南黄海表层沉积物稀土元素分布特征及其物源指示意义

Distribution of rare earth elements in surface sediments of the South Yellow Sea and its implication to sediment provenances

  • 摘要: 对南黄海表层沉积物稀土元素数据进行了系统总结,旨在揭示其赋存特征、分布规律及主要来源。结果表明,南黄海稀土元素含量为77.2~261.78 μg/g,平均值为166.46 μg/g;空间上分布规律显著,高值区出现在南黄海中部泥质区,含量基本在180 μg/g以上,而低值区则呈斑块状出现在靠近山东半岛近岸一带,含量多低于130 μg/g。稀土元素的球粒陨石配分模式和上陆壳(UCC)配分模式显示各海域总体特征较为一致,与中国大陆的稀土元素配分曲线类似,指示了较强的陆源特征,河流携带的陆源入海物质是其主要的物质来源。通过对稀土元素各特征参数进行相关性分析,发现南黄海稀土元素组成与沉积物粒度呈较为明显的正相关,表明了沉积物粒度、矿物组成对稀土元素含量具有显著的控制作用。对比分析稀土元素空间分布规律和南黄海主要入海河流沉积物稀土组成,结果表明南黄海绝大部分沉积物来自于中国大陆河流,包括长江、黄河和老黄河等大型河流。在不同环流体系控制下,大型入海河流控制了南黄海不同区域的物质分布:西北部主要来自黄河入海物质,山东半岛沿岸流是其主要输运动力;老黄河物质主要沉积在西部海域,主要驱动力是苏北沿岸流;南部物质主要来自长江入海物质,长江冲淡水和闽浙沿岸流控制了其分布范围;东部近岸区域则以朝鲜半岛入海河流携带陆源物质为主,主要输运动力为朝鲜沿岸流。在此基础上,以La/Yb=11.7为界,可将整个南黄海划分为两个物源区,西部大部分海域为中国大陆来源,而东部近岸区则为朝鲜半岛来源,两者分界线基本接近于黄海海槽的位置。总体而言,大中型河流带来的陆源物源、沉积物粒度以及海域流系格局控制了南黄海表层沉积物稀土元素的组成特征和分布格局。

     

    Abstract: To reveal their compositions, distributions, and provenances of rare earth elements in the sediment from the South Yellow Sea, the data in the surface sediments in the area were studied systematically. The results show that the content of rare earth elements ranged from 77.2 to 261.78 μg/g, with the average value of 166.46 μg/g. The spatial distribution pattern of rare earth element is distinct, showing relative higher value in the muddy area in the central of the South Yellow Sea, where the content is generally more than 180 μg/g, while the lower value area appears as patches close to the coastal regions of Shandong Peninsula, and the content is mostly less than 130 μg/g. The normalized rare earth elements patterns of chondrite and upper continental crust (UCC) show overall pictures of the entire study area, which is similar to the distribution pattern of rare earth elements in Chinese mainland, indicating clear terrigenous imprint of riverine materials, reflecting the intimacy as the main sediment provenance of the South Yellow Sea. Meanwhile, as shown in the correlation analysis of the characteristic parameters of rare earth elements, the composition of rare earth elements in the South Yellow Sea is significantly positively correlated with the grain size of sediments, indicating that the sediment grain size and mineral composition controlled the content and composition of rare earth elements in the study area. Based on the spatial distribution pattern of rare earth elements and those from the main rivers into the South Yellow Sea, we believed that the sediment of South Yellow Sea is mainly from the Chinese large rivers, including Yangtze River, modern Yellow River, and old Yellow River. The northwest part is mainly from the Yellow River materials, and the coastal current of Shandong Peninsula is its main transport power. The material of the old Yellow River mainly deposit in the west of the South Yellow Sea, and the main driving force is the coastal current of Jiangsu Province. The material in the southern part of the South Yellow Sea mainly come from the material entering the sea from the Yangtze River, which is controlled by the Yangtze River diluted water and the coastal current of Fujian and Zhejiang. The east coast of the South Yellow Sea is dominated by terrestrial materials carried by the rivers in the Korean Peninsula, and the main transport power is the Korean coastal current. Taking La/Yb=11.7 as the demarcation line, the entire South Yellow Sea can be divided into two realms. Most of the western materials are from Chinese mainland, while the eastern coastal area from the Korean Peninsula. The boundary between these two realms is close to the middle line of the Yellow Sea trough. Therefore, we confirm that the terrestrial provenance, sediment grain size, and marine current system pattern control the composition and distribution pattern of rare earth elements in the surface sediments of the South Yellow Sea.

     

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