Yangtze Delta And The Adjacent Waters Sediment Element Geochemistry And Provenance Analysis

Based on a comprehensive survey of China's Coastal Sea Investigation and Research Project (908-01-CJ08, 908-01-CJ09, 908-01-CJ10, 908-01-CJ11), 375 surficial sediment samples from Yellow Sea and East China Sea were utilized in this study. The geochemical analysis and grain size analysis were conducted to reveal the distribution of 8 major elements (SiO2,Al2O3,TFe2O3,MgO,CaO,K2O,Na2O,TiO2) and 8 trace elements(Cu,Ba,Sr,V,Zn,Co,Ni,Cr). The relationship between geochemical characteristics and grain size,the controlling factors of geochemical distribution were also discussed. Q-cluster analysis was carried out to make an elemental geochemical division;enrichment factors and a mathematical model were applied to make quantitative provenance identification.The element distribution is mainly controlled by grain size. The distribution can be divided into 4 types. Type 1, represented by Al2O3,TFe2O3,Cu,Zn, has high content in fine grain size area and low content in coarse grain size area; Type 2 has low content in fine grain size area but high content in coarse grain size area, which was represented by SiO2,Na2O; Type 3 (CaO and Sr) were mainly controlled by calcareous biotic matters; Type 4, represented by TiO2 and Ba, has little correlation with grain size, and it is mainly controlled by the heavy metal minerals from terrigenous matters.The results of Q-cluster analysis show that the study area can be classified into three geochemical divisions. ProvinceⅠ, which covers the whole off-shore study area, is characterized by comparatively concentrated SiO2,Na2O,besides, some samples are extremely concentrated in CaO and Sr; ProvinceⅡis located in the Yangtze Estuary, Hangzhou Bay and the mud area of Yangtze Estuary , which is rich in Al2O3,Fe2O3,MgO,K2O,TiO2,Cu,Ba,V,Zn,Co,Ni,Cr; ProvinceⅢ, which lies to the north and south part of the tidal sand ridges along North Jiangsu coast, has a similar element content to the average lever of the whole study area, except for relatively high Cu content. The primary controlling factors of element division are sedimentary dynamics, biogenic sedimentation and the provenance of the sediments.The concentration factors of trace elements in the study area are all around 1, which indicates that most of the sediments are coming from the crust. Compared with the element contents in the crust, Ba and Zn are relatively enriched, while Sr,V,Co,Ni,Cr are relatively depleted. A mathematical model on quantitative provenance identification was applied to identify the ratio of different origins in the whole sediment. 8 elements were selected as the index. The results show that the matter from Yangtze River distributed in the area south of 32°N , west of 123°E, and the matter from Yellow River (including abandoned Yellow River Delta ) distributed in the area north of 32°N , east of 123°E.