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

Key words: 
• Hangzhou Bay /
• intertidal sediments /
• clay minerals /
• provenance

Abstract: 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.