长江口沉积物地球化学—物源、风化作用的响应

发布时间：2018-04-16 18:48

本文选题：长江口 + 沉积物　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：本次研究对取自长江口地区崇明岛东滩的沉积物CM-A柱样的放射性测年数据与粒度数据作了分析,同时分析了沉积物的主量元素、微量元素以及稀土元素的含量数据,主要目的在于阐明沉积物的元素组成特征,揭示CM-A沉积物的物质来源,分析CM-A沉积物的化学风化程度以及它们所经历的搬运、分选作用。同时,将CM-A沉积物与黄河、珠江的样品数据进行对比,试图在中国河流沉积物的大框架中去理解长江口CM-A沉积物的地质学意义。放射性测年数据表明,CM-A柱样的沉积年代为1973~2010年。福克分类图解表明,CM-A沉积物主要为粉砂质组分(粒径63μm),特别适合于运用REEs进行沉积物的物源示踪研究。CM-A沉积物中主量元素Al_2O_3、Fe_2O_3、K_2O、TiO_2的含量高于黄河样品而低于珠江样品,可能主要受到长江流域气候和化学风化作用的控制。CM-A沉积物中微量元素Cr、Li、Sc、Cu、Zn、Y、Nb的组成特征与前面几种主量元素类似,可能主要受到长江流域源岩类型和风化作用的影响。CM-A沉积物主量、微量元素的含量在深度上的分布曲线总体上由一种双谷模式主导,即在对应于1988~2002年和2002~2005年的两个深度区间内表现为含量低谷,可能主要受到人类活动因素的控制。REE配分模式图表明,CM-A沉积物和黄河样品、珠江样品类似,可能暗示其主要物质来源为陆源。REE配分模式图表明,CM-A沉积物的配分曲线最接近于长江上游的干流悬浮物,可能暗示CM-A沉积物主要来自长江上游地区。这一结论和已有研究成果是一致的,即长江口现代沉积物主要来自长江上游地区。A-CN-K化学风化图解表明,CM-A沉积物化学风化程度为中低等,高于黄河样品而低于珠江样品,可能主要受到长江流域的气候条件的制约。CM-A沉积物的化学风化程度也低于平均页岩,可能表明长江口或者长江干流沉积物的化学风化强度要低于世界平均水平。化学风化三角图同时表明CM-A沉积物风化源岩的组分可能类似于花岗闪长岩。SiO_(2-)(A1_2O_3+K_2O+Na_2O)化学成熟度图解表明,CM-A沉积物的化学成熟度要高于珠江样品和平均页岩,这可能暗示长江口沉积物经过了较长时间的搬运。Zr/Sc-Th/Sc水动力分选程度图解表明,CM-A沉积物的分选程度低于黄河样品,高于平均页岩。
[Abstract]:In this study, the radioactive dating data and granularity data of sediment CM-A column samples taken from Dongtan of Chongming Island in the Yangtze River Estuary region were analyzed. At the same time, the main elements, trace elements and rare earth elements in sediments were analyzed.The main purpose of this paper is to elucidate the elemental composition of the sediments, reveal the material sources of the CM-A sediments, and analyze the chemical weathering degree of the CM-A sediments and their transport and sorting.At the same time, the data of CM-A sediments are compared with those of the Yellow River and the Pearl River in order to understand the geological significance of the CM-A sediments in the Yangtze Estuary within the framework of the river sediments in China.The radioactive dating data indicate that the sedimentary age of CM-A column is from 1973 to 2010.The Fogg classification diagram shows that the CM-A sediments are mainly silty components (63 渭 m of grain size), which are especially suitable for the source tracer study of sediments using REEs. The content of the principal element Al _ 2O _ 3Fe _ 2O _ 3K _ 2OO _ 2 in the sediment of CM-A is higher than that of the Yellow River sample and is lower than that of the Pearl River sample.It may be mainly controlled by climatic and chemical weathering in the Yangtze River basin. The composition characteristics of the trace element Crlorius scintifolia Cuznzhnianb in the sediments of CM-A are similar to those of the previous main elements.It may be mainly affected by the source rock type and weathering in the Yangtze River basin. The distribution curve of trace elements in depth is dominated by a double valley model.That is to say, in the two depth ranges corresponding to 1988-2002 and 2002-2005, the contents were low, and the REE partitioning pattern, which was mainly controlled by human activities, indicated that the CM-A sediments and the Yellow River samples were similar to the Pearl River samples.It may be suggested that the main material source is land-based. REE partition pattern diagram shows that the partition curve of CM-A sediments is the closest to the main stream suspended matter in the upper reaches of the Yangtze River, and that the CM-A sediments mainly come from the upper reaches of the Yangtze River.This conclusion is consistent with the previous research results, that is, the chemical weathering diagram of chemical weathering of CM-A sediments mainly comes from the upper reaches of the Yangtze River, indicating that the chemical weathering degree of CM-A sediments is lower than that of the Yellow River samples but lower than that of the Pearl River samples.The chemical weathering degree of CM-A sediment is also lower than that of average shale, which may indicate that the chemical weathering intensity of Changjiang Estuary or Yangtze River main stream sediment is lower than the world average.The chemical weathering triangulation also shows that the composition of the weathering source rocks in CM-A sediments may be similar to that of granodiorite. SiOSP, A12O3K2ONa2O3) chemical maturity diagram shows that the chemical maturity of CM-A sediments is higher than that of the Pearl River samples and the average shale.This may imply that the hydrodynamic separation degree of the sediments in the Changjiang Estuary is lower than that in the Yellow River and is higher than that of the average shale. The diagram of hydrodynamic separation of the sediments in the Changjiang Estuary shows that the concentration of CM-A sediments is lower than that of the Yellow River samples and is higher than that of the average shale.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P736.41;P512

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