杭州湾潮滩沉积物黏土矿物空间差异与物源指示

通过对杭州湾潮滩沉积物中主要黏土矿物成分及组合类型的研究,分析了杭州湾潮滩沉积物黏土矿物的空间分布特征。借助聚类分析等手段,同时结合杭州湾水动力特征,探讨了研究区黏土矿物的来源和成因。研究结果表明,杭州湾潮滩表层沉积物主要为黏土质粉砂,其余为砂质粉砂。本区沉积物黏土矿物成分复杂,主要为伊利石,其次是高岭石和绿泥石;还有少量蒙皂石和蛭石及1.4 nm过渡矿物。根据其相对含量可分为3种组合类型:Ⅰ型为伊利石-高岭石-绿泥石-蛭石类-蒙皂石型,Ⅱ型为伊利石-绿泥石-高岭石-蒙皂石-蛭石类型,Ⅲ型为伊利石-高岭石-绿泥石-蒙皂石-蛭石类型。在空间上,北岸的蒙皂石和绿泥石平均含量高于南岸,而伊利石、高岭石和蛭石(含1.4 nm过渡矿物)平均含量则低于南岸。高潮滩和中潮滩黏土矿物对比,除了蒙皂石含量高潮滩大于中潮滩外,其他矿物含量均无明显规律。表层沉积物黏土矿物的分布特征与水动力条件和物质来源密切相关,杭州湾北岸乍浦以东潮滩受潮流和长江沿岸流影响明显,沉积物主要为长江和东海源的;南岸由于曹娥江和甬江两条河流的注入,流域物质所占比例明显比北岸高。柱状岩芯样品中各黏土矿物含量自下而上的变化则反映了物源区风化强度的波动特征。

Spatial Difference and Provenance of Clay Minerals as Tracers of Intertidal Sediments in Hangzhou Bay

Intertidal sediments in Hangzhou Bay were collected and analyzed by XRD. The clay minerals distribution characteristics and the source and origin of clay minerals in the study area were discussed by means of cluster analysis, combined with the hydrodynamic characteristics of the Hangzhou Bay. The results showed that surficial sediments in the tidal flat of Hangzhou Bay were mainly clayey silt and the others were sandy silt. The complex composition of clay minerals in the study area were mainly illite, kaolinite and chlorite, as well as a few smectite and vermiculite and 1.4nm transitional mineral. According to each clay mineral's content, it could be divided into three kinds of combinations:typeⅠ of illite-kaolinite-chlorite-vermiculite-smectite, typeⅡ of illite-chlorite-kaolinite-smectite-vermiculite, typeⅢ of illite-kaolinite-chlorite-smectite-vermiculite. 0n the spatial distribution, the average contents of smectite and chlorite in the northern shore were higher than which of the southern shore; while the average contents of illite and kaolinite and vermiculite(containing 1.4nm transitional minerals) in the northern shore were lower than which of the southern shore. Smectite in surficial sediments in high tidal flat was greater than in the central tidal flat, and the other clay minerals had no obvious difference. The clay minerals distribution characteristics are closely related to the hydrodynamic and material source. The intertidal sediments in eastern areas of Zhapu in north shore were significantly affected by the tide and Yangtze River coastal current, the sediments were mainly from Yangtze River and the East China Sea. As a result of the input of Caoe River and Yong River, the proportion of deposits from Qiantang River basin of sediments in the southern shore was obviously higher than which of the northern shore. The changes of each clay mineral's content from bottom to top in vertical section sediments reflected the fluctuation of weathering intensity in the source area.