-phosphatized crust layers are mainly composed of vernadite; Phosphatized crust layers are mainly composed of vernadite, carbonate fluorapatite(CFA) and todorokite.2 The concentrations of usable elements in the Co-rich crusts have been changed by phosphatization. The Ni, Cu, Pt and rare earth elements are enriched and the Mn, Fe, Co are depleted in the phosphatized crust layers compared to the non-phosphatized crust layers. The enrichment of the elements such as Ni, Cu, Pt and rare earth elements genetically relates to fluorapatite(CFA). The depletion of the elements such as Mn, Fe, Co genetically relates to todorokite.3 The ratio and relationship between platinum group elements(GPEs) as well as Re-Os isotopes show that the PGEs in the Co-rich crusts mainly come from oceanic crust and mantle as well as the weathering products of PGEs-bearing rock on continent, and that cosmic dusts are not its main sources, the mechanism for platinum enrichment in the Co-rich crusts is deduced to be that the PtCl42- in the seawater was reduced to Pt metal by Mn2+ in the vicinity and interior of the oxygen minimum zone, and that the Pt metal was introduced from seawater and was enriched in Co-rich crusts.4 According to the study of the effects of phosphatization on the Co-rich crusts, the author analyzes the mechanism of forming Co-rich crusts and constructs a correspondent model in this paper..更多还原