【作者】 卜文瑞；

【导师】 石学法；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质学， 2008， 博士

【摘要】 中西太平洋富钴结壳稀有气体核素含量和同位素组成具有明显的区域性特征。依其He同位素比值与大洋中脊玄武岩(MORB)He同位素比值的相对大小,可将富钴结壳分为低~3He/~4He型和高~3He/~4He型两类,麦哲伦海山、马尔库斯-威克海岭、马绍尔群岛海山链和中太平洋海山产出低~3He/~4He型结壳,莱恩群岛海山链产出高~3He/~4He型结壳。富钴结壳稀有气体以下地幔来源为主,低~3He/~4He型与高~3He/~4He型结壳稀有气体特征的差异是二者产出海山链下地幔源区类型不同的表现。低~3He/~4He型结壳中的稀有气体主要来自受俯冲再循环大洋地壳影响的HIMU型地幔源区,高~3He/~4He型结壳中的稀有气体主要来自受捕获大气组分沉积物再循环作用影响的EM型地幔源区。地幔源区类型的差异是引起两类结壳稀有气体组成差异的根本原因。富钴结壳铂族元素(PGE)特征随海山链而变化,PGE各元素之间也有明显的分异,暗示了结壳PGE来源的多样性和富集机制的差异性。地外物质对富钴结壳PGE的贡献有限,富钴结壳PGE主要来自海底幔源岩石的蚀变作用和陆源物质输入。PGE来源印证了富钴结壳稀有气体的地幔来源说。大洋岛屿玄武岩(OIB)低温蚀变作用研究和质量平衡理论计算表明,OIB低温蚀变作用为海水提供了大量金属,OIB是富钴结壳重要的矿源场。地幔在富钴结壳成矿中起着重要的作用。更多还原

【Abstract】 The nuclide contents and isotopic ratios of ferromanganese crusts from the western and central Pacific Ocean vary significantly with regional characteristics. Based on the relationship between the He isotope ratios of samples and that of MORB, the samples can be classified into two types: a low ~3He/~4He type and a high ~3He/~4He type. The sample from the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain and the Mid-Pacific Seamounts are low ~3He/~4He type crusts, while the samples from the Line Island Chain are high ~3He/~4He type crusts.The noble gases in ferromanganese crusts originate predominantly from the lower mantle of the Earth. The differences in noble gas characteristics between the low ~3He/~4He type and the high ~3He/~4He type crusts indicate the differences of lower mantle end-member of the correspondent seamount chains. Noble gases of the low ~3He/~4He type crusts originate mainly from a HIMU-type lower mantle source contaminated by recycled oceanic crust, whereas noble gases in the high ~3He/~4He type samples originate mainly from an EM-type lower mantle source contaminated by recycled sediments which captured the air component. The difference in the lower mantle end-member is the fundamental reason results in the differences in the noble gas composition between the two type crusts.The platinum group elements (PGE) contents of crust samples vary from one seamount chain to another and there are significant differentiation between different elements of PGE, indicating the diversity of PGE source of crusts and the variation of the enrichment mechanism in seamount chains. The PGE in crusts origin mainly from alteration of mantle-deirived submarine basalts and river and eolian input, while the contributin of extraterrestrial material is limited. This proves the mantle origin hypotheses of noble gases in ferromanganese crusts.The study of low-temperature alteration and the mass balance theoretical calculation of oceanic island basalts (OIB) indicate that low-temperature alteration of OIB can supply abundant amount of metals to seawater and OIB play as an important source of transition metals for the formation of ferromanganese crusts.更多还原