中北太平洋铁锰结壳钕同位素演化研究  

Neodymium Isotope Evolution of Ferromanganese Crusts from Central Pacific Ocean

作　　者：周枫[1] 凌洪飞[1] 蒋少涌[1] 

机构地区：[1]南京大学内生金属矿床成矿机制研究国家重点实验室南京大学地球科学系,江苏南京210093

出　　处：《地球学报》2005年第B09期199-199,共1页Acta Geoscientica Sinica

基　　金：本研究得到大洋协会“十五”项目（编号：DY105-01-04-6）资助.

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结壳可以恢复新生代海洋Nd同位素演化历史，进而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同位素研究表明，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。Nd isotopes of hydrogenous ferromanganese crusts 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 authors 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. It is found that the evolution trends of the PB isotope ratios of the crust is similar to those of eolian dust recovered from Core LLA4-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. Additionally, the εNd 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 Cenozoic 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 εNd value of central North Pacific Ocean in Cenozoic resulted mainly from increased erosion of volcanic arc rocks around the Pacific rims.

关 键 词：铁锰结壳 ND同位素 新生代 古海洋 北太平洋 同位素演化 古海洋环境 大陆边缘 热液蚀变 古气候变迁 

分 类 号：P744.3[天文地球—海洋科学] P732.6