The Mineralogical And Geochemical Characteristics Of Modern Sediments From The Changjiang And Huanghe Rivers

Huge sediments from the Changjiang(Yangtz) and Huanghe(Yellow) Rivers to the eastern sea of China are the most important components of the Yellow Sea and the East Sea sediments. In order to better understand sediments deposition process, development and evolution of the eastern shelf as well as effects of rivers on the seas in detail, we should know their sediments sources and oceanographic conditions first. While how to discriminate the sediments sources on the eastern shelf (either derived from the Changjiang(Yangtz) River or the Huanghe(Yellow) River) effectively .these parent sediments' distributing and transportation process are mainly aspects to solve this problem. In this paper, mineralogical and geochemical characteristics of sediments from these two rivers are studied thoroughly.By using scanning electron microscope (SEM), energy spectrum microanalysis, X-Ray diffractometor and ICP-AES, mineralogical and geochemical characteristics of the sediments of the Huanghe and Changjiang rivers were studied. These samples selected well represent the sediments from these two rivers to the sea.Study on surface sediments indicates:(l)Quartz from the Huanghe ane Changjiang Rivers have the general characteristics of fluvial quartz, and quartz from the Huanghe River inherited some surface micro-structrure features of quartz in eolian loess. Calcite minerals from Huanghe are mainly cryptocrystalline grains with high Mg and the intact rhombi structure are few in these minerals. While calcite minerals from Changjiang,are non- autogenous and some of them linked with quartz. Dolomite minerals are the characteristic part in Changjiang but few in Huanghe. They keep better crystal shape than Calcite minerals do. (2) Quartz concentration decrease with decreasing size fraction in the range of <63 u m and there are less than 10% when size <4 V- m in the sediments from these two rivers. Calcite concentration increase,then decrease with decreasing size fraction and reach max at 16um-8um in Huanghe sediments. While in Changjiang sediments calcite concentration decrease with decreasing size fraction and there are few when the gain size <16 u m. In the two rivers sediments, plagioclase and k-feldspar concentration increase, then decrease during the grain size 63 u m~8 u m and plagioclase concentration is one-third of k-feldspar. When the grain size <8 u m, there are no plagioclase or k-feldspar, but kaolinite and mica concentration increase in the sediments.Eight major elements(Fe2O3, MgO. CaO. A12O3 Na2 OK2 OTiO2. MnO) and seven trace elements (Ba. Sr. Pb Cu.. Zn. V.Ni) analysis of suspended particles from the two rivers show that the concentration of CaO, Na2O and Sr in the suspended particles from Huanghe are higher than those in Changjiang, while the other elements concentrations are just the reverse...