| 中北太平洋铁锰结壳钕同位素演化研究 |
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| 引用本文：周枫,淩洪飞,蒋少涌.2005.中北太平洋铁锰结壳钕同位素演化研究[J].地球学报,26(z1):199. |
| DOI：10.3975/cagsb.2005.s1.65 |
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| 中文摘要:现代海洋中的水成 Fe－Mn 结壳的 Nd 来自当时周围海水，因此利用 Fe－Mn 结壳可以恢复新生海洋 Nd 同位素演化历史，进面了解古海洋环境和古气候变迁信息。海洋中 Nd 的来源包括河流或陆源 Nd、大陆边缘沉积物和风成粉尘中的可溶 Nd，以及洋中脊热液蚀变来源的 Nd。对海水、水成成因铁锰结壳和结核、洋脊热液喷发和河流输入的 Nd 同位素研究发明，陆源物质控制着大洋中溶解的 Nd。对于风尘输入对大洋中的REE的影响还存在争议。有研究表明来自大陆和火山的风尘是某些局部大洋中的 REE 的重要来源，风尘与海水间的 REE 交换引起了某些洋区中 Nd 同位素组成的变化。相反，另有学者认为风尘对北太平洋中的溶解 Nd 总量没有影响。笔者分板子一块来自中北太平洋的铁锰结壳样品（MDD53）的 Nd，Pb 同位素，得到了该区新生代以来的 Nd，Pb 同位素演化历史。通过对比该结壳和岩心 LL44－GPC3 中粉尘的同位素演变曲线，发现二者的 Pb 同位素变化规律十分相似，证明结壳中的 Pb 主要来自粉尘。与 Pb 同位素相反，二者的 Nd 同位素演化完全不同。中国黄土的ENd值远低于中太平洋深水中的ENd值。因此，笔者认为风成粉尘对太平洋深水中溶解的 Nd 总量的影响可以忽略不计。结壳的 ENd值介于大陆和岛弧火山的值之间，说明新生代太平洋海水中的 Nd 主要来自河流、大洋边缘大陆风化及大洋环流携带大源自其他大洋的 Nd，新生代 Nd 同位素比值的增长主要是国为太平洋边缘岛弧的风化剥蚀作用和火山活动的增强。 |
| 中文关键词:铁锰结壳 Nd 同位素 新生代 古海洋 |
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| Neodymium Isotope Evolution of Ferromanganese Crusts from Central Pacific Ocean |
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| Abstract:Nd isotopes of hydrogenous ferromanganese in the oceans recorded paleoenvironment information, Previous studies show that terrestrial sources control the Nd isotope compositions in the oceans. The importance of REE input to the oceans through eolian dust remains controversial. The arthors analyzed Nd and Pb isotope data of a ferromanganese crust (MDD53)from central North Pacific Ocean,and hence discovered Cenozoic Nd,Pb isotope evolution of the deepwater. Iis found that the evolution trends of the Pb isotope ratios of the crust is similar to those of eolian dust recovered from Core LL44-GPC3,which indicates that Pb in the crust is mainly derived from the eolian dust. However,the crust and the core show completely different Nd isotope evolutions Pb in the crust is mainly derived from the eolian dust. However,the crust and the core show completely different Nd isotope evolutions. Additionally,the ENd ratio of Chinese loess is much lower than that of central Pacific deepwater. It is thus held that the eolian Nd input is negligible to the oceanic Nd budget. The Cenoziic Nd of deepwater in central North Pacific Ocean is a mixture of Nd from river runoff and weathering of continental margins and Nd transported from other parts of the oceans. The rising ENd value of central North Pacific Ocean in Cenozoic resulted mainly from increased erosion of volcanic arc rocks around the Pacific rims. |
| keywords:ferromanganese crust Ndisotope Cenozoic Paleooceanography |
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