南海西北陆缘多金属结核地球化学及其与大洋结核的对比

多金属结核化学成分组成的差异能够反映其赋存环境的差异与变化,也能够指示结核的成因。利用ICP-MS方法分析了分布于南海西北陆缘、太平洋、印度洋等不同区域的多金属结核样品的地球化学组成,并对其特征进行了对比。研究数据显示,南海西北陆缘多金属结核富Fe、Si、REE,而Mn、Co、Cu、Ni含量低于大洋结核,轻稀土元素(LREE)更为富集。依据结核TMn/TFe的比值特征以及w (Mn)-w (Fe)-w (Cu+Ni)三组特征显示,南海结核和太平洋海山结核符合水成成因,太平洋海盆结核属成岩成因,印度洋结核具有成岩和水成双重成因。与太平洋、印度洋等大洋型结核不同,南海结核元素组成中,标识陆源物质来源的Fe、Si、REE、Al等元素含量丰富,具有典型的边缘海特征,反映了南海结核成长发育的过程中,边缘海独特的沉积条件和多变的古海洋环境因素对其产生了重要的影响。

COMPARISON BETWEEN NORTHWESTERN CONTINENTAL MARGIN OF THE SOUTH CHINA SEA AND OTHER OCEANS OF GEOCHEMICAL CHARACTERISTICS OF POLYMETALLIC NODULES

Geochemical characteristics of polymetallic nodules can reflect differences of their growth environments, and can show origins of their dominative factors. In this study, different samples of polymetallic nodules collected from the South China Sea, the Pacific and the Indian Ocean were analyzed using ICPMS(AES). Their geochemical compositions and characteristics were compared among samples from different regions. According to the data, samples collected from the northwestern continental margin of the South China Sea were rich in Fe, Si, and ∑REE, while poor in Mn, Cu, Co and Ni. Heavy REE (HREE) was depleted relative to light REE (LREE) very obviously, the latter being 19.54 times less than the former. The ratio of Mn/Fe and element correlation of w(Mn)-w(Fe)-w(Cu+Ni) suggested that the origins of samples from the northwestern continental margin of the South China Sea and from a seamount of the Pacific may be of hydrogenic. Samples from sea basins of the Pacific may be diagenetic in origin, and the Indian Ocean samples were both hydrogenic and diagenetic in formation. Different from ocean samples, polymetallic nodules from the northwestern continental margin of the South China Sea have typical characteristics of a marginal sea which were marked by terrigenous sediments including rich elements of Fe,Si,Al and REE. These characteristics showed that the unique terrigenous sedimentary conditions and the changeful paleoceanic environment have an important effect on the growth of nodules in the South China Sea.