南海北部湾东部海域表层沉积物地球化学特征

Geochemical characteristics of the surface sediments in the eastern Beibu Gulf, South China Sea

通过对南海北部湾东部海域61个站位表层沉积物粒度和地球化学组成的相关分析和因子分析,探讨了其空间分布特征、元素相关性以及元素组合特征,揭示了元素在区域上的分布规律和主控因素。结果表明:绝大多数常微量元素具有相似的平面分布特征,而Mn O、Zr、Ca O和Sr空间变异系数较大,在部分区域出现了异常高值,表明其沉积环境受到正常陆源沉积以外其他因素的影响。元素和Al2O3的比值分布特征表明,广西和海南岛近岸沉积物主要由陆源碎屑沉积组成,在潮汐和近岸径流作用下,由近岸向远海输送;而研究区西部海域沉积物主要为来自红河的物质。元素相关分析和因子分析结果表明,研究区表层沉积物中绝大多数常微量元素主要受沉积物粒度的控制;Ca O和Sr含量主要受生物活动活跃程度控制;Zr含量分布主要受控于源区母岩矿物组成以及自源区的搬运距离;而Mn O含量则受陆源、海底热液以及自生作用等多种来源共同影响。

Based on the correlation analysis of the grain size and geochemical compositions of 61 surface-sediments samples from the eastern Beibu Gulf, South China Sea, the features of spatial distributions, correlations and com-binations of the elements were characterized, and the main controlling factors of the elements were identified. The results showed that most of elements, such as SiO2, Al2O3, Fe2O3, MgO, Na2O, TiO2, TiO2, P2O5, V, Co, Cu, Ni, Zn, Ba, Sc, Ga, Pb and Cr, have similar spatial distributions, indicative of the stable sedimentary environment and material sources. Based on the distributions of the elements/Al2O3 ratio, it can be concluded that the sediments in Guangxi and Hainan nearshore are mainly composed of terrigenous materials and transported from the coastal area to the offshore, and the sediments in the central area of the gulf are mainly from the Red River. The results of the correlation analysis and factor analysis suggest that the grain size is the main factor controlling the distribution of most of the major and trace elements in the study area. The CaO and Sr are controlled by the biogenic substance. The contents of Zr mainly depend on the geological features of source area and the distance from its point of origin. However, the distribution of MnO is affected by terrestrial input, submarine hydrothermal solution and authigenous minerals together.