浙闽近岸海域表层沉积物稀土元素的物源指示

RARE EARTH GEOCHEMISTRY OF COASTAL SURFICIAL SEDIMENTS OFF ZHEJIANG AND FUJIAN PROVINCES AND ITS IMPLICATIONS FOR PROVENANCE

通过对浙闽泥质区近岸海域的151个表层沉积物样品和周边入海河流的71个表层沉积物样品进行粒度和稀土元素测试分析,研究了该区的稀土元素分布、Eu和Ce异常、稀土元素的球粒陨石标准化和上陆壳标准化配分曲线特征等。对研究区表层沉积物与长江、瓯江、闽江表层沉积物的稀土元素进行对比,以Ce/La和Sm/Nd作为元素对进行FD判别函数分析,结果表明研究区表层沉积物并不是单一物源形成,是长江、闽江、瓯江共同作用的结果。为了探究3条河流对浙闽近岸海域影响程度的大小,用物源指数进行判别,结果表明,3条河流对研究区内陆架、外陆架的影响程度都是长江>瓯江>闽江,内陆架表层沉积物中长江源占有明显优势,外陆架表层沉积物物源比内陆架更复杂,3条河流的混合作用更明显。

151 surface sediment samples taking from the argillaceous deposits off the Zhejiang-Fujian coasts and 71 samples from surrounding rivers have been tested in order to reveal the distribution pattern of grain size,rare earth elements,δEu and δCe,and chondrite-normalized and UCC-normalized REEs.The rare earth composition is compared with those of the surface sediments from the Yangtze River,Oujiang River,and Minjiang River.The F_D discriminating function is adopted taking Ce/La and Sm/Nd as the element pair.The results suggest that the surface sediments in the study area are not formed from a single source,but a mixed source of the Yangtze River,Oujiang River,and Minjiang River.The contribution of the three rivers to the deposition on continental shelf surrounding to the study area is in a decreasing order from the Yangtze River to the Oujiang River and finally to the Minjiang River.The Yangtze River is doubtlessly the major contributor of clastic sediments to the inner shelf.However,the sediment sources of the outer shelf surface sediments are rather complex.It seems that the mixingt of the sediments from the three rivers is more important and pronounced on the outer shelf.