珠江口及琼东北海区元素地球化学特征及物质来源

Geochemical Characteristics and the Source of Major Elements in the Surface Sediments from Pearl River Estuary to Hainan in South China Sea

为了更好的了解南海北部近陆表层沉积物特征及分布,通过对珠江口至海南岛东北海区进行表层沉积物取样测试,共获取了约3 500个样品粒度数据,700余个样品元素地球化学数据。该区域沉积物粒度以粉砂及细砂为主,分选性为较差及差,沉积物常量元素组合以SiO2、Al2O3、Fe2O3、CaO、K2O、MgO及Na2O为主,这7种氧化物占沉积物总量的90%以上(平均值)。对沉积物常量元素百分含量值进行了相关性分析,最终将调查海域沉积物划分为3个不同的区域,分别为珠江口及粤西区域(Ⅰ)、琼州海峡东分布区(Ⅱ)及琼东分布区(Ⅲ),同时综合分析得出了各区域沉积物运移的路径趋势。

About 3 500 surface sediment samples were got by grab and box sampler in the north of South China sea, for the sample intervals are 3 km,5 km ＆ 10 km, all the samples grain size were tested by Mastersizer 2000 which produced by Malvern company, and more than 700 samples were tested for Major Elements by Magix-pro 2440. From the test, we found that most of the sediment are Silty sand, the mean grain size are mostly between 36 and 8φ, the sediment were mainly composed of SiO2 , A12 03 , Fe2 03 , CaO, K20, MgO and Na2 O, which occupied more than 90% in the sediment for the average value. Relativity analyse were used for the value of the major elements and mean grain size（ φ）, the result is that SiO2and CaO have a negative correlation with mean grain size（φ）, the other major elements have a positive correlation with mean grain size（ 6）, A1203 ,P205 ,K20 and TiO2 are related to each other, which mostly came from the continent, CaO has a negative correlation with most major elements, and the correlation- ship is low, which indicate that CaO mostly formed by calcareous. The sediment were divided by quick clustering method, and 3 different areas were plot out at last, they were Pearl River Estuary and the west of Guangdong area （ Ⅰ ） ,the east of Qiongzhou strait area（ Ⅱ ） ,the east of Hainan area（ Ⅲ） ,at the same time we also got the sediment transport trends and routes. For the area Ⅰ , which is very wide, the sediment mainly came from Pearl River which spread radially to the open sea, and much suspended matter from Pearl River was transported to the west of Guang- dong sea by the coast current, the transport route is close to the coast until arrived at Dianbai sea area, than turn to the south, this route is very long and many major elements have the same indication. For the area Ⅱ, which is loca- ted in Qiongzhou Strait and its east, most of the sediments are medium and coarse sand that is very different from other areas, the sediments are mainly from the side and bottom of the Qiongzhou Strait, the transport route is from inner to out of the strait, and the route is short. For the area m, which is located in northeast of Hainan, the obvious charac- ters of the sediments in this area is that the content of CaO is much higher than other places, which indicate that the biological activities are extensive in this area, we also can figure out that the sediments mainly come from the conti- nent after the comparison with the content of major elements in the middle of South China sea, Chinese continent and Pacific, as we known there were many residual sediments which formed in late Pleiocene, so in this area the sedi- ments mainly deposit in early stage, and also were reformed obviously by the biological activities, the transport route is not clear in this area.