黄河宁蒙段沉积物地球化学元素组成及分布特征

Geochemical element composition and spatial distribution characteristics of sediments in the Ningxia-Inner Mongolia section of the Yellow River

黄河宁蒙段穿越腾格里沙漠、河东沙地、乌兰布和沙漠和库布齐沙漠,风沙水沙交互强烈,形成典型的沙漠宽谷冲积河道。对黄河河道及周边沙源区沉积物进行了系统的采集、测定、分析工作。结果表明:宁蒙河段沉积物相对富集SiO_(2)、CaO、Al_(2)O_(3)、Ce、Zr、Hf和Nd,亏损K_(2)O、Na_(2)O、Rb、Zn、Ni和Sr。与周边沙源区对比,黄河宁夏段下河沿上游河道、清水河、腾格里沙漠和河东沙地沉积物均富集Co和Ti,亏损Sr、Ni、Hf和Y,且Hf、Ni、Y、Zn、MgO和CaO含量的变异系数较大。在内蒙古段,来自乌海上游河道、乌兰布和沙漠、库布齐沙漠和十大孔兑的沉积物相对富集Co和Ti,亏损Hf,Ni和Y,其中Cr、Hf、Ni、Y、Zn和MgO的元素含量变异系数较大。黄河宁蒙河段沉积物化学元素空间分布特征具有明显的波动和差异性,主要受到岩性、气候和局地物源输入的影响。

The Ningxia-Inner Mongolia section of the Yellow River flows through a large area of desert including Tengger Desert,Hedong Sandy Land,Ulan Buh Desert and Kubq Desert,and have formed representative desert-gully alluvial reaches with the interplay of aeolian-sand and flow-sand. We had systematically collected the samples at the river channel and source areas. The results show that sediments in the Ningxia-Inner Mongolia section are rich in SiO_(2),CaO,Al_(2)O_(3),Ce,Zr,Hf and Nd,depleted of KO,Na_(2)O,Rb,Zn,Ni and Sr. Compared with the surrounding source regions,the sediments from the upstream channel of Xiaheyan,Qingshui River,Tengger Desert and Hedong Sandy Land are rich in Co and Ti,depleted in Sr,Ni,Hf and Y. The element contents of Hf,Ni,Y,Zn,MgO and CaO show larger coefficients of variation in the Ningxia-Inner Mongolia section. In the Inner Mongolia section,the sediments from the upstream of the Wuhai channel,Ulan Buh Desert,Kubq Desert and the Kongdui are relatively enriched in Co and Ti,depleted of Hf,Ni and Y,and the elements with larger coefficient of variation are Cr,Hf,Ni,Y,Zn and MgO. The spatial distribution of chemical elements shows an obvious fluctuation with distance,which is mainly controlled by the climate condition,source rocks and sediments input of aeolian and tributaries.