南海东部海域的沉积作用和物质来源研究

Research on sedimentations and material sources in the eastern South China Sea

1998年在南海东部海域采集了195个表层和24个柱状沉积物样，对沉积作用和物质来源研究表明：(1)南海东部海域具有典型的边缘海沉积特征，沉积物主要由陆源碎屑、生物碎屑、火山碎屑、浊流沉积物组成，沉积作用具有多样性；(2)黄岩岛以北海区沉积物中基性岩组分含量为23．2％，陆源硅铝质组分含量为76．8％，这两种组分的理论计算值与海底沉积物实际分布相一致；(3)由碎屑矿物分析得出陆源矿物、混合矿物、自生铁锰矿物和中基性火山矿物四种矿物组合区，矿物组成和含量差异反映了物源和沉积环境的变化；(4)对沉积物中大于0．063mm的物质全组分分析表明，生源组分占66．97％，其中钙质生物含量为23．43％，硅质生物含量为43．54％，钙质生物高值区主要分布在水深小于3500m的海区，硅质生物高值区主要分布在水深大于3500m的深水区；(5)南海东部海域火山沉积作用明显，海底扩张区沉积物中铜、钡、铁、锰、钴、镍、砷等金属物质分布与海底构造和海底中基性火山活动密切相关；(6)对沉积物粒度、物质组成和生物化石组合分析表明北部陆坡区69柱187．5～190．0，287．5～280．0，377．5～380．0cm，深海平原区149柱157～187，187～194cm，南部陆坡区323柱280～350cm在粒度上表现出浊流沉积特征；(7)对锶同位素物源示踪和粒度、矿物的研究表明，北部陆源碎屑向南一直扩散到约17°N，西吕宋海槽是亚洲大陆物质特别是我国大陆物质向南海东部海域输运的主要通道。

One hundred and ninety-five surface sediment samples and 24 piston core samples were collected from the eastern South China Sea in 1998. Based on these samples, the study of sedimentation and sediment source shows that:(1) The eastern South China Sea has the typical sedimentary charecteristics of the marginal sea; the sediments are composed of the terrigenous clasts, biogenous debris, volcaniclasts and turbidity deposits, and sedimentations are multiple origins;(2)the intermediate-basic constituent of sediments in the north area of Huangyan Island is 23.2% and the terrigenous fraction is 76.8%, the theoretical estimates of the two components are quite consistent with the distributions of the submarine sediments.;(3)the mineral analysis shows that there are four mineral assemblages of terrigenous minerals, mixed minerals, authigenic ferromanganese minerals and intermediate-basic volcanogenic minerals, and the mineral constituents and content differences reflect the changes of the material sources and the sedimentary environments;(4)the constituent analysis of being greater than 0.063 mm sediments shows biogenous debris is 66.97%, of which the calcareous fraction and siliceous one are 23.43% and 43.54% respectively. The high value of calcareous fraction is mainly distributed in the region of the water depth of being less than 3 500 m and one of the siliceous fraction is distributed in the deeper area of being greater than 3 500 m;(5)the volcanogenic sedimentation in the eastern South China Sea is very obvious, the distribution of Cu, Ba, Fe, Mn, Co, Ni and As in the sediments in the sea floor spreading areas is closely related with the submarine volcanic activities; (6)analysis of grain size, composition and biogenic fossil assemblage of the piston core sediments, shows that the grain sizes of sediments in the layers of 187.5～190, 287.5～280 and 377.5～380 cm in 69 sediment column collected from the northern continental slope, the layers of 157～187 and 187～194 cm in 149 column from the abyssal plain, and the layer of 280～350 cm in 323 column from the southern continental slope are characterized by the turbidity deposits;(7)study of Sr isotope and grain size and mineralogy in sediments shows that the terrigenous sediments from the northern area spreads southward to about 17°N,the west Luzon Strait is a major passage of Asian continental weathering debris, specially China's Mainland terrigenous material, into the eastern South China Sea.