太湖现代沉积物的物质组成和形成条件分析

对太湖现代沉积物进行了X射线衍射分析、粒度分析和常量元素分析，由此推断它们的矿物成分、化学风化程度差异，并分析了不同的水动力条件和物源。太湖沉积物的主要矿物组成是石英、云母、正长石和钠长石，粘土矿物为伊利石、绿泥石、高岭石和蒙脱石。化学组成显示，太湖沉积物的烧失量较高，与上部陆壳平均化学成分相比，Na、Na、K、Mg亏损，Mn、Ti富集，上部陆壳成分标准化图表明其风化程度明显强于下蜀土。化学风化程度指标CIA、Na/K值和Fe/Mg值的变化也表明太湖沉积物的化学风化作用比下蜀土强，，并存在地域的差别。太湖沉积物的CaCO3含量明显较低，反映了太湖流域本身的特点。所有这些特征表明，太湖沉积物的形成不仅与物源、地域位置有关，而且明显受人类活动的影响。

Compositions and the Formative Conditions of Sediments in Taihu Lake, Eastern China

On the basis of X-ray diffraction, sedimental size and major elements analyses, we deduce the chemical weathering degree of sediments in Taihu Lake and illuminate the hydrodynamic condition and the source of sediments. The main mineral compositions of sediments in Thai Lake are quartz, sericite and albite; some clay minerals are illite, chlorite, kaolinite and montmorillonate . The compositions of sediments show a high LOI content from 4.91% to 11.20% and are depleted in Na, Ca, K, Mg and enriched in Mn, Ti, compared with the average composition of the upper continental crust. The sediments in Taihu Lake suffer more intense chemical weathering than the Xiashu loess and paleosoil do. The weathering proxies CIA, Fe/Mg as well as Na/K also show the sediments in Taihu Lake have reached a high degree of chemical weathering and there are some small regional differences. But Na/K reveals a reverse trend in sediments of Taihu Lake compared with the conclusionmentioned by some references. The CaCO3 content of sediments in this area is obvious low which reflects the character of the Taihu watershed. All the above characteristics suggest that the formation of sediments in Taihu Lake are not only related to relief and source, but also to anthropic activities.