鸭绿江河口及近岸地区沉积物的稀土元素对物质运移的指示意义  

Rare earth elements in sediments in the Yalu River Estuary and its offshore area, China and indicative significance for sediment transport

作　　者：石勇[1,2] 高建华[2] 刘治帅[1] 汪小勇[1] 李明亮[3] 

机构地区：[1]国家海洋技术中心,天津300111 [2]南京大学地理与海洋科学学院,江苏南京210023 [3]江苏省地质调查研究院,江苏南京210018

出　　处：《地球化学》2016年第1期52-61,共10页Geochimica

基　　金：国家自然科学基金(41576043;40976051)

摘　　要：稀土元素(REE)的稳定性使其在物源示踪中得到广泛应用,而针对沉积物REE在运移过程中的微弱变化却往往被忽略。本文以鸭绿江河口地区沉积物为研究对象,探讨该区沉积物Ce、Eu的分异特征及其对物质运移格局变化的指示作用。鸭绿江河口地区沉积物的REE含量与平均粒径呈显著正相关关系,而与δEu呈较好的负相关关系,即随着REE的富集,Eu的亏损程度加剧。Eu的异常发生于岩浆结晶过程,长石类矿物的Ca^(2+)与Eu^(2+)发生置换,造成富集REE矿物的Eu亏损。河流来源的溶解态Ce的氧化沉淀作用,造成河口地区沉积物的Ce呈正异常。此外,柱样历史时期与表层样的δCe差异及河口地区不同亚环境间的δCe差异,有效指示了河口地区物质的运移及沉积环境的变迁。辽东半岛南侧沉积物中砂组分(大于63μm)的δEu指示,水深超过50 m后,Eu呈显著正异常,该处可能为鸭绿江砂组分的运移极限。Rare earth elements （REEs） are widely used as a source tracer because of their high stability duringtransport. However, small changes in REEs concentrations during sediment transport were rarely studied. In thisstudy, the distribution of REEs in sediments in the Yalu River Estuary and its offshore area was analyzed and itsindicative significance for sediment transport was discussed. The REEs concentrations of surface sediments werefound to be highly related to the mean grain size of the sediments. δEu is negatively correlated with the totalconcentration of REEs, namely the more enrichment in REEs, the more depletion in Eu. Depletion in Eu occurredin the crystallization process, due to its replacement by Ca2＋. Dissolved Ce from river discharge results inenrichment in Ce in sediments by oxidation precipitation during sediment transport. In addition, the verticalvariation of Ce anomaly in sediment cores and the horizontal differences among different depositionalenvironment can well indicate the change of sediment transport pattern and sedimentary environment in the YaluRiver Estuary. In addition, the 50m contour was probably the offshore deposition boundary for coarse sediments（〉63 gm） from the Yalu River, as its δEu turns to be positive in water at depth larger than 50 m.

关 键 词：δCe δEu 稀土元素 物质输运 鸭绿江河口 

分 类 号：P595[天文地球—地球化学]