东海陆架细颗粒沉积物组成分布特征及其物源指示

IOCAS-IR > 海洋环流与波动重点实验室

	东海陆架细颗粒沉积物组成分布特征及其物源指示
其他题名	THE SOURCE AND COMPOSITION OF FINE-GRAINED SEDIMENT DEPOSITED ON THE EAST CHINA SEA SHELF
	周晓静
学位类型	博士
	2009-05-21
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	东海陆架长江黄河粘土矿物常量元素微量元素物源
摘要	沉积物由源到汇的搬运过程是整个地球物质循环的一个重要环节；在这一过程中，载有当时主要地质历史事件信息的沉积物汇入海洋；但因受到复杂的海洋环境的改造以及人类活动的影响，这些信息的表现形式可能已经发生了改变。因此，如何反演上述地质历史进程、预测其发展变化，成为海洋地质学研究的重要内容。本文通过对长江、黄河、钱塘江、瓯江和闽江等5 条中国东部入海河流沉积物稀土元素（REE），以及东海陆架表层细颗粒沉积物中粘土矿物、元素组成等的综合研究，借助数学统计，分析探讨了陆架区细颗粒沉积的物质来源、现代长江入海沉积物在东海陆架区的影响范围，以及由源到汇输运过程中沉积物示踪标记数值改变等问题。长江口沉积物REE 在<2μm 和2-31μm 粒级中较富集，但全岩REE 总量（ΣREE）在数值上受物质组成占优的2-31μm 粒级控制；因粉砂对水动力环境的反映最为敏感，在输运过程中该粒级组成不稳定即可引起全岩REE 含量的变化。全岩REE 含量在河口附近较高，在东海陆架区由岸向海有减小的趋势，轻重稀土比值自28°N 向南有增大的趋势。在长江口和东海内陆架，水动力对沉积物的作用可能对REE 含量空间分布模式的形成起着重要作用。长江、黄河等五条河流沉积物的ΣREE、轻重稀土含量比值（L/HREE）等参数在数值分布上有所不同。但陆架复杂的水动力环境可造成砂粒级沉积物中轻重矿物分异、粉砂与粘土粒级间级配调整，并由此引起沉积物中REE 含量的数值变化。此时，单由砂、粉砂等较大粒级区间内REE 含量的分布已经不能准确判断沉积物物源的改变。在长期稳定的陆架沉积环境下，借助沉积物输运模型，有可能解决因水动力因素造成的REE 分布变化的问题。东海陆架区未能发现在数值上绝对不变的示踪标记物，而引起示踪指标变化的决定性因素尚未明确。因此，本文采用前人研究中可以明显区分沉积物河流来源的指标，借助统计学中聚类和判别分析方法定性地判断东海陆架区沉积物常、微量元素和粘土矿物的可能物源。根据四种主要粘土矿物相对含量与细颗粒沉积物微量元素的构成特征，推断研究区表层类长江细颗粒物质主要为现代长江入海沉积物；它们主要分布在东海陆架中、西部区域，在中部可以跨越123°E 向东继续延伸，在北部可以达到外陆架的东部边缘。研究区东侧、东海外陆架边缘表层细颗粒沉积物的微量元素构成与现代长江沉积物存在较大差异，具有类黄河沉积物的性质，可能是在更新世冰期干冷气候下形成的产物与现代河流入海细颗粒的混合物。
其他摘要	It is an important task to analyse the change of sediment properties during transportation from rivers to marine settings. Total of 146 sediment samples were collected from the East China Sea Shelf (ECSS) and five rivers, including Huanghe River, Changjiang River, Qiantang River, Ou River and Min River. The sediment grain-size and the contents of rare earth elements (REE) were measured with laser particle size analyzer and ICP-MS respectively. Results show that absolute REE content (ΣREE) and the ratio of LREE (light REE)/HREE (heavy REE) are different in the sediments between rivers. There are higher REE contents in <2 μm and 2-31 μm fractions in Changjiang Estuary surface sediments, and the bulk sediment REE contents are dominated by the value of the advantage size fractions. In the study area, absolute REE contents of sediments are higher near the estuaries, and it trend downward in seaward direction on the inner shelf of East China Sea. The LREE/HREE ratio has a tendency of increase southward from 28°N, whilst hydrodynamic conditions dominant the spacial distributions of the surficial sediment’s REE parameters. In some cases, the current flows tend to remove the coarser light grains from initial populations, whilst deposit the finer heavy mineral grains. In most situations, the currents will change the ratio of sediment constituents, for example between silts and clays. As a result, the various values of absolute REE content or LREE/HREE ratio in different bulk sediments arose from the change of size-fractions, rather than represent their different sources. Under the long-term stable hydrodynamic environment i.e. the East China Sea Shelf, new sediment transport model based on the size and density gradation concept may help to understand the spatial distribution patterns of REE parameters. About 260 surface fine-grained (<31μm and 2μm, mainly) sediment samples were collected from ECSS, and measured with ICP-MS, ICP-OES and X-Ray Diffraction. Similar to the bulk sediments, those fingerprints, i.e. clay minerals, major elements and trace elements in the surface fine-grained sediments of the ECSS, are variable in spacial distributions. By now, we haven’t found the absolute stable numerical fingerprints and the reasons of changing. Therefore, we choose the indicators (e.g. clay minerals and trace elements) which can discriminate different river sediments, and use the statistical Clustering and Discriminant Analyses to judge the source of ECSS sediments qualitatively. According to clustering analysis results based on four main clay minerals and trace elements, we conclude that the <31μm fractions sediments of the Changjiang-Like mainly distribute in the central and western regions of ECSS, and they come from modern Changjiang River; the fine-grained sediments in southeastern part of ECSS might originate from the Yellow River, or from the relict sediments formed in dry and cold climates such as Pleistocene Ice Age and then mixed with fine modern riverine sediments under marine hydrodynamic processes.
页数	151
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/1497
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	周晓静. 东海陆架细颗粒沉积物组成分布特征及其物源指示[D]. 海洋研究所. 中国科学院海洋研究所,2009.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
10001_20061800681205（11022KB）			限制开放	--	浏览