东海表层沉积物碎屑矿物组合分布特征及其物源环境指示

Detrital Mineral Distributions in Surface Sediments of the East China Sea: Implications for Sediment Provenance and Sedimentary Environment

为进一步明确东海陆架区的沉积物物源及水动力环境,对研究区表层沉积物的碎屑矿物进行了鉴定分析。研究区共鉴定出49种重矿物、8种轻矿物。根据碎屑矿物的组合分布结合矿物形态特征,将东海陆架区划分为三个矿物区,内陆架矿物区、外陆架矿物区及虎皮礁矿物区。内陆架矿物区,动力分选是影响碎屑矿物分布的主要因素,物质来源相对单一,碎屑矿物主要来源于现代长江物质,闽浙沿岸近岸河流的输入,人类活动也对该区的矿物组成产生一定的影响;外陆架矿物区,重矿物分布的主控因素是长期的分选作用,主要是长江物质经后期改造形成,现代长江物质可从内陆架中北部扩散至124.5°E左右,此外外陆架东南部地形的变化也对碎屑矿物的分布起到一定控制作用;虎皮礁矿物区,有来自黄河、长江、火山物质的多重影响,且水动力环境相对复杂。

The East China Sea continental shell is an area characterized by complicated hydrodynamic conditions and large variability in sediment texture. Detrital mineral examinations were carried out on 69 surface sediment samples （0 -5 cm） collected from the East China Sea continental shelf to investigate the spatial variations of sediment composition and their underlying mechanisms. The average content of heavy minerals in the study area is 16.3%. The high value zone is located in the middle and outer continental shelf while the inner shelf and the southwest of Jeju Island have much lower content. A total of 49 species of heavy minerals were discovered in the study area, dominated by horn-blende and followed by epidote, schistose mineral and carbonate mineral; metallic minerals and pyroxene are in the third row; the rest are tremolite, garnet, sphene, zircon, olivine, glauconite, andalusite and so on. Light minerals mainly consist of feldspar followed by quartz; schistose minerals and calcite are respectively in the third and fourth row. According to the characteristics of detrital mineral assemblages, the East China Sea continental shelf can be di-vided into three districts： I nner - shel f area （ Unit I） , Out er - shelf area （ Unit II） and Ti ger Reef area （ Unit III）. Sedi -ments in Unit I are mainly from the Yangtze River and the Fujian and Zhejiang coastal rivers. Hydrodynamic sorting is the primary factor that controls the distribution of detrital minerals in this unit; besides human activities also have a certain impact. However the long-term separation is the main control factor of the distribution of heavy minerals in U-nite II. In the vicinity of the 29oN, fine-grained sediments from the modern Yangtze River were spreading to the north-east into the sea make an obvious effect on the detrital mineral composition in Unit II. Unit III has relatively varied provenances and complicated hydrodynamic environment. The materials from the Yellow River, the Yangtze River and submarine volcanos both influence there. Thus it has a bigger difference in detrital mineral assemblages with the first two.